Troubleshooting Cold Radiator - Boiler Fall Start Up

[Greg Bernhardt]

Turned the boiler for the first time this fall and an upstairs bathroom rad is stone cold. All other rads heat up. I fiddled with the valve, which is new, with no luck. What is strange is that even the pipe from the floor leading to the valve is cold. This is a water system. It must cycle. How can that part be cold? All rads were bled in spring. What are some simple things I can check or do before I call the pros?

 

[phinds]

Turned the boiler for the first time this fall and an upstairs bathroom rad is stone cold. All other rads heat up. I fiddled with the valve, which is new, with no luck. What is strange is that even the pipe from the floor leading to the valve is cold. This is a water system. It must cycle. How can that part be cold? All rads were bled in spring. What are some simple things I can check or do before I call the pros?

The last time I had the same problem with the last radiator in the line, the problem was not with the steam valve but with the air vent at the other end. It was clogged and since it wasn't letting any air through, the steam wasn't even coming up into the pipe at that radiator.

Try removing the air vent and seeing what happens (put a pan under it in case).

Radiators, as I assume you know, are not a closed loop, they are just pipes with steam running up and the condensed water running back down the same pipe, not "circulating" as we normally think of that term.

 

[Greg Bernhardt]

Radiators, as I assume you know, are not a closed loop, they are just pipes with steam running up and the condensed water running back down the same pipe, not "circulating" as we normally think of that term.

I'm pretty sure my setup is a closed water system, not steam.

 

[phinds]

I'm pretty sure my setup is a closed water system, not steam.

Oh, sorry. I was assuming steam. I don't even associate "radiators" with water, but I guess that's just my ignorance.

In that case I don't see how it is possible. Are you SURE it's just water and a closed loop? Your problem sounds exactly like what I experienced with my steam radiator system.

 

[Greg Bernhardt]

Oh, sorry. I was assuming steam. I don't even associate "radiators" with water, but I guess that's just my ignorance.

In that case I don't see how it is possible. Are you SURE it's just water and a closed loop? Your problem sounds exactly like what I experienced with my steam radiator system.

yeah definitely water, I had a valve leak over the summer.

 

[JBA]

Is the new valve a thermostatic one that controls the radiator/room temperature? If so, if that valve is not opening then it is like your kitchen faucet, no flow, or circulation in your case, means no hot water even in the inlet pipe coming up from the floor.

 

[Tom.G]

Valve re-assembled incorrectly or, if it is more than just a simple valve, installed backwards?
(edit) Take it off and check that you can either see thru it or blow air thru it.

 

[DrClaude]

Turned the boiler for the first time this fall and an upstairs bathroom rad is stone cold. All other rads heat up. I fiddled with the valve, which is new, with no luck. What is strange is that even the pipe from the floor leading to the valve is cold. This is a water system. It must cycle. How can that part be cold? All rads were bled in spring. What are some simple things I can check or do before I call the pros?

Have you purged all your radiators? Have you checked that the water pressure in the system is correct?

 

[sophiecentaur]

Have you purged all your radiators? Have you checked that the water pressure in the system is correct?

Try bleeding radiator first.
Does the pump run normally? Pumps are quiet so you may need to put your ear close.
Old radiators can clog up at the bottom with iron oxides.
PS I never heard of steam heating in domestic systems. Unless the whole system is at 100+C the water would condense. Also 100C is a huge accident risk in the home.

 

[sophiecentaur]

Supply pipe will be cold because there's never any hot water through it. Kirchhoff 1 rules. [emoji6]

 

[Greg Bernhardt]

Is the new valve a thermostatic one that controls the radiator/room temperature?

basic open close valve

Have you purged all your radiators?

This past spring the system was drained and rads bled.

Supply pipe will be cold because there's never any hot water through it.

So this is a pump or boiler issue?

 

[NTL2009]

If the other radiators get hot, then it would seem that this radiator is in parallel (using electrical circuit terms), or somehow by-passed. So if the valve is truly open, I'd want to check the pipes leading to and from the cold radiator. Is there another valve there, is there a clog in that part of the loop?

Was the system tested after the valve was replaced? Maybe another valve was shut off to facilitate the repair, and was forgotten about?

I'm assuming the pump is OK if you are getting good circulation to the other radiators, but I suppose those might be able to get hot from convection? Maybe, but unlikely?

 

[phinds]

PS I never heard of steam heating in domestic systems.

Huh? I'm in central NY and pretty much every house here older than a few decades is heated by steam. My understanding is that that is common across the Northeast.

EDIT: I might need to make that several decades, not just a few.

 

[sophiecentaur]

Well well. You live and learn. It obviously (I now appreciate) has advantages in big instalations (High power transfer) but the hazard of hot pipes and the problem of two states in one circuit would imply that specialists would be needed to design and instal systems. Not common in single dwellings, apparently.

 

[sophiecentaur]

Is that rad the highest in the system? You may have lost water down to that level. Header tank could be empty or pressure vessel low. Minor leaks don't always show as dribbles can evaporate with heat.
Remote fault finding is difficult, even for PF. [emoji846]

 

[Greg Bernhardt]

Is that rad the highest in the system? You may have lost water down to that level. Header tank could be empty or pressure vessel low. Minor leaks don't always show as dribbles can evaporate with heat.
Remote fault finding is difficult, even for PF. [emoji846]

2bd floor but no higher than the others nearby. Boiler apparently has an auto fill feature.

 

[sophiecentaur]

Go for easiest first. Bleed rad then take next step. Is the boiler only for your home?

