Shutting off a two-pipe steam radiator

georgearoush · January 16

On a two-pipe steam radiator, if I want to shutoff the radiator so it won't get any steam, is all that I have to do is close the two valves? In doing so, will I be impacting any other radiators?

EdTheHeaterMan · January 16

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What two valves? I believe that you just shut off the inlet to the radiator so no steam enters the radiator and that will accomplish what you want.

georgearoush · January 16

@EdTheHeaterMan Here is a picture of the radiator. The valve on the left is the intake:

Here is my situation. I have several radiators just like the one shown in the picture. One radiator on the third floor heats up end to end, but I don’t need heat in that room, so I am considering closing its valves. Meanwhile, a radiator on the first floor only heats about 1/4 of the way at best.

Given this, my thought was to close the valves on the third-floor radiator because I don't use that room, in hopes of getting more steam on the first floor. However, I am not entirely sure what’s causing the first-floor radiator to heat only 1/4 of the way.

Since this is a two-pipe system, should the vent on the radiator be fully open or completely closed? For clarity, all radiators in the house have both valves fully open.

Jamie Hall · January 16

Yours is not a true two pipe system. It's what is called a two pipe air vvent system, and came earlier. They usually work pretty well…

In direct answer to the valves, if you want to shut off a radiator, yes — you have to close BOTH valves. But… you need to be quite sure that both valves are, in fact, steam tight. Otherwise, some steam will enter and condensate will build up — but not be able to escape, which can cause problems. It's a little safer to close the vent and accept a little heat anyway — just like a one pipe system.

On the radiator which doesn't heat. That vent has to be working. If the vent is not open, or is very slow, the radiator won't heat much — as you are observing. Again, this is much more like a one pipe system than a two pipe system.

dabrakeman · January 16

That Ventrite #1 should be virtually closed at its lowest setting. Is there also venting at the end of the returns in the basement? If so the radiator should still get some steam even if the vent is closed. If there is no venting at the end of the returns then closing the vent should significantly reduce the steam to the radiator, assuming the vent is not stuck open. Yes you can just shut the valves but watch the radiator closely during a heat cycle and make sure it is not getting hot in the first section.

P.S. - Beautiful radiators! If you don't need it send it my way😄

guzzinerd · January 16

Beautiful radiator!

georgearoush · January 16

Thank you all for your insights, and no, I cannot give up the radiator. 😄

A follow-up question: based on what I have, is the return on the opposite side (the pipe going down on the right side in the picture), or is it on the left side where the intake is? Also, why isn’t the entire radiator heating up?

This happens even when I run the boiler for hours by intentionally setting the thermostat to 80. I have replaced the air vent and set it to fully open. I also checked both valves and they are fully open and free of debris. One thing I have not checked yet is the pitch of the radiator. However, the correct pitch depends on the answer above, specifically which side is the cold return.

I found a picture that suggests the cold return is on the right side of my radiator, which means I need to make sure the left side is pitched higher. Do you agree?

Jamie Hall · January 16

The return is usually the side with the vent. Also, usually — but not always — the return pipe is smaller than the feed.

But… in a two pipe air vent system, neither is always true!

As I said earlier, check the vent for operating correctly first…

mattmia2 · January 16

your not heating problem probably won't be helped by shutting off radiators. either the local vent is bad or steam is getting someplace it shouldn't or water is collecting someplace it shouldn't.

which end of the radiator that wont' heat fully heats first? it should start with the end away from the vent.

georgearoush · 1:42AM

@mattmia2, I have already replaced the air vent on the problematic radiators and verified that the valves are fully open and nothing is clogged. The affected radiator only heats about 1/4 of the way from the intake pipe (left side in the photo I shared above of my radiator). I have also set the air vent opening to the maximum.

Tomorrow, I will check the level of the radiator. Based on the diagram above, it looks like the radiator need to pitch downward toward the dry return pipe.

mattmia2 · 2:17AM

my guess would be that either water is trapped in the supply somewhere or steam is coming in through the return and closing the vent before the radiator can vent

dabrakeman · 3:02PM

Probably not the issue but do you have the same type of Ventrite vents on all your other radiators? Only ask because it is a rather slow vent even wide open, somewhere between a Gorton #4 and #5. If other radiators are venting much faster then could be simply balance.

pecmsg · 5:34PM

3rd floor I wouldn’t shut it off. If any water is trapped it might cause it to freeze and break the radiator and or piping.
just cover it with a towel or blanked and let the steam flow.

Shutting off a two-pipe steam radiator

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