Theory time.

Charlie from wmass

What would happen on a small one pipe steam system if I were to plug all the radiator vents and apply a deep vacuum to the main vents?

Canucker

Constant vacuum at the main vents or bringing the system under vac at that point then isolating it?

Charlie from wmass

Once the system is purged of air we would control the out put by varying the amount of vacuum or pressure needed for the heat loss.

Charlie from wmass

@Canucker vacuum until air is purged then isolate it.

Canucker

Charlie from wmass said:

@Canucker vacuum until air is purged then isolate it.

Well, you would have a much lower boiling point, depending on the amount of vacuum, but i don't think it would travel through the system any faster unless you had a vac supply at each radiator

Charlie from wmass

I actually looked at a system like this only two pipe in Vermont several years ago. It had a control like they use to control pasteurizing equipment for milk. The controls were controled by an outdoor sensor but had long ago gone into disrepair.

Hap_Hazzard

The water will start boiling at ~25 mbar (~.0246 atm) at room temperature.

izhadano

Charlie from wmass
What would happen on a small one pipe steam system if I were to plug all the radiator vents and apply a deep vacuum to the main vents?
--------------------------------------------------------------
Charlie, welcome to "vacuum" club !!! That's a point where I've started my tinkering ...
In perfectly sealed one-pipe system under vacuum, you'd get many benefits:

• reduced heat up time
  
• controlling vapor temperature by oscillating boiler within chosen temperature/vacuum interval
  
• reduce corrosion,
  
• improved boiler operation.
  
• zero water loss/treatment
  
• etc.
  

Unfortunately, in real world the steam systems are old and leaking. Air sucked into the system prevents vapor entering into radiators and deteriorate system performance.
The trick can be done, though, with "vacuum boost" method.
Please, let me know if you may have a project ready for "vacuum boost".

Charlie from wmass

@izhadano I will try it in my own home first. We can discuss te details when I am closer to starting it.

AMservices

A recommendation.
Pressure test the system (25 psi) to find leaks before pulling vacuum.
Hopefully all your piping is exposed and you can soap all the joints.
I would try heat silicone if you find a leak in the middle of a main rather then going crazy pulling it apart until you know it will work the way you want it to.
Have you thought of a control your going to use for the burner?

Charlie from wmass

@AMservices , do you know who I am? Lol

jumper

Evacuate air and isolate. Control by enclosing radiators in louvered boxes or simply throw blankets on rads when you're too warm. Air is bad,bad,bad.

Charlie from wmass

Okay, you guys are just messing with me now.

AMservices

Only from the post here. I sure your on top of it.
Vacuum/steam heat technology is a new found obsession with me and I wanted to know how your going to go about it.
I've been trying to help izhadano find a test site and I asked him the same question about just plugging the radiators and pulling 1 good vacuum.

Charlie from wmass

See I was not meaning pull the vacuum.and plug the pipe.

AMservices

So you would always have a vacuum in place tied into the main vents? Controlled by a vacuum switch

Charlie from wmass

My question really should have been if I draw a vacuum from my Mains in the basement will the steam displace the air throughout the rest of my system without pulling from each individual radiator? If it does not does that mean that I would need to run tubing like in a Paul system down from each radiator? If I did run individual tubing could I run that to a location on the same floor and then run an individual drain down to the basement? I ask this because I live in a two-story duplex Upstairs Downstairs not side by side.

AMservices

"the devil is in the details"
It was explained to me that because you won't be able to create a perfect vacuum, there will still be air left in the system when the steam is starting to fill. You only need 15-18" vacuum to have 180-170 degree steam in the radiators.
The steam will then push the remaining air up into the radiators and that's why the vacuum lines needed to be there instead of at the ends of the mains.
You won't have a balanced system if you can't get all the air out of the radiator

Charlie from wmass

Steam is less dense than air. Why would the steam not displace the air?

AMservices

This team is going to push the air up into the radiator and it will be trapped. How is the are going to go backwards down through a single pipe system?

Charlie from wmass

Same way the condensate does. That is why we use such large diameter pipes.

