Photograph of  a modern oil-fired heating boiler Heating System Repair FAQs

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Heating system installation, repair, maintenance questions & answers:

Q&A on how to inspect, diagnose & repair a heating system furnace, boiler, electric heat, heat pump, or other heating equipment.

These heating system articles answer questions about all types of building heating systems and describe how to inspect, diagnose, and repair heating system problems, how to cut heating bills, and heating system safety, heating system efficiency and heating trouble-shooting advice.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Heating System Inspection Methods, Diagnosis, Safety, Repairs

Gas furnace schematic (C) Carson Dunlop AssociatesThese Q&As were posted originally at HEATING SYSTEMS- home. In these heating system articles we explain how to inspect and detect all defects and hazards on heating systems, boilers, furnaces, and other equipment.

[Click to enlarge any image]

On 2017-11-26 by (mod) -


I would look for an electric motor that is seizing or a jammed coupling or blower fan or a seized fuel unit any of those would easily cause a humming sound from the motor that might sound like it was the Transformer.

On 2017-11-20 by Warren Jones

One site said that I should call a heating or electrical contractor. Another, that I'd probably have to buy a new system. Then, there's this one, but the one that finally helped me in an instant was the one that said this: If the thermostat runs from the house's electrical system, check on the circuit breakers.

One of them might have tripped and cut off the power the thermostat. Reset the breaker. THAT DID IT. I NOW HAVE MY HEATING SYSTEM WORKING AGAIN. Now I only have to wonder if I should be worrying about why the circuit breaker tripped.

On 2017-11-16 by Phil

I have a Beckett afg model burner wasn't coming on intermirtingly and a humming noise was coming from the transformer. When I have it a whack it would start up. I replaced the transformer thinking that was the fix. No go next morning had same problem. Sound still sounds like it's coming from! Anyonne

On 2017-11-15 by (mod) -


If your building is in the U.S. the usual arrangement is such that the circulator should run when the thermostat is calling for heat. The boiler itself may be on or off depending on the water temperature. The thermostat turns on and off the circulator, and the water temperature, via the aquastat, turns the boiler's burner on and off as needed.

If your building is in Canada it's often the case that the circulator runs continuously during the heating season and the thermostat turns the heating boiler on and off as needed.

Catherine: the system you describe sounds unsafe to me, as if there is an electrical problem. Leave the heater OFF and turn off the circuit breaker or fuse that delivers power to it, then call your electrician to ask for repair help.

On 2017-11-14 by Brian Brownawell

When should my circulator pump be running on my smith boiler system ?

On 2017-11-08 by Catherine

My wall mounted electric heater are making pow noise even loud ones and even when I set them at 5 celcuis wich is off ..only time they stop is when I turn off the power Switch they also made a strange buzz in the corner of the cord

On 2017-10-30 14:51:51.936237 by Lorna

Where is the pilot light?

On 2017-10-16 by Anonymous

if condensaate drain from ac coil and the air handler connect, you may need to install air gap or vent in hard piping. the air handler blower fan and or power vent will cause neg. air pressure in conensate plplng

On 2017-10-16 by Anonymous

you may too adjust rhe volume control valves or install these valve at every heating panel.

On 2017-10-16 by everett

@barbq australia,

On 2017-10-10 by (mod) - circulator pumps and circulator control relay switches are usually generic


Both circulator pumps and circulator control relay switches are usually generic: you can replace the pump or its controller with any of a variety of brands

On 2017-10-09 by Krystyna

Noticed the water pump running when the heat is off. Have located the issue and in need of an obsolete part for a Hydrotherm Boiler. The part is: Hydrotherm Circulator Control LS50. This part came from a Hydrotherm Model HC-85B. How can I locate this part? Is there an alternate part I can use to fix this issue?

On 2017-10-09 by Anonymous

Do the radiant heat plates in a Williams vented room heater circa 1990 contain asbestos?

On 2017-09-01 by (mod) -

Should be easy to make 4th he system run long enough to check basic burner operation, blower fan, air delivery.

Measuring temperature rise would be more difficult if thst were to be included, ehich its not in a normal home inspection

On 2017-08-30 by bill

how effective is a furnace inspection with temperatures above 70 degrees

On 2017-06-27 by barbq australia

I have a hot water hydronic system using panel radiators. I am living in a 2 story house. 3 panels on the ground floor stopped working. They are on the same side of the house. Replaced the panels instead of trying to fix them but they were still cold.

Called in a repair tech who installed a brand new boiler/pump unit as the old one was faulty.

The repair tech then bled the entire system and put in anti corosion treatment. One of the previously cold panels got hot and then went cold again it is full of water and no airlock as there is water coming out under pressure from the bleed valve., the other 2 panels stayed cold.

When the air bleed valves on these 2 are opened no air or water comes out and when I apply some vaccum to the outlet it stays in the negative for a few minutes until it gets some water comes in. I know some water is coming in as a trickle comes out of the drain valve at the bottom of the panels and no air rushes back in when I open the air bleeder.

There is water to the inlet and outlet valves as I unscrewed the pipe couplings and the water sprayed out everywhere. Hope you can shed some light on this, thanks

On 2017-05-13 by (mod) -


In my opinion you need to drain the condensate to a drain system or to the building exterior; you might need a condensate pump if you can't make the drain work by gravity.

Continuing to wet a crawl space invites wood destroying insect damage, mold, rot.

On 2017-05-13 by Zoom

Hi, I had a high-efficiency gas furnace installed last year and within just a couple days, it wouldn’t stay on. The owner of the company came out right away and told me it was because the drain pipe for the condensation had been installed in a way where a section was run up before back down again.

