Photograph of  a modern oil-fired heating boilerHeating Boiler Diagnostic FAQs
Boiler diagnosis & repair questions & answers

  • BOILER REPAIR DIAGNOSTIC FAQs - CONTENTS: questions & answers on how to diagnose loss of heat for heating boilers, hydronic heat systems, baseboards, radiators. Troubleshoot heating boiler oil or gas burners & controls.
  • POST a QUESTION or READ FAQs how to fix a heating boiler that is not working - how to diagnose the loss of heat in a building

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Heating boiler repair questions & answers for no heat or loss of heat.

Frequently asked questions (FAQs) about how to diagnose & repair a heating boiler (hot water heat) that is not working.

This article series explains the diagnosis and correction of no heat conditions for water or hydronic or hot water or radiator or baseboard hot water heating systems. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.

Green links show where you are. © Copyright 2017, All Rights Reserved.

How to To Diagnose a "no heat" call: the Homeowner or Heating System Inspector Must Know the Equipment

Heaing system emergency switch (C) Daniel FriedmanQuestions & answers about troubleshooting and fixing heating boilers, posted originally at BOILERS, HEATING - home

Question: understanding heating system in Spain - health risks of no heat?

2016/02/11 Mary said:

I don't entirely understand our system as we live in Spain. Our central heat runs off of liquid oil like kerosene. We haven't had heat for several days. Several technicians have come out and it still doesn't work. The languAge barrier makes it difficult to understand and we are relying on our landlord. It sounds as though the furnace is on and running, but there is still no heater air blowing into the house. My first concern is if there is a potential health risk of fumes and secondly what are possible causes of still having no heat.


If your heat is by hot water and the boiler runs but you have no heat then a circulator or check valve is not working. If you have forced air heat then the furnace system must be shut down for safety. No heat can risk frozen pipes, cold, bronchitis.

Question: hot pipes but no heat at baseboards

2016/02/13 Felix said:
Hi my boiler has 2 zones, 1 is for my second floor apartment and the other is for the attic. The pipes past both zone valves are burning hot but the baseboards are not getting hot all. What might be wrong? Can you help?



Search InspectApedia for AIR BOUND RADIATORS as I suspect that the rads or in your case baseboards or piping to them are air bound

Question: move circulator pump to the hot side of the boiler?

(Sept 15, 2015) Dan said:
I have an American Standard G5 Gas Boiler powering my Hydronic Heating System. There are two hot water lines running out of the top of the boiler - one goes to the expansion tank and the other to the house. There is a third hot water line on the side of the device that is currently connected to the blow off valve. The pump is on the return side. I plan on updating a few components - valves, expansion tank, air scoop, etc. and I planned on switching the pump to the hot side. My question is, what are all three outlets and can I cap the expansion tank tube if I put the new expansion tank and pump in line with the line that runs to the house?


The pump will last longer on the cooler, return side of the boiler. See WHAT GOES WRONG WITH HEATING CIRCULATORS?

and also


Question: banging boiler

Oct 4, 2015) keith said:
peerless boiler (oil) after thorough cleaning is banging when it fires. major rumbling noise. totally frustrated


See BLEVE EXPLOSIONS as that's what you're heading for.

Watch out: what you describe is unsafe.


Question: boiler is leaking water in the fire box

(Oct 9, 2015) doug said:
my central boiler is leaking water in the fire box how can I patch it.


First you need to know exactly what's leaking; a badly cracked or rusted through boiler needs to be replaced. There are leak-stop products sold to buy time on a leaky boiler, not something I prefer to use.

Question: not enough hot water from tankless coil

(Oct 9, 2015) Ed said:
The domestic coil isn't producing reliable hot water. pipe coming out of coil is quite hot then goes thru temp. balancing valve and gets less warm as it continues on. We have had coil cleaned less than a year ago and to have someone come out again is costly. Any thing I can do on my own? Thanks



Question: why is our boiler making banging noises?

(Oct 19, 2015) sally said:
Making banging noises. so loud the kids cant sleep.what is going on?



Search for "BANGING RADIATOR NOISE" to read the causes and cures for this problem.


Question: how to fix an air-bound hot water heating system boiler, piping, radiators, or baseboards

(Oct 26, 2015) Anonymous said:
how to bleed air

(Dec 7, 2015) Paul Didier said:
There's noise in the pipe and we drained all the baseboards and the air valves , the thank has 22 psi or air and we still have noise in the pipe , what should I do ?

(Feb 13, 2016) Ggolden39@verizon.nen said:
Just had a new floor registers replaced in bathroom . should the system be bled of air?

(May 12, 2016) Anonymous said:
How to bleed air from a carrier boiler

Scott said:
Can I bleed 2 zones at once as the return lines from the basement and the first floor merge into one down pipe that only has a cutoff valve just before it enters into the boiler. The drain spigot is located just beyond where the 2 return lines meet and the nearest cutoff valve is the one just before it goes into the boiler some 5 feet down.

Reply: how to bleed air from a hot water heating system & how to fix an air-bound heating system or a boiler system with air noises


Paul / Anon:

Please see the articles beginning at for methods to get ALL of the air out of the system piping.

G Golden, yes bleed the air.

Anon: first check that the boiler has working air bleeder(s) installed as those should be doing the job for you. You can also bleed air from air-bound radiators or baseboards using individual bleeder valves. Search for AIR BOUND HEATING SYSTEM to read details.

