FAQs on how to Troubleshoot cold radiators, baseboards, convectors in hot water heating systems.

This article series describes the diagnosis & repair of cold "hot water" heating baseboards, convectors, radiators, or "hot water" radiators.

Cold Radiator, Baseboard, or Convector Diagnosis & Repair FAQs

These questions and answers about cold "hot water heat" radiators were posted originally at COLD HEATING RADIATOR REPAIR (hot water / hydronic heat) - be sure to see that page for help fixing a hot water heating system (hydronic) radiator that is not heating up as it should.

If your heating system runs on hot water (it's a hydronic heating system) but it uses those skinny horizontal baseboards instead of radiators, you will be happier if you

see BASEBOARD HEAT REPAIR for cold baseboard diagnosis and repair.

If your heating system uses steam radiators or steam convectors see STEAM HEAT RADIATOR REPAIR for help in diagnosing and fixing steam radiators that won't get hot.

The leaky radiator valve shown here is discussed below in these FAQs.

[Click to enlarge any image]

On 2018-07-23 by (mod) - when to call a trusted heating service tech

Shirley,

Cold radiator but no cold shoulder. Sorry.

I am, however a little confused between your discussion of boilers, chillers, furnaces (those are forced warm air heaters), radiators, and chillers. And "broken line" - to what?

If we're trying to add air conditioning to a building that uses forced hot water heat then yes, adding "split system" air conditioners such as Mitsubishi units can avoid the disruption of trying to run ductwork through a home that doesn't have it, as well as that rather big cost to which you'd still have to add the cost of some kind of air conditioner itself .

On 2018-07-22 by Shirley Fabel

My home, built in 1974, had a boiler and a chiller in the furnace room with radiators in each room - hot water was pumped to heat and cold water pumped to cool. Each room has its own thermostat. We purchased the home in 1988.

The chiller was not working efficiently. I became a widow in 2003 and when trying to get the chiller back into working condition I was informed that the line was broken in the cement foundation and could not be fixed! I still use the boiler and it works very efficiently. My home is 3600'.

I foolishly had a heating and cooling system installed but because I have a high vaulted ceiling which separates the living and sleeping areas I have not been able to get either the heat or cold back to the sleeping area so I still have to use the boiler for heat and only have comfortable cooling in the living half of the house.

My next option is to put a duct across the vaulted foyer or to return to the chiller/boiler system. The chiller, which was probably perfectly good, was removed and disposed of. (stupid) I have since been informed that the plumbing could have been installed overhead!!

I don't know why I am telling you all of this. I am 91 and just needed a shoulder to cry on. I just need some honest advice as to which direction to go - the ducting across the foyer, $11,000. (quote I received) for 3 Mitsubishi units in the bedrooms, or a chiller reconnected to the existing registers in all the rooms.

I don't know how much that would cost.

Is the Air Conditioning/Heating unit I have large enough to cool this large a home? Need to know that before I install the duct across the foyer.
Or you could use this letter as a problem solving test at your next Board Meeting.

On 2018-02-06 by (mod) - cold spot on rad, try to bleed but get no air

Sounds as if the rad valve is closed or system pressure low or feeding line is airbound -

see AIR-BOUND HEATING SYSTEMS - home

On 2018-02-05 by patrick john walsh

cold spot on rad, try to bleed but get no air or water escaping from valve whats wrong??

On 2018-01-25 by (mod) - leaky hot water heating radiator valve

Indeed, Anon, a radiator valve can break internally so that even when you turn the handle closed (clockwise) the valve does not actually close. IN that case the fix is to replace the valve.

Leaks anywhere in a hot water heating system can not only leak water out, but also air into the system (when it is cooling down).

The accumulating air in a radiator or in hot water heating (hydronic heat) piping can eventually cause the system to become air-bound .

If that happens to you see AIR-BOUND HEATING SYSTEMS - home

You can try to fix the leaky radiator valve in your photo by gently tightening the packing nut - shown in my arrow on your photo. That might work to stop the leak.

Watch out: do not over-tighten the packng nut - don't use a gigantic wrench. You might break the valve entirely, resulting in both a flood of hot water and a loss of heat in your home.

If tightening the valve stem packing nut does not stop the leak, with heat OFF and pressure and water drained from the system, your heating service tech might be able to repair or replace the radiator control valve stem packing or if necessary (a bigger job) replace the entire valve.

More help is at RADIATOR VALVES & HEAT CONTROLS.

