Vapor System

Matt_30

Love the site...I've run across a system which looks almost identical to the Trane Vapor system shown in the Library. I've had a real problem returning condensate, although it seems better when I take the returns loose downstream of the direct vent & receiver. Boiler was replaced last year w/ a cracked section. A water vent had been installed on the equalizer, pressure set to 6#, and so on. I have a real problem building steam as well. My first inclination is to put vents on the second floor radiators (1st floor works fine), though I think Dan will tell me no. I've opened the check valves and cleaned one wet return. I want to take the direct trap and receiver apart, but I'm convinced my problem is differential pressure. The receiver has a vacuum breaker (rather than a vacuum check) on it, and I may be light on main vents. Also, they have a flat plate exchanger running some baseboard, which is doing a lousy job. I know I only need 6 oz. to make this work, technically, but this client has had this problem for 20 years, and I'd like a chance to shine; so I need help. Thanx!

Fred Harwood

Vents

You should not need to "build pressure." Get really big vents (or, say, four Gorton #2s) on your master vent. Then make sure no steam gets through the rads. If necessary, after turning down the pressure, choke the rad valves (make them work as if orificed). Steam in the returns wrecks the pressure differentials needed to make steam flow to the rads. Vent, vent, vent those returns. Then let us know how it goes.

Matt_30

Vacuum Check

Thanks for the reply....Also, the previous mechanic had installed a vacuum breaker at the receiver. I believe I need a vacuum check. I'm in Colorado, can't seem to find any here (ditto for the Gortons, though I can get Hoffman #75H).

Fred Harwood

Forget

the vacuum. Use plain vents, and big ones. Look up Gorton on the web. You can order direct. Oil-fired boiler does not use vacuum, just needs very good venting.

Steamhead

The later-model Trane Vapor systems

with the Direct Return Trap, used standard main vents rather than the Float Trap/Air Eliminator used by Dunham, Webster and others. There are many of these in Baltimore; I just did a vent job on one today.

What is the "receiver" you mention? Take a pic and post it here if you're not sure.

You need to make sure that not only the steam mains are vented, but also the dry returns as well. Typically you will find the dry return vent placed near where the various dry returns connect above the waterline, before dropping into the DRT piping. This is the exit path for air leaving the radiators, and should be vented with a minimum of two Gorton #1 vents, going to a Gorton #2 as the system size increases. If there is no vent here, parts of the system will not heat properly.

I've seen some Tranes that did not have vents on their steam mains and others that did. I suppose it depended on who the installer was. If yours doesn't, you can drill and tap to add steam main vents. Measure the length and diameter of each steam main to determine vent size.

If you suspect a differential-pressure problem, feel the dry return after the system has run awhile. Chances are you'll find it is steam-hot. This indicates a bad trap or traps somewhere, follow the heat to find it. There should be no steam at all in the dry return.

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Matt_30

Sez "#30 Hoffman Receiver" on it, as best I can read in the mirror. I think what it is is a float vent valve...probably the vent at the end of the dry returns of which you speak. The float vent then feeds the DRT, which would then feed the boiler. I guess.

Steamhead

That #30 vents the dry returns

and yes, it's a Float Trap/Air Eliminator. The vacuum check in the top should be removed. Seems like you have a hybrid Vapor system, using components from different manufacturers.

Is there any kind of vent at the ends of the steam mains? Maybe thermostatic traps piped between the steam mains and dry returns?



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Matt_30

Funny you should ask. Main steam runs in a loop-there was a #67 (water-I know. i've shut it and will replace) by the header on the equalizer line, as well as a #75 at the end of the main. However, also at this point there is a 1/2" line between the dry return and main steam. No trap, valve, or anything on this line, which looks like it's been added after the original install as the fittings are malleable rather than cast.There is also a 3/4" blk iron line from the end of the steam main to the Hartford loop below the water line( in the same area where the main is connected to the return. The only vent I see at the dry return is on the #30. There is also an equalizer at the boiler between main steam and the wet return. Something tells me others have had a guess or two at this. If you look in The Library, under Trane Vapor System, the schematic looks very much like what I've got, except for that main/return connection. Thanks again, so much, for your replies. I'm definitely buying some bricks.

Steamhead

There's your problem

Remove that pipe connecting the steam main to the dry return. That had a trap in it at one time to act as an air vent, and someone removed the trap. Now the dry return is being pressurized. There should be no connection between the steam and return side without something to stop the steam (trap, water seal, orifice etc.).

Measure the length and diameter of your steam main and we can tell you what vents it needs. If it loops around the basement I'm almost positive the Hoffman is too small.

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