Scott: whether you can bleed air out of one or two zones at once depends on where the air is located. Usually we need multiple air bleed points to successfully purge all of the air in an airbound heating sytsem.

Question: boiler rough start, intermittent start-stop

(Nov 1, 2015) nick said:
why does my burnham v 85 hot water boiler start to fire up then stops or fires up and stops very quickly

(Dec 29, 2015) Glenn said:
The flame burns well for a few seconds and stops, no hot water goes through the pipes and no heat.
I already vacuumed off dust from thermostats.
When it worked both thermostats had to be on high to get heat.


Tere can be several causes of funny start-up, Nick, including a loose electrical wire or thermostat wire, a bad contact between the aquastat sensor and the side of the well into which it's inserted, or a bad primary control; I've also on occasion found improper control settings or a low limit control on an aquastat that could be benefit from being disabled when no tankless coil is installed.

See BOILER OPERATING PROBLEMS - chances are the burner needs cleanign, service, repair, a new nozzle, air bleeding etc. - without more details we won't know exactly what's wrong; even a loose wire can cause the trouble you cite.


Is this gas or oil? If gas I suspect maybe a bad thermocouple;

Watch out: If oil heat is used, don't keep pushing the re-start or you may get an puffback explosion.


(Dec 29, 2015) Anonymous said:
This is a gas flame.

Mod said:

(Dec 29, 2015) (mod) said:
Try cleaning, adjusting the location of the sensor tip (in the flame) or just replace the thermocouple.

WATCH OUT a mistake can cause burns or a fatal gas explosion.

Question: fish smell in my classroom

(Nov 4, 2015) Jenn said:
I work in an old school building and we use a boiler system for heat. We recently turned the heat on and now there is a lingering fish smell in my classroom. Should I be worried? What is causing this smell?


Gee I dunno. Assuming there's no actual leak of boiler water in your building, there may be contaminants on the radiators.


Question: high pitched ringing boiler

(Nov 7, 2015) Henri Desbiens said:
How do you stop the high pitch ringing?


Check for a bad motor bearing; also see BOILER NOISE SMOKE

First we need to find its source, Henri. Then we can understand what's happening and what repair is needed.

Question: 2006 burnham hot water boiler model 206NCL TE 12 basement too hot, steam coming out of boiler

(Nov 15, 2015) Dennis said:
I have a 2006 burnham hot water boiler model 206NCL TE 12 . The problem I have is that it makes the basement like a sauna, I don't see any signs of a leak but you feel the steam coming out just under the electric damper. It fogs up the basement Windows in no time. I don't hear any thing that sounds like water hitting the flame. Could this be that the boiler has a slight crack in it or is there an adjustment to make?



If steam is coming out of your hot water boiler then there is definitely a leak that needs to be found and fixed - ask your service tech for help; it may be necessary to remove all of the external jackets to see the leak, but she'll probably also take a quick look first in the combustion chamber. If you're lucky it's repairable.

Watch out: this situation is unsafe.

Question: boiler blows steam

(Nov 18, 2015) Jimmy said:
When my boiler has been running for while (~30 minutes) to heat up on a cold morning it suddenly will blow steam and dirty water out of the bottom spigot. It seems like too much pressure is building up when it is asked to work for a long time? My boiler has 3 release valves. Can these be blocked and cause the pressure to build up? Other thought? Thanks



Watch out: "the bottom spigot" ? if you mean the boiler drain this sounds horrible - as if the boiler has run out of water and is about to be destroyed or blow up. Shut if off if you see this, and call for repair.

If there is some obscure leak high on the boiler that runs down inside of a jacket and comes out around the boiler drain that may be a different issue.

A TP valve can certainly become blocked, especially if it has been dripping or leaking over time.

That case would be extremely dangerous, risking a BLEVE explosion - search for BLEVE EXPLOSION to read details.

(Nov 29, 2015) Carol said:
I have had this problem for years and the plumber supposedly repaired it twice

Moderator: What repair was performed?

(Dec 7, 2015) Anonymous said:
any repairs have been done, only maintenance checked has been done

Question: Blower will not come on

(Dec 16, 2015) mary said:
Blower will not come on

(Jan 3, 2016) Anonymous said:
how do I fix problems with the blower air in the boilers? Boiler serial number is 0802279013 and the name is Raypak. thank you


(Dec 16, 2015) (mod) said:
Mary as you use the word "blower" I am guessing you are referring to forced hot air heat and a furnace blower that won't start. If so see BLOWER FAN OPERATION & TESTING at

If you mean an oil burner won't run search for OIL BURNER DIAGNOSIS for help.

Anon if you are asking about air in the boiler and piping, just search for AIRBOUND HEATING SYSTEM to see diagnosis and repair suggestions.

Question: How do I turn down my hot water.

(Jan 6, 2016) carl said:
How do I turn down my hot water.



Depending on the kind of water heater, electric, gas, oil, the controls may be in different locations.

Search InspectApedia for SET HOT WATER TEMPERATURE to see details in a series of articles that describe anti scald devices and other hot water controls.

