What Size For This One Pipe Wet Return??

JUGHNE

I have the remains of a single pipe system which will now have it’s own boiler with gravity return.

The boiler is a PB 63-05L, input of 206,500, steam capacity of 171,000, EDR of 533

Net rating of 128,000.

Connected EDR is only 414, which X 240 = 99,360.

I oversized the boiler because of the 145’ of (6”...4”...2 1/2”) steam main that feeds only the 4 remaining radiators
About half of the main is uninsulated to heat the basement.

The main piping weighs 1460 pounds.
.
There were about 13 take offs on the original system.
Building improvements have cut the heat loss down that much.

The 2 1/2” EOM drops down 5’ from 10’ ceiling and previously went into a 1” F&T then into a cond pump......the F&T and pump will no longer be part of this system..........it is to be converted to gravity return.

I am hoping that 1” copper will suffice for wet return to the boiler (I have plenty of old stock).

What do I size that pipe on based on the info above??

Thanks for input.

Jamie Hall

I would first look at the volume of condensate expected -- 100 pounds of steam per hour (that 100,000 or so BTUh divided by 1,000 BTU/pound of steam). Which comes out after some back of the envelope juggling to somewhere less than two quarts per minute. Then I would say to myself... hmm. I can run that through a very small pipe... which clog badly if I look away from it... and use the 1" copper which you have (which is ample for the flow rate!) and be happy.

Amazing how little water it actually takes to heat things with steam, eh?

EBEBRATT-Ed

OOOOh

Think I found a typo on PG 148 of the LAOSH revisited

1"wet return 700edr, 168,000 btu/hr (which looks right) and 700 lbs/hr (which can't be right

I am guessing the lbs/hr should be 168

JUGHNE

Thanks Jamie and Ed, yes I had been looking at page 148 and it was confusing.
The larger pipes showed less pounds per hour.

I will install Valves for flushing the wet return.

clammy

Generally for wet returns the mim I install Is 1 1/4 no sense in making smaller as it allows for no build up of crap being it s usually about every 50 years till they get flushed . There’s a few things that I ll never change and that’s doin 2 inch equalizer mim 1 1/4 Hartford’s and the same for wets unless it’s a very small system . Peace and good luck clammy

Steamhead

I would definitely not size that return to the minimum. At least 1-1/4".

JUGHNE

Steam head, I assume you would go to the larger pipe because of the typical plugged wet return problems.
This wet return will be only 15’ of horizontal 1” copper on the floor of the boiler room.
It will be connected to 5-6’ of 2 1/2” drop with dirt leg and strainer with blow down valve.
This previously was connected to a 1” F&T then to the old cond pump.

There was no problems with the reduced flow thru the 1” F&T into the now abandoned cond pump.

There will also be easy back flushing thru the new return.

So if any problems in the future I will gladly report back.

Thanks for your input and will certainly appreciate any added comments in the future.