Recent hydronic (hot water) heating boiler problem diagnosis and repair FAQs #2.

This website answers questions about all types of heating systems, advising on troubleshooting, inspection, diagnosis, and repairs. 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.

Heating Boiler Diagnostic FAQs2

These questions & answers about troubleshooting or fixing a heating boiler (hot water heat, hydronic heat, baseboards, radiators &c) were posted originally at DIAGNOSE & FIX HEATING PROBLEMS-BOILER - home. Be sure to review that article.

On 2019-03-11 by (mod) - we have heat but no hot water

I would look for a clogged tankless coil, or a closed valve, or a scale clogged tempering or mixing or anti scald valve

On 2019-03-10 by Matt

I have an oil operated boiler the runs both my hot water and heat to my house. I have heat for my house but no hot water what could be the problem?

On 2019-03-07 by (mod) -

Arnoldo

If all of the apartments are using the same boiler, then the issue is with thermostats or - assuming it's hot water heat - zone valves or circulator pumps and their controls

OR

The zones could be air -bound

See the ARTICLE INDEX to find our diagnosis and repair articles for AIRBOUND HEATING SYTEMS

On 2019-03-07 by Arnoldo

Only working in 4 apartment other 2 is cold
I have the water heater furnace

On 2019-02-19 by (mod) - boiler won't fire-up or run

Manley

Try the diagnostics at NO-HEAT BOILER https://inspectapedia.com/heat/Heating-Boiler-Diagnosis.php

On 2019-02-19 by Manley Brown

Boiler want Fire up are run

On 2019-01-24 by (mod) - why are all of the baseboards warm instead of hot?

Jay

Excellent question.

There are a number of things to check when he does inadequate throughout the building and your report of low temperature at the baseboards are radiators is consistent.

But let's start with a report from you on what are the aquastat settings at your boiler and what is the actual temperature that you see on the pressure in the temperature gauge there.

With those question answeed we will address the other common causes of inadequate heat throughout the system such as a circulator that's not working, a blocked line, a valve or zone vakve that's partly closed, wrong circulator velocity, or partial air blockage in the system.

Also relevant, is this an oil or gas fuel heater and when's the last time it was cleaned?

On 2019-01-23 by Jay

Lots of sites cover no heat or heat in some zones and no heat in other zones.

But what if low heat in all baseboard heaters?

Furnace is hot and pipes going up and down are hot. But the rooms dont heat up enough.

On 2019-01-13 by (mod) -

Gary

What you describe is unsafe and risks a BLEVE explosion.

I suspect a bad aquastat or bad aquastat-sensor, but of course you need to first confirm that the aquastat itself is set to 200F or lower.

On 2019-01-12 by gary

i have a weil-mclain oiled fired boiler for heat and the temperature started going to over 200 degrees with a high temp light coming on . What may be the cause ?

On 2018-12-02 by (mod) - signs of air bound heating pipes, baseboards, or radiators

Patricia

If the circulator pump is running and the boiler is hot snd radiators or baseboards are cold most likely the system is airbound.

See details at AIRBOUND HEATING SYSTEM

In the ARTICLE INDEX found near the eff nd of this article or use the search box to find that phrase.

On 2018-12-01 by Patricia

Hi I have oil heating which isn't working.

There is oil in tank, the burner is firing up but my radiators will not heat!

I think my problem is in my hotpress, either the valves or pump but I don't know how to check, it's an old system I believe

On 2018-11-29 by (mod) -

Anon

I want to help but have too little information.

Temperature set where? at the room thermostat?

Are the room radiators or baseboards hot?

I can't tell if the issue is a house losing heat faster than the boiler can provide heat or if there is a problem with the boiler itself.

If you set the thermostat to say 70F and the boiler runs continuously and room temperature never reaches 70 AND the radiators or baseboard is HOT
THEN I suspect that the amount of radiation = heat delivery to the occupied space - is not enough for the home's rate of heat loss.

If that's the case we start by fixing drafts and air leaks.

On 2018-11-29 by Anonymous

My gas boiler will not hold the temperature that I set

On 2018-11-09 by (mod) - boiler can't get the room to the thermostat set temp?

Anon:

I want to help but have too little information.

Temperature set where? at the room thermostat?

Are the room radiators or baseboards hot?

I can't tell if the issue is a house losing heat faster than the boiler can provide heat or if there is a problem with the boiler itself.