For electric water heaters see where you will find photos and text beginning at "Electric Water Heater Internal Reset Switch & Temperature Setting Dial on the Thermostat"

Question: Non-Condensing Weil McLain GV4 series 2 natural gas boiler is condensing all the time

(Jan 15, 2016) Alan said:
Non-Condensing Weil McLain GV4 series 2 is condensing all the time. Mo matter what the return water temperature is. Sometimes you can see water vapor come from the condensate drain along with the dripping water. Can you please shed a little information as to what's causing this?


Improper combustion air adjustment or inadequate combustion air can cause condensation as can a boiler leak.

Watch out: inadequate combustion air supply produces not just water but fatal carbon monoxide - see COMBUSTION AIR REQUIREMENTS

Question: xtrol tank/valve - the valve is leaking an oil like substance

(Jan 16, 2016) Ron said:
Have a hot water heat system -question is on the Extrol tank/valve - the valve is leaking an oil like peoduct. In fact a lot of oil. What should I do?


Replace the valve or entire assembly; it doesn't contain oil, this is probably dirty heating water.

Question: capped off some radiant heat lines, now what?

(Jan 19, 2016) Anonymous said:
Recently remodeled my upstairs bathroom and my radiant heat line had to be eliminated. I capped the lines. Would that affect the other rooms? When I did my diagnostics, my feed lines are temped at 120 and the return was 60-70 f. Which I'm assuming that I ruined the flow of the system. If I looped the system back together would it regulate the other rooms or would it not make a difference? Please help new baby will be here in a week.


If the lines you capped were in series with other heating system piping then you've stopped hot water flow and won't have heat. As I can't guess from so little detail, you need to ask for an on-site inspection by a trained radiant heat service tech.

Question: LP gas water heater turning off the boiler

(Jan 20, 2016) kris said:
my instant gas(bottle) hot water heater is turning off the burner after some time while running a shower or just a hot tap. I haven't been able to find anything specific to this in the archives. anyone able to suggest a diagnosis? thanks...


Your service tech will probably check for a failing thermocouple device at the burner

Question: water on top of burner after heavy rain fall.

(Jan 26, 2016) John said:
Notice water on top of burner after heavy rain fall.

Water looks like it comes down the flue pipe notice splash around area


Ask your chimney sweep to inspect and repair the flue, chimney top, or rain cap; check also for surface water leaks into the chimney base if that's above the flue vent connector.

Watch out: what you describe is unsafe.

Question: overflow pipe dripping

(Jan 28, 2016) Denny zufall said:
I have a hot water oil furnace with baseboard heat. There is a overflow pipe across the top and halfway down the back that is dripping about 1 soup can of water a day. Is this a concern. Thank you!


Watch out: what you describe is unsafe.


Question: how to adjust upstairs vs downstairs temperature

(Feb 1, 2016) Anonymous said:
I have hot water heating .I would like to know how to keep my upstairs cooler than my down stairs'


Anon if all of your home is on a single zone your heating company may be able to put your second floor on a separate heating zone with separate thermostat.

Also, cutting air movement up the stairwell can help, though hanging a blanket across the stairs is dangerous and thus not recommended;


(Feb 8, 2016) dave said:
Question .... church boiler... ALL thermostats are at or below 65. i have ten (10)zones
it's 75 degrees in church now . it's monday 02/08/16 and about 45 degrees outside does this come into play?


Check for a zone valve stuck or latched onpen or for thermostat wires shorted together calling for heat

Question: Can a R8182 D1189 be replaced with a newer aquastast?

(Feb 15, 2016) said:
Can a R8182D1189 be feplaced with a moremordern aquastat


Yes. ,E.g. see AQUASTAT L7224U UNIVERSAL for an example of a universal replacement aquastat.

Question: what are the boiler temperature settings?

(Feb 15, 2016) Mike said:
What should the temperature be at the boiler mine only reaches 100 then shuts off house is cold


Mike, normal home heating boiler temperatures run usually between 180 and 200 F at the HIGH limit.


Question: thermostat calls for heat but no heat is coming out of one of my zones

23 Feb 2016 Paul said

Paraphrasing: thermostat calls for heat but no heat is coming out of one of my zones



Go to the zone valve and watch it while a helper turns the thermostat to well above room temp. If the zone valve does not open try jumping the two thermostat connections right at the zone valve. That will rule out a bad thermostat or thermostat wire. IF the valve still doesn't open you may be able to open it manually - if your valve includes a lever to do that - so that you can have heat while waiting for a zone valve motor replacement. If the actual valve body that lets the heating water flow is corroded stuck shut you'll have to replace the whole valve.

Question: burnham furnace with 1 circulator pump on feed side and have 4 zones - return pumps don't stop running

(Mar 16, 2016) Bob callanan said:
I have a burnham furnace with 1 circulator pump on feed side and have 4 zones each with circulater pump on return. When a zone called for heat return pumps would go on but within 3 min furnace would reach high temp kickout but return pumps would run endlessly with pipes on either side getting warm at best. Hot wired feed pump and everything is fine. So would it be the Honeywell l8148e relay or the burnham mixing vs3000 controller that has gone bad


Good question. Assuming no airbound piping it'd probably be one of the two problems you suggest, or perhaps a stuck flow control check valve. Or a zone valve may have lost power or have a seized motor.

OR the system is air bound. See AIR-BOUND HEATING SYSTEMS - home

First check to see if the feed pump runs on a call for heat, ... without hot wiring it.