AMservices

The condensate can drain back through the steam, but air won't.

Charlie from wmass

Guess we will see.

ChrisJ

My idea was to build an all copper steam system, all brazed joints and properly sized radiation for each room as well as proper lengths to each radiator to maintain balance, i.e. meanders to closer ones.

Then pull deep vacuum, fill with water and then top off with argon, nitrogen, helium etc to raise the pressure to what I want to boil at.

A 100% hermetic steam system. No leaks, no vents, no air.

I picture it sort of like a huge multi-legged heat pipe.

hvacfreak2

I think that pulling from the mains would work just as well. A call for heat starts the pump , pump is stopped when vacuum setpoint is made , burner starts ( or something similar to that ) . Maybe Paul ( Paul System Paul ) had to run his pump differently ( constant , no start / stop control available ? ) , or perhaps just going for the theoretical ideal ? Another idea would be to place the vacuum transducer ( for pump control ) at the furthest radiator to ensure complete evacuation. Either way there should be no air to deal with if the system holds in a negative pressure.

AMservices

Paul was using his own "steam exhauster" (not a pump) to make a vacuum.
He could do that because there was usually a process steam boiler in the vicinity making electricity for the building.
Having a pump make the vacuum is different. You can't let the steam hit the pump.
The thing is, your not going to get all the air out of the system pulling a vacuum, lighting the burner and expect to have a balanced system.
If you could get the vacuum down to something like 300 microns, ok you have a chance. In fact steam would already be in the radiators at that level. You will be boiling water without lighting the burner.
If you try to pull a vacuum from 1 spot, then steam starts to fill the system, all the air that hasn't been removed is going to show itself in the top of the radiators, with no way out. Even if it's not found in all the radiators or its only stopping half of half the radiators from heating up all the way, it causes an in balance.
Paul had special valves too, that would work just like air vents, closing when the steam was there.

hvacfreak2

I see what you mean regarding " balancing " , it's not as simple as pulling a vacuum and everything be wonderful. But I have to imagine that much of this balancing has to take place on the entering steam side of the radiator for a system like this ( fixed oriface plate for example ). But aside from that I can assure you that many evacuations take place evey day from a single point.

Lets say that 300 microns with water present isn't going to happen and that our target is something like 20 inches hg ( another wild guess ). With our pump control at the furthest radiator I have to believe that all of the air is comming out of the system when the pump stops ( and the safety valve closes to protect the pump , Belimo B series ball valve example ).

AMservices

20 Hg is only 72% of a full vacuum, leaving 38% of the air in the piping.
On a 2 pipe system the steam could push the air out through the return side and you can control the balance with an orifice, but only a single pipe system , the steam is going to be pushing the air into the top of the radiators. That's why the Paul system had them at every radiator.
Job cost was always a concern for these guys and if they could have done it with 1 vacuum line, I think they would have.

hvacfreak2

I pulled 20 inches out of the air for the conversation , but with that water in the system I can't see going down too much below that from practical experience. But you are right that there has to be air in the piping up to 28 plus inches , I was mistaken in my thinking on that. The Hoffman catalog lists " Paul " radiator vents as " current production " items as of last year when I was browsing. I'll bet that we have better pumps ( for smaller systems ) and controls available these days since the previous generations efforts on this subject just to say.

jumper

Air is bad but 28" is only about 3%. That's better than 0" and eliminating air with steam at each radiator vent. You burn valuable fuel to produce steam and it's a poor use of that steam to move air. Especially when that rad vent is going to let all the air back regularly.

Jamie Hall

@Charlie from wmass -- I have very seriously considered replacing the vents on my system (one Gorton#2 and one Hoffman #75 with three or four #76 vents. Trouble is, they aren't cheap. Nor do I know how tight the rest of the system is... Might be interesting to look at, though.

Charlie from wmass

The 76 vents are far slower than the Gorton 2. I think changing the cross over traps could really speed things up.

