Heating system installation, repair, maintenance questions & answers set #7

Q&A on how to troubleshoot & repair heating systems in buildings.

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.

Heating System Q&A Set #7

These questions & answers about troubleshooting heating systems in buildings were posted originally at HEATING SYSTEMS - home - that's a great place to start finding diagnostics for your heating system type and its problems. aces, and other equipment.

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• What kind of heat have I got? If you don't know whether your heat is provided by a furnace (hot air) or boiler (hot water), or whether your fuel is oil, gas, or electric, and whether your heat is hot water, steam, or warm air,
  
  see HEATING SYSTEM TYPES.
• How to fix the heating system: If your heating system is not working properly choose one of the following diagnostic procedures:
• see DIAGNOSTIC GUIDE A/C or HEAT PUMP
• or DIAGNOSE & FIX HEATING PROBLEMS-BOILER
• or DIAGNOSE & FIX HEATING PROBLEMS-FURNACE

On 2019-11-07 by (mod) - Duomatic-Olsen Ultramax gas furnace

JW

Handling the breakaway jumper or pull-out tab on a new fan limit control switch:

I don't know which brand and model limit switch you've got but removing a tab may be for use with low voltage - that breakaway or pullout is explained in the article I'll cite below.

Hop over to FAN LIMIT SWITCH INSTALLATION & WIRING where you'll find installation instructions and manuals for fan limit controls.

On 2019-11-05 by JW

Thanks -- The wiring seems to check out OK. Went ahead and replaced the Honeywell L4064B limit switch with a new one. This switch has a break-away jumper in it. How do I determine if I need the jumper or not (already discarded the old switch) ? I have three wires running to the limit switch. Thanks again .....

On 2019-11-04 by (mod) - Duomatic-Olsen Ultramax gas furnace

JW I'm no smarter than you on this but it does sound as if the limit switch isn't working;

Watch the limit switch dial on the furnace.

On a call for heat, as the plenum heats up the dial should begin to rotate; the blower ought not come on until the dial rotates to show FAN ON under the pointer.

Also typically the fan will continue to run for a bit after the end of a call for heat, to extract and use the remaining latent heat in the furnace though the burner is off, and to cool down the heat exchanger, reducing thermal stress and cracking risk there.

You might also check thermostat wires and thermostat setting - first to be sure there are no shorted wires and second to be sure that the settings on the TT are correct (such as fan AUTO & HEAT modes)

Show us a photo of your thermostat and of your Duomatic (one photo per comment)

On 2019-11-04 by JW

I have an older Duomatic-Olsen Ultramax gas furnace (1990) that has always worked well. Lately, the main furnace blower starts and stops at the exact same time the thermostat(Honeywell programmable) calls for and cancels heat. The blower limit switch, a Honeywell L4064B, was replaced about 3 years ago. The inducer blower works as it should. It almost seems like the limit switch no longer controls the furnace blower, but the thermostat instead. Help !

On 2019-11-01 by (mod) - Lennox furnace has a condensate tank/trap at the side of the "box"

Let's be sure we're talking about the same function. When the valve instructions say that the end switch closes what they mean is that an electrical switch is closing or making contact in order to turn on the circulator pump.

On 2019-10-31 by Josh

I have Watts brand zone valves that needs replacing. On the side of the housing in a simple wiring diagram of the end switch and it states that "the end switch closes". Does this mean it is a normally closed valve and can I replace it with say a Honeywell normally closed valve?

On 2019-10-19 by (mod) - Lennox furnace has a condensate tank/trap at the side of the "box"

If your condensate drain overflow Outlet connect to a safe destination that will not leak into the building then yes you are to be able to use that as a temporary bypass for a problem with the main condensate system. However be sure to correct the base problem otherwise you risk overflow leak and water damage in your building.

On 2019-10-19 by Karen

Lennox furnace has a condensate tank/trap at the side of the "box". Our HVAC serviceman attempted to repair the cracked tank, though water is still puddling around the furnace. Is it reasonable to connect the overflow tubing directly to the spout that lets condensate leave the system? Checking with the Lennox website, I was unable to find out if the "trap" serves other functions than collecting water.

On 2019-10-03 by (mod) -

Daniel,

There are several ways you could accomplish what you asked about.

Remember that a thermostat is essentially an on-off switch controlled by temperature. You could easily enough wire low voltage wires from each Zone control to a central point where you provide your own on off switch. The disadvantage of that approach is that you give up individual Zone temperature control. I

instead, the most effective solution, one that would require the least special wiring and would continue to allow you to provide individual temperature control for each Zone, would be to install a smart thermostat that can talk to an app on your cell phone. If you search inspectapedia. Com for NEST THERMOSTATS you'll see an example.