(Mar 16, 2016) Anonymous said:
Ty for the reply but due to living with a wife and three kids, time (showers)was a key factor. So I grabbed my trusty multi meter and found c1/c2 were not getting power so went with relay being the problem. Got new 1 installed and every thing is good all in 4 hrs . Not bad for a Piledriver by trade. Again try for reply

(Mar 16, 2016) Bob callanan said:
As hot as the return circulators got those will probably be next on the list lol

Moderator reply:

Excellent going, Bob. You actually did what many repair techs will do to speed troubleshooting and lower the cost to the client: try replacing the most-suspect part, especially if it's not a costly one. Thanks for the follow-up as that will surely help other readers.

Sometimes we can get a clue that the problem is the relay by

1. visual inspection for burns and arcing

2. hearing buzzing at the relay, or chatter

3. observing that the relay does not pull in when it should

4. DANGEROUS: pressing on the relay to see if by manually closing it the system runs (also risking death by electrocution if you don't know what you're doing)

Question: radiant heat troubles following a puffback explosion

2016/05/24 Diann said:
Hi we own a home with a hot water/ radiant heat system. It has fin tube heat registers and 7 zones. We only use 5 zones the other two are for future expansion of the home. We rented this house out and just received it back from our tenant. Unfortunately we have what looks like smoke damage. It has been suggested that it's puff back from the boiler. We have had plumbers to inspect the boiler. We have been told we should just replace it at thousands of dollars. They are unaware of pass back as a real issue. They said it's impossible. I have found a number of articles that say it's rare but real. I am getting put off by them even after providing copies of articles. Am I wasting my time? Is it real? Thank you


Diann, see RADIANT HEAT - home, for a series of diagnostic and repair articles.

A puffback explosion can be caused by simple lack of maintenance, but if the explosion damaged the boiler it needs to be replaced. Ask the heating company to show you the actual trouble spots.

Be sure you have someone who actually is trained on heating boilers and understands the causes of puffbacks. If your plumbers aren't expert on this problem they may not be the best people to be working on your heating system.

Watch out: the system could be unsafe.


Question: what do you call the heating system that pumps hot water to "radiators" inside of a forced air system?

2016/05/29 Pat said:

The house I just put an offer on has a boiler, however, it does not have traditional radiators. It pumps hot water to radiators inside the forced air system. I have never seen a system like this. What isint called and is it efficient? Also, I am planning on doing a renovation to the home and was wondering should I replace the system with a traditional forced air system?

Reply: fan coil unit, hydronic coil, fan convector heater properties, efficiency, references

Thanks for the question, Pat. You are describing a water-to-air heating system. Synonyms include "hydronic coil" and "fan convector" or "fan coil unit" heating system. Hot water heated by a heating boiler (a hydronic heating system) is circulated through a finned coil placed in an air handler or in some cases right in an air duct. Air is blow through the duct (or through the air handler) across the heated coil, thus heating the air as it passes by.

Your system may be a "blow through" (fan pushes air through the heating coil) or a more thermally-efficient "draw through" (fan sucks air thorugh the duct system and through the heating coil).

This approach to heating is often used when a designer wants to use the same duct system for distributing heated air or cooled air; In some designs the use of a a boiler-heated fan coil to warm air can be quite efficient. These systems are also often used as backup heat in a heat pump system.

Take a look at

Question: hot spots on boiler, burning smell

(Aug 27, 2016) carole said:
My boiler is getting really hot on certain parts. There is a burning smell when is it lit that smells like burning vegetables and really smells up the house. I turned off the electricity and so the burners are off. Because of this I have no hot water. I'm concerned that if I turn the boiler back on that something will burn out or some part will be damaged. Help. Thanks Crole



Watch out: I would SHUT OFF the heating boiler right away. My concern is that damage in the combustion chamber, lost boiler insulation, or a burner malfunction may have made the heater unsafe.

Leave it off and ask your heating company to inspect and repair the system.

At BOILER OPERATING PROBLEMS at you can see a photo of a boiler with burn marks on its side jacket. We left this unit OFF pending repair.

IF there are heat marks or burn marks on the boiler exterior surfaces those are certain marks of a malfunction and an unsafe heater. If you want to send us photos for comment use the page top or bottom CONTACT link.

Question: Westinghouse LP Combi unit hot water problems

(Oct 1, 2016) Barb said:
We just installed a Westinghouse LP Combi unit. It's been working just fine for the past several days. However, this morning we tried to draw DHW and it was not hot. We went to look at the unit and it said ER16. We have tried all the troubleshooting listed and more but cannot get it to work properly. Any help would be appreciated. Thank you.
Operating Temperature
Sensor detects Water
Temperature Greater than
F (95
Press the Power button to clear the Error Code.
If Error happens again:
1. Check if dip switch High Fire setting is ON. Switches 6 and 7 should be OFF for normal operation.
2. Check if CH inlet pipe is blocked. Ensure there is enough water flowing to the appliance.
3. Check Operating Temperature sensor at CH heat exchanger outlet. If resistance is zero, replace the
4. If the problem persists, replace the main control.


Barb, before attempting to replace the control - as the instructions suggest - I'd ask for help from a trained service tech. She might see something that you didn't, and she might also review the safety of the system.

Question: hardy heater float?

(Nov 11, 2016) Linda Chaney. said:
How do you get the float to work on hardy heater?


