steam

Jon Silva_2

We have a two pipe steam system w/ zone valves and a boiler feed pump. The Mcdonnell Miller # 150MD has been tested and checked, yet every morning for three weeks this fall the boiler has flooded. Could this be because we aren't really in the heating season or is something else wrong?

Geno_15

Something else is wrong

probably, zone valves on steam can play tricks on you, I prefer them to be normally open, watch it cycle this weekend, does it run and the water dissapear and then the feeder comes on???? When your zv's close the pressure built up in the boiler may be forcing the water up the return and your feed comes on, after a couple of times you're over filled. You've got a problem if that's the case, you may lose your boiler, it'll crack with no water in it eventually, you are going to have to watch it and see exactly what it is doing to be sure. Turn one t-stat up and run it a while, get some steam up and then turn the t-stat down making sure the other zone is off. If your system has been installed this way for a long time with no problems you may have a mud problem, is there check valves in the return in the back of the boiler, they may be shot, some will install them with zv's to keep the water in the boiler when the zv's shut.

Good luck.

jim_40

flooded boiler

A steam boiler in a multi-unit building is suddenly flooding out about every six days. Two pipe steam, gravity, running on 2 psi, nothing recently done on the system. Radiator trap elements all replaced about a year ago. F&T traps (3) replaced about the same time. Returns checked for flow at that time (line were open). Boiler is Peerless, about 20 years old. No history of flooding. There is banging on one of the distribution loops on start-up. We suspect this is due to sagging in the piping. System has been working fine until the flooding started last week. Local distributor suggests installing a condensate return pump. Ideas?

Steamhead

Jon, watch the pressure gauge

to see if it goes below zero when the boiler cools down. If it does, the closed zone valves allow vacuum to form in the boiler as it cools, which can pull water out of the feed tank and into the boiler.

The cure is a vacuum-breaker installed somewhere on the near-boiler piping where steam won't hit it.

Also, if the boiler has a tankless coil, it may be leaking into the boiler. Shut off the water to it to see if that stops the flooding.

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Steamhead

Jim, check your water feed valve

I'll bet it's leaking. If it's automatic, shut off the water to it and see if the flooding stops. If it does, you've found the leak.

If you do not have an automatic feeder, the shutoff valve in the feed line may be leaking. Repair or replace it.

If the boiler has a tankless coil, it may be leaking into the boiler. Shut off the water to it to see if that stops the flooding.

Don't waste your money on a return pump. Just fix the leak.

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