 

[phinds]

Well well. You live and learn. It obviously (I now appreciate) has advantages in big instalations (High power transfer) but the hazard of hot pipes and the problem of two states in one circuit would imply that specialists would be needed to design and instal systems. Not common in single dwellings, apparently.

No, I am TALKING about single dwellings. Steam heat was very widespread in new houses for many decades in the Northeast and hundreds of thousands (probably more) of these older houses are still around.

The hot pipes are trivially easy to insulate and the radiators have covers to prevent kids touching them but you are right about it being an issue that there is both steam and water in the same pipes. This is the cause of the notoriously obnoxious "banging" that you can get in steam systems. It happens in live steam systems because the condensed water rolling back down hits live steam going up and this causes the water to suddenly become steam again and thus there is a rapid expansion in the gas volume and this causes banging in the pipes.

 

[rootone]

Maybe the water is preferentially going through the radiators which are working because that path offers much less resistance to the flow.
You could try closing valves on the working rads and see if that results in the hot water now going through the one which wasn't working,
(As that is now the only path available).
If you get some success with that, then you can try setting those valves to some intermediate setting.

 

[russ_watters]

I'm pretty sure my setup is a closed water system, not steam.

Can you post a picture of it?

Even if you bled it in the spring, it is still a good possibility that it is airbound now (edit: especially if you had a leak).

 

[russ_watters]

Well well. You live and learn. It obviously (I now appreciate) has advantages in big instalations (High power transfer) but the hazard of hot pipes and the problem of two states in one circuit would imply that specialists would be needed to design and instal systems.

A single pipe steam system is actually pretty elegant in its simplicity; no pump needed. The radiators are thick cast iron, so they don't get to be 100C to the touch.

 

[phinds]

A single pipe steam system is actually pretty elegant in its simplicity; no pump needed. The radiators are thick cast iron, so they don't get to be 100C to the touch.

True, but in a live steam system they get DAMNED hot when the steam is flowing. There's no way you could keep your hand on one. Just touching them briefly is painful. The covers are perforated metal several inches away from the radiator and even the tops of these can get too hot too keep your hand on.

 

[russ_watters]

True, but in a live steam system they get DAMNED hot when the steam is flowing. There's no way you could keep your hand on one. Just touching them briefly is painful. The covers are perforated metal several inches away from the radiator and even the tops of these can get too hot too keep your hand on.

View attachment 107982

Yeah, I know; my sister's 100 year old apartment in Boston didn't have covers on them though. I'd guestimate they can be 130-150F, which is hotter than modern standards would allow.

 

[CWatters]

This past spring the system was drained and rads bled.

Did you put in any corrosion inhibitor when you refilled the system? Gas is a typical corrosion product.

Here in the UK I dose our system with Fernox F1 which is suitable for copper and plastic pipe systems. Other makes exist. You will probably have to estimate the volume of water in the system to work out how much inhibitor to put in. The recommended concentration is usually stated on the bottle. Overdosing isn't usually harmful so better to slightly overdose rather than under.

Perhaps see..

https://www.sentinelprotects.com/uk...se-circulation-issues-central-heating-systems

 

[sophiecentaur]

Maybe the water is preferentially going through the radiators which are working because that path offers much less resistance to the flow.
You could try closing valves on the working rads and see if that results in the hot water now going through the one which wasn't working,
(As that is now the only path available).
If you get some success with that, then you can try setting those valves to some intermediate setting.

There are many possible strategies but, firstly, air in the rad is the most likely cause and bleeding is the quickest and easiest remedy. If there is air in the rad, the 'response' to increased pressure may be very 'non-Ohmic' as the flow could start after a threshold pressure difference, enough to push water over the tops of the vertical columns. This is far too high a level of analysis, I think. Just go through the check list and gradually ramp up the effort. It's the equivalent of changing valves in a faulty TV in the order that they 'usually' fail. It's a method that used to pay the wages of the TV repair man. Strictly not PF, though.

 

[Averagesupernova]

So have we decided whether it is water or steam yet? The usual obvious way is steam radiators have only one pipe going to them and circulating water systems would obviously need a supply and return pipe.

 

[sophiecentaur]

So have we decided whether it is water or steam yet? The usual obvious way is steam radiators have only one pipe going to them and circulating water systems would obviously need a supply and return pipe.

That really confuses me! What happens to the steam then, if there's no return? Vented to the outside? The existence of steam boilers in homes explains a lot of comedy sequences in US films where people struggle with this heaving, clanking thing down in the basement which needs homage paid to it and is out to get you. I can't believe that fresh water is boiled all the time. It would generate a hideous amount of limescale, compared with a closed, recirculating system. I still can't imagine how those things behave when they're getting started from cold. What happens to the condensate in the initially cold pipes and radiators? The flow design must be pretty critical to avoid serious 'bumping effects'.

 

[DaveC426913]

+1

Cold rad == rad needing to be bled.

Don't matter how recently it was previously bled.

 

[DaveC426913]

No, I am TALKING about single dwellings. Steam heat was very widespread in new houses for many decades in the Northeast and hundreds of thousands (probably more) of these older houses are still around.

I live in a SFD in S.Ontario and I've never even heard of steam heat. Though I confess I'm not an HVAC aficionado.

 

[phinds]

I live in a SFD in S.Ontario and I've never even heard of steam heat. Though I confess I'm not an HVAC aficionado.

Well, Canadians have not discovered steam yet. Give it time. After all, you guys just got fire a few years ago