On 2018-01-22 by Anonymous

It’s my radiator and it’s leaking water and when I try to turn it off it’s still heating up.

On 2018-01-05 by (mod) - Heat is on and all radiators are working but one is cold

Open the radiator valve, then find and use the air bleeder on the cold radiator.

See AIR BLEEDER VALVES - home

On 2018-01-05 by Robin

Heat is on and all radiators are working but one is cold...what to do

On 2017-04-12 by (mod) - radiators don't work on cold days

Jin

If you use the search box just above to search InspectApedia.com for THERMOSTAT ACCURACY & CALIBRATION you'll find several articles that discuss the problem you describe. It may simply be that the thermostat is in a bad location or is affected by sunlight, drafts, etc.

Dindo: aside from being air-bound a radiator may stay cold for other reasons discussed in the article above.

On 2017-04-11 by jin

I am in a high rise building with a thermostat that is meant to turn off at 22 degrees.

However, on warm or hot days above 22 degrees it works very well hot to the touch yet on cold days well below 22 degrees it is not heating and only warm to the touch.

I'm sick of excuses by the landlord and plumbers who come including the engineer. It's like the thermostat is inversed. Any idea please?

On 2017-01-24 by Dindo

The bottom part of my hot water radiator is cold , no air coming out from air bleeder. Only water, but the bottom stays cold.

On 2017-01-23 9 by Anonymous

I turned on my heat as normal and it fired up but didn't stay on as long as usual and went off an after a few minutes came back on again but radiators remains cold. What could this be

On 2017-01-22 by (mod) - Thermomax tankless heater not working

I'm not clear on what you're opening, what water you're trying to use or remove. Are you trying to drain heater or obtain hot water.

If you're using (as I think) a demand type water heater for hot water for washing and bathing, then a safety device may be shutting off the boiler if it thinks the water flow rate is too slow- so water flows but is not heated.

See TANKLESS WATER HEATERS

You can of course contact Thermomax at (800) 776-5277 or (410) 997-0778

On 2017-01-22 4 by plimper

I have a Thermomax boiler and when i open the water and wait for the hot stream to come it comes for 3 seconds and then it stays cold.Can anyone tell me what it might be wrong?

On 2017-01-10 by bob

3 zone system 1 zone wont heat radiators on third floor but is very hot at circulator

On 2017-01-01 by (mod) - when I bleed the radiators no water comes out

Hot water,not steam heat, right?

Perhaps the system pressure is a so low that no water is in the radiator

OR

the radiator inlet valve is closed or clogged.

On 2016-12-31 by headley

My heaters are hot but when i bleed them no water comes out.

On 2016-12-20 by (mod) - Air in the system will prevent a radiator from heating up.

Missy:

Air will prevent a radiator from heating up. If you radiators are still cold, either there's an air-blockage somewhere in the system or there's (of course) another cause such as

- thermostat not calling for heat

- building heating system water pressure is too low

- one of the other causes listeed in the article above.

See AIRBOUND HEAT SYSTEM REPAIR

On 2016-12-20 by (mod) - who do I call to fix a radiator system?

Anon:

Call a local plumbing / and / heating contractor.

On 2016-12-20 by Anonymous

What professional is required to hire to repair and/or check a radiator system?

On 2016-12-20 by Missy

My hot water radiators stopped putting out heat after I bled them.

On 2016-12-01 by Anonymous

what do I need to do if the valve doesn't turn in either direction I have bleed the valve cold water came out for a while, radiator did not get hot.

On 2016-11-28 by Simon

When I bleed my radiator just water comes out no air?

On 2016-11-28 by Simon

My radiator gets to a certain heat then turns off

On 2016-10-31 by (mod) - If the radiator valve is open (on) and you open the air bleeder valve and no air and no water emerges

Jack:

If the radiator valve is open (on) and you open the air bleeder valve and no air and no water emerges there I suspect that either the bleeder is clogged or the radiator supply / inlet valve is not really opening.

As long as the boiler is at operating temperature there ought to be pressure in a hot water heating system.

On 2016-10-30 by Jack carlson

I have no water coming out of radiator on second floor and have only one first floor is all good pressure is up wondering about exspansion tank in basement would new one help

On 2016-10-30 by Jack carlson

I have no water coming out of radiator on second floor and have only one first floor is all good pressure is up wondering about exspansion tank in basement would new one help

On 2016-10-12 by Dennis

WE have Weil McLain GV boiler ,some baseboards do not heat at all.

