Vent placement in home 2-pipe steam heat system

pacoit · June 9

Hi, I have a roughly 110-yr-old house. It takes about 10-15 min for the radiators to heat up, and the boiler turns off before they heat half-way. In the basement, each return has a Hoffman air vent near the ceiling. They were I think added ~50 years ago. I don't know what the previous setup was. The beautiful quiet boiler from circa 1924 was replaced 25 years ago. The original header piping was retained.

I can provide much more info; but to start off with a simple question, I would like to know generally if the venting location described is reasonably proper or inherently improper? Thank You.

Cheers

EBEBRATT-Ed · June 9

The vents can go at the end of the steam mains or back by the boiler if you have dry returns. Pictures will help

pacoit · June 9

Here are some photos. Thanks.

JUGHNE · June 9

That is a radiator vent, too small for the steam main vent, only a fraction of what you should have.

Do you have any more? You should be able to hear this small vent pass air upon start up and for quite a while after starting.

Jamie Hall · June 9

Is this one pipe or two pipe steam? The best venting locations are different… among other things.

Steamhead · June 9

First off, that asbestos insulation needs to be removed. You will need a licensed abatement company for that.

Second, the piping around the boiler is all wrong. That Carrier boiler is a re-branded Dunkirk, and Dunkirks are extremely sensitive to improper piping. The manual is here:

https://dunkirk.com/wp-content/uploads/2024/08/240013806-Rev-B-Generic-Steam-IOM.pdf

The steam needs to enter at one end of the header, and the drip must be at the other end. The present piping has steam coming in from two directions, which can interfere with condensate (water) drainage.

The vent in the pic is a radiator vent, which is too small. Are there vents at the ends of the steam mains?

How about a pic of a radiator that has an original shutoff valve and return fitting?

EBEBRATT-Ed · June 9

NBP is all wrong but with a header that size…………………………..

Venting is all wrong

pacoit · June 9

Thanks for the comments and manual link! It is 2-pipe steam. The vent in the photo is indeed a radiator vent (Hoffman 1A) attached to a return pipe. There is a vent on each return.

The radiators have no steam traps. See radiator pic.

The header is original configuration. It looks pretty fat, but it may be thick insulation; I'm not sure. Is the mains between the two outlets necessarily that bad always?

EBEBRATT-Ed · June 9

I wouldn't change it if the boiler steams ok and you don't get any banging its probably ok. But if you change the boiler then it should be fixed.

mattmia2 · June 9

It is a vapor system of some sort. The radiator valves are special metering valves that admit less steam than the radiator can condense so it all condenses before it reaches the return. The boiler needs to keep the pressure under 8 oz/in^2 or so. The main vents need to be much larger because that is where all of the venting of the system takes place.

Steamhead · June 9

@pacoit , can you get a close-up of the emblem on the side of the shutoff valve? This may help us ID your system. Also, where are you located?

pacoit · June 9

Here's a close-up of the radiator valve (they are all the same).

The house is ~3,400sqft over 3 floors (including the originally finshed attic floor). It has 19 radiators. The mains travel around the perimeter of the basement with risers branching upward every so often. There are I think 2 places in this basement distribution with initially weird looking piping. But I think now that they provide a wet return opportunity when some steam may condense before rising to the radiators?

There is a riser to the master bedroom that bangs and the radiator doesn't heat unless it is very cold outside. It will heat if I loosen the return pipe (let air escape); but replacing the vent didn't fix the problem.

What I would like to know is if the system radiators should heat up within 3min?, 5min?, 10min?, 15min? What is normal for a proper functioning system? Mine takes 10-15min and turns off before the radiators a half hot (or warm). I'm guessing that is too long and so I may be consuming more gas than I should. Thanks.

Steamhead · June 10

That looks like a spring-packed valve. The "S" might mean Sterling, but might not. This may be a Vapor system that was put together from a mix of standard parts. There is a dizzying number of possible vapor variations- go here to see:

https://forum.heatinghelp.com/discussion/178152/a-listing-of-vapor-systems-that-dont-yet-appear-in-lost-art

It's important to remember that when your system was installed, the boiler was coal-fired. A coal fire typically begins generating steam in the morning after someone shakes the grates, throws on more coal and opens the dampers. So it only fills the system with steam once a day- so what if Junior's bedroom is the last to get hot? Once the steam arrives, the radiator stays hot all day.

With oil or gas and their on-off-on-off firing cycles, the situation is very different. This can result in uneven heating, since the radiators closest to the boiler get steam first. This is why main vents are so important now- if the air can get out of the mains faster, the boiler doesn't have to run as long to get heat to all the rooms. There should be large vents at the ends of the steam mains so the first minute or so of steam production fills the mains, after which the steam can rise to all the radiators at the same time.