Sorry don't understand the question


(Nov 16, 2016) John said:
Late 1960-1970 Crane Sunnyday 102A Gas Boiler; cannot get the gas valve & circ. pump 2 run at same time- can make gas valve or pump work seperately


John, this sounds like a wiring error.

Question: Boiler comes on but no heat in house

(Mar 3, 2016) tom said:
Boiler comes on but no heat in house, one zone system, pipes are hot at boiler but cool on other side of zone valve (zone valve is not wired)
- See more at:


If you mean that you have a zone valve but it is not connected by wire to a Thermostat then you need to lock the valve into an open position.

Next check that the circulator pump is running. If the circulator is running in the zone valve is open and no other valves are closed and I suspect your system is airbound.

Search inspectapedia for "AIRBOUND HEATING SYSTEMS" to read repair procedures

Question: Have to tap the cad cell relay box to get the burner to kick on

(Mar 15, 2016) Sheehan said:
Every morning I have to go downstairs and tap the Cad Cell Relay Control box to get the burner to kick on. Same thing when I get home from work- not much of a tap either.

The thermostat is the Honeywell RTH2300 / RTH221 series and its set to be 63 at night and when I'm not home, and 70 from 5pm-11pm. I've been waking up to 55 degrees.

We just had the control box replaced last week and nothing has changed.

What could be the issue?


Tapping to get any electrical component working sounds to me as if there is a loose wire or failing connection or relay inside the control. If replacing the control box did not address the problem then the failure is probably not inside the control box itself but perhaps in a connection to it or a connection nearby - even the plug-in socket of the cad cell sensor itself.

You might call your oil company service manager and ask for help from an experienced, senior service technician. Keep us posted. What you find will help others.

Here is a copy of the Honeywell RTH2300/RTH221 Series Programmable Thermostat Owners Manual [PDF]

Question: rebuild a Hoyt water heater control?

(Sept 7, 2016) Bob DeGroot said:
Hoyt water heater, serial number 93355, 75 gallon copper storage tank, has quit working. the thermocupler (sic?) was not the issue according to our plumber. The control mechanism itself may need to be repaired or rebuilt in order to fix the problem. Can I find this original piece, or can it be rebuilt?


Bob we discuss Hoyt water heaters a bit at

Your question is posted on a home heating boiler article - perhaps because Google's search found "hot water heating boiler" or somesuch.

I'm not sure just what "control mechanism" we're looking for here. Hoyt water heaters went out of production in about 1989 or 1990. Many water heater parts are, however, generic an can be replaced by a generic control. Hoyt - at least the Hoyt water heater brand, was purchased by American Water Heaters.

So you might also find a suitable part from that company. Contact information for American water heaters is at

Question: no heat on first floor

(Oct 25, 2016) MB said:
I have baseboard water heat with a boiler. The upstairs is working (2nd floor) but the main floor is not. the pipes get warm but wont produce heat. What could the problem be?

(Nov 22, 2016) Marc said:
Three pipes coming of boiler. Two are hot to the above the valves, one isn't. The one going to the first floor. They are cold on the first floor.
- See more at:


So a pipe that's not hot when others are suggests that whatever zone that is, it's either not calling for heat, or its circulator isn't running, or the zone may be air bound.

Search for AIRBOUND HEATING SYSTEMS as that's where I'd start

Check for a zone valve not opening

Check for broken or loose thermostat wires

Question: my gas boiler giving got water but no heat

(Nov 5, 2016) carmen said:
my gas boiler giving got water but no heat


Check for a bad thermostat wire, connection, or zone valve, or for airbound heating pipes. Search InspectApedia for AIR-BOUND HEATING SYSTEMS - home

Question: gas boiler goes off intermittently

(Nov 14, 2016) Joel said:
Have a Weil-McClain HE II boiler that wants to work intermittenly. Heating Tech has cleaned, replaced gas valve and control module. Still won't run as programmed. Sometimes will run all day, then shuts down overnight. Any suggestions as to what could cause this condition. Thanks.


Look for a loose or corroded wire or connection. Check for flue gas spillage.

Question: radiator doesn't get hot

(Nov 17, 2016) Jeeva said:

The heater is pumping hot water to radiator when we set the thermostat to max(30degree) if we keep it at 25 nothing happens, the room is getting very cold. Could you tell me what could be the issue?

gary spinda said:

1st floor radiators are not as hot as 2nd. floor radiatore



Question: low boiler pressure

(Nov 25, 2016) Anonymous said:
Can't get pressure up to where it calls for


Check the boiler temperature when the heating system is cold. The minimum normal residential hot water heating system boiler temperature is typically about 12 PSI. if your boiler is below that starting pressure when cold there may be a problem with your water feed / pressure reducing valve.

Question: where to get aquastat replacement parts

(Dec 9, 2016) randy said:

can I get parts for a aquastat l8148e



Check with your local plumbing and heater supplier. A few sell parts such as a replaceable relay. Usually a service technician installs a whole new control. Beware that modifying a control could make it unsafe.

Try a universal control replacement. See AQUASTAT L7224U UNIVERSAL

Question: gas boiler hot water baseboard - boiler can't keep up with thermostat setting

(Dec 11, 2016) Wmig said:

I have a NG hot water baseboard heating system in a split level 1350sqft house. My problem is the boiler is not keeping up the temperature set on the thermostats. The Thermostat on the second floor will be set at 71 and the temp dropped to 66 before the boiler fired. The first floor thermostat was set at 73 and the temp. dropped to 72 there.

