water feeder low water cutoff

Bill_110

I've got a PS-802 probe type low water cutoff and a M&M Uni-Match water feeder. My understanding of function is that in low water condition probe loses contact with water, after delay cutoff shuts off burners, waterfeeder feeds for set period(s) with time delay until probe is energized (ie covered with water), burners refire).

The way it works in my case, the probe has never come on to shut off the burners (and actually the water has never been low enough in the site glass to cause it to come on). But what happened every couple of days is that the water feeder would feed for one cycle about 2 minutes after the boiler shut off on the thermostat. The probe red light will blink and stay red just before it does this. At this time condensate is just beginning to return, but the water in the site glass is still well above the minimum level. When the condensate does all return the water level is actually a little higher than recommended. I would eventually have to drain some water to keep the level correct.

So my questions are : should the waterfeeder even be coming on if the low water cutoff hasn't shut down the burners? Should the low water cutoff and waterfeeder ever come on after the thermostat has already shut off the burners? I should also point out that I've never seen the cutoff blink red at any time when the boiler was actually firing.

I'm going to have these things replaced when I get my boiler re-piped, but I'm just curious to know why this thing works the way it does?

What I know from the intallation manual on the waterfeeder is that it should be upright on a horizontal run of pipe. These guys installed mine on a vertical pipe in a non-upright position.

Problems with condensate flow might be the 2 1/2" pipe in the wet return (where a union joined 2 returns) was replaced by them with a 1 1/4" copper pipe. I'm assuming that feeding a larger pipe into a smaller pipe might slow down the flow. Also the equalizer pipe is undersized per the mfgs specs. But although the return flow of condensate is definitely slower than it was with the old boiler, I don't think the water level in the gauge glass ever comes low enough for the waterfeeder to need to come on.

Sorry for the long post, but I'd appreciate anyone who has worked with these things to propose a theory of why this low water cutoff & waterfeeder works the way it does.