So, in this section, the water was getting trapped and was turning off the heater.

Anyway, they came out and cut the pipe at that section and left it where the condensation just drained directly below into the crawl space under the house. I have a raised foundation and he said letting the condensation drain into the dirt won’t be a problem short term and would get back to re-route the pipe as soon as he could.

He finally returned today to tell me the pipe can’t be re-routed to drain outside for some reason related to framing of the house and the only other thing he could do would be to put in a pump but he didn’t really explain how that would work because he was pushing me to just leave it forever to drain under the house.

He said the condensation only makes about 1/2 cup of water a day when running the heater all day and it will never cause any damage.

I live in Los Angeles and we do have mild winters but it still gets cold enough that we run the heater almost every day for a good 4 or 5 months.

I wanted to get professional opinions on this matter to either give me assurance that what he is telling me is correct or explain why I need to insist that he do what is needed to drain the water away from my house. Thanks!

On 2017-04-21 by (mod) - Venting a direct-vent furnace into an existing masonry

Venting a direct-vent furnace into an existing masonry chimney may

- violate the manufacturer's installation instructions
- be unsafe risking fatal carbon monoxide poisoning

And I am totally baffled by the second part of your question: combustion air from the return air plenum?

What? Perhaps I misunderstand, but if I don't, I have to ask

1. who's going to live in this house?

2. does someone want to kill them?

Not to be too silly about it, the situation you describe sounds unsafe and improper.

I suggest noting the brand and model of the furnace, giving the the manufacturer a call, and ask them for an opinion. Keep me posted.

No one should be sleeping in the home you describe without working smoke and CO detectors properly installed, located, tested, and resolution of the question you raise is so urgent and sounds so unsafe to me that I suggest that any occupants be informed immediately of the concerns you've raised.

On 2017-04-20 by Mike Hickens

A home that I'm considering buying here Michigan had a 96+ furnace installed on 2015. The PVC exhaust vent is venting into one of a two flue chimney. The PVC pipe for combustion air is routed directly from the furnace to the return air plenum. Is this correct?

Isn't the combustion air pipe usually routed to the outside of the home. Also, I don't see the exhaust vent pipe exiting through the top of the chimney. Won't the moist exhaust air rot the inside of the Chimney?

On 2017-04-08 by (mod) -

Pete, using the Search the InspectApedia website box just above I found

MANUALS & PARTS GUIDES - HVAC - that has both links to direct PDF files of many manuals and also company contact information for manuals we don't already offer free to our readers.

On 2017-04-08 by Pete manual for a 1968 'american standard' gas forced air furnace

Need a manual for a 1968 'american standard' gas forced air furnace

On 2017-04-03 by (mod) - Amtrol Extrol heating boiler expansion tank


The Amtrol Extrol heating boiler expansion tank does not use a condensate drain.

I think you probably have an air conditioning/heat pump system - that does use a condensate drain.

For detailed help un-clogging that drain see CONDENSATE DRAIN CLEAN & DE-CLOG at

(found by using the InspectApedia search box just above to look for "clogged condensate drain"

On 2017-04-03 by Anonymous


On 2017-03-26 by (mod) -

This sounds to me as if a safety control is not working properly, perhaps a gas spill switch or a burner control. I'd ask for repair from an experienced gas boiler service tech. Do keep me posted - as what you find will help other readers.

On 2017-03-26 by RG

I have a gas utica boiler that stopped working last week. The circulator kicks on but the furnace would not fire unless I shut off the electric for approximate 5 mins.

Once I turn electric on system fires up and baseboard heat up appropriately. Will continue to operate for like a week than stops firing up again.

On 2017-03-14 by (mod) - what are the procures and tools used by a service technician in determining what's the problem with a furnaces.

Myles you ask a perfectly wonderful question, but far more than would be appropriate to try typing in to an off-the-cuff reply window.

Since you mention furnaces specifically, I add that there is a series of detailed, step-by-step heating system diagnosis and repair articles here at, addressing various areas of problem and solution. Start at NO HEAT - FURNACE -

Techs start with the basics: is there power, is there fuel, does the burner run, does the fan run, does air come out of registers; each of those general areas becomes a focus for a more-detailed look depending on the yes or no answer.

Separately, depending on the fuel type, e.g. oil or gas, we have flowcharts showing what a tech considers, for example, if the oil burner doesn't run.

It sounds as if you are taking a test - I hope you're not cribbing.

On 2017-03-14 by myles J.

I would like to know what are the procures and tools used by a service technician in determining what's the problem with a furnaces.

On 2017-02-25 1 by (mod) -

Sorry Tom, I don't understand your text. From what I can make out it sounds as if condensate return to your boiler may be blocked; water logged radiators will block steam and won't heat. I'm totally baffled about what "walls" you would open.

Condensate from radiators has to return to the steam boiler.

It's time to call for help from an experienced steam heat technician.

On 2017-02-25 12:56:03.709893 by tomcatcardona

2 Family 3 level home new gas boiler 1 yr.old. Old baseboards no cut off valves.

Top flr. start of heat run the last 3 baseboards 2 in livngroom. spray water from varivalve then it goes to Bthrm. no heat I take off varivalve it sprays alot of water then steam. Some told me to open walls cause there is a low point where upon cooling the water sits until system starts up again. Please advise.

On 2017-02-25 by (mod)

Sorry Tom, I don't understand your text. From what I can make out it sounds as if condensate return to your boiler may be blocked; water logged radiators will block steam and won't heat. I'm totally baffled about what "walls" you would open.

