STEAM HELP/DIFFERENTIAL PRESSURE LOOP

MATT SRC

----- Original Message -----
From: Matt Pugh
To: mailroom@ mailroom@heatinghelp.com heatinghelp.com
Sent: Friday, January 04, 2008 8:28 AM
Subject: STEAM BOILER HELP


GENTLEMEN,
I HAVE A CUSTOMER WHO REPLACED A OLDER A-509 BOILER WITH A WEIL MCLAIN BL-580-S.ITS IN A LARGE HOUSE AND IS LOW PRESSURE STEAM.THE TOTAL SQ FT OF RADIATION IN THE HOUSE IS 1577 SQ FT.WE ARE FIRING AT 3.25GPH RIGHT NOW.WE HAVE THE PRESSURETROL SET TO CUTOUT AT 1.2LBS AND CUTIN AT .4LBS THE HOUSE IS ALL A TWO PIPE RADIATOR SYSTEM WITH TRAPS ON ALL THE RADIATORS.
THE BOILER IS APPROX IN THE CENTER OF THE HOUSE AND OUR SUPPLY MAIN GOES OUT IN 4 DIRECTIONS AND GOES AROUND THE PERIMETER OF THE HOUSE WITH SHORT RISERS UP TO THE RADIATORS.AT THE END OF THE MAINS THE HAVE A 1/2 PIPE THAT GOES OVER TO THE DRY RETURN MAIN WITH A THERMOSTATIC TRAP #8 HOFFMAN MOUNTED.MAINS THEN DROP TO THE FLOOR AND RETURN TO THE BOILER.THE DRY RETURNS GO BACK TO THE BOILER ROOM AND TIE IN TO A #0 HOFFMAN DIFFERENTIAL LOOP.IT SAYS "WATCHMAN OF THE WATERLINE" ON IT.MY QUESTIONS ATER ALL OF THIS IS, WHAT WAS THE PURPOSE OF THIS CONTROL? HOW IT OPERATE?SHOULD IT HAVE REMAINED OR BEEN REMOVED?WHAT SHOULD WE HAVE DONE ON THE REPLACEMENT IN REGARD TO THIS AS FAR AS WATER LINE HEIGHT?
WE ARE HAVING SOME PROBLEMS WITH CONDENSATE RETURN TO THE BOILER NOT COMING BACK SOON ENOUGH FOR THE LOW WATER CUTOFF TO STOP THE BURNER ND ALSO WANTING TO FILL WATER .
ONE OF MY OLDER HANDBOOKS SHOWED A DIFFERENTIAL PRESSURE LOOP PIPED WITH 2 COLUMNS THAT IS SIMILAR TO THIS #O.IT RECOMMENDED NOT CHANGING THE SYSTEM WATERLINE ON REPLACEMENT. THIS PARTICULAR BOILER SETS IN A PIT AND THE BOILER HEIGHT IS NOT EASILY CHANGED.WE HAVE BEEN ABLE TO CHANGE OUR HARTFORD LOOP HEIGHT IN RESPECT TO THE WATER LINE BUT HAVE LOWERED OUR OVERALL WATERLINE BECAUSE OF THE SHORTER BOILER I CANNOT FIND ANY INFORMATION FROM HOFFMAN ON THIS PARTICULAR CONTROL.AND DO NOT KNOW IF OR WHAT IT NEEDS AS FAR AS BOILER WATERLINE
I HAVE ALSO NOT SEEN THE CROSSOVER TRAPS AT THE END OF THE MAINS BEFORE.TYPICALLY YOU WILL SEE F&T TRAPS HERE.HOW WOULD YOU TEST THOSE TRAPS?TEMP DIFFERENCE?WHAT WAS THEIR PURPOSE?
I APOLOGIZE FOR THE LENGTH OF THE E-MAIL .THANKS FOR ANY HELPFUL SUGGESTIONS YOU MAY HAVE
Matt Pugh
Southern Refrigeration Corporation
Winchester, VA
540 665-0033 Office
540 667-3501
www.southernrefcorp.com

Unknown

why are you

Why are you YELLING with the caps letter? If you get one of Dan's steam book, there's a chapter that will explain what the diff loop do and where its suppose to be installed regarding to water line.

Steamhead (in transit)

Matt, you have

a Hoffman "Controlled Heat" Vapor system. Vapor was the Cadillac of heating in its day and is still one of the best out there.

This system was designed to run on about 8 ounces pressure. The Differential Loop maintained the proper pressure differential between the steam and return sides of the system. This ensured that the radiators would heat when someone opened the valves on them, also that the water could return to the boiler if its pressure exceeded 8 ounces. I'd leave the Loop in place.

As long as the new boiler's waterline is not higher than the old one, you should be OK. But you can have trouble if there are loop seals at the ends of the steam mains and the waterline falls below them. A loop seal is where two drop lines connect- on Hoffman systems they generally did so on the way down to a wet return. This connection MUST have water standing in it so the steam cannot jump from one drip to the other.

The crossover traps acted as main vents, routing air from the steam mains into the dry returns, and closing when steam reached them. Air left the dry returns thru a large main vent mounted on or near the Differential Loop.

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