LWCO Blowdown....Under a Little Pressure?

AdmiralYoda

I have a 44 year old Peerless boiler and I test the float type LWCO weekly. I generally have two different methods.

1. While the boiler is running, but not steaming I will open the drain on the LWCO and verify the boiler shuts down when the float drops. I'll let it drain until the water is clear and top the water back off, then let it boil to drive off any free oxygen.
2. Open the LWCO valve while the boiler is making steam and under pressure, maybe 0.5-1psi. This doesn't shoot the water out of the LWCO drain but actually allows the water in the LWCO to boil and become turbulent. Kind of a LWCO steam cleaning. Since the boiler is really hot I'll let it cool a bit before toping it off, then fire it back up to drive off the free oxygen.

Any harm to the LWCO while doing the blowdown while under pressure? Seems to keep it clean. Thoughts?

And to be clear I'm not bypassing any safety controls when I do the blowdown under a little pressure. I just set the thermostat a couple degrees higher and let the system fill up with steam and build some pressure. My Vaporstat cuts out at 18 ounces with a 12 ounce differential. I have a Pressuretrol backup too. 2psi cut out with 1psi differential. I measure this with a 0-32oz gauge.

ethicalpaul

It looks like they recommend flushing it during boiler operation:

http://s3.supplyhouse.com/manuals/1350816480646/83711_PROD_FILE.pdf

Jamie Hall

Whatever works. I see no particular problem with either of your methods. Main thing is to get that blowdown valve fully open. My own preference is to not just open it, but to open it, let it swoosh, close it, let the LWCO refill, open again, rinse and repeat until the swoosh is clean — then top off and go. Usually two or three swooshes will do… but as I say, whatever works.

ChrisJ

For me, the main thing is to make sure the burner automatically shuts down while you're dumping the LWCO.

If it doesn't, the LWCO doesn't work and that's bad.

EdTheHeaterMan

I told my customers that the LWCO flush is better done under pressure. And if the water feed is connected to the wet return before the HL, then you can add water right away.

EBEBRATT-Ed

The above answers are fine with me. My only comment is to assure that the piping connecting the LWCO to the boiler is clear. It can be partially plugged and the LWCO will shut the burner off on a blowdown but if the boiler loses water and the connections are compromised the LWCO may not trip on low water.