Condensate from radiators has to return to the steam boiler.

It's time to call for help from an experienced steam heat technician.

On 2017-02-25 by tomcatcardona

2 Family 3 level home new gas boiler 1 yr.old. Old baseboards no cut off valves.Top flr. start of heat run the last 3 baseboards 2 in livngroom. spray water from varivalve then it goes to Bthrm. no heat I take off varivalve it sprays alot of water then steam. Some told me to open walls cause there is a low point where upon cooling the water sits until system starts up again. Please advise.

On 2017-02-18 17:46:45.688485 by (mod) - heat won't turn off

Mr. Walker:

First confirm that nobody used a switch at the thermostat or at the air handler to put the fan into always FAN ON

Check for shorted thermostat wires or a bad fan relay control.

Search InspectApedia for HEAT WON'T TURN OFF to see more detailed diagnosis and repair suggestions.

On 2017-02-18 17:45:53.476731 by D Walker

Re-posting comment made on an obsolete version of the article above:

AUTHOR:D. Walker (no email)
COMMENT:Our fan has been running for 12+ hours. We tried turning the heat off and it continues to run.

On 2017-02-13 17:04:05.771196 by (mod)


Take a look at the very top of this page and click on NO HEAT - FURNACE if your heat is by forced hot air, or NO HEAT - BOILER if your heat is by forced hot water or steam. Each of those articles is a great starting point for step by step procedures to figure out why your heat is not working and to fix the trouble, or to recognize when it's time to call a trained repair person.

From your comment it sounds as if your boiler is working - the water is hot - but your radiator or baseboard is not heating enough. That could be water not hot enough or a circulator not forcing water through the system, or a clogged or blocked readiator or, of course, something else that would be more obvious to an on-site expert.

On 2017-02-12 23:45:44.054559 by Jason m not sure how i would check if u answered didnt ask for an email but heres mine if u can
Hi,just wondering if u could help?.

i live in an apartnent building.only my heat isnt working.thermostat is working.bled the lines and right when we do hot water comes up but then notbing after that.changed the curculater.theres hot water going up the line from the furnace and in the return.we dont understand why its not oushing hot water up.theres not a blockage cuz when u bleed it hot water comes up but yhats it,then it cools right back!

On 2017-02-10 21:42:43.820090 by Dave

I'm having a problem with our baseboard Heat system. We have a multiple zone set up and thermostats for both zones.

Each are set in the low 60's. Our downstairs zone reads 80 degrees on the thermostat yet it's set at 62. This zone will run at 80+ till I turn off the burner using the emergency switch.. .

I tried new thermostat, no luck.
My other zone is Upstairs and I have no problem..64 degrees. Rooms are at proper temp.. Can someone help me out and point me in the right direction as to what's causing the problem?
Beckett oil burner
Newport Boiler
Honeywell electronic aquastat L7224/L7248
Honeywell Mercury thermostats

On 2017-02-07 18:27:55.668452 by Paul

Infloor radiant heating:
I have 2 wall thermostats in a 1100 square foot house with infloor radiant heat. I normally leave one at 21 and the other at 18. The house to me feels cool but to the wife warm. My question is is it better to have both thermostats close to or even at the same temp setting.

I am wondering if by having the two thermostats at a different temp setting if one side of the house is trying to fight with the other resulting in uneven temps. It is an open system and heated with a Nautral gas direct power vent hot water tank.

On 2017-01-09 18:43:01.680054 by (mod)

Steve is it possible that the boiler sports an extra, obsolete hi-limit that's no longer needed? What does your heating service tech say?

I've seen extra limit controls on older heating boilers that made domestic hot water with a side-arm coil or a range boiler system.

I speculate that particularly with a cast-iron boiler residual heat in the combustion chamber and in the cast iron may heat the water a bit at the end of a burner on-cycle. As long as the burner is off at the limit and as long as system pressure remains below the spill point of the relief valve (typically 30 psi on a residential hydronic boiler) you should be ok.

On 2017-01-09 by (mod)

RE-posting from old copy of this web page

AUTHOR:Steve S (no email)

COMMENT:Hi. I have a hydronic heating gas boiler. In addition to the combination aquastat, there is a high limit manual reset thermostat by Honeywell. The manual reset thermostat keeps tripping at 205 degrees which is what it's set at. On the combination aquastat, the high limit temperature is set for 190 degrees.

The low limit is set for 170. It seems that after the burner goes off, the temperature still increases. Any idea if the setting is wrong, if I have a bad aquastat, or what else might be causing it to trip.
One thing to note, there are a few other boilers in this room that are set to very similar settings and they do not trip.

I appreciate all your help.

On 2017-01-09 y (mod) problem with freezing water, at my water pellet stove

Turn off the pump as running it dry or unable to move water or frozen will perhaps ruin it.

Suggestions for un-thawing frozen pipes are in our series of "winterizing" articles that will appear in response to searching for "thaw frozen pipes"

Use the search box just above or the one at page top.

On 2017-01-09 by klod

I have problem with freezing water, at my water pellet stove. I have well covered pipes on outside, in balcony, but they are well protected, but the part where main house tubes where the cold water gets in heating system, where its the pressure bar meter installed I think has frozen. The crazy think its that the bar meter has gone to maximum from the cold. the pump doesn't work, it tries but the water doesn't gets around on pipes. I would like your advice please on this issue. Thank you

On 2017-01-04 by (mod)


What you describe sounds very dangerous, risking fire or death from shock. It is possible that the main breaker you are turning off is a defective switch that
is not turning off internally even though you switch the toggle to OFF.