IF you set the thermostat to say 70F

AND the boiler runs continuously and room temperature never reaches 70

AND the radiators or baseboards are HOT

THEN I suspect that the amount of radiation = heat delivery to the occupied space - is not enough for the home's rate of heat loss.

If that's the case we start by fixing drafts and air leaks.

See ENERGY SAVINGS PRIORITIES

On 2018-11-2 by Anonymous

My gas boiler will not hold the temperature that I set

On 2018-11-09 by (mod) - house can't get warm enough unless thermostat set WAY up

Mark there are a lot of possible explanations - without more information from your installation I'm afraid my speculation is more arm-waving than helpful. I have no idea even what kind of heat you have: oil, gas, (presumably a hot water boiler), radiators, baseboards, convectors, multiple zone, one zone, zone valves, circulator pumps, etc.

In general there are a few very basic things that can be done like noting the temperature of the water in the boiler and noting that on a call for heat the circulator(s) run and zone valves open and heating pipes at the boiler get hot.

If all of that looks ok the problem could be air in the heating lines blocking or reducing hot water flow.

It's worth a call to your heating service company, asking for diagnostic help from an experienced technician.

Let me know what you're told and what further questions arise.

On 2018-11-09 by mark

had newer put in a few years ago but it seems not to get house warm unless thermostate is turned way up and then cost runs around 700 dollars and not super hot what could be the problem

On 2018-11-04 by (mod) -

Anon if some radiators have heat and others not, the problem isn't the boiler itself, it's more likely a closed radiator valve or a steam vent that's not working.

Diagnosis and repair advice for cold steam heat radiators is

at STEAM HEAT RADIATOR REPAIR https://inspectapedia.com/heat/Cold-Steam-Radiator-Repair.php

On 2018-11-04 by Anonymous

I have a gas boiler steam heat on the second floor radiator in the bedroom is called the radiator in the living room has he what can I do to fix this

On 2018-11-03 by (mod) -

Bruce:

Causes of abnormally high pressure in a residential heating boiler (hydronic heating system - i.e. hot water heat) include

1. a defective automatic water feed valve

2. a defective or improperly-set building water pressure regulator

3. a leaky tankless coil in the boiler: a hot water coil or tankless coil in the boiler, if leaky, will leak water into the boiler from the higher-pressure building water pressure side.

More details are at:

TANKLESS COIL / HOT WATER COIL LEAKS https://inspectapedia.com/plumbing/Tankless_Coil_Leaks.php

RELIEF VALVE LEAKS https://inspectapedia.com/plumbing/TP_Valve_Leaks.php (because some of the causes of a leaky relief valve can also cause high boiler pressure)

PRESSURE & TEMPERATURE SETTINGS, CONTROLS https://inspectapedia.com/heat/Heating-Temp-Pressure-Settings.php

On 2018-11-03 by Bruce

What can cause the boiler pressure to rise spontaneously to over 30 psi,even though the pressure was 12 psi when filled? Note the expansion tank and PRV are brand new and the water feed ball valve is shut.

On 2018-10-26 by (mod) -

I'm not sure that's a good idea, Fred.

You could install a mater Flo-Control valve and pipe two zones downstream from that feeding two circulators on the return side of the two loops (where they belong), but the problem would be that when just on zone is calling for heat and its circulator running, the pressure drop will open the common FLo-Control valve to both zones.

That means that heat can circulate by convection up through the "off" zone even though it's not calling for heat.

On 2018-10-26 by Fred

Can you use ONE common Flo Control Valve With TWO Circulators?

On 2018-10-25 by (mod) -

Susan

I infer this is a gas boiler with a standing pilot whose burner won't ignite. I suspect the gas valve is not opening. That could be a control wiring problem or a bad gas valve.

On 2018-10-25 by Susan Ohara

Need some help: for our boiler....the pilot light is on, thermostat is on, heat kicking on but not igniting so no heat coming from radiators. Any ideas??

On 2018-10-13 by (mod) -

Your home's heat may be divided into zones, each controlled by an individual thermostat.

When some zones have heat and others not, the fault could be (among common causes)

- a thermostat is not working

- a circulator or zone valve is not working - search InspectApedia.com for NO HEAT for diagnostic suggestions

- a zone piping section to the cold zone is air bound - search InspectApedia.com for AIRBOUND HEATING SYSTEM

On 2018-10-13 by Mary

Mclain oil heater only heats part of the house, what is causing this issue?

On 2018-08-30 by (mod) -

Felix

click on ARTICLE INDEX to HEATING BOILERS at the end of this page

and in that master index find the article series on AIR BOUND HEATING SYSTEMS - or search this site for that phrase, as that's were I'd start the diagnosis.

