Question about large apartment building steam system and venting.

Rmasci

So I have take over management of a decent sized, 50+ unit, 4 story, residential apartment building with an old Warren Webster steam system from the 1930s.

It has a two pipe system, with one carrying steam to the risers and then a wet return bribing condensate from the steam traps.

Today on one of the steam loops off the main that serves one corner of the building I noticed where the steam loop drops to join up with the wet return to the boiler that there
A: Did not seem to be an air vent on the pipe anywhere
B: That where it met the wet return it had a Hoffman 17c steam trap instead of a larger Float & Thermostatic Trap like I am used to seeing.

The building has been maintained and managed by a series of absentee landlords with jokers for maintenance crew for the last few decades who have let it fall apart, so my gut tells me that a large watts trap went bad and somebody slapped the 17c on there.

So my question is should this return have a larger trap on it? And should their be an air vent at the end of the loop before it drops down to meet the wet return?

gfrbrookline

Where are you located?

Jamie Hall

Important! The Warren Webster is one flavor of vapour -- or very low pressure -- steam system. Best bet is to purchase your very own copy of The Lost Art of Steam Heating and study it...

In the meantime. Systems of this type have at least two, and often three runs of pipe. One, which you have identified, is the steam mains. Their job is to carry steam to the radiators. The second, which is critically important, is the dry returns. These carry condensate and air from the radiator outlet traps. The third is wet returns, which are below the boiler water line and carry condensate from assorted drops -- usually the ends of the steam mains, the ends of the dry returns, and possibly other places.

Now. The steam mains are vented into the dry returns by means of crossover traps -- one of which you have identified as the Hoffman 17C. There are probably others. These crossover traps are there to vent air from the steam mains. They should be mounted above the steam main, and the outlet goes into the corresponding dry return. There is usually a drip from both the steam main and the dry return which drop independently to a wet return.

Do not substitute a F&T for a crossover trap. It won't work.

There should not be any vents on the steam mains. However, there should be a good bit of venting -- depending on the size of the system -- where the dry returns get together back at the boiler.

Before you start "fixing" the system, clearly identify which pipes are steam mains, which pipes are dry returns, and which pipes are wet returns. Then locate any and all traps -- especially crossover traps. It is very likely that over the years people have "fixed" things, so it may take some effort to figure out what was supposed to be there so you can replace it.

One other (for the moment anyway!) -- check the relationship of the boiler water line to all your wet returns and drips. The bottom ends of all the drips, where they meet wet returns, must be below that water line, ideally several inches to a foot below. It is not unusual for a boiler to be replaced and wind up with a lower water line, which will dry out the bottoms of those drips and cause quite an interesting array of hard to diagnose problems (hard to diagnose until you look at the water line, that is).

dopey27177

Does the system have a condensate tank collecting the buildings condensate.

Jamie Hall

dopey27177 said:

Does the system have a condensate tank collecting the buildings condensate.

If it does, he may be in big trouble...

Rmasci

dopey27177 said:

Does the system have a condensate tank collecting the buildings condensate.

Yes.

Okay. So perhaps I have misused "wet return" and "dry return"

This particular loop of the steam supply is in the boiler room. That as well as the return it goes into via the 17c trap are well above the boilers water level. The return itself feeds into a condensate tank, that then pumps water to the boiler when it needs it.

So the return to the condensate tank would all be "dry return"?

EBEBRATT-Ed

@Rmasci

Yes, it should have an air vent after the trap if it drops into a wet return. If the return goes to a condensate tank by gravity then you can skip the air vent.

If the return only drains 1 radiator he 17C is ok if not replace it with an F & T

Jamie Hall

Oh dear. Well, that is a good sign that the system has been knuckleheaded, perhaps irreversibly.

Keep in mind that that return to which you refer is a dry return. It carries air from the radiators, and it must be vented. If the outlet where it goes into the condensate tank is below the water level in the tank, it won't vent, and you need to put a vent -- a big one -- on the line where it turns down.

Now go out into your system -- everywhere -- and locate all the drips, whether from a steam main or a dry return. If they go into what once was a wet return, check the level of the wet return at that location with relation to the lowest water level in the condensate tank into which the return empties. If the level is low enough -- well below the condensate tank -- you may have gotten lucky. Otherwise, every single drip will have to have an independent trap on it. Sorry about that.

These systems worked so well... and were so simple... sigh...

Rmasci

gfrbrookline said:

Where are you located?

Lansdowne, PA.

Rmasci

EBEBRATT-Ed said:

@Rmasci

Yes, it should have an air vent after the trap if it drops into a wet return. If the return goes to a condensate tank by gravity then you can skip the air vent.

