Radiator stone cold

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.

 

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.

 

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.

 

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.

 

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.

 

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

 

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?

 

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.

 

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.

 

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.

 

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

 

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.

 

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.