On 2018-08-29 by Felix

No heat circulation. Replaced my circulation pump. Refilled my gychol.

On 2018-04-07 by (mod) -

at DIAGNOSE & FIX HEATING PROBLEMS-BOILER

On 2018-04-06 by Tina

Powers on but the boiler does not turn on

On 2018-03-07 by (mod) -

Karl:

Watch out: if your heating boiler is empty of water TURN IT OFF IMMEDIATELY and leave it off to avoid damage or unsafe conditions.

Your heating service tech will look for and fix the leak if that's the issue - or repair or replace the water feeder.

On 2018-03-04 by Karl

No water in it water system. Tried to purge air but no water

On 2018-03-07 by (mod) - no water in the boiler, water on the floor

Karl:

Watch out: if your heating boiler is empty of water TURN IT OFF IMMEDIATELY and leave it off to avoid damage or unsafe conditions.

Your heating service tech will look for and fix the leak if that's the issue - or repair or replace the water feeder.

On 2018-03-04 by Karl

No water in it water system. Tried to purge air but no water

On 2018-03-03 by Steve

My power just got restored after 30 hours and my baseboard heaters are kicking on. The furnace is lit and running but don't even feel them heating up at all.

Also, upon power turning back on, I went down to check on furnace to see if it was lit or not and found some rusty water around furnace....also as I type this I do hear the baseboards starting to kick on....any insight is much appreciated!

On 2018-03-03 by lenny

my boiler has water thermostat set properly burner is lit but not getting heat

On 2018-02-06 by (mod) - one zone isn't working

There are several possible causes, sounds like a stuck or defective the zone valve or circulator pump or relay depending on how your hot water heater is controlled. Or an air bound heating system piping Loop.

On 2018-02-05 by Shelly

We have a Utica Boiler, 2 thermostats. One controls the living room, dining room, kitchen etc and is working just fine.

The second thermostat controls the bedrooms and main bath and isn't working. Not sure what is wrong, we changed batteries in thermostat, tried a few things. Any suggestions?? Thank you

On 2018-02-04 by Kris

@Wendy, we installed a thermostate in the basement. Worked like a charm.

On 2018-01-18 by (mod) - radiators still get hot with boiler switched off!

Art

at HEAT WON'T TURN OFF https://inspectapedia.com/heat/Heat_Stays_On.php (found by searching InspectApedia.com for that phrase) we list a number of reasons that heat may continue to pour out of radiators even with the boiler off.

Examples include normal thermal mass remaining in the water-filled steel or cast iron radiators and thermal convection circulation of hot water out of the boiler, perhaps because a check valve isn't functioning.

On 2018-01-18 by Artb

Why would radiators still get hot with boiler switched off!

On 2018-01-07 by (mod) - pressure reducers not reliable water feeders

Darius

Yes, probably that's the problem.

I have run into this problem too: nobody knew that the automatic water feeder/pressure reducer was not feeding the boiler until we drained the boiler for service.

YOu'll want to replace that valve. Meanwhile if there is a manual bypass loop and valve you can fill the boiler by that means.

On 2018-01-07 by (mod) - radiator air bleed valves

Sandra

On each radiator there should be an air bleeder valve that can be opened manually - let out air until water appears then close the valve.

Details are at COLD HOT WATER RADIATOR or BASEBOARD https://inspectapedia.com/heat/Cold_Radiator_Repair.php

On 2018-01-07 by Sandra

How do I bleed forced hot water register

On 2018-01-07 by Darius

i have a dunkirk boiler that had a bad temp/pressre gauge go bad replaced it now i can get boiler to fill back up is the reducing vavle bad u think ? the boiler was still hot when trying to refill or burp

On 2018-01-07 by (mod) -

Mike,

Consider that as long as the thermostat is calling for heat, hot water should be circulating through the whole loop and back to the boiler.

Even for radiators located at the end of a heating loop the rads ought eventually to get warm, even if they're not hot. It's possible they're air-bound (need to be bled of air) or that their valves aren't open.

On 2018-01-07 by Mike C

I have a gas hot water boiler/baseboard cast iron radiator system. All the radiators are working very well on the main floor.

However, the two basement radiators, (one in the attached garage and one in the laundry area on the other side of the home), are not.

All the radiators come off of one main loop of pipe from the boiler. It seems as though maybe the boiler and circulator pump are not on long enough, even though the main floor has reached the correct temperature from the thermostat, to allow the basement radiators to pull down heated water. Am I thinking this through correctly? Any suggestions on a fix? Thanks.