Use the page top or bottom CONTACT link to send me photographs of the switch and of the furnace, being sure to include any visible labels or markings on the electrical box and switch.

Meanwhile, I suggest keeping people away from the furnace, keeping aware that ALL of the electrical components in the system might be unsafe, and that you should call a licensed electrician for help.

On 2017-01-04 by (mod)

RE-Posting comment made on obsolete copy of this web page:

AUTHOR:MikeHamilton (no email)

COMMENT:I have an electric coleman 3400s furnace. In the beginning it will run fine and get the trailer to temp but shortly after the elements will light and the blower will stay off. I put a new sinkurnizing relay on it and thought that fixed it. Lastnight I woke to the smell of the elements cooking and no blower. What should I try next?

On 2017-01-04 by daniel.caruso54

How is it possible that I'm getting a fairly substantial shock from the housing on a mobile home furnace even when all power has been turned off at the power pole?

On 2017-01-02 by Alex

Just moved into my new home in August. The oil furnace was cleaned + serviced then and we've been using it since. We have an indirect hot water heater on it as well as baseboard hot water heat. It is 15 years old and is a peerless. Everything has been fine.

We had our oil tank refilled in October and now again the other day (it was down to 1/8), and perhaps coincidentally, the boiler has been making a strange "rattling" sound intermittently since after it was filled.

Is this anything I should be concerned about and if so, what should be done?

Noise can be heard:
from 00:00 to 00:04
Briefly at 0:19
from 0:24 to 0:29
Link to video with sound:

On 2016-12-26 18:37:10.798375 by (mod)

I don't know, Clarence, as I don't know what fuel is being used, what sort of heater we're discussing, nor any other site conditions.

Watch out: I caution you that if you are describing a gas burner and the flames are principally yellow the system is UNSAFE and should be shut down and you should call for service/repair.


On 2016-12-26 18:34:30.271727 by Clarence Jones

My burners are producing a yellow flame. What is the cause?

On 2016-12-26 17:49:21.270133 by (mod)


Check for a bad or blocked steam vent, for a radiator valve that's closed, or for other problems found by searching for COLD STEAM RADIATOR

On 2016-12-26 17:48:34.046280 by (mod)

Re-posting question left on old version of this web page

AUTHOR:Crystal (no email)
COMMENT:I have natural gas steam heat radiators and baseboard radiators. There is only one thermostat to control all rooms. Every radiator is working except for the baseboard in the kitchen. Not sure why that is the only one not getting hot??

On 2016-12-11 03:45:57.739867 by (mod)

perhaps a bad control, relay, or blower motor.

On 2016-12-10 14:54:56.965658 by Ed

Gas furnace. Blower starts to turn but shuts down immediately. This happens with thermostat in heat or cool and fan in auto or on.

On 2016-11-21 21:10:36.785846 by (mod)

Yes, Tom, simply by

1. not calling for heat at a thermostat
2. turning off or disonnecting the circulator pumps

combined with checking that the FLOW CONTROL VALVES over the boiler are working to prevent hot water circulating through the heating zones by natural convection

On 2016-11-21 21:08:58.446102 by (mod)

RE-posting from comment made on obsolete copy of this web page

AUTHOR:tom (no email)
COMMENT:On a boiler that produces hot water for heat and domestic hot water can I isolate the boiler to Just Produce hot water and not circulate hot water or heat

Question: I'm trying to find how to determine the age of my Lennox gas furnace

I am trying to find the age of my Lennox gas, gravity fed air, furnace model GN1-105C which the only thing I've had to do to it besides cleaning is change the thermo-couple in the last 40 years


Jack, please see our article "How to Determine the Age & Life Expectancy of Heating Boilers & Furnaces" at AGE of HEATERS, BOILERS, FURNACES where we explain the decoding heating and cooling equipment data tags to learn the date of manufacture of the device.

That article also refers you to some texts, including one free and visible here at InspectAPedia that offer more model/serial number decoding to see the equipment age.

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer
: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.

InspectApedia has no financial connection with the sale of this book.


hi,like to know what is normal pressure range of two gauges pressure reading in heatpump running in heat mode?and is that right,when heatpump run in heat mode,the compound gauge turn in to high head pressure gauge?thanks - Jason 9/30/11


Jason, if you click on the AIR CONDITIONING link at page top you'll then find at the "More Reading" links at the bottom of this article articles on refrigerant pressures that will answer your question.

Question: how do I identify the wall heater in my apartment?

I was wondering if I could find out what type of wall heater is in my apartment I only have the Cat no FC257, Watts 2509/1875, Volts 240.

I can't make out anything else and the landlord had someone glue knobs on the heaters so I can not take the covers off I need to know if they have ever been recalled.- Kim Amundsen 11/5/11


Kim: If you like, send us some sharp photos of the heater and its data tags and I may be able to advise. Use the CONTACT link for direct email.

Question: Books & resources for heating boiler troubleshooting

Is there a book on troubleshooting residential heating boilers? Kevin 1/5/2012


Sure Kevin. In addition to the free "Diagnose ..." boiler troubleshooting & repair articles we provide (see links at page top & page left) see books listed below at the end of this article. Also we welcome specific questions and are glad to research if needed.

Question: My heating unit is running on emergency heat for the whole winter - my electric bill is too big

my problem is my heating unit have been running on emergency heat for the hole winter period and my light bill is outregious. I've had repair man come to my house and they tell me that my unit has to be run on that emergency heat because i live in a town house. What should i do im going to go broke just because my light bill is like $300 dollars. HELP!!! - Hector Toledo 2/24/2012


Hector the statement that you need to run your heater on "emergency heat" because you live in a townhouse makes no sense to me at all.