Some baseboards do not heat at all

On 2016-03-05 by (mod) - before trying to bleed air out of a radiator be sure the heat is on

David,

Before trying to bleed out air be sure the heat is on and the boiler up to full pressure .

On 2016-03-04 by David

I tried to bleed the radiator but no air water would come out. What can I do?

On 2015-11-11 by (mod) - an air block in a chain of radiators / baseboards can keep the downstream ones from getting hot

It's possible to mix radiators and baseboards;

an air block in any of them stops the downstream ones from feeling heat

On 2015-11-11 byAnon - it looks like someone connected a baseboard radiator to a hot water loop system there is only one pipe to the radiator

it looks like someone connected a baseboard radiator to a hot water loop system there is only one pipe to the radiator

On 2015-11-07 by (mod) - bled lines now won't ignite?

Sorry Rich I'm confused. Bled what lines: air vents on radiators? If so that won't have an effect on whether your heating boiler turns on or not.

See https://inspectapedia.com/heat/No_Heat.php for some help

On 2015-11-07 by Rich

Bleed lines now not igniting to light
Is making ticking notice

Question: how do you get heat out of a steam radiator in and out

(Dec 17, 2012) Chuck Arkle said:
How do you get heat from a steam radiator using hot water in and out of the bottom of the radiator?

The supply should come in the bottom and the return out the top with a bleed on each radiator or the use of a Spiro vent or similar vent device installed in the return at the boiler in the return in accordance with the vent manufacturers recommendations.

Reply:

Chuck,
Steam radiators are heated by steam, not hot water. It's condensate returning from that bottom outlet.

Question: cast-iron steam radiators not hot

(Jan 13, 2013) Carla said:
Hi!

I live on the second floor of a two-story house and I'm having heating issues. I have natural gas powered, cast-iron steam radiators.

The two radiator's in my living room (where the thermostat is located) will not heat up during normal operation, i.e., leaving the thermostat set at a constant temperature and the thermostat is calling for heat.

When the boiler runs, the radiator's on the other side of the house (bathroom & bedroom) will heat up. The radiator in the bedroom heats up partially and the one in the bathroom, fully, and the two in the living room not at all but you can hear the air hissing.

The only time the two in the living room will heat up is when the thermostat is turned up really high, like if it's set at 68 degrees then turned up to 80 degrees, then they'll put out heat. Is this normal?

Additional info: Landlord came yesterday and turned the boiler up from 3 psi to 3.5 psi (should work at 2 psi or less);

told me to leave the supply valve in the bedroom only partially open and that it can't be closed completely because it's going bad (I opened it fully after he left); there's also no insulation on the pipes and you can hear hammering in the pipes when the boiler runs.

I hope I explained the situation well... thanks in advance! Forgot to mention... hot water will run out at the end of a shower even when no other hot water has been run... relevant?

(Jan 25, 2013) Vik said:

I have a Thermolec electric boiler to heat a duplex (2 stories). I have heat on the upper floor but none in the basement. The boiler operates in a weird manner. I am not certain whether the pump is working or not, however the water heating cycle comes on and off every two minutes, which means that the thermometer starts from 60 C to 80 C within 30 seconds, then cools off till it is back to 60 C and it restarts.

My neighbor's boiler takes a full 12-15 minutes to do the same cycle. Do I have air in the system, is my pump not working (although I have very high heat on both ends of it),. What could my problem be?

(Jan 27, 2014) Kevin Clennan said:

We have a 2 zone baseboard hot water heating system. The 1st zone going to the down stairs works good. The 2nd zone going to the up stairs has 6 base boards and 3 are working and 3 are not.

They each have there own bleeder valve on them and when I went to bleed off one of them I got just a little air and then nothing. No water came out either. even when its not calling for heat shouldn't there be water coming out of the bleeders when opened or is that normal to have no pressure when not calling for heat.

Reply:

Hi Kevin,

For steam heat radiator problems it's best to start

at STEAM HEAT RADIATOR REPAIR

Presuming that in the second zone we are sure that all 6 baseboards are on a single pipe run - that is there are no intermediate valves or controls that might have split the zone into two sub-loops of 3 baseboards each, I would look for

1. a clogged bleeder valve - debris may have blocked air exiting from the bleeder valve when you tried to open it.

