Steam Return with Condensate Pump

3labs

I looked at a large boiler in a church. The return line is severely backpitched for about 20'. The 3" inch return has been reduced to 2" at a tee (the bull side) then goes another 15' where it rises about 8" into the 100 gallon receiver. They are not getting condensate to return to the boiler. I suspect the lines are clogged. Is it possible that the lines are not clogged, the line is in vacuum from the f&t to where the line rises to meet the reciever? There is enough room to have the proper pitch all the way back to the receiver.
Once this is fixed, I can check the traps to see if they need to be repaired/replaced.

Pumpguy

It's not likely the back pitched return line is clogged. More likely it's due to wanting the condensate to flow up-hill, which can't happen without some sort of pressure differential.

IMO, the only real solution is to have a condensate pump with receiver installed at the lowest point in the system, allowing a gravity drain from all returns. This would then pump into the 100 gallon tank which I assume is a boiler feed receiver.

Another possible solution is to install a vacuum/condensate pump and use this to keep the low returns drained of condensate. This would then pump the condensate into the 100 gallon tank. With this arrangement, lift fittings and/or an auxiliary accumulator tank arrangement must be used to keep the low returns drained of condensate.

Nagato1

Why is there 8" rise going to the tank? Condensate should flow back naturally via gravity and be piped down hill into the receiver.

Pumpguy, with all due respect, I don't think a vacuum system will help keep the return lines low of condensate. A vacuum system is designed to help move the steam thru the system better. That's why folks are able to use smaller pipe, fittings, and valves. That's also why low pressure is possible.

Also, vacuum systems don't like hot condensate. If the current system is returning above 180 degrees, and a vacuum system is installed, the risk of no vacuum and cavation is possible.

Pumpguy

Depends on the difference in elevation between the lowest point in the return line and the inlet to the vacuum condensate receiver.

Condensate flows by gravity to the lowest point in the system.

If the return is below the receiver inlet, then vacuum can be used to lift the condensate. If the vacuum lift is needed out in the system, then a lift fitting piping arrangement is constructed.

If the lift is needed right at the inlet of the receiver, an auxiliary accumulator tank with vent and float switch is installed.

With this arrangement, condensate flows by gravity to the auxiliary accumulator tank. When this tank fills, the float switch turns on the vacuum pump to make the lift up into the vacuum condensate pump's receiver tank.

Of course, the best arrangement here is to drop the condensate pump's tank into a pit so we get a gravity flow to it's inlet, and no lift is needed.

And yes, you are absolutely correct about high temperature condensate's effect on the performance of the vacuum pump.

Typically I tell customers that for vacuum operation, the temperature should not exceed 175 degrees F. A typically expected condensate temperature might be in the 140 degree F. range, but as far as vacuum pump operation and efficiency goes, the colder the better.