Upstairs radiators are very oversized

MilanD

Fantastic thread, guys! I am wondering if a check valve like this before a vent on a 1-pipe system radiator would achieve the same effect if installed on all radiators and main vents...

ChrisJ

MilanD said:

Fantastic thread, guys! I am wondering if a check valve like this before a vent on a 1-pipe system radiator would achieve the same effect if installed on all radiators and main vents...

Perhaps.
The problem is how will you balance the system if anything is wrong? For example my bedroom radiators are grossly oversized.

MilanD

> @ChrisJ said:
> Fantastic thread, guys! I am wondering if a check valve like this before a vent on a 1-pipe system radiator would achieve the same effect if installed on all radiators and main vents...
>
> Perhaps.
> The problem is how will you balance the system if anything is wrong? For example my bedroom radiators are grossly oversized.

I'm thinking put a check valve in line with the vent? Or, a small ball- valve with which to control venting? I keep thinking how to do Igor's vacuum system without adding lines to rads and a pump...

ChrisJ

MilanD said:

> @ChrisJ said:

> Fantastic thread, guys! I am wondering if a check valve like this before a vent on a 1-pipe system radiator would achieve the same effect if installed on all radiators and main vents...

>

> Perhaps.

> The problem is how will you balance the system if anything is wrong? For example my bedroom radiators are grossly oversized.



I'm thinking put a check valve in line with the vent? Or, a small ball- valve with which to control venting? I keep thinking how to do Igor's vacuum system without adding lines to rads and a pump...

Once you create a vacuum, the stronger it gets, the faster all radiators will heat......regardless of vent size.

PMJ

@ChrisJ,

I'm not sure what you mean by this:

"Once you create a vacuum, the stronger it gets, the faster all radiators will heat......regardless of vent size."

I don't find this to be the case.

Natural vacuum cycles every burn from its deepest to zero/slightly positive pressure when you push out a small amount of air that has leaked back in every burn cycle. I charted this cycle somewhere in another post. I don't find that big rads just keep filling and filling. I find that the fill amount is pretty consistent (partial on all) and a little more or a little less is grabbed by colder area ones depending on conditions. But all remain partially full cycling at roughly 3cph.

I can't say for sure but I suspect that if the checks were after your current vents your one pipe would be the same. A portioned first partial fill by your current venting. Vacuum/small and short pressure releases again by your venting each cycle after that. If all the checks had a .5psi cracking pressure and for those short 2 minutes 3 times and hour that I do to push out a little more air your whole system had to go that much higher I don't think it would hurt a thing.

ChrisJ

> @PMJ said:
> @ChrisJ,
>
> I'm not sure what you mean by this:
>
> "Once you create a vacuum, the stronger it gets, the faster all radiators will heat......regardless of vent size."
>
> I don't find this to be the case.
>
> Natural vacuum cycles every burn from its deepest to zero/slightly positive pressure when you push out a small amount of air that has leaked back in every burn cycle. I charted this cycle somewhere in another post. I don't find that big rads just keep filling and filling. I find that the fill amount is pretty consistent (partial on all) and a little more or a little less is grabbed by colder area ones depending on conditions. But all remain partially full cycling at roughly 3cph.
>
> I can't say for sure but I suspect that if the checks were after your current vents your one pipe would be the same. A portioned first partial fill by your current venting. Vacuum/small and short pressure releases again by your venting each cycle after that. If all the checks had a .5psi cracking pressure and for those short 2 minutes 3 times and hour that I do to push out a little more air your whole system had to go that much higher I don't think it would hurt a thing.

We can and do often use vent speeds to cheat and hold. back rads that are oversized. My point is you won't be able to do that with check valves.

PMJ

@ChrisJ ,

What is it about a check valve that would make your vents no longer variably resist the flow of air out just as they do now whenever it was needed that air flow out?

ChrisJ

> @PMJ said:
> @ChrisJ ,
>
> What is it about a check valve that would make your vents no longer variably resist the flow of air out just as they do now whenever it was needed that air flow out?

I'm thinking the lack of air in the radiator might have something to do with it.