2. low system pressure; because most circulator pumps do not have much lift or push capacity, they depend on two conditions to be able to circulate hot water through the upper floor zones:

2.1. sufficient heating system pressure to overcome the head pressure of water in pipes going to upper floors

2.2. no air in the piping system (which you know since you're trying to bleed air out)

If you search InspectApedia for the article titled

PRESSURE & TEMPERATURE SETTINGS, CONTROLS

you'll get more help.

Also search for AIR-BOUND HEATING SYSTEMS to see methods used to force air out of a partly air-bound system.

Question: problems with zones freezing up

(Jan 27, 2014) Roni said:
Have an Ultimate oil burner/boiler ( DHW coil removed), with 4 zones.

1st zone main floor

2nd zone upstairs

3rd zone sunroom addition

4th zone Amtrol indirect HW maker

Problem:

2nd zone piping freezes up with cold weather (usually below 20F). Thermostat in master br must be kept at 59-60F otherwise other two bdr's get way too hot.(poorly designed loops for the pipes, too $$ to fix)

Question:
Is there a way to add a recirculating pump to keep a small flow of HW moving thru the 2nd zone even when the zone isn't "officially" calling for heat?

Kinda like the idea where a pump is added to the furthest HW faucet in a home that keeps HW flowing so there's no need to run the water forever to finally have the HW reach the faucet...

Only other way to describe it would be for the 2nd zone valve to have variable flow-trickle to prevent pipe freeze and fully open when stat calls for heat. Crazy idea? Impossible solution?

Reply:

Roni:

Yes there are several solutions:

1. immediately pending other steps, keep the temperature high enough to avoid freezing - in your case 60F

2. assuming that your system runs with a single circulator and multiple zone valves, you can have your heating tech wire the circulator to run continuously

- this is how homes in Canada are usually heated; it's custom in the U.S. to have the thermostat call for heat by turning on the circulator and the boiler temperature turn on the boiler via the aquastat.

But in Canada the circs run all during the heating season (at least on many systems) and the TT is wired to turn on the heating boiler.

3. You could install a variable speed circulator for the above application (see extra notes at 4. below)

4. you could install a booster or extra circulator just on the freeze-prone zone.

In this arrangement you would think you'd want to latch open the zone valve manually so that the circ could push water around, but you may have to also change the zone valve wiring to NOT call for heat - otherwise when the zone valve is manually latched open, its internal end-switch will also turn on the main circulator.

In other words, you can convert the problem zone to one that is always circulating. If you install a variable speed circulator you can circulate water more slowly through that zone (or all zones) continuously. When the boiler temperature drops below the cut-in the boiler will cycle and provide heat.

Alternatively if you disconnected the trouble zone's zone valve end switch wires (that normally turn on the main circulator), then latch the zone open, then add an additional variable speed circulator just for that zone, you'll circulate water more slowly.

This is slightly garbled as I'm typing off the cuff - if the ideas are not clear, ask again.

To find variable speed circulators search InspectApedia for that term or search for the article title

Guide to Circulator Pump Relays & Other Controls for Heating System Circulator Pumps

Question: adiator does not have a knob to turn it off and on.

(Jan 30, 2014) Mz diva said:
My radiator does not have a knob to turn it off and on. We bled it to release air. It still is not getting hot, only warm. Any suggestions?

Reply:

Mz

You may need to bleed more air - open the air bleeder until you begin seeing water coming out of the valve, then shut it off.

If that does not fix the problem the heat piping itself may be air-bound elsewhere in the system, or a valve partly closed.

...

Continue reading at COLD HEATING RADIATOR REPAIR (hot water / hydronic heat) or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• AIR BLEEDER VALVES - find and operate those cute little controls on baseboards (or radiators)
• AIR-BOUND HEATING SYSTEMS - home
• BASEBOARD HEAT REPAIR - home
  • AIR-BOUND HEATING SYSTEMS
  • BASEBOARD HEAT DAMAGE REPAIR
  • COLD HEATING RADIATOR REPAIR (hot water / hydronic heat)
  • STEAM HEAT RADIATOR REPAIR
  • LEAKS at BASEBOARD, CONVECTOR, RADIATOR
• DIAGNOSE & FIX HEATING PROBLEMS-BOILER if the boiler is just not working like it should
• NO HEAT - BOILER / FURNACE DIAGNOSIS If none of your heating radiators, baseboards, etc. are getting hot, start your diagnosis at this article
• RADIATOR VALVES & HEAT CONTROLS

Suggested citation for this web page

COLD HOT WATER BASEBOARD / RADIATOR FAQs 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 RADIATORS

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