Water level jumps suddenly while filling boiler

gypsydoctor

In my steam boiler with an auto-feeder the water level will jump several inches every several weeks, as indicated on the sight glass. I will drain about a gallon and the level will be reasonable for a while until it happens again.

I disabled the feeder by shutting the ball valves and the problem stops. I lose about 1/4 inch a week and manually reset the level.

I opened the ball valve and disabled the feeder by disconnecting the wire from the LWCO--it is still disconnected. The problem did not return, so I suspect the feeder does not have a slow leak. (I cleaned the strainer way back at the beginning.)

Today, with the boiler off and cold, I noticed the level was down an inch, and I tried feeding water by holding the red button on the feeder, which feeds water pretty slowly. I held it for about 45 seconds and could hear water flowing, but the level did not rise. Then suddenly the level jumped up about 3/4 inch and then continued to rise slowly as it normally does. (I have not drained water from the pipe between the feeder and the boiler.)

What would make the water level suddenly jump? I suspect this "jumping" behavior has something to do with the "filling too high" problem.

Note that the feeder and LWCO seem to be working properly. If I lower the level significantly, it feeds for about 30 seconds or until the LWCO contacts open up when the proper level is reached.

The LWCO is a McDonnell Miller MH1067 205195 (millivolt)
The feeder is McDonnell Miller WFE-24 Uni_Match (DIP switches are set properly)

KC_Jones

Have you checked to make sure the lower valve on your sight glass is clean and isn't filled with gunk?

gypsydoctor

I think that's on the right track, and would explain the sudden jump in the water level in the sight glass, but would not explain the larger problem of the level going up an extra gallon. The "gunk" must be blocking both the sight glass and the LWCO's float that turns off the feeder.
Perhaps there is gunk somewhere in the piping so that the feed water rises up into the condensate return pipe until it gets enough "head" to push through the gunk and get into the boiler, including the LWCO and sight glass. (The feeder line connects into the wet return (I think). See the lower left corner of the attached photo.)

Jamie Hall

Hatterasguy said:

When was the last maintenance performed? They do require annual cleanings that address the accumulation of rust at the bottom of the system (many locations).

Trying to determine the culprit on a system that could have many is an exercise in futility.

I'm not sure it's an exercise in futility -- but it surely can try one's patience!