steam boiler going int vacumm

ed wallace

working on a Burnham 906A boiler in a church hes 2 zones with newer honeywell zone valves its 2 pipe with a condensate feed pump has a wierd problem on shut down unit goes into as vacumm found out when i removed the pig tail to clean it thinking it was plugged what could cause this problem any ideas 1 zone valve is always open need to rewire it so it closes on shut down could it be a problem with the traps?

Steamhead

That's typical of zone-valve setups

Even if one valve is stuck open, if the traps or vents are closed when the boiler shuts down it will form a vacuum.

First make sure if the system has main vents that they're not the vacuum type. If so replace them with non-vacuum units.

When you fix that stuck zone valve, install a 1/2-inch vacuum breaker somewhere between the boiler and the zone valves. This will break the vacuum that forms when the boiler shuts down and the zone valves close. Read the instructions carefully as some of these units require a water seal to keep steam from damaging them.

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

ed wallace

steam boiler going into vacumm

i replaced the the vacumm breaker today old 1 I installed 5 yrs ago I will check for main vents this week

thfurnitureguy_4

Should a single pipe system go into vacume when shutting down? If it held a vacume would it heat up faster on the next run? A vacume should lower the boiling point of water and have less air to push out at the vents when it restarts.

Steamhead

That only works well

with coal or other solid-fuel firing. With oil or gas, you'll get vacuum long before all the air is out of the system. Then the air will expand and block the flow of steam on the next cycle.

If you're getting a lot of vacuum, check for missing pipe insulation. This causes steam to condense much faster, creating more vacuum.

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