Intact a trv with a stuck vacuum breaker even can cause issues even without check valves on the other rads

PMJ

> @ChrisJ said:
> > @PMJ said:
> > @ChrisJ ,
> >
> > What is it about a check valve that would make your vents no longer variably resist the flow of air out just as they do now whenever it was needed that air flow out?
>
> I'm thinking the lack of air in the radiator might have something to do with it.
>
> Intact a trv with a stuck vacuum breaker even can cause issues even without check valves on the other rads

The only time you need to expell air the entire system would be at positive pressure. I'm not seeing the problem. I think at positive pressure checks will open and vents will variably resist the flow as per always.

ChrisJ

@PMJ I mean..... I don't even know what to say at this point.

MilanD

@Chrisj @PMJ

Guys, I think issue is making sure cracking pressure is in fact 0... for what I understand it's often not the case in the field with production check valves. Also, issue is making sure that check valve continues to work through many cycles on that low pressure and does not hang up. That being said, see this -

https://forum.heatinghelp.com/discussion/163498/back-to-vacuum#latest

There was another post on 0 psi cracking pressure check-valves, in addition to one above, but now I can't find it. It was actual production valve, with a gate but without a spring - or you can remove the spring. I can't find it now nor remember...

In my mind, I think the biggest issue may be having, say, 10-12 rads and 10-12 check valves of which 1 or 2 may hang-up and throw the whole system out of balance, let alone having cold rooms on those rads on which this mechanical check valve hangs up. Most of us here on this board are ok with managing our systems, but the vast majority of steam-heating home owner folks out there are at best clueless on how their heating works exactly.

Thus, for a fool-proof system on 1-pipe, Igor has done the vacuum lines instead of vents, on some kind of controller, and your average home owner does not have to worry about it... Definitely more work to retrofit and more moving parts, but again, for an average home owner, more stable and consistent operation.

I have in the neighborhood of 33 radiators in our building on a 1-pipe system, plus a condensate tank on the boiler float-controlled pump... That would be a lot of check valves to buy and install.. including on the tank that's not pressure rated... (it'd probabaly do fine, but again...) Then, one has to monitor all of this so that it all work as it should...

I can see why vacuum is such an elegant solution on a 2-pipe, and so obviously easy to implement on a 2-pipe, as PMJ has in fact achieved, creating for all practical purposes a modulating steam system. Not saying it's not possible on a 1-pipe, just that it is very much dependent on a every single vacuum vent (aka check valve with a vent) working as it should. There used to be 1-pipe mechanical vacuum vents in the past, no? They are no longer being manufactured and I am venturing to guess it's precisely because a little bit of dirt that nowadays can hold the regular vent open or closed can do the same thing on a vacuum vent, with the exception that vacuum one staying either open or closed will throw entire system out of balance. More so on fail open than fail closed.

Koan

@PMJ and others: Wondering if you think this might work:
CONBRACO (APOLLO) 61-104-01-A1 . There is a Zero psi cracking pressure option if you remove the spring and operate vertically. I called Apollo and they said the spring can just be removed.

Koan

here is a link

https://supplyhouse.com/Apollo-Valves-6110401-3-4-Threaded-Bronze-Spring-Check-Valve

MilanD

Koan said:

here is a link

https://supplyhouse.com/Apollo-Valves-6110401-3-4-Threaded-Bronze-Spring-Check-Valve

that's the one I was referring to in my earlier comment... Thanks @Koan !

nicholas bonham-carter

I think I now understand what Chris is talking about:
If the system has had all the air removed, then the steam will fill all the radiators, assuming a long burn. This means that any rooms with larger than needed radiators will be overheated.
Is this correct?
At least on two pipe systems, there is the option of throttling down any oversized rads, but not so on one pipe, unless you have a sort of Paul setup where the supply is into the vent tapping, with a needle valve there.—NBC

ChrisJ

> @nicholas bonham-carter said:
> I think I now understand what Chris is talking about:
> If the system has had all the air removed, then the steam will fill all the radiators, assuming a long burn. This means that any rooms with larger than needed radiators will be overheated.
> Is this correct?
> At least on two pipe systems, there is the option of throttling down any oversized rads, but not so on one pipe, unless you have a sort of Paul setup where the supply is into the vent tapping, with a needle valve there.—NBC

Yes except I bet even a partial vacuum will cause the problem.