If the return only drains 1 radiator he 17C is ok if not replace it with an F & T

The return does drop into the condensate tank by gravity. It is approximately 8-10 feet above the condensate tank.

The 17c off of this returning steam loop is serving 9 radiators on 3 risers. So I guess replacement with a F&T is what is needed.

Rmasci

Jamie Hall said:

Oh dear. Well, that is a good sign that the system has been knuckleheaded, perhaps irreversibly.

Keep in mind that that return to which you refer is a dry return. It carries air from the radiators, and it must be vented. If the outlet where it goes into the condensate tank is below the water level in the tank, it won't vent, and you need to put a vent -- a big one -- on the line where it turns down.

Now go out into your system -- everywhere -- and locate all the drips, whether from a steam main or a dry return. If they go into what once was a wet return, check the level of the wet return at that location with relation to the lowest water level in the condensate tank into which the return empties. If the level is low enough -- well below the condensate tank -- you may have gotten lucky. Otherwise, every single drip will have to have an independent trap on it. Sorry about that.

These systems worked so well... and were so simple... sigh...

The return heading into the condensate tank thankfully is well above the water level of the condensate tank and the boiler by 8-10 feet. The boiler room is very deep. Because it is above the condensate tank and drops into it by gravity I do not need a vent?

I did order a copy of The Lost Art of Steam Heating. I am a novice when it comes to running these systems but I like them and want to become as much of an expert as I can be. Steam systems fascinate me.

Rmasci

Here is a little diagram of that steam loop.

Jamie Hall

The 17C is ample for your 9 radiators. It's mostly serving the steam main anyway -- the radiators go into that high return (or should, anyway...).

On the drop into the condensate tank -- if the end of the return is above the water level in the tank, you don't need a vent. If it can be submerged, you do. And you certainly do NOT want any sort of trap on the return itself.

As I said earlier, please, please read up on vapour steam systems and the Warren-Webster before you start changing things. It's in the Lost Art, and very well presented. It's very easy to do much more harm than good on these things (the condensate tank being a spectacular example) and you really truly want to figure out how it was meant to operate first.

EBEBRATT-Ed

@Rmasci

Your condensate tank should have a vent on it (and an overflow pipe as well) so no need for a vent on that pipe unless the pipe has a low spot (water trap) between the vent and the condensate tank.

As far as the 17C trap if it is an end of main drip it may be ok but an F & T would be better.

JUGHNE

Are all the return pipes 8-10' above the boiler?

Do you actually need a pump?
Does the pump/piping look to be original, or perhaps added later?

Jamie Hall

Originally, when built and first operating, there would not have been a condensate return tank at all (though there might have been a condensate reservoir at the boiler water line). The wet returns would have fed into that, and the dry returns -- which would have been vented -- would turned down and gone to that.

Makes me wonder what else has gotten knuckleheaded.

Rmasci

JUGHNE said:

Are all the return pipes 8-10' above the boiler?

Do you actually need a pump?
Does the pump/piping look to be original, or perhaps added later?

Yes, all of the return pipes are above the boiler's water line by several feet at least and go into a condensate tank.

When the boiler needs water a pump on the condensate tank turns on and pumps the water to it.

Jamie Hall

All of the return pipes at the same level? At or near the same level as the steam mains? That arrangement is at least feasible, if the returns all pitch towards the boiler. Which way do the steam mains pitch? How does condensate in the steam mains return to the boiler? If they pitch towards the boiler, well... OK. If they pitch away from the boiler, where does the condensate go at the far ends? And how does air get out of the steam mains?

Rmasci

Jamie Hall said:

All of the return pipes at the same level? At or near the same level as the steam mains? That arrangement is at least feasible, if the returns all pitch towards the boiler. Which way do the steam mains pitch? How does condensate in the steam mains return to the boiler? If they pitch towards the boiler, well... OK. If they pitch away from the boiler, where does the condensate go at the far ends? And how does air get out of the steam mains?

The returns are below the steam mains. In the North side they run under the basement level in a crawl space with the returns about a foot lower. On the South side of the building the mains run at ceiling height through the basement level and the returns slope from floor level downwards to meet up at the same level in the crawl space just off the boiler room.
The returns all slope to the boiler and return condensate as far as I can tell.

On the far ends of each steam main loop the line drops into a F&T traps that connect with the returns.

No air venting I have found other than air vents on the radiators themselves.

Jamie Hall

There are air vents on the radiators? Someone did have fun, didn't they. The F&Ts should be venting the mains after a fashion (they're venting capacity is nowhere near what either a real vent or a crossover trap such as a Hoffman 17C would be).

Study up some more on these systems and you'll see why I'm having some trouble here...