Perhaps the heating service tech just didn't give a clear explanation of what's wrong. I infer from your question that your heat is supposed to be provided by a heat pump that also provides air conditioning in hot weather.

Emergency "backup" heat in such systems is there to handle cases of unusually cold outdoor temperatures - below a certain temperature the heat pump may be unable to provide enough heat for the building and the backup heat kicks in. But in all other conditions you should not be running on "emergency" or "backup" heat.

So if I've got the right picture, something is wrong with the heating system. See if you can get some details and let us know what you are told.

Question: exploding radiator on hot water heating system - what's going on?

Heather  said:

I have a boiler for heat in my home with two circulator pumps that supply two different zones (upstairs and downstairs).

My circulator pump for the first floor went bad and was replaced, fixing the problem. The boiler itself had no issues. An hour later, a radiator upstairs (different zone supplied by the other circulator pump) exploded and a 6 inch piece of metal was cast from the radiator causing water to flood the house.

This happened in a different zone connected to the other pump from the same boiler.

Could the exploded radiator in the other zone have been affected by the replacement of the circulator pump to the other zone? I cant understand how this coincidentally happened when there seemed to be no problems with the supply to the zone on the second floor where it happened. Any feedback is appreciated. - 1/30/2014



This sounds horrible - and peculiar. Forensic investigators start by disbelieving coincidences.

But it's not clear why a radiator would explode under any circumstances. Really "explode" ? We're talking about hot water heat, at normal pressures under 30 PSI.

WATCH OUT: if your heating system pressures were abnormally high (over 30 psi) then either your system was missing a critical safety device - a Temperature/pressure relief valve at the boiler - or the valve was installed but was jammed, or subverted, or not working.

IF that is is the case this is a VERY DANGEROUS condition as an exploding boiler can cause a BLEVE explosion of tremendous force. (See details at BLEVE EXPLOSIONS).

In short, a normal hot water heating circulator pump does not have great pumping power; if there was an overpressure problem in the system it seems more likely it came from another component. Naturally everbody involved in working on your system will be scared to admit fault. Focus on a thorough inspection of the heating boiler starting with

The location, type and condition of pressure/temperature relief valve - see

The normal operating pressure and temperature of the boiler - see

If on your own, before the heating company shows up, if you see high pressure readings on the boiler gauge (30 psi or above) or if you see water spilling out of a relief valve I would SHUT OFF THE SYSTEM immediately and would get the heck out of there.


(Dec 13, 2012) qhia said:

in my reading energy saving device using capacitor bank does not function efficiently for high wattage equipment(heating)..i need to know why so confuse


sorry we are confused too - and don't understand the question.

These articles may help you identify and diagnose the trouble:



Question: Mobile home furnace not working

(Dec 14, 2012) Sean Newcomer said:

I have a brand new thermo pride furnace for my moble home it ran fine for two months the furnace started cylcling, it would burn then the fan would come on after a couple minutes the call to burn would shut off, then the fan would shut off a few mins later, upon fan going off the burner would cycle for heat again and the fan would come on heat would stop and so on.

But the heat keeps climbing it doesn't stop so i got ahold of the installer he told me it was the thermostat, i replaced it and still does the same its under warranty but i can't afford to pay a serve man 200.00 to come to tell me the problem. is it the burner control or is it the computer board can it be reset and how



IF the warm air output from a supply register is blowing right onto the room wall thermostat, then "the thermostat is the problem" could be a correct statement.

Otherwise I suspect a bad fan limit switch or improper installation of that control. For example, if the limit switch is mis-adjusted or if its sensor spring is binding, the system won't work properly.

Watch out: a fan limit switch that is bent, damaged, mis-handled, even mis-adjusted, can be dangerous, risking damage to the heating equipment or even a fire.


Question: fire hazard from damaged fire bricks in Arco Boiler

(Dec 15, 2012) Isaac said:

Need help with my Arco - ideal water boiler
I have Arco - ideal water boiler tow days ago was shut down I went to see what is going on I found out the thermal bricks was collapse inside the boiler which is result of blocking the fire opening, I need help and advice how to fix it if it easy to fix or who to call so I can get it fix or it is okay to run it with out thermal bricks



Watch out: Turn off, and Do not run the boiler. a Heatinbg boiler with a collapsed combustion chamber is unsafe.

Call your heating service company. They can replace, rebuild, or reline the fire box.

Question: short cycling heating system diagnosis

5/15/2014 Susan said:

Furnace -Carrier Weathermaker 8000 all works fine.Tech came out for a checkup. I declined the AIC special and pressure switch (both bad he stated) bc all furnace works fine. All still works just fine, but every 5-7 minutes now, 24 hrs. a day, an intermittent. mechanical sound for about 5 seconds clicks on 2-3x in that period and then stops.

What is that sound? Is it happening bc I did not get the AIC and pressure switch? Hope to find out exactly what is the sound? Sorry for the limited info. just want to find out and stop it. Trying to get the company to come back out and put in to parts and hopefully, identify the sound and correct it. Any thoughts? Thanks.



With no data about your system other than your message I can't diagnose the issue accurately, but there seems to be a contradiction between saying the system works fine but it is not working normally and is cycling every 5-7 minutes.

Anderson Instrument Corporation (AIC) produces a line of HVACR pressure control switches and gauges. If the pressure switch on your system is faulty that *could* explain the symptom you describe. Below I give contact information for AIC who produces the control that you ask about.