This occurred at the same time. The thermostats were calling for the boiler to fire the entire time because the zone valves were open the entire time. I changed the electronic gas valve per the recommendation of the heating company that I had come troubleshoot my system last winter.

The water pump circulator runs the entire time while the thermostats are calling for heat as well. It seems to me that the circuit that tells the boiler to light or ignite isn't transmitting correctly. Thanks to anyone in advance for their expertise.


If the boiler temperature is dropping below the burner cut-on temp AND there is a call for heat AND the boiler doesn't turn on then the AQUASTAT CONTROLS control or its temperature sensor needs repair or replacement.


Question: clicking when I turn up the thermostat - boiler won't run

(Dec 20, 2016) Jamie said:
I have a New Yorker boiler it fires up fine to heat the water but when I turn up the thermostat to heat the house it just clicks. I replaced the thermostat turned it up and it turned the heater on but only ran for a couple minutes then turned off. Have plenty of oil and is serviced yearly any suggestions



Question: Old Arco Gas Boiler, no heat for seven days

(Dec 25, 2016) Peter Chechopoulos said:

I have had no heat for seven days. I have an old Arco gas burning Boiler No. 11, American Radiator Company, W 0811G 1 BJ with a Bell & Gossett booster water pump. I called the company and went to their distributor with the old pump which I had removed and bought and installed their new recommended pump according to their instructions.

I also had an old White Rogers Thermostat, and bought and replaced it with an new Honeywell Thermostat, as per the company's telephone tech instructions. When I first replaced the new booster water pump and restarted the system, the Arco Gas Burning fired up, but only ran for five to ten minutes and then shut down again. I next opened the water fill valves on all my homes radiators and bleed the air from each one, until water came out. Next, I turned up the new thermostat to 90 degrees and waited for something to happen. Nothing happened. The boiled did not fire-up and the radiators remained cold.

I can not afford to have a professional come in to trouble shot and repair this heating system. CAN ANY KIND SOUL, ON THIS CHRISTMAS DAY ADVISE AND OLD MAN WHAT TO DO NEXT TO GET HEAT BACK INTO MY HOME. THANKING YOU IN ADVANCE.



I'm as confused as you. It's understandable, and sometimes it works to just try swapping some parts, but sometimes we discover, as you seem to have found, that the parts being replaced are not finding nor fixing the trouble. I suspect the problem is in the burner itself - needing cleaning and perhaps a new nozzle, fuel screen, fuel filter. - See more at:

Question: yellow burner flame

the flame in my boiler is yellow is this correct


A gas boiler yellow flame is UNSAFE.


An oil burner yellow flame with no smoke is normal.


Question: Bryant boiler no heat

(Feb 21, 2016) Paul said:
We have a Bryant boiler, it has worked for years, for the last 2 days it is heating up but not circulating through the pipes for heat,

I'm thinking that the pump isnt working and it looks like the tap above it has a slight drip and is all green, thinking that it might have blown the motor, need help... need HEAT!

This is Paul again with the Bryany boiler, my email is


Check the circulator; if it is running either it has a damaged impeller or I suspect that your heating system piping is air bound. Search for AIRBOUND HEATING SYSTEM for details

If your system uses a typical flow-control check valve at the boiler, a device that prevents hot water from circulating by convection when the circulator is not running, and if the problem is found to be the circulator, you can get heat temporarily, though it will rise more slowly, by placing the FLO-CONTROL valve in the OPEN position.

Search InspectApedia for CHECK VALVES, HEATING SYSTEM or see for details.

Question: does my Burnham residential boiler require annual service?

Does my Burnham residential boiler need annual service. It worked fine last season. - Dick 9/19/11

Reply: yes

Yes, Dick, there is no Santa Claus; your heating boiler needs annual service not only to assure safe, reliable operation, but because without an annual cleaning, particularly for oil fired heating boilers, my experience is that the cost of operating the equipment will be significantly greater - the improvement in operating efficiency of an oil fired heating boiler following annual cleaning and adjustment can be significant - I've seen a 33% reduction in operating cost following cleaning and adjusting a dirty oil fired boiler or furnace.

Question: Boiler trips circuit breaker - intermittent failure of boiler to turn on

I have a 3 year old Peerless WV-DV boiler, 1 zone (thermostat), 2 circulator pumps, no valves, serviced annually. This year when turning thermostat up the boiler refused to come on. The 20 amp circuit breaker had tripped. It wouldn't reset, kept tripping immediately. I turned the power switch off at the boiler, reset the breaker, turned the power back on at boiler, turned thermostat up and boiler came on normally.

I then, over the course of an hour, turned thermostat up and down, each time boiler shut off and came back on normally. Then is got warm here for a few days, didn't use. When it got cold again, same problem, I had to turn off power at boiler, reset breaker, turn power back on at boiler, then boiler works. I also replaced the breaker in case that was a problem. So what is the issue here? Any help would be appreciated. - Scott Moberg 10/14/11



It sounds as if there is either a wiring short circuit or an electric motor (perhaps on the burner) that was seized. A seized motor can draw high amps and trip the breaker. You can sometimes get the motor running again by repeated attempts or by adding an electric motor hard start capacitor, but on an oil burner I'd expect it's time to replace the motor.

