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

 

[phinds]

That really confuses me!

And did you read posts 2 and 18?

 

[russ_watters]

That really confuses me! What happens to the steam then, if there's no return?

Gravity! The condensate returns itself down to the boiler through the same pipe it came up in.

 

[sophiecentaur]

So, when you have a slight dip in a horizontal run, there will be constant banging as the steam bubbles past the falling water? Installation of a good system must require a lit of skill and experience. It sounds a nightmare. Does anyone actually prefer steam to hot water or do they just make a virtue of necessity because that's what they have?

 

[sophiecentaur]

And did you read posts 2 and 18?

Mea culpa - I just edited out what I didn't 'want to' understand. I just couldn't believe such a system could exist, I suppose.

 

[phinds]

So, when you have a slight dip in a horizontal run, there will be constant banging as the steam bubbles past the falling water? Installation of a good system must require a lit of skill and experience. It sounds a nightmare. Does anyone actually prefer steam to hot water or do they just make a virtue of necessity because that's what they have?

I think it was considered the best possible system for decades in some areas (cost and efficiency). Yes, it has problems.

A couple of times I had to have the service people come out and shim up a radiator to eliminate excess banging. On rare occasions, the banging is AWFUL; usually it's minor.

Heating bills are high but not what they would be if my house had electric heat.

 

[sophiecentaur]

I think it was considered the best possible system for decades in some areas (cost and efficiency). Yes, it has problems.

A couple of times I had to have the service people come out and shim up a radiator to eliminate excess banging. On rare occasions, the banging is AWFUL; usually it's minor.

Heating bills are high but not what they would be if my house had electric heat.

And haven't they heard about water circulation systems? They are excellent and last for years with very little maintenance (or banging).
I remain gobsmacked by what I have learned on the thread!

 

[JBA]

Back to assuming this is really a water circulation system (and such systems are common for floor heating systems). It would be assumed that the discharge pressure of the pump (I am assuming the pump is a centrifugal and is in the basement) would be greater than the head required to lift water to this highest point in your system even if the discharge pipe started full of air and therefore not acting as siphon to balance the elevation pressure differential created.

At the same time, maybe as suggested earlier, the flow through the lower system is preventing this required level of pump discharge pressure required to overcome the elevation head to be attained.

Based upon this, and that your problem radiator has a manual valve, which suggests that all of the radiators would also be so equipped, I would suggest that you systematically try reducing the flow through some (but not all, for safety) of the lower radiators by successively closing the inlet valves on those units and checking after each closing to see what effect this might have in restoring flow to the problem bathroom radiator.

 

[phinds]

And haven't they heard about water circulation systems?

There ARE hot water radiators, I understand, but I've never experienced them. Greg is sure that's what his is although I'm perplexed as to how he can have the situation he has if it is a closed loop system with a feed and a return all the way around the house.

I think perhaps hot water just doesn't cut it in really cold climates. Live steam provides a lot of heat and some of the old houses are large.

 

[phinds]

Back to assuming this is really a water circulation system (and such systems are common for floor heating ...

But he's not talking about floor heating he's talking about radiators.

 

[JBA]

The basic heating principle is the same and just as a note, in industrial installations closed cycle thermal transfer fluid heating systems are common. We used that process in the original design of the heating system for the entire Alyeska terminal facility in Valdez Alaska some 45 years ago.

To this point the target of this thread has become an "it is vs it isn't this kind of system" debate which is no help in assisting to try and address the original problem as posted.

To the best of my knowledge, the radiators for all steam systems have air vent valves that are temperature operated, so if he has one of these on his radiator I would suspect he would know that. If it does not have one then I doubt it is a steam system.

At the same time, I am not contesting the fact that due to the heat carrying capability of steam that those systems are more efficient; but, that doesn't mean that is the only type of liquid heating system ever installed in a residence.

 

[CWatters]

This is a water system. It must cycle.

The vast majority of houses in the UK are water system, either open vented or pressurised so we are very familiar with them over here.

Most of ours have the radiators connected in parallel not in series so if one is blocked that doesn't stop the flow to the others.

It's very common for corrosion products to create gas (which tends to stop rads near the top of the house/system getting hot) and/or sludge (which tends to stop lower rads getting hot or blocks the whole system).

It's very common for these systems to have problems if they are off over the summer. The gas tends to build up and the sludge settles out. Some systems run the circulating pump at regular intervals even when the heating is off to prevent the sludge settling out and to circulate gas past the auto bleed if fitted.

See also my earlier post about corrosion inhibitor. Saves a lot of trouble.

 

[DaveC426913]

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

Aw man, fire was a b*tch! We couldn't pick it up from lightning, our lightning freezes before it hits the ground.Then again, we invented flash freezing before we invented the wheel!

 

[Averagesupernova]

To this point the target of this thread has become an "it is vs it isn't this kind of system" debate which is no help in assisting to try and address the original problem as posted.

I would think that is the first thing that needs to be established.

 

[sophiecentaur]

This has happened before. The OP has gone and scarpered when we all want to get this thing working for him. Greg, of all people. (Do you think this could be a test, guys?)

 

[Greg Bernhardt]

This has happened before. The OP has gone and scarpered when we all want to get this thing working for him. Greg, of all people. (Do you think this could be a test, guys?)

Still here, got busy and a little lost with some of the tangent discussion. My system is water. Bought a key to bleed the Rads tomorrow. A new dev though. I turned the heat up 10 degrees and the rad did heat up then, but if I raise by 2-3 degrees it will stay stone cold. Just strange that every other rad heats up nice.

 

[Averagesupernova]

My guess is that raising the heat by 2 to 3 degrees causes a short run time. The room which the thermostat is in warms up quickly. When you bump it by 10 degrees the boiler runs longer and is long enough to get hot water to the troubled radiator. The cause? Probably something nearly blocked off.

 

[sophiecentaur]

Cold top = air
Cold bottom= sludge
Slow / never heating= could be both.

 

[DaveC426913]

Cold top = air
Cold bottom= sludge
Slow / never heating= could be both.

What is strange is that even the pipe from the floor leading to the valve is cold.

Gotta be d] other.

 

[Greg Bernhardt]

Cold top = air
Cold bottom= sludge
Slow / never heating= could be both.

What about one side not heating. I have a few where a few back vertical coils don't heat up. fyi, I believe several of my rads are original and nearly 100 years old.

 

[DaveC426913]

What about one side not heating. I have a few where a few back vertical coils don't heat up. fyi, I believe several of my rads are original and nearly 100 years old.

I think we can pretty safely conclude that there's some blockage, though that might not be the gamut of the problem.