PMJ

There is a lot of misconception about what natural vacuum will and will not do because of a great lack of actual experience with it.

The only actual INCREASE in the fill amount of steam in any radiator can only occur with the burner on and the system in positive pressure. In the pressure condition the rate at which new steam flows into rads and they are "filled" any more than they currently are or were last cycle is determined by adjustable valves in two pipe systems and adjustable vents in one pipe systems. This is the same way everyone runs now.

To go into vacuum the boiler must first turn off. From the very instant it does the fill level of every rad( big and small) begins to DECREASE, not increase from wherever it was when the flame went out. The total amount of steam condensing in all the rads is way more than can be supplied from what is in the mains with the boiler off. Natural vacuum merely causes the rate at which the fill level in the rads DROPS to be much lower than it would be in a vented system. It does this by causing the boiler to continue to make a small amount of steam as the pressure drops(whereas a vented system makes none) and this small amount of steam continues flowing forward to the rads(whereas in vented systems it does not). The net effect of these two things is a moderately more efficient system with significantly more even heat.

Look at it this way - vacuum does not cause any filling of radiators to a level beyond where they were with the burner on at the end of the last run. Vacuum only resists emptying when the burner goes off. Vacuum also causes some adjusting of fill levels favoring colder areas by steering more flow to those areas. But temperature around the rad is the driver there, not its size. In fact if a bigger rad were to heat its room to a higher temp than others it would then begin to draw less than others while in the vacuum state automatically.

ChrisJ

@PMJ So now you're saying your system fills with air on the off cycle so it still has to push it back out every cycle

Before you were saying it did not and that was the best part of a vacuum system.


Either it does and vents will regulate or it does not and vents will not regulate good.

Which is it?

PMJ

ChrisJ said:

@PMJ So now you're saying your system fills with air on the off cycle so it still has to push it back out every cycle



Before you were saying it did not and that was the best part of a vacuum system.





Either it does and vents will regulate or it does not and vents will not regulate good.



Which is it?

Where did I say my system fills with air on the off cycle?

ChrisJ

So being it does not how would vents hold certain radiators back more than others during each cycle to keep a system balanced where some radiators are oversized for the areas and others are not?

PMJ

1. You run your system on the first burn to fill levels controlled by your vents to appropriate balanced amounts as you do now.

2. From that point when the burner goes off and if all vents were checked, vacuum starts forming, rads start emptying, but emptying much slower than you do now because some steam is still entering from the mains. Not as much as is being condensed, but significantly more than zero.

3. Some time later at the deepest part of the vacuum the burner fires again. Steam races out to fill the void left by all the steam that has collapsed. It fills back up your system exactly to where it was when the burner went off but much faster and more easily than pushing an entire system worth of air out each time. The vacuum is slowly disappearing during this burn. At the point that the system pressure just hits the same as the outside atmosphere (no more vacuum) you are almost exactly filled to where you were in all rads all places like it was when the burner went off the previous cycle but not quite as some air has leaked back in.

4. From the point at which you just hit positive pressure inside your system you continue to run and push out the very small amount of air out that leaked back in. In this very short time period of positive pressure your venting controls the exit of the air just as it always has and holds some rads back the same way you always have.


I charted all this in a post somewhere. I can find it again if you like. I am at positive pressure maybe 9 minutes an hour. That is when all the additional "filling" goes on and it is controlled by my valves.

I think this is what is missed. It isn't one or the other, vacuum or pressure. Each cycle is a combination - heavily in favor of vacuum. Because when you don't let air back in there is very little (re)filling to be done - very little time spent in pressure pushing air out. It is fill once and all cycles after that are simply putting steam back into the void. But whatever further filling of rads and the additional pushing out of air that requires is done in a pressure condition and controlled by vents and valves just like a vented system.