Question: hot water re circulating loop is not maintaining temperature

having a problem with a hot water recirculating loop from boiler to storage tank with tempering valve to building. not able to maintain proper temp. any ideas? - Vivek 10.26/11



If the hot water recirculating loop (I am guessing you mean domestic hot water for washing and bathing, not a building heating system) is not maintaining the required temperature I'd check in this order:

- is this a change in behavior or has it always been this way. If it's a new condition I'd look for a change in hot water use or a failure of a tempering valve (or someone messed with the valve) or a change in the water heater temperature settings

- if the problem has always been there, to the above I'd add a check for missing insulation on the water piping

Question: how do I figure out the age of my heating boiler or furnace?

Would like to know the age of a National U.S. Radiator boiler, Boiler # 109-5. It is a five section boiler, with Crane forged into the sections. Only can see the two end section numbers, F10900201 and F10900301. Just curious, thanks for any help. - Gary Forbes 11/5/11


Gary, see AGE of HEATERS, BOILERS, FURNACES (article links listed at the "More Reading" links at the bottom of this article ) for tables, charts, and links to books that give means to decode the age of heating and cooling equipment using the model and serial number.

Question: no heat on upper floor, no air bleeder valves

its just the upper floor and i don't have bleeder valves at the base board the expansion tank at the boiler is hard to tell how full it is - Luke 11/10/11


Luke, at AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE we describe a variety of ways to get air out of an air-bound hot water heating system.

Question: books on troubleshooting residential heating boilers

are there any books on troubleshooting residential boilers & how to wire them - Kevin 1/12/12


Kevin, at References, related articles we list a variety of books on heating system installation & troubleshooting; when I was servicing heating systems, in addition to attending trade school for absolutely-required practical knowledge and theory, I found too that quite a few manufacturers gave away free booklets and pamphlets with excellent detail about their equipment. And don't forget to check the installation and service manual for the specific equipment you are examining.

Question: How to diagnose gurgling sound coming from boiler and radiant heat tubing

I have radiated heat at night tub gurgles and boiler makes noise - Jeff 10/8/12


Jeff, gurgling in hot water heating lines is often due to air in the piping. Check for a leak and for an air purging device that is not working.


(Oct 5, 2014) Elizabeth said:

Smoke stains are being left on the bottom of the unit where yu open to light the pilot - I assume that means it needs cleaning inside. Is this something a homeowner can do themselves?



WATCH OUT: if your boiler is gas fired you are describing an unsafe condition that could produce fatal carbon monoxide gas. If that's the fuel you're using I'd shut off the system and ask for inspection and repair by a licensed plumbing and heating contrator.

This is not a homeowner repair job.


(Oct 11, 2014) Regine said:

Moved in a renovated/insulated/new thermal windows home in April Southern Maine. Home has boiler with tankless water heating system+cast iron radiators. Boiler runs well, no problem. Upon maintenance "tankless coil plate was found to be in poor shape, but does not leak" and we noted having use "lots of oil" during summer.

Want to wait until next March to change the boiler. In the meantime we would like to install a separate electric water system and remove the water heating function off the boiler by sealing/welding permanently the tankless coil: is this feasible? would any heating system contractors do this? We have read that it is possible to weld a coil patch plate over rust to save a good boiler, then switch to either indirect tank or standalone unit.

30 Oct 2014 Kory said:

I have Allied Boiler Super Hot SG180, just a month old. Strangely enough it suddenly stopped working, giving Error Code 59; AC voltage out of specification high or low. Boiler gets call for heat, ignites pilot, ignites main burner and then turns off, and proceeds to repeat sequence. How do I solve this mystery?

I have Allied Boiler Super Hot SG180, just a month old. Strangely enough it suddenly stopped working, giving Error Code 59; AC voltage out of specification high or low. Boiler gets call for heat, ignites pilot, ignites main burner and then turns off, and proceeds to repeat sequence. Checking main wiring going into boiler. It reads 80v AC when connected to boiler, yet when disconnected it reads 120v AC. Not sure why power would drop like that? It is 100yr old house renovated in the 1970's but I am unaware of aluminium wiring (as far as I can see anyway). The ground appears to be ok. How do I solve this mystery?


Kory, that sounds like either a true voltage problem - check the actual voltage level and see if you can find out if there are significant voltage variations in your area - OR a control board problem. As the system is brand new I'd expect it to be under warranty and that a service call would be appropriate.

On voltage variations, that's not a feature of old houses but might be a feature of the house wiring, electrical service incoming voltage, or problems in wiring or in an overloaded circuit supplying the boiler.

Do let me know what you find - what you learn will assist others.

Question: New Allied Super Hot SG180 boiler stopped working - Error Code 59

(Oct 29, 2014) Kory said:

I have Allied Boiler Super Hot SG180, just a month old. Strangely enough it suddenly stopped working, giving Error Code 59; AC voltage out of specification high or low. Boiler gets call for heat, ignites pilot, ignites main burner and then turns off, and proceeds to repeat sequence. Checking main wiring going into boiler.

It reads 80v AC when connected to boiler, yet when disconnected it reads 120v AC. Not sure why power would drop like that? It is 100yr old house renovated in the 1970's but I am unaware of aluminium wiring (as far as I can see anyway). The ground appears to be ok. How do I solve this mystery?