If the steam mains have no vents, they should be added. But the asbestos must be removed first.

mattmia2 · June 10

The weird piping is probably drips to return condensate to the boiler. The drips from the mains and the returns must drop below the water line before they connect or steam will get in to the returns and stop them from venting and stop some radiators from heating. Given the …creative… near boiler piping it is very likely that this boiler has a lower water line than the original boiler and there is now a connection above the water line somewhere that was not corrected when the water level was lowered.

pacoit · June 10

@mattmia2 I frivolously used the term "wet" return. The "weird" piping appears to be as you describe. They also appear to be original (at least not 1999 change). Thanks.

As to changes to the waterline, I don't see or recall anything to suggest there was a change, but I can't say for sure.

@Steamhead You got it right! I found the original heating system plans. It says, "Kelmac vapor heating system". I did not know "vapor" and "steam" heating referred to different systems. The original boiler was a "#845 Pierce Down Draft Steam boiler", coal fired. The first gas boiler was first installed circa 1924, and was replaced around 1999. I don't see the tops of any risers in the attic spaces anywhere, much less riser vents.

So, since the heating cycle is long 10-15min, can we say I have a poorly running system? And can we conclude I have a poorly converted vapor to steam system? If so, what should a proper conversion look like?

An aside: Funny thing. I have been thinking about converting my system to vacuum steam heat (including a vacuum pump) for the last couple years; from a physics point of view, pushing air out each heating cycle seems an enormous waste of energy.

mattmia2 · June 10

The new boiler likely has a much lower water line than the original coal boiler had and even mid century gas or oil boilers so unless they checked and lowered wet returns as necessary they would have broken the system by replacing the boiler.

A 2 pipe system would be vented through the dry portion of the returns and usually at the end if the mains. The returns might have a vent at the end of each main or might return to the boiler and vent at the boiler or might all collect at one central point, possibly to some sort of supply/return equalizing device or other unique device to that vapor system. The mains might have vents, might have crossover traps at the end that vent them to the returns, or might vent through the radiators in to the returns.

If there is steam in the returns, the air can't get out. In a vapor system pressure that is too high can also put steam in the returns.

Jamie Hall · June 10

Your time to heat radiators is a bit long. Maybe not outrageous. But — fully explained by woefully inadequate main venting.

Vapour systems are a little tricky on main venting, as there are two distinct approaches. One approach uses what are called "crossover traps" at the distant end of each steam main. These allow air, but not steam, to go to the associated dry (high level) returns. The other places main vents — which must be generous, say Gorton #2 even on smaller systems — at the ends of each steam main.

Either approach above also requires generous main venting on the dry returns where they join near the boiler. Again, at the very least one, if not two or even three, Gorton #2s. Those are the only way that air can get out of the radiators so steam can get in.

Generally speaking no other vents — main or otherwise — are needed on a vapour system.

On the radiator which doesn't heat unless you loosen the return pipe and let air escape. Chances are excellent that somewhere in that return line there is a low spot (maybe a sag, or maybe just pitched backwards) which has let condensate accumulate and that means the air can't get out.

Adding adequate main venting on both the mains and the returns may cut your time to heat the radiators significantly.

However, you relatively short cycle time may not indicate a problem, and the fact that the radiators only get half hot doesn't mean there's a problem at all. The question there is — how frequent are the cycles (should be around one per hour. Possibly more often in colder weather, depending on the thermostat) and are the rooms warm enough? If the rooms are warm enough, you don't want the radiators hot all the way across, do you?

Now a word on thermostats. If the cycle interval is too short, or the system doesn't run long enough to get some of the rooms warm, look into the thermostat. Some thermostats, particularly older ones, have an anticipator which can be set to control the length of run. It needs to be set to match the boiler and building properties, and take some fiddling — but if it's set correctly the temperature at the thermostat should only vary by about a degree. Newer thermostats may, instead, have a control for cycles per hour or sometimes only system type. It's not uncommon for them to be programmed incorrectly; they need to be set for one cycle per hour or steam or gravity hot water.

Jamie Hall · June 10

Now a separate comment. You mention thinking about vacuum. I can't recommend that. It will add a great deal of complexity and maintenance with essentially no gain. You have to remember that vapour systems operate on very small pressure differentials between the mains and the returns — typically a few ounces, not pounds! Unless the vacuum were to be applied to both the mains and the returns, it will upset the balance of the system. Essentially this means that the vacuum must be applied to draw down the entire system — returns, mains, and boiler, the lot — before the boiler is allowed to run. Worse, to maintain the vacuum during the run, it will have to be switched off and on — cycled — by a differential pressure transducer rather than an atmospheric vapourstat — so that the power output of the boiler matches the power demand of the rest of the system, which will be much lower at the reduced pressure.