On 2019-10-02 by Daniel Dillon

I have hot water radiators in my house which is divided into two zones. How can I have a control panel for both zones in one location that allows me to control both zones separately or together and just have two temp sensors, one in each zone? I can't get a knowledgeable answer from any of the tech support people for the manufacturers, as they all seem to be off-shore contract customer service call centres and don't know much about heating system design. Everyone tells me I need two thermostats. Tell me it ain't so.

On 2019-08-19 by (mod) - how many supply air? "vents" are needed per square feet of floor space

Steve it's a great question but sorry I can't answer it. In my opinion any rule for how many "vents" are needed per square feet of floor space would have to be adjusted for quite a few factors such as

- the velocity of air being delivered

- are we heating or cooling or both

- the expected supply temperature

- the building's country and city thus climate

- obstructions to air flow

- an assumed ceiling height

- duct materials (smooth metal vs spiral flex duct for example) and duct sizes and run lengths

There are indeed some HVAC "rules of thumb" such as 400-600 sq/ft per ton of AC but that doesn't tell us the duct parameters

On 2019-08-14 by Steve

Our 13 x 24. Living room currently has 3 heat vents. One each on the. North, South, and East walls. We're considering eliminating the vent on the east wall in order to achieve better ceiling clearance in the basement bedroom. Is there a rule of thumb or basic guideline as to how many vents per so many sq ft? Thanks in advance.

On 2018-11-01 by (mod) - replacing a Lennox Model G12D2-82-3 ,fan and limit control part # 38619.

Mike, The best Installation and Operation manual including wiring diagrams that I have at hand for t

he Lennox G-12 SERIES FURNACE IO MANUAL


Or see LENNOX Air Conditioners, Furnaces, Heat Pumps, Manuals https://inspectapedia.com/heat/HVAC-Manuals-Air-Conditioners-Boiler-Furnaces-J-O.php#Lennox

On 2018-11-01 by Mike

I am replacing a Lennox Model G12D2-82-3 ,fan and limit control part # 38619. All the replacement ones do not have wire connection prongs on the bottom.

these wires hook to the gas control box. I have been trying to find a diagram for this fan and limit control to see what the wires do, but unsuccessful so far. Will this be okay or is there something else I should do? Or am I just out of luck? Any info is appreciated.

On 2018-10-28 by (mod) - DO NOT keep pressing the re-set button.

Dave

Watch out: DO NOT keep pressing the re-set button. IF the unit won't start and keep running for 10-15 minutes or longer, you are risking a dangerous puffback explosion as un-burned oil in the combustion chamber ultimately gets ignited all at once.

The problem could be a dirty nozzle, dirty filter, ignition trouble, combustion air or vent.chimney trouble - you need a service call from a trained heating service tech.

A good place to start reading yourself is at

NO HEAT - https://inspectapedia.com/heat/Heating-Boiler-Diagnosis.php - Boiler & Furnace Diagnosis Guide - where to start in figuring out why the heating system is not working. How to diagnose loss of heat, when the oil burner, boiler, or furnace won't run, or when the system runs but heat is not delivered to the living area

On 2018-10-28 by dave

oil furnance wont fire unless you press the reset button, but then it stops a few seconds later and then if you tap the top of the reset box it will restart and then shut off again a few seconds later
this continues for three or four taps and fires for about a half hour coming up to temperature and delivering heat and hot water.

Once the boiler shuts down,you have to start this process all over again.

What is the problem,how to fix and is this process ultimately but inderecly reseting and dumping unspent fuel in the chamber

On 2018-09-29 by (mod) - when to call for gas fired heater repair

Cindy

Because there are fire and life safety questions involved, if I were buying a new home that had gas-fired heat that wasn't working normally, I don't think I would feel with it myself I would call a trained service technician to be sure that the heating equipment and the chimney were working properly. The risks of a fire or fatal carbon monoxide accident are just too serious to be casual about this.

Your service tech will check that there is a fuel supply and then check the ignition system and safety controls. When the burner ignites she will check to see that the combustion is proper and that the combustion air is proper in order to be sure that you're not facing a carbon monoxide Hazard.

Also be sure that you have working smoke and carbon monoxide detectors in your home.

On 2018-09-28 by Cindy

Coleman 7900 series mobile home furnace ....just bought this place as is condition....furnace won't start ..gas furnace...

On 2018-09-1 by ResidentPGH - Model: G8T08012UHA11A - Red Light Blinks 11 times

Furnace - Model: G8T08012UHA11A - Red Light Blinks 11 times - Blower runs continuously - Even with Thermostat disconnected

On 2018-08-21 by (mod) -

There are also steam boiler heating systems that also provide hydronic heat to a liwer floor by adding a circulator pump and separately piped hot water zone loop. You'll also need tne necessary controls.

Why not ask your heating company to make an estimate of both methods?