AMservices

Charlie from wmass
Your theory is haunting me. Mostly because I've had the same one. Even though my head is saying "if it could work like that, it would have been done", my Hart still wants it to work.
So here's how I would test it.
The goal here (in my mind) is to have a single pipe steam system, without having a mechanical vacuum pump in place, no air vents with Check valves, just a system that will maintain its own vacuum to first lower the boiling point of the water so to have lower temperature steam finding it's way to the coldest spots in the system, making it self balancing. You would only have to fill it with water once, because it will be locked in the system. The piping will stop rusting inside because there won't be any oxygen to oxidize with the steel pipe and you could heat your house with a couple of candles under the boiler.

If it sounds to good to be true, it's probably a pipe dream

First the piping needs to be tighter then a frogs A-hole, So plug the vents, but I would put hot water bleeder vents in place rather then plugs. pressure test the system 25-30 psi. Patch it up and move on
Second open all the bleeder vents and fire the boiler, and just as you would purge air from a hot water system start closing vents as the steam is filed in the radiator (probably with a long screwdriver).
When all the pipe and radiators are all the way hot and all the vents are closed, let the boiler cycle off on 1 or 2 psi just to pack it in there a little, then shut it down and watch the vacuum gauge drop.
I would hope to get 27-28hg. If you can get that much of a vacuum to hold ideal between heat cycles, then the little air that's left would displace and not have a huge impact on the radiators (I'm guessing) .
Then I'd probably control the firing with a tekmar or something else with outdoor reset.
Getting that level of vacuum will be easier with the steam then a vacuum pump. And if you want it to do that every time after, might as well let it from the start.
Again I would think if it could be done like that it would have been done.
I would be afraid to perform this test because of what the Mythbusters did with steam and a tanker truck.
https://youtu.be/UpWeU2fvFGs

You never know

Hap_Hazzard

AMservices said:

It was explained to me that because you won't be able to create a perfect vacuum, there will still be air left in the system when the steam is starting to fill.

You can't get a perfect vacuum in a system with water in it. You could probably evacuate all the air, but then the water vapor would take its place.

AMservices

I know you can't have a perfect vacuum, that has been proven to be impossible.
My thinking is if the steam piping can hold 27 - 28 inches of mercury, only having 3- 5% air in the system, then Steam vapor would have the room to reach all of the radiators displacing remaining air. The boiler can be controlled by temperature, 180°F will put the vacuum at 15hg.
Then one the burner is off the steam will condense and return the 27-28 Hg.
Unless the system is hermetic it will be impossible. it's still fun to talk about

ChrisJ

I personally see no reason the typical steam system, with all valves removed couldn't achieve 500 microns.

Cast iron radiators aren't like a thin steel tanker. An oil tank is closer to that if anything.

Think of how strong a cast iron radiator is compared to the typical aluminum or copper condenser and yet we can pull 200 microns on those.

AMservices

I don't think the radiators would collapse. But if somebody had used say a copper pipe on a run out to a radiator that might have a dent or imperfection about it, that might collapse.
I know what you mean though I pull vacuums on a daily basis and never collapse the coil or a line set.

ChrisJ

Perhaps it's time to stop with the theory.

Who has an extra boiler and some radiators on hand?
Slap it together out in the garage using some soft copper tubing or something and pull a vacuum on it. Anything with 3 or 4 radiators should be plenty.

Even some baseboard, just give it some pitch.

Canucker

There is a practical limit to how much vacuum you want in a heating system. Too much vacuum will lower the boiling point to a level that won't heat the room. The rads will be warmer than the steam in the system, possibly causing them to sweat. At that point you've got AC using R-718 refrigerant

AMservices

I was thinking more like a copper pot, 1/2 gallon of water, some sterno's for heat and some fin tube baseboard

ChrisJ

Canucker said:

There is a practical limit to how much vacuum you want in a heating system. Too much vacuum will lower the boiling point to a level that won't heat the room. The rads will be warmer than the steam in the system, possibly causing them to sweat. At that point you've got AC using R-718 refrigerant

If you go back you'll see I mentioned topping the system off with nitrogen, argon or helium to get the pressure you want.