On 2018-01-07 by (mod) -

Wendy

It's possible that your circulator pump is not running.

Use the on page search box to find our article on

CIRCULATOR PUMP DIGNOSTICS

On 2018-01-07 by Wendy

We have insralled a new boiler in our small 5 floor brown stone building. however, the basement unit now does not get enough heating. what could be the problem?

On 2018-01-07 by Anonymous

I have a hot water gas furnace. I have hot pipe 2ft coming out of furnace after the 2ft the pipe is cold as well as all the baseboards

On 2018-01-01 by (mod) -

Rosario

I'm totally baffled by this question as well and apologize that I can't immediately think of a useful diagnostic suggestion. I think it's time to call a service technician

On 2018-01-01 2 by Rosario Garibay

We woke up to no hot water, we can get some water through the hot side but it's not hot and we have a natural gas water heater it has a light on it to indicate it's on but it hasn't turned on yet even when we have hot hot water on. We have a Reliance brand.

On 2017-12-30 by (mod) -

Leaving the circulator on might reduce the chance ofca frozen heat line

On 2017-12-28 22:33:35.964065 by (mod) -

Shieka

Once the plumber has thawed your frozen pipes and gotten heat working, this article

HEAT SOURCES to AVOID FROZEN PIPES explains where and how to add heat to keep the pipes from freezing again.

Also see ANTIFREEZE for BOILERS as another approach to avoiding this trouble in the future.

On 2017-12-28 3 by Shieka

My radiant heat boarders are cold. The Plummer says pipes may be froze I'm the main unit that don't have heat

On 2017-12-28 by Stevec

I have a boiler that is down and want to know if the circulation pump (multi zone) should be turned off of left on while the system is fixed (2 days)? Any harm either way?

On 2017-12-23 by (mod) -

Lori,

If your hot water is made by the same heater that circulates hot water (a boiler) to heat the house then I suspect a circulator or air bound problem. Time to call for service.

On 2017-12-23 by Lori

I have hot water but I have no heat it’s an oil furnace comes on I had heat and every couple days another radiator stopped working none none of the radiators are working and I don’t know whether it’s air around our electrical

On 2017-12-02 00:15:06.764282 by Keenan

Raypack Boiler feeding fan coil units to side of hotel , 140° waster leaving and entering the boiler , cold air coming from diffusers that fan coils are feeding , boiler keeps tripping off , may be a fire damper closed ? But it would not feed air at all then wouldn't it ?

On 2017-11-14 by James DeMaio

I hear my Burner turn on, but both circulators don’t turn, I have two line thermostats with no
power.

Circulators work when jumped, I found a loose connection where the common legs to each thermostat was tied, the common legs to the therms at tied to the red wire on my Aquastat (W) ,

have a Honeywell L4081 Aquastat, I have the hi set to 180 deg, lo at 160 deg, It worked fine, I had current to my thermostats, but a couple of days later it stops working again, could the Aquastat be bad?

Please
Help, I’m very good at diagnosing & fixing things, but this I can’t figure out, it’s happened twice already.

On 2017-11-14 by Jing

My williamson boiler mod 1135-601 is only 2 years old. My hi limit is set at 200 degrees, but the boiler only heats up to 140 before it shuts the burners off. It continues to circulate and call for heat but will not get up to temp.

I checked the continuity of the limit switch and rollout switch, both of them are good.
Please help me out.

On 2017-09-23 by (mod) -

Joey,

If we are discussing an electric water heater then you'll find a series of articles describing how to test the heating element to see if it needs to be replaced. Please use the search box on this page to search for ELECTRIC WATER HEATER REPAIR

On 2017-09-23 by Joey

I have power on both sides of timer and element but no hot water

...

Continue reading at DIAGNOSE & FIX HEATING PROBLEMS-BOILER - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• BOILERS, HEATING
• BOILER OPERATING PROBLEMS
• DIAGNOSE & FIX HEATING PROBLEMS-BOILER
• OIL BURNER INSPECTION & REPAIR.
• GAS BURNER FLAME & NOISE DEFECTS
• GAS BURNER SOOT CAUSE & CURE
• GAS BURNER PILOT LIGHT PROCEDURE
• RADIATORS for ROOM HEAT - topic home, for cold radiator or baseboard diagnosis and repair

Suggested citation for this web page

DIAGNOSE & FIX HEATING BOILER, FAQs-2 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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