Posted by B.T. Bill on March 03, 2001 at 15:17:03:
In Reply to: McDonnell & Miller 902-m posted by TB on February 23, 2000 at 19:21:36:
: I got 2 McDonnell & Miller 902-m low water cut offs on my hot water boilers, one on each. Both operate the same, that is, when the test button is pushed, the indicator lamp turns on, apparently as its sposed to, but the burner circuit is not opened, dropping out the burner. This happens because the indicator light is wired parallel to the test button, and when the test button opens, the water sensing electrode signal is directed through the light and the relay ciol, holding it closed. When I disconnect the light, the circuit is broken, as the test button opens and the burner drops out. Is this normal operation for these controls or Is this goofy. I ask because our Hartford inspector didnt like the fact that it didn't drop out the burner, but it dosent seem to be designed to, while testing anyways. If I disconnect the lead from the water sensing electrode, the burner does shut off, even with the test light connected.
In most installations the test button is to be pushed when blowing down the columns and you DON'T want the burner to trip. Test this out by blowing down the column without holding the test button, the burner should trip.
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