Residential vacuum system?

ProblemSolver

looked at a job recently; there are two supply mains leaving the boiler area, one of them has another main branching off of it which makes a total of 3 mains. None of the mains have main air vents near the end "but" somewhere in the past, radiator air vents were drilled and tapped into the ells at the end of the main, before it drops vertical into a wet return. Just after the last radiator, on each main, the size of the pipe changes from 2" to 1". The 1" runs across the ceiling and then drops down to a wet return that is about 25 ft long.
None of this made sense to me; who would build a one pipe system like this - no main vents. Talking with someone about this, they mentioned a vacuum system. The house is about 90 to 100 years old, and about 1,800 sq. ft., 2 story; with a 5 year old Weil McLain boiler.
I have never seen a residential (average size home) vacuum system; how did they - what did they use to create the vacuum? (If this was originally a vacuum system). If it wasn't, then this thing must have eaten up a ton of gas to heat this home! I will get pic's on my next visit; I will be correcting all this; plus, moving one of the mains back about 18". Oh, just one more thing; No boiler header - No equalizer - No Hartford - No mud pipe! OK, that was 4 things...

Steamhead

If this is one-pipe and it was vacuum, there are two possibilities:

1- the air vents were a type that let air out but not in, which would cause the system to form vacuum as the coal pile burned down, or

2- each radiator had a special air vent that connected to a small air line that ran back to a vacuum exhauster in the boiler room. This was called an air-line or "Paul" system, after Andrew Paul who successfully marketed it. In this case you may find some of the old air-line piping still on-site.

Vacuum-type radiator vents are no longer made, but I think you can still get Hoffman #3 vents for the Paul system.

The lack of main vents was common, since many people reasoned they weren't needed because, with the original coal-fired boiler, the steam only came up once a day- so what if Junior's bedroom took an hour to get steam? Obviously with oil or gas firing we don't have that kind of time.

ProblemSolver

"The lack of main vents was common," 'Steamhead'
That might explain why on some systems the main air vents were right at the end, instead of 8" back from the end. Because they were added when converted from coal to oil. I always felt that if the dead men were so smart at engineering these systems, then why are the air vents in the wrong location.

Steamhead

It's not always a problem. They'll work fine installed like that, as long as there isn't water hammer or too much condensate in the pipe.

ProblemSolver

I forgot to mention. The home owner was unhappy with this steam system last winter, so he removed the radiator vents and added some plastic plugs. Based off how each radiator heated or not heated, he drilled a 1/16 or 3/16 hole in the plastic plug. He played with it awhile until every radiator heated at the same time. This, of course, also gave him humidity.

Dave in QCA

And of course, it will kill the boiler too.

ProblemSolver

was there yesterday to material list the job, and the trouble never stops. The boiler's EDR is 258 and the tally of radiators is 324. There is a small office room that is 70 sq. ft. (3,360 BTU), but the radiator in there is 67.5 EDR (16,200 BTU). There are two 2" mains; one with 5 radiators and the other with 4 radiators, and they return into a wet return that wraps around half of the basement. My suggestion is to tie the two mains together; re-pitch one of the mains, and make it a "one pipe - dry return" system. That will eliminate the wet return piping, give us about a 3 ft mud pipe at the boiler and reduce the maintenance on the boiler. Found out the house is 95 years old, and it did begin with coal.

ChrisJ

ProblemSolver said:

was there yesterday to material list the job, and the trouble never stops. The boiler's EDR is 258 and the tally of radiators is 324. There is a small office room that is 70 sq. ft. (3,360 BTU), but the radiator in there is 67.5 EDR (16,200 BTU). There are two 2" mains; one with 5 radiators and the other with 4 radiators, and they return into a wet return that wraps around half of the basement. My suggestion is to tie the two mains together; re-pitch one of the mains, and make it a "one pipe - dry return" system. That will eliminate the wet return piping, give us about a 3 ft mud pipe at the boiler and reduce the maintenance on the boiler. Found out the house is 95 years old, and it did begin with coal.

