VAPOR SYSTEM

B.BART

INSTALLED NEW V-95 STEAM BOILER IN SMALL COMMERCIAL BUILDING.SYSTEM HAS WET AND DRY RETURNS THEERMOSTATIC STEAM TRAPS ON ALL RADS AND ON END OF MAINS IN BASEMENT.ALSO HAS #76 MAIN VACUUM VENT ON END OF DRY RETURN OVER BOILER.SYSTEM IS PULLING A VACUUM ON SHUT DOWN CAUSING AUTOFEEDER TO FILL BOILER AND FLOOD.IT ALSO HOLDS BACK CONDENSATE IN RETURNS NOT LETTING CONDENSATE PUMP TURN ON.MY QUESTION IS THIS THE RIGHT VENT VALVE FOR THIS SYSTEM??SYSTEM OPERATES WITH VAPORSTAT AND CYCLES GREAT UNTIL SHUTDOWN.THANKS

Unknown

Hi.

> INSTALLED NEW V-95 STEAM BOILER IN SMALL

> COMMERCIAL BUILDING.SYSTEM HAS WET AND DRY

> RETURNS THEERMOSTATIC STEAM TRAPS ON ALL RADS AND

> ON END OF MAINS IN BASEMENT.ALSO HAS #76 MAIN

> VACUUM VENT ON END OF DRY RETURN OVER

> BOILER.SYSTEM IS PULLING A VACUUM ON SHUT DOWN

> CAUSING AUTOFEEDER TO FILL BOILER AND FLOOD.IT

> ALSO HOLDS BACK CONDENSATE IN RETURNS NOT LETTING

> CONDENSATE PUMP TURN ON.MY QUESTION IS THIS THE

> RIGHT VENT VALVE FOR THIS SYSTEM??SYSTEM OPERATES

> WITH VAPORSTAT AND CYCLES GREAT UNTIL

> SHUTDOWN.THANKS

Unknown

Hi.

> INSTALLED NEW V-95 STEAM BOILER IN SMALL

> COMMERCIAL BUILDING.SYSTEM HAS WET AND DRY

> RETURNS THEERMOSTATIC STEAM TRAPS ON ALL RADS AND

> ON END OF MAINS IN BASEMENT.ALSO HAS #76 MAIN

> VACUUM VENT ON END OF DRY RETURN OVER

> BOILER.SYSTEM IS PULLING A VACUUM ON SHUT DOWN

> CAUSING AUTOFEEDER TO FILL BOILER AND FLOOD.IT

> ALSO HOLDS BACK CONDENSATE IN RETURNS NOT LETTING

> CONDENSATE PUMP TURN ON.MY QUESTION IS THIS THE

> RIGHT VENT VALVE FOR THIS SYSTEM??SYSTEM OPERATES

> WITH VAPORSTAT AND CYCLES GREAT UNTIL

> SHUTDOWN.THANKS

Unknown

Hi.

That vent induces vacuum. Use a vent sized for the system that doesn't have a check valve in it.

The traps aren't holding steam, in all cases. That's likely why the system is storing up water, which will come back when the steam satisfies and the piping cools.

Noel

Steamhead

You probably don't need that pump

but since it's there, the dry returns are supposed to vent thru its reservoir. Why isn't this happening? Is there a trap at the inlet to the pump reservoir? Does the return drop to near floor level and then rise to the reservoir inlet? If you find either of these, that's probably what's messing up your return flow.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

Unknown

Some pics to go with the post

There were 4 steam carrying mains - 2 went left , 2 went right . At the ends of the mains they joined into a common return via 2 traps , and returned to the boiler down low .

The separate return pipes from the rads joined into a common return pipe , one for the left side of the building , one for the right . These returns teed back at the boiler up high with a vacuum vent in another tee , and dropped down into the lower main returns .

The picture of the traps is of the left side of the building . The right side had a similar setup , except that each steam carrying main also had a separate trap connected to the high radiator return pipe .

While we were there , the lower steam main returns came back hot , while the radiator returns stayed cool . And when the boiler shut down on low water it went into a deep vacuum and the water disappeared out of the boiler quick - too quick for such a large content boiler .

We replaced the pressuretrol with a vaporstat . We had the cut in set at 14oz and the diff at 10oz . The cycles were very short ( burner would kick back on right after the post purge , probably every 30 seconds ) till the boiler ran a good 1/2 hour , then the cycles were in minutes .

Also , what kind of temp difference should we be looking for - before and after the trap ? And where is the best place to take these readings with an IR thermometer ? I checked a few at the end of the main and one was 205 before and after the trap . Is it common for them to fail open ?

Thanks in advance for any help . I believe a replacement of every trap in the buiding is in the cards for the near future . It looks like they weren't touched in decades .

Unknown

Get the vent off there.

Run it with no vent (for a minute) You'll see what the cycling SHOULD be, and you'll also eventually see steam where the vent goes.

That steam has to get through a trap to reach the vent on the return. When all of the traps hold steam, you won't see even a puff out of that vent hole; only air. A steam main vent only serves to catch steam WHEN the traps won't hold. It's only there for insurance. Condensate tanks don't even have that, only an open pipe for a vent. Take it out for testing.

When you put a vent back in, it shouldn't make the boiler short cycle, if it is big enough. It certainly shouldn't hold a vacuum.

Notice that those traps are reverse from a normal one? They called those "outboard traps" because the seat is towards the radiator or steam main, and the bellows is in the return side. Seems pretty odd to Noel, but they do actually work. They are a bear to get the cover on without the element flopping around inside.

If all the traps work, you'll see 205 on the trap and 90-150 on the return piping. If you start it up from cold, and quickly shut it off as soon as you see a hot return, you can follow the hot return back to the trap that's blowing.

If you wait to stop the steam, the whole return will be 205, the traps will all be shut TIGHT, and the radiation will be filling with water. Where else can it go? No air can get in, only steam, which condenses and pulls in more steam, which condenses.....

I bet those traps are MilVaco, or maybe Illinois brand. You can run that one on REALLY low pressure.

Noel

Mad Dog

I've seen traps fail in both positions

Mad Dog

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

Unknown

me too

The ones stuck closed are easy to find. Cold room. Radiator won't vent.

Noel

Woody

in most cases

the the traps that are failed closed are due to some water hammer in the system. or traps will fail closed on higher pressure (over 50 psi). most low pressure traps fail in the open position because the loose their "fiz" ( bellows or diaphram leak) hope this is helpful. tp tunstall

Unknown

Update on the job

Seems that the owner came clean and told my supervisor that the system started acting this way last season . Installing a new boiler was a necessity - the old one was a leaker .

I only checked a few traps on the rads while I was there the other day and I was getting a room temp reading on the return pipe after the traps . Not any of the handful of return pipes I checked got hot in the basement - only the lower , steam main returns came back hot . One steam main return trap had 204 in , 204 out , so that was one of probably many that were bleeding steam into the radiator returns .

We are recommending that the owner change each and every trap , I will keep you posted on what happens . Thanks Noel and everyone for taking time to help out with this one .