Other reports of the Carrier Weathermaker 8000 units (you don't give your model but this note is for the Carrier Weathermaker 8000 Model 58WAV090-LC) that are short cycling may display an error code No. 34 or No. 14 or both, indicating a problem with the furnace's ignition system. The system may eventually shut down on safety with Code #34.

Ignition problems are often traced to a mis-located flame sensor, a failed thermocouple, or even dirt (or in a few cases I've seen spider nests) on the sensor assembly.

Watch out: if you see sooting conditions on gas fired equipment the unit is unsafe and should be shut down while you wait for professional service. Sooting gas fired appliances may be producing dangerous, even fatal levels of carbon monoxide.

Other problems can cause a furnace to shut down under control of its temperature limit switch, such as a dirty air filter or dirt-blocked cooling coil in a combination heating/cooling unit. Obstruction of air flow through the heating plenum or het exchanger can cause the system to heat up and shut down before the thermostat is satisfied.

You can detect this condition on furnaces or on systems that provide both heating and cooling and that short cycle in heating mode on units that use a fan limit switch by noting that the switch indicator dial is rotating to the HI LIMIT temperature shutoff during system operation. See FAN LIMIT SWITCHFAN LIMIT SWITCH TROUBLESHOOTING.

If you do not have the installation and operation manual for your furnace, you can also look for error code signals and their decoding information on data tags right on your Weathermaker 8000 unit.

Question: expansion tank pressure problems

(Sept 8, 2014) Don F. said:

This may or not be a problem. Please tell me what you think. Thanks for your help.

Expansion tank set at 14psi same as the 14psi auto feeder. Cold fill when boiler is at 80F shows 14psi on the pressure gauge.

Pressure verified with separate test gauge. Start boiler and pressure increases to 20 psi at 180F. When boiler cools back down to 80F overnight the pressure does not return to 14psi. It stays at 19/20psi. I've dropped pressure to 0psi and cold filling several times and it is always the same outcome.



I suspect that the pressure gauge itself may be sticking. Check that first (tap gently to see if it will move, or replace it).

Alternatively, you could have leaks INTO the boiler if a tankless coil is installed. \

Reader follow-up:

(Sept 8, 2014) Anonymous said:

Well, the separate pressure gauge when when connected verifies the installed pressure/temp gauge as accurate. If the indirect water heater has a coil leak... Why does the pressure stop at 20? Until I can understand that I can't move forward. For now the 20psi is holding very steady.


OK so we like the gauge.

Your question is on point; the stopping pressure would depend on the house side water pressure.

Try this:

Shut OFF completely the boiler water feed - the valve should be ahead of the boiler and pressure reducer / water feeder.

With the boiler OFF and cold and sitting over night, if the pressure doesn't change then we would suspect the water feeder.

Reader follow-up:

Been there done that in 2 different ways... Way 1--- Boiler cold 80F and pressure reduced to 0psi. Then turn on boiler street valve which feeds auto reducer feeder. Pressure now goes to 14psi and stays there. So many hours latter (like 18 hours) I turn on the boiler and as it gets hotter the pressure gradually increases from 14psi to 20 psi at 180F. Then when all is quiet and the boiler is idle overnight for 12 or more hours the boiler is around 80F the pressure is still 19/20psi.

I can repeat this procedure with the street feed valve turned off after filling from the pressure reducer fill valve. But the outcome is the same. Street pressure here is 70psi.



If even sitting idle the boiler is still hot (e.g. if it's keeping some heat in the boiler for a tankless coil) then it pressure would stay up in the range you describe.

But if you turned off power to the boiler over night, we can be sure the boiler ought to be "cold" or at least room tempreature, the next morning. And we'd expect to see lower pressures, though possibly slightly above the 12 psi cold if cold water from the street side were really cold on original insertion.

Reader follow-up:

Only heating indirect heater this time of year. I just took some pressure off. Brought it back down to 12psi. I had to let 2 quarts of water before the pressure reduced to 12. I'm thinking coil leak again :(


Yeah. If you shut off water supply INTO the indirect-fired water heater tank AND drain pressure off of the tank - if you can stand having no hot water for a time - you can repeat these tests to confirm that water source leaking into the boiler. :-{

Question: radiant heat not working

(Sept 11, 2014) Bill Mills said:

radiant hot water base board don't work in one room and does in all the other rooms


Look for a clogged or broken radiant heat line. You might first check the control valves at the start and end of that radiant tubing leak; then use a simple infra red scanner or a thermographic camera to map the heating tubing - that'll tell you if it's leaking.

Question: furnace pilot goes out

(Sept 28, 2014) theresa said:

how do I clean the burners on a early 1900's hot water boiler heating system?

(Oct 22, 2014) John Slaughter said:

Need to identify a DayNight furnace age serial number is KDGHG 30314.

(Nov 3, 2014) Todd said:

lennox g12 furnace pilot light keeps going out. sometimes it will stay lit for weeks sometimes not even a day . Ive cleaned Ive checked for fresh air. My only thought is when it calls for gas, the gas shoots out to fast and blows pilot out.



WATCH OUT what you describe sounds dangerous - unsafe. I would shut down the system and have ot repaire. Sounds like a gas regulator problem.

(Nov 5, 2014) Todd said:

I am fully aware of the hazard. And if I could simply afford to have it repaired , I dont think i would be on here trying to get help. sorry if I seem rude but not a flipping idiot.


Sorry, Todd. Please appreciate the iffiness of giving repair advice for remote systems involving life safety and where only very limited information about site conditions is known. No one thinks you're an idiot. A service tech would probably check gas pressures, the regulator, piping for blockages, etc.