So the boiler's DOE output is 82,354 and radiation is 77,760?
Sounds like it'll work fine to me as well as the system is balanced correctly and that's one thing the homeowner proved with his plastic plugs.

Replace the plugs with proper vents that vent at the right speed and the boiler will do fine even if it's so called "undersized". From my view you have a boiler that's 4,600 btu's too much!


** Just noticed this is a vacuum system?
Either way the boiler is clearly not too small to heat the system. I wouldn't look at that as "another problem".

Steamhead

I'd replace that oversized radiator with a more-suitable one. If the room is that small they'd probably like the additional space it would leave.

ProblemSolver

Steamhead: That has been already determined; thanks.

ChrisJ: 77,808 is the total heating capacity of all the radiators in the home. 62,000 is the steam BTU the boiler can produce. Or, the total EDR of all radiators in the home is 324.2, and the total EDR the boiler can produce is 258. No, the boiler is not big enough, and it is no-longer a vacuum system. We are going through every room and re-designing this system in hopes that we can make the existing boiler work.
Thanks for your reply guys!!!...

BobC

With a plate rating of 258 sq ft that boiler should produce 343 sq ft of steam. The difference is for pickup factor (33%).

If you can produce 343 cu ft of steam and you have to feed an EDR of 324 you should have steam to spare IF YOU INSULATE ALL THE PIPING YOU CAN REACH.

With care that boiler should be ok, a bit close but ok.

Bob

ChrisJ

ProblemSolver said:

Steamhead: That has been already determined; thanks.

ChrisJ: 77,808 is the total heating capacity of all the radiators in the home. 62,000 is the steam BTU the boiler can produce. Or, the total EDR of all radiators in the home is 324.2, and the total EDR the boiler can produce is 258. No, the boiler is not big enough, and it is no-longer a vacuum system. We are going through every room and re-designing this system in hopes that we can make the existing boiler work.
Thanks for your reply guys!!!...

BobC said:

With a plate rating of 258 sq ft that boiler should produce 343 sq ft of steam. The difference is for pickup factor (33%).

If you can produce 343 cu ft of steam and you have to feed an EDR of 324 you should have steam to spare IF YOU INSULATE ALL THE PIPING YOU CAN REACH.

With care that boiler should be ok, a bit close but ok.

Bob

Like Bob said, the boiler's alleged sqft rating includes a 33% pickup factor which in my opinion often isn't necessary.

I'm also confused, you say none of the piping is big enough and the boiler is way too small and yet all of the radiators heated fine? What's the problem?

If he could balance it using plastic plugs you can balance it using vents or orifices.

ProblemSolver

Sorry Chrisj, I didn't mean to lead you into thinking the plastic plugs balanced the system through & through; it did not!
He still had radiators that would not give out much heat, but it was an improvement.

ChrisJ

ProblemSolver said:

Sorry Chrisj, I didn't mean to lead you into thinking the plastic plugs balanced the system through & through; it did not!
He still had radiators that would not give out much heat, but it was an improvement.

Ah, I see.
Sorry for the misunderstanding.

ProblemSolver

BobC said:

With a plate rating of 258 sq ft that boiler should produce 343 sq ft of steam. The difference is for pickup factor (33%).

Bob

The beauty of getting back into this stuff. That pickup factor slipped my mind; thanks for mentioning it. If he replaces that over sized radiator with one smaller, he'll be just fine.

ProblemSolver

Bob

Folks get confused a bit when only the full output of all the rads is considered. This would only be necessary if the rads exactly matched the heatloss of the building................very rarely the situation.

Good information to consider. But it will be used on future systems I encounter. The home owner (an aerospace engineer) lost his patients with my schedule and accepted another quote. I guess the other contractor wasn't as busy as I, and was able to get to him quicker.
I was working on 3 large bids; I lost the steam job, but gained a 4 furnaces - 3 A/C's - 4 humidifiers - 4 high efficient air filters - and improving the duct system on the 2 larger systems.
The engineer had most of the summer to get his steam lines moved and corrected, but he waited until September. Does this sound familiar guys?