Vacuum to Gravity

S Armstrong

> I am involved with an old school building converted to a day care center
> that has a vacuum condensate return system. The vacuum pump is leaking
> and has bad bearings. All but one of the returns drop down from the
> ceiling of the floor above. One of the returns comes from a coil in a
> air handler in the basement, this return is low. There were other coils
> in the basement that have been disconnect so the load is light.
> The vacuum pump then pumps into a boiler feed unit.
>
> I was going to replace the vacuum pump with an atmospheric condensate
> pump and add a small unit near the air handler to handle its condensate.
>
> The system is a two pipe steam system, operating at 3-5 psi. (which I
> believe is too high).
>
> Is there anything else I need to look for? Do you think, with the
> limited info I have provided, this can be done? I wait anxiously for
> your response.
>
> Thank in advance,
Steve

[Deleted User]

I would

repair the vacuum pump and all traps. If the pump unit cannot be repaired, there are several companies that manufacture combo vacuum/feed water units that work well.

Short cuts can come back to haunt you. Vacuum systems that are converted to straight steam never work as well. The customer is the first to notice. They will make sure you are the second.

The "Lost Art of Steam Heat" has a section on vacuum pump sizing for older systems. The radiators start to heat w/ 160 degree water under a vacuum. Try that w/ steam.

We heat a 208 unit vacuum fitted apartment building w/ 1 1/2# pressure. If it was still coal, we wouldn't need that. Kind of hard to modulate any lower. Don't need much. Good luck.

Unknown

Vacuum systems and pressure

The maximu steam pressure that a vacuum system should have is 2 PSIG. This pressure should occur when the out door temperatures reach single digits.

Normally the system should operate from vacuum to 1 PSIG.

The vacuum systems should not return temperatures greater than 160 degrees.

If all the steam traps work the return temperatures can be from 140 to 90 degrees.

The lower the return temperature the higher the system vacuum will be except when the system goes into pressure.

You mentuione that the vacuum pump bearings were bad, this happens when condensate temperatures are consitantly to high or dirt got into the seal area of the pump.

Repair or replace the pump. You do not want to change that system to gravity as many other problems may surface.

Jake

Ben_3

The first thing you should check are your steam traps. But not just your radiator traps. If you follow the end of the steam mains you will find traps at the end of each steam main, these are actually cleverly disguised air vents. They vented the mains so the steam would reach the risers quickly. It sounds to me that they failed which would cause the building to heat slowly. The next step was someone would crank the pressure up. WRONG!!! That system should have a vaporstat. Throw away that pressuretrol. I have heated two pipe vaccum systems with 1200+ radiators on 4 to 10 ounces of pressure!!