Kory, that sounds like either a true voltage problem - check the actual voltage level and see if you can find out if there are significant voltage variations in your area - OR a control board problem. As the system is brand new I'd expect it to be under warranty and that a service call would be appropriate.

On voltage variations, that's not a feature of old houses but might be a feature of the house wiring, electrical service incoming voltage, or problems in wiring or in an overloaded circuit supplying the boiler.

Do let me know what you find - what you learn will assist others.


(Nov 10, 2014) Super X said:
I have a burnham boiler , installed in 1996. A few yrs ago, I had no heat. A tech came out and opened something to get heat, since then, when its warm out I get overheated, and underheated. when warmer outside Stat set at 65 and temp at 80. when cold outside stat set at 70 and no more than 60 temp. so I got tired of paying for service calls and, have been manually adjusting water temp to compensate for outside temp.

CORRECTION ..... Underheated when cold out, overheated when warmer

Question: someone stole my heating pipes

(Nov 20, 2014) merkraw said:
My pipes were stolen from my heater. My question is can i replace pipes to my boiler with pex or pvc?



Yes - just check the temperature rating before buying any plastic piping .

Question: gurgling in hot water heating piping

(Jan 1, 2015) Anonymous said:
I can hear the water in my pipes trickling around the room. I never heard this before and was wondering is this a sign of something going bad. I have a hot water heating system that is about 18 yrs old. I changed the pump 2 yrs ago and its been working fine.I have heat just worried about hearing the water flowing in the pipes


Chances are that means there is air in your heating system.


Question: loud bang from hot water heating system

(Jan 3, 2015) bob e said:
I have a closed system hot water heat. Had a circulation pump installed and i started to get a loud bang in my system every so often. Tech couldn't figure it out. My boiler was 18 yrs. old and i had it replaced, but I still have that problem. sometimes it makes a slight whistling noise before the band. other times not. The system has been bled.

25 January 2015 Anonymous said:

My hot water boiler is banging at 12 pound and above.



First confirm that the noise is in the water circulating system not the burner itself - the latter can be quite dangerous and may presage a puffback if it's oil or a gas explosion if it's gas fuel and there's a leak or a defective gas control valve.

water hammer can also be the trouble you are experiencing - see

Some modern circulators or zone valves can shut off water rather abruptly.

Anon and Bob:

Anon please see our guide on dealing with banging pipe noises at

where several types of banging heating pipe noises and causes and cures are discussed.

Watch out: Also see PUFFBACKS, OIL BURNER

Question: how to turn the water off but keep the heating boiler on

28 Jan 2015 Scott said:

I have a forced hot water system. if i shut the water off at the main can the system still run if I close the shutoff where it feeds into the system.


Scott, you can shut off all water and the boiler will run - presuming this is NOT a steam boiler - that is, it will run just fine AS LONG AS there are NO LEAKS in the entire system.

A hot water boiler that has a small leak could be ultimately damaged if the burner fires while boiler water is low or lost completely - risking even an explosion and severe damage or injury. Some boilers include a low-water cutoff safety control to protect against this hazard.

If your boiler is a steam boiler it needs a regular water supply.

If your boiler is a hot water (hydronic) heating system and has a low water cutoff then you can run it with water turned off, risking loss of heat but at least protected from a boiler explosion (as long as the LWCO works).

Otherwise you can more safely keep heat on while turning other water in the building off by making sure that you do not turn off the boiler's water supply.


Question: frozen heating boiler first steps

(Feb 20, 2015) James Saunders said:
I think my boiler is frozen up, what can I do, because it shut down everything so I don't have any heat.


James, if the boiler is literally frozen you'll need another heat source to thaw it out, followed by fixing leaks or if it burst, unfortunately it'll probably need replacement. This is a job for your heating service company.



(Mar 14, 2015) Mike said:
How can I have great hot water in the bathroom sink but only lukewarm or cold water in the shower which is next to the sink?



Is there an anti scald device on the shower?

Check for a blockage in the hot water piping and stop valve at the shower

Question: combustion chamber damage - repair urgency

(Mar 28, 2015) thomas tate said:
i looked on the inside of the furnac and there is a piece of the fire wall laying on the inside is there any danger and can it wait until Monday to call someone



Watch out: Sorry but yes what you described is unsafe - the risk is that the burner burns through the boiler wall and starts a fire in your home.

Leave the system OFF

Question: one of 3 heating zones not working

(Mar 28, 2015) Dean said:
Have 3 zones on my boiler. The first one is not working. Have hot water and heat to the other 2.



Question: sealant on boiler section push nipples

(Mar 28, 2015) Anonymous said:
whe installing nipples back in water jacket do you need to use some kind of sealent on them



It depends on the boiler brand, model, design. Some push nipples use gaskets. Tell us your boiler brand and model and we can help find the assembly instructions if you don't have them.

Question: boiler gas pressure readings

22 May 2015 Kevin said:
Have a combi boiler, domestic works great, but when heating, the boiler shows the main pump is on, the demand for hest is on, but gas input valve is at 0. Im thinking the controller is faulty, but need some reassurance



Before replacing the gas regulator at the appliance I'd check: thermostat connections, thermocouple (if one is used), spill sensors, flue operation, or other safety controls to be sure that the valve is not being shut down for safety reasons.


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