Further I would note that all the vents must be returned to the vacuum pump to have it work at all, or you would need to use all vacuum tight vents, such as the Hoffman #76 (which is a very expensive widget) plus the vacuum connections to the returns, mains, and boiler.

Don't do it.

Steamhead · June 10

@pacoit , that was also known as the K.M.C. system. It was marketed by the Kellogg-Mackay company, If you have a copy of @DanHolohan 's book "The Lost Art of Steam Heating", you can find a detailed discussion of that system. Get your copy here:

https://www.heatinghelp.com/store/detail/the-lost-art-of-steam-heating-revisited

mattmia2 · June 10

@Steamhead It looks like there is something important that happens between the return and the air return out in the system piping that isn't shown in tlaosh.

pacoit · June 10

@mattmia2 , Forgive me for not crediting you earlier for correctly recognizing a vapor system.

As to the waterline, the wet returns are roughly 6" from the ground around the perimeter, with a couple below the floor where they cross the room. They and the Hartford Loop were unchanged in 1999. The new boiler was set on blocks presumably to match up its waterline to the existing Hartford Loop? So, can we conclude the waterline is likely correct for the existing piping design?

mattmia2 · June 10

Do all the drips from the mains drop to that level before they connect to another drip? The diagram in the lost art shows the returns above the water line but something else they call air returns so your system may be different than that system. there was also a mercury sealed air vent and a condenser tank at the original boiler if it follows that design

pacoit · June 10

@Jamie Hall , Thanks for the detailed info. I'll have to study it to understand my venting needs in detail.

Regarding the one radiator, I imagine you are right. I recall removing the vent temporarily, but it didn't seem to help. It does heat up when it's very very cold out.

My system cycles as you say, about once per hour, or 45min if its colder. I have the old standard Honeywell thermostat. Years ago I adjusted the little lever under the cover to its longest cycle position. I hope that's OK? Before it would cycle every ~10-15min. The temperature range in the cycle is ~2-3deg.

I have adjusted the radiators so that the rooms heat up evenly; and I have doors to close the first floor from the second so that I can maintain even heating (or keep 2nd floor cooler as preferred).

The system works and is comfortable. But my bills are comparably high, and so I am principally trying to decipher whether the system is running efficiently or not. If so, I could then look at the insulation of the house.

pacoit · June 10

@Jamie Hall , Regarding the conversion to vacuum steam heat, I'm intrigued by it. However, I don't know enough, yet; I need much more practical info to make progress; and I don't want it if it becomes mechanically complicated. Still, pushing air each cycle bugs me……maybe I'll go back to a coal-fired system!!! One long cycle per day, basically; push air once per day. Right?

pacoit · June 10

@mattmia2 , Yes, the drips from the mains drop into the vertical return lines just above where they connect to the horizontal return line 6" from the ground.

I can't speak about the original boiler. Nor much about the replaced 1924 gas boiler, in the sense that it was in an elegant enclosure, with built-in gauges, and a door that opened; but I don't recall if there were mechanicals in there beyond the boiler. Nothing else outside was removed that I can recall.

pacoit · June 10

Last post for tonight. My system seems to consist of only a boiler, pipes, and return pipe vents. I saw this old vent(?) lingering on one pipe (the related radiator works, hmm, maybe poorly? Must check), see pic:

And then this Y thing on one of the mains. Any ideas? See pic:

mattmia2 · June 10

the things on the tree are a thermometer and a very old relief valve. the relief valve can be operated remotely with a chain.

the cast iron cylinder things looks similar to but not exactly like some of the vapor specialties in the kmc system diagram. looks like some sort of an air vent.

mattmia2 · June 10

tlaosh has a kmc vacuum system. I think the kelmac vapor system was similar but somewhat different. the radiators are fed from the top in this system and none of the original parts hanging around seem quite the same.

Steamhead · June 10

https://forum.heatinghelp.com/discussion/comment/1857587#Comment_1857587

Possibly. I'm not where I can access my Holohan books. Does anyone in this thread have "The Lost Art of Steam Heating Companion"? It might be in that long section with all the pages from ASHVE Guides or similar publications………………

mattmia2 · June 10

I have it at home but have not actually opened it. Is that reprints of all the references at the back of TLAOSH?

Steamhead · June 10

More than that- it's brief descriptions of a whole list of systems. Some we're familiar with, but I doubt anyone on here has seen, for example, an Imico system:

https://www.heatinghelp.com/systems-help-center/vapor-heating-the-imico-system/

All the ads in that section look like this one.

EBEBRATT-Ed · 12:06AM

I went through the LAOSH Companion but I did not recognize anything

Vent placement in home 2-pipe steam heat system

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