Any downsides to closing feed valve (round knob) on the radiator in empty rooms to save oil ?

CoachBoilermaker

Any downsides to closing feed valve / shut off valve (round knob) on the radiator in empty rooms to save oil?

This article talks about how motorized zone valves throw off the pressure balance in a steam system, which makes condensate not flow back, which causes knocking. The boiler is also now oversized for the system, creating too much steam. More knocking. Does closing off a radiator also disrupt the pressure balance like this?

If "zone valves = bad"

https://heatinghelp.com/news-and-media/dead-men-tales/a-disastrous-decision/

But now, you've decided to add some motorized zone valves to the boiler side of the steam main. You're doing this to save energy. It seems to make sense with a steam system because it makes so much sense with hot-water-heating systems. And how different can those systems be? So you do it.

Now, as long as those motorized valves are wide open, everything will be just fine. But as soon as one of them closes, the “leftover” steam pressure that you were depending on to be at the end of the main suddenly vanishes. Now, all you have going for you is gravity, and there’s not enough of that to put the returning condensate back into the boiler because there isn't enough vertical stacking space for the water to build static pressure. So the condensate backs up into the main and lays there. It's waiting for the motorized valve to reopen. And when the valve does reopen, Mr. Steam comes raging through the valve at about 60 miles per hour. He meets Mr. Condensate and knocks him on his keister and then sends him flying down to the end of the main where Mr. Condensate hits with enough force to knock the building off its foundation. They can hear it in New Zealand.

Jamie Hall

It depends entirely on whether you are talking about one pipe steam or two pipe steam. If you are talking about two pipe steam, closing — or adjusting — the inlet valve on a radiator will cause no problems at all. Go for it. Just try to avoid having that now cooler room warm enough to avoid condensation problems in there!

Yes, it will oversize the boiler a little more — but so long as you don't have a water hammer problem now, you won't cause one by closing off a radiator. What you will do is shorten the on cycle time of the boiler, but you probably won't notice that unless you are a fanatic.

Now if you are talking about one pipe steam, that's a different story. Don't do it. Why? Because that valve will almost certainly leak just enough to let a little steam in there — which will then condense, but that condensate will have nowhere to go and you can get hammer problems. With one pipe steam, the simple way to reduce heat from a radiator is to close the vent. Most vent types that's easy — just turn them upside down. Done.

The article you referenced —which is quite correct — refers to zone valves on mains. There you can have serious problems with water hammer, and the piping and valving has to be arranged so that the lack of return pressure doesn't happen. Yes it can be done, and on some systems it's easier than others, but it takes thought.

But a single radiator, at the radiator, on a two pipe system? Not a problem.

bburd

No, radiator valves are different from zone valves.

For two pipe steam, feel free to turn off the supply valve.

For one pipe steam many people say not to shut off the supply valve because some condensate may get into the radiator and back up there. I have had good luck doing it if the valve is in good condition and shuts off tightly. If not, you can completely close the air vent if it's adjustable, or turn it upside down if not to prevent the radiator from heating.

Do beware of the possibility of condensation in unheated rooms that are part of a heated structure. This can cause mold, mildew and structural damage. Keep an eye on them, especially in very cold weather.

CoachBoilermaker

Thanks for the replies.

I have single pipe. Inlet valve on one side, air vent on the other side. The air vents are not adjustable

If you end up with condensate stuck in the radiator, how do you drain it? Turn off heat for a few hours until radiator cools and drains?

Maybe this is a chance to replace air vents with modern adjustable ones? I think it makes sense to at least have some low heat in the room to prevent mold/mildew

DCContrarian

The thing to keep in mind is you won't save as much oil as you might think.

The shut off rooms will be somewhat colder. The rooms that are adjacent to them will lose heat into them, the heat in those rooms will have to work harder to make up for that lost heat.

A numerical example: Let's say it's 70F inside and 20F outside. You decide to cut off the heat to half the house and now that half is at 55F. The average temperature of the house is now 62.5F, instead of a 50F difference with the outside there is now a 42.5F difference. This reduces the amount of heating needed by 15%. So cutting off the heat to half the house reduces the heating load by 15%.

bburd

If condensate is stuck in the radiator, open the valve and let it drain out. If it won't, you may have a pipe pitch problem.

Most here seem to like Vent-Rite for a quality adjustable vent. Dole, now owned by Tunstall, is another good one, though I am only familiar with their older models. The ones that home centers sell are usually poorly made and do not close down well.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1809716#Comment_1809716

Good point, but does it really average out like that? 3 bedrooms, 2 are shut, doors closed, I can't imagine all 3 rooms will have the same average temp

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1809717#Comment_1809717

Oh, that makes sense. Just open valve and it should drain immediately.

I saw MikeyPipes recomend this brand also:

925005-00 Angle VARI-Valve (Heat Timer)

CoachBoilermaker

Main reservation I have with DIY vent replacement is worried that it breaks off.

Air vents could be 100 years old and stuck

bburd

The heat timer vari valve has a very high venting rate and does not close down well. It's not an effective choice if what you want to do is greatly reduce or stop heating from a radiator.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1809748#Comment_1809748

Can you explain what you mean by "high venting rate and does not close down well" ?

So, I should stick with this?

https://www.ebay.com/itm/383301771227

CoachBoilermaker

The Heat Timer Vari-Valve is a type of air vent used on steam radiators. Steam heating systems work by pushing steam through pipes and into radiators, where the steam gives off heat. The air inside the pipes and radiators needs to escape for the steam to take its place, and that's the role of air vents.

The Vari-Valve has an adjustable venting rate, meaning you can control how quickly air escapes from the radiator. A higher venting rate allows steam to enter the radiator faster, heating the room more quickly. However, it has limitations in controlling or stopping heat altogether.

Here’s why:

1. High Venting Rate: Even at its lowest setting, the Vari-Valve has a relatively high venting rate compared to other radiator vents. This means that air is vented quickly, allowing steam to enter the radiator and heat up the room faster.
2. Doesn't Close Well: Unlike other vents that might close completely to stop steam from entering the radiator once it’s filled with steam, the Vari-Valve isn’t designed to fully stop heating. This means that even if you try to reduce the heat by adjusting the vent, it might still allow enough steam in to heat the radiator, making it ineffective for completely shutting off a radiator or reducing heat significantly.

In short, if you're looking to have precise control over how much heat a radiator emits—or to stop heating from a radiator altogether—the Heat Timer Vari-Valve may not be the best option. You'd likely want a vent that can close completely or a thermostatic valve that provides more precise temperature control.

bburd

https://forum.heatinghelp.com/discussion/comment/1809778#Comment_1809778

I would.

delcrossv

Had a world of problems with a boiler that would consistently overfill. Until I found the "closed" radiators that would fill with condensate triggering the auto feeder and then drain back between cycles, flooding the boiler.

Easy way to shut off a radiator is to replace the vent with a 1/8 brass plug. If the air can't leave, the steam can't enter.

CoachBoilermaker

https://forum.heatinghelp.com/discussion/comment/1809863#Comment_1809863

This was due to a faulty shut off valve? I am not going to risk this.

I will try to install variable air vents and just keep the closed rooms on lower heat, and not totally off