On 2018-08-21 by david

I have a one pipe steam system. I would like to know if I can hookup a radiator to a return line. It’s in the laundry room. The main steam line runs just below the ceiling of the laundry room and runs to another room one level higher than the laundry room. The laundry room is next to the garage.

Located in the wall between the laundry room and garage is a pipe which connects the ceiling steam line with the return line that runs in the floor of the laundry room which then heads to the basement. I had the floor of the laundry room open so I replaced the return line in the floor put in a tee so I could put in a short piece of black pipe and a valve which would connect to a radiator

. The return would continue on under the laundry room floor and reach the basement. when the return reaches the basement there is a ninety degree elbow and a drop of about two feet and then the return line runs along the perimeter of the basement dropping about another two feet until it enters the boiler.

I placed a varivent on the side opposite the valve, about midlevel.

The radiator is sloped back to the valve. When I ran the heat after a few minutes, water started pouring out of the varivent air valve. I thought that steam also runs in the returns in addition to condensate and I would be able to get some steam out of the return line into the radiator.

Is the problem that the radiator is filling up with condensate water from the return. Or is there a problem with the varivent air vent.

Could i just put a 1/8 plug instead of the varivent and get some heat out of the radiator from the hot condensate or would the air in the radiator prevent this as the air would have no place to go. Is there a work around to this so I could get some heat in the laundry room from the return line in the floor

On 2018-05-29 by (mod) - Rheem tankless water heater

Rheem and some other companies make heaters specifically designed to work with integrated heating and water heater systems, including a Rheem tankless water heater (that's more efficient than the tank type that you have). https://www.rheem.com/products/integrated_systems/

The advantage of Rheem's approach is that during a call for heat in cold weather you'll also still be sure to have hot water for washing and bathing. A clip from the company's catalog (again this is NOT your system though it might be a replacement for it when your water heaters die).

On 2018-05-29 by (mod) -

Sure, Tim.

A water heater is sometimes hooked directly to heating baseboards or radiators, usually for a small heating load application.

Your system is a hydro-coil or hot-water-to-air heating system. The water heater(s) pipe hot water through a heat exchanging coil (finned copper tubing) that is inside of the air handler (s). House air blows across the coil to absorb heat to deliver warm air to the occupied space.

The presence of two 50 g. water heaters, assuming they're both dedicated to this purpose, could mean there are two separate air handlers, or two hydro coils in the duct system, OR if there's just one, then the installer figured that one water heater wouldn't have enough capacity.

The advantage of a 2-heater system of this type, IF the controls are set up to do this, is that you can run it as a "cascaded" boiler system. When the demand for heat is modest, just one of those water heaters runs. In very cold weather they both run to provide more heat. I'm just speculating since I have no details about your system.

You're adding complexity (two heaters instead of one), buying a heater that probably costs less than a conventional heating boiler, and maybe gaining some efficiency, and maybe paying in shorter life of the heaters than would be the life of a hydronic (hot water) heating boiler designed for that purpose.

I would want to know the brand and model of the water heaters, and I'd then check the manufacturer's specifications for those heaters to be sure that using them for a hydro coil or fan coil heating application is approved and that such use won't void the warranty on the water heaters.

I'd also like to see photos of the system and its controls, and of the water heaters and their data tags.

Watch out: if the condo is well-insulated and not to large the heating system may be just fine. For a larger building in a very cold climate I'd be cautious in what I assume about the system you describe. Electric water heaters are the least expensive to buy and install, but are the slowest in water re-heating capacity.

I'd also like ot know the age of the condo. In Colorado, for example, in 2001 the state enjoyed particularly low electric rates, making an electric water heater attractive. Since that time, electricity rates have increased over 60%.

See WATER HEATERS for HOME HEATING USE? inspectapedia.com/plumbing/Electric_Hot_Water_Home_Heating.php

You'll see that we issue some warnings about the duty cycle and life of the water heater when used for home heating purposes. But a number of water heater manufacturers have water heater models that they describe as usable in that way.

Hydro-coils or Hydro-Air or water-to-air heating systems are described at FAN CONVECTOR HEATERS - HYDRONIC COILS https://inspectapedia.com/heat/Fan_Convector_Heaters.php

On 2018-05-29 by Tim

I am interested in purchasing a townhouse condominium in the Sierras and it currently has two 50 gallon electric hot water heaters linked to a forced central air system with the hot water could providing the only heat to the system and simultaneosly providing hot water to the home. Could you please point me to some articles that cover this type of system?
Thanks

On 2017-12-10 bby (mod) - Where to find the serial number on a heating boiler or furnace:

Kip:

Where to find the serial number on a heating boiler or furnace:

Unless it has been burned or physically removed, even old heating boilers and furnaces sport a data tag, often secured to the exterior of the heater, on the top or on one of its sides.

If you do not find a data tag on the exterior then you may find it on the inside of the heater's front access panel, rarely on the interior of the door panel itself, more-often on the left or right side of the interior of the heater's metal jacket.