The simplest repair that's worth trying first is to just replace the thermocouple that senses the flame. It's a standard part - just buy the proper length and check the mount fittings that hold the sensor element in the proper position.

Question: tracking down calls for heat

(Nov 4, 2014) Mike said:

Dan I was wondering about something. in a commercial building and all the thermostats off and the outdoor temp is 70F I keep getting a call for heat, since it's a large size boiler the cost for this running on warm days is a lot, it ends up with gas bills of about $2400 a month.

The thermostats are all updated to electronic T-stats, but if I could somehow lower the temp on which it will cut off or just not have it almost always running would be good.. OR at least find out what keeps asking for heat would be a big help!

I know at least one thing says Heat & Pump lockout and another one is a Honeywell push button with it changes to Setpoint A and Setpoint B and it shows the temps.. I forgot what it's called.

Also I can't figure out but a 3-way valve comes off the boiler and it used to be connected to a zone valve, why would they disconnect a zone valve from the 3-way? I can't figure that one out.


Mike: check the aquastat controller. It may be a unit that's wired to keep heat in the boiler on for a tankless coil that you're not using.


Question: wire color hookup information

(Dec 1, 2014) Ed McGinnis said:
need to know what color wire to hook up to which color wire



I'm sorry but I don't know what you're hooking up to what. Thermostat wire colour codes are at

Question: frost on the outside heating unit

(Dec 3, 2014) Dwayne said:
Whats wrong when my heating and air unit outside is covered with frost?



if you are talking about a heat pump and the outdoor compressor condenser unit, a heater coil may have failed or there could be a refrigerant metering issue.

Sounds like a heat pump that is either low on refrigerant or has lost its defrost cycle or base heater.

Question: loud drip heard in ceiling - a gas furnace is above

(Dec 4, 2014) David said:
We have what sounds like a loud drip in the ceiling above our closet. The gas furnace is located directly above this closet. It's been "dripping" for a few days now but there is NO discoloration of the ceiling in the closet, indicating standing water which I had expected, but am pleased about.

Any ideas what it is and if it needs to be fixed? (The house is only about 10 years old, we've lived here about 6 years, and we've never noticed the dripping sound before.) I'd appreciate any input/ideas. THANKS!



I would investigate and find and fix the drip cause before you run into a costly mold contamination issue. Start with a visual inspection of the heating equipment, condensate handling, safe venting, and then as needed test cuts from the ceiling side to look for mold or to see the extent of wetting.

Send along some photos and I can comment further. Email is at CONTACT US.

Question: Heating zones controlled by a Belimo LM24-T actuator

(Dec 31, 2014) Jim said:
I have a zoned heating system in my home. The zones are controlled by a Belimo LM24-T actuator. When one of the zones closes the actuator moves to the closed position but wants to keep on moving. As a result it makes a clicking noise over and over and over again. So I disconnected the wires from the actuator and manually opened the zone.

My question is can these actuators be adjusted. Second question are the actuators hard to replace?

Question: steam pipe leak repair

3 Jan 2015 Greg said:
I have a small leak from one of the steam pipes in my basement. What is the most cost effective way to repair.



Since steam heat in residential buildings is operating at low pressure - less than 1 psi typically, you may be able to make a temporary fix using a clamp-around pipe seal sold by plumbing suppliers.

WATCH OUT: messing with corroded steam supply or condensate return piping, even just poking at it, can disclose a bigger problem with more extensive corrosion than first met the eye. I would not touch the system unless it's at a time when repair parts and materials and expert help can be obtained quickly enough that having to shut down the heating system won't be a catastrophe.

Question: Taco zone valve operating diagnosis & repair

Aric said:
Forgive me for the long intro, I want to make sure you have proper context. I have a gas-fired boiler with 3-zone hydronic heating system. 25 yr old boiler. Taco zone valves (power heads are 1 yr old) and a Taco circulator (1 yr old).

Last year, I had a contractor come in since my system was not distributing heat very well to various areas of the house. The contractor ended up draining the system and installed: a backflow preventor, a pressure reducing valve, and a new air removal (1 1/4" Honeywell) device. My system did not have these previously. The air removal device was installed in series a few feet prior to the circulator pump. The backflow preventor and PRV were installed in series from public water supply line and which ties into the system just below the circulator and prior to the boiler entrance. I think when this contractor left, there was a LOT of air in my system.

A few weeks ago, I installed two Nest thermostats. One on the main floor (zone 2) and one upstairs (zone 3). For the upstairs thermostat, I actually had a dedicated AC tstat and a dedicated zone 3 tstat for heat and I combined those two functions into a single Nest. When I tested zone 3 on the Nest, the radiators lit up (pinged, got heat, etc.) but I only let run for 2-3 minutes and thought all was well.

Cutting to the chase, I think I have a number of problems and there is some bizarre behavior I'm trying to troubleshoot.

First, When my zone 2 tstat calls for heat, three of my zone 3 radiators get hot! I have no check valves in my system. These radiators only get a little hot though, they really don't produce much meaningful heat.

Second, when I have only zone 3 tstat call for heat, only the same 3 radiators get hot, and again, not very hot but they do heat up.

Third, my circulator pump started to make noise a few days ago.

Zone 1 will not heat AT ALL, zone 2 heats well but very slowly, zone 3 as described above.

All 3 zone valves have 24V and trigger the circulator properly both automatically and manually.



It sounds as if there is a wiring error in the thermostats or zone valves or both, or shorted wires is causing un-wanted heat in zones not calling for it; Other causes are a stuck-open check valve or zone valve on the other zones.

