Steam boiler sucks

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the water out of the condensate feed tank each time the system goes into night setback. Boiler is tied into a common feed with the returns separated. We were losing water from the tank and found after watching it that when the system shuts down at the end of the day, the system goes into a vaccuum (the gage shows that) and water is being pulled from the feed tank and flooding the boilers. What to do? Can we use a vaccuum breaker? If so,what size, model, etc....Where would it be installed? Any other ideas? No zone valves and this only happens when system shuts down at night.

Ken_8

If you install a vacuum breaker...

it will solve the problem. But it will accelerate the corrosion within the boiler.

If however, you install a synchonus solenoid valve just after the feed pump the vacuum will be broken by system vents and/or other sources and reduce internal boiler corrosion by a small fractional amount.

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tim smith_2

sucking water

I would think an equalizer line between the steam main and the return line before. install a swing check on the equalizer with direction towards the steam main. So when the steam main goes into vacuum it will through the check to return. This way it won't pull from the condensate tank. Any other comments to this option?

Unknown

I kind of like this option best.

I've done the electric valve, and it's noisey.

I might put a spill trap (F&T) on the equalizer that drained to the return at a height that maintains the maximum cold water line that you can tolerate inside the boiler.

Space and piping will dictate what you chose, though.

Noel

Steamhead

Do you really need the tank?

If that's an old Vapor system like the ones Noel restored so beautifully, you may not need the tank and pump. Many of these old systems run perfectly with gravity return, and a Vaporstat keeping the pressure below 1 pound. Some contractors install pumps to replace Return Traps or Differential Loops, but a Vaporstat eliminates the need for forced return by keeping the pressure low. Have a good steam contractor look it over to be sure. Check the Find a Professional page of this site- and if you're in the Baltimore area, e-mail me!
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Its a two pipe low pressure steam system and the 100 gallon feed tank was there before the replacement. I think it was installed because we neede make-up water due to the fact that some of the returns are 100 yards away from the boiler room and we would be asking forwater long before it could make it back after condensing. We had to add another pump(which the tank had a duplex option)so we could split the returns and feed only the boiler that was calling for water. The system works great and it saved the school over 35 percent on their gas bill due to the lo-hi-lo burner option which runs almost continuous on low fire. The only problem was this syphoning and we neede to get a handle on it. I cannot remove the tank or I'm sure that we will run out of water. Even though the tank is vented, I cannot expect the retur to let air back in as the traps are closed. I obviously like thje vaccuum breaker option but was usure where to locate it. Thanks for the help.

Unknown

With 2 boilers and 2 pumps

I certainly would put a 3/4" F&T trap about 2-4" above the water line on each equalizer. This is the easiest way to both break the vacuum, and to return the extra water that condenses in the off boiler. It's the only step you'll need to take. Run a 3/4" line back to the return piping that serves both spill traps.

Noel

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