Below is an example data tag for a boiler. More examples of data tags and notes on finding them are at DATA TAG IDENTIFICATION & LOCATION

On 2017-12-10 by (mod) - how to wire up a zone valve

Gene

On the page where we started this discussion - ZONE VALVE MANUALS & WIRING INDEX https://inspectapedia.com/heat/Zone_Valve_Wiring.php

you will find in that article on that page a section titled
Honeywell Zone Valve Wiring Wire Colors
where you will see details about connecting the red and yellow wires of the Honeywell zone valve

On 2017-12-10 by Gene 12/8/17 - Where to find the serial number on a heating boiler or furnace:

12/9/17, I forgot to say my zone valve Honeywell V8043F yes I see where the wires go onto the valve but what to do on the other end the wire ?

On 2017-12-10 by Anonymous

In past I have seen where people has said some things about my problem but I cannot get to those pages from the past . I have saved I had to tell it where to do it I have never had to do that in past.

On 2017-12-10 by (mod) - zone valve wiring tips

Gene,

Our discussion with you about zone valve wiring is at

inspectapedia.com/heat/Zone_Valve_Wiring.php

Print out that page and you will be able to read and go to it again.

On 2017-12-10 by Gene 12/9/17- 6 zone valves and 6 thermostats 3 Taco small pumps and 6 Omron relays G 2R-2-S

I have been trying to get some info. on wiring for zone valves I have 6 zone valves and 6 thermostats 3 Taco small pumps and 6 Omron relays G 2R-2-S I have been working on this system for a few years and I had to change the 24 volt transformer .

when I put the piping in I put in 6 zone valves when I would ad another zone I would add another pair of wires to the thermostat wires when I get done adding zone wiring 6 sets of wires at the trans former the transformer went bad I needed to replace it I called a heating contractor and he ask for a blueprint and I have none so since I am 76 if I would dye they would want to tear system out so I have wired it with different colored wire I need to get this all straightend out .

have had it running on 4 zones for a few years and I wanted to add 2 more zones and I have and I needed get it all done with colored wires and make a print made if I was to dye they would need to know what it all was for..I have all this running with a Polaris high efficient water heater .

found out after I ordered it there were people that had a lot of trouble with these so before I connected it there I seen there was a condensate place to catch and pump it out but they had it to high it probable would run it back inside the burn chamber which is one of the things they were complaining about they were burning out igniters but then they also had a plus or minus 3 degrees shut off to back on again

I bought a temperature controller that I control the on and off temperature at 25 degrees I bought a new igniter and have not used it and I have had it about 10 years no problem but they were trying to use to bathe I only heat the house with this one. . I just need a little help with this wiring .

On 2016-05-20 by Rob Navien NHB-150 with TACO ZVC403 and three honeywell V8043 zone valves.

newly installed system and getting no were with manufacturers support hotlines because of mixed brands. Any help would be great

Navien NHB-150 with TACO ZVC403 and three honeywell V8043 zone valves.

three zones for heating and one zone for indirect tank

indirect tank tstat and pump are wired to the Navien and work great

boiler pump and system pump are wired to the Navien as well.

when no call for heat I can manually open the zone valves and press the end switch to cause the boiler and pump to kick on.

when there is a call for heat the red light (tstat) on the taco zone controller turns on but the yellow (zone valve) does not. when it is energized I cannot for the life of me manually open any of the zone valves. Its as if the zone valve motors seize.

I've uninstalled the t stats and crossed the wires. I have also jumpered the end switch ports on the TACO.


any thoughts?
cheers

On 2016-05-19 by Hissing

We have base board heat throughout our home It is a bit disturbing a very new unit and hot water.

Today there was hissing throughout the first floor and the system worked perfectly up until and still does but the hissing I have no experience with. It is a high end system continues to work perfectly. Although it is rather annoying. Thoughts?

On 2016-04-14 by (mod) -

Sorry Juan, I don't understand the system you describe.

On 2016-04-14 by (mod) -

RE-Posting reader's comment from an older copy of this web page:

AUTHOR:Juan marquina (no email)
COMMENT:Hello I have a question so I have 5 steam pots going to my DI tank and I am building pressure

I have three relief valves one raided for 15psi and two for 35psi the DI tank feeds water into a zink that's it's a burner so the DI tank is building pressure inside I check all of my check valves and relief valves and some wat

I am not pushing water into the zink but only steam so can anyone help

On 2016-03-03 by (mod) -

Christy:

remove the thermostat wires at the furnace end of the circuit. If the cycling on/off stops then we suspect the thermostat or its wiring.

...

Continue reading at HEATING SYSTEMS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see HEATING SYSTEM FAQs-8 - recent Q&A on fixing your heating system

Or see these

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HEATING SYSTEM FAQs-7 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING SYSTEMS

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