A zone that does not heat or heats too slowly may be air bound.

8 Jan 2015 Aric said:

Do you know how I can check to see if a zone valve is fully or partially stuck open? I pulled the power cap off of zone 3 yesterday but I don't know where the lower piston should be sitting relative to the base plate. I verified I could move it. I pulled off the functional zone 2 valve power cap as well to compare the zone 3 valve to it and they looked identical, height-wise. How much distance do those piston actually depress? It seems the manual lever would only depress them a few mm at best?

Another test I ran was to physically lock down zone 2 and zone 3. I then manually opened zone 1 (which had no heat over the last day due to the tstat being shut off and the room was 54F) and there was zero flow to that entire zone. That completely baffled me.

Thanks much for the advice/help!


If you pull the motor head and look at the position of the valve stem or see if you can turn it that may help. But you'll need to refer to an un-damaged or working valve of the same brand and model for reference.

Before trying that see if you can move the valve with its manual operation level.

To be more specific we need to know the brand and model of zone valve.

1/9/20145 Aric said:
Got it. It is a Taco zone valve and is stamped with 556 on the bottom side next to the directional flow arrow. Not sure if that is sufficient.

When you refer to "...see if you can turn it", what do you mean, specifically? The zone 2 valve I have I believe works entirely correctly.


Aric the Taco 556 has a twist-off head that will expose the valve mechanical parts and it also has a manual bypass lever. If you push the bypass lever and it's frozen then the valve is not operating.

(Jan 9, 2015) Aric said:
I flushed every zone/sub-zone of my system this morning and it behaves MUCH better. An amazing amount of air had been trapped in one of the two circuits in zone 2. There was some air in the other zone 2 circuit. Main floor and basement were good (no air). All radiators get hot now. I will double-check later whether or not the zone 2 valve still remains partially stuck open. Thanks for the help!


Good news.

If air returns in any quantity in less than a year I think there is a leak somewhere.

(Jan 11, 2015) Aric said:
Interesting. I'll keep an eye out for signs of any new air.

My zone 2 valve is definitely partially stuck open. When main floor or basement call for heat, hot water is being circulated on top floor (a bit, not full flow rate). Any suggestions or good references for getting Taco 556 zone valves unstuck?


Aric you might free a stuck zone valve temporarily by moving it manually between open and closed positions but in my experience that repair will not be reliable. The zone valve needs to be replaced.

Question: Keeprite OLR105 oil fired furnace making oil odors

(Jan 25, 2015) Al Hahn said:
Installed a new Keeprite OLR105 oil fired furnace. Have had two technicians inspect service and complete combustion tests yet we still have an oily odor now on every startup.

Looked at the heat exchange assembly drawings and only thing I can think of is that some gaskets werent properly installed at the factory? An other ideas? I hate to disassemble a new furnace.



If the techs are confident that the burner itself is working properly AND that the chinmey is in perfect condition and that draft conditions are proper, then it might be worth simply adding an oil delay valve to the system. That often solves problems such as the one you describe.

Details are at

Question: furnace turns on for 5 seconds then shuts off - cycling

(Feb 10, 2015) Anonymous said:
I have a a.c and it has a heating system the furnace turns on for 5 seconds and then shuts down and it keeps repeating the same thing



I can't know what's happening for sure with your system but it sounds like a control or motor failure. I would turn the system off to avoid further damage and then call for service. Your service tech will probably start by checking for loose or shorting thermostat wires.

Keep us posted - what you find may help others.

Question: no heat after new furnace blower installed

(Feb 23, 2015) Michellle said:
Recently I had the blower motor replaced on my furnace. Now I cant get the furnace to heat the house over 65 and it kicks on every 3-5 minutes.

One cycle it seems to blow cold air and then the next it blows medium warm air. I changed the thermostat too because I set it at 70 and it wont get any higher than 65 so I thought maybe it was that but it is still doing the same thing.

Even if I set it above 70 I don"t get that click to let me know it registered the change. Any ideas? I have a 2002 Bryant 80+ that I've not had any problems with before. Thanks for your input.


Michelle this certainly merits a call back for your heating service company.

Question: Thermo Pride OC5 oil furnace - humming sounds

(Mar 14, 2015) Max Frese said:
We have a Thermo Pride OC5 oil furnace. Today we replaced the blower motor that worn out. We made sure to label all the wires so as to reattached correctly. We also vacuumed the flue and clean out ports. We turned on the heater and both the burner and fan come on and shut off correctly. We thought it was fixed.

When we went to put the front panels on we heard a humming sound coming from the fan center relay area. It kind of sounds like the contacts are frozen closed. We tapped on the relay but that didn't change anything. Now, we're not sure if the sound was there before we replaced the motor. Any thoughts?



I hope you turned off the system rather than risk further component burnup;

A failed relay, bad control board, short during wiring, seized motor can cause the type of noise you describe.

Question: actual heating oil storage tank capacity

(Mar 30, 2015) Nancy said:
On a recent tune up bill its listed i have a 275 oil tank,listed next to this is a 256 actual cap..What does "actual cap" mean?



Most likely the service tech is saying that you have a "generic-275 gallon" oil storage tank but that its actual capacity is less than that - 256 gallons.

That makes some sens in that there are plenty of oval above-ground storage tanks that have a 250g capacity. If you take a look at your oil tank you may see a metal tag (if it's an older tank) or a sticker or decal (if it's a newer tank) somewhere on the tank's upper surface that actually states that tank capacity in gallons.


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