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OT - 'Super Hot' boiler question

Time to get the heat back on in this neck of the woods. My workshop has floor heat, with a boiler (natural gas). This boiler (placards indicate "MG-125-N-E Mini Gas 'super hot' with Honeywell electronics) does not have a pilot light, but it fires up a piezo sort of lighter which ignites the boiler and it heats the circulating water until it reaches the required temperature, then shuts off. Cycling this scenario over and over. It normally runs for about 3 minutes, and is off for about 10 or so. I noticed at the end of the heating season in the spring that the boiler would not always stay running, and have to restart several times just to get thru one 'cycle'. The unit is 3 years old, and I just do not trust the shop that installed it to call them up about this problem. They tried to double the quote when the job was first completed, and I have soured of that relationship.

You can see (and hear) the piezo fire then the boiler lites and runs for maybe 10 - 15 seconds. It shuts off, then retrys to lite. Basically it will not stay running for as long as it needs to, and it seems like something is shutting it off. As with so many other things these days, the unit has an electronic control panel, with LED's and such, but no error codes are apparent. I guess it must be time to call a different repair person, but I thought I would try the group first, and see if anyone has any ideas. There is a couple of wires going up to something that looks like a temperature sending unit in the chimney, so maybe there is a problem with that unit not sending the proper signal back to the starter, so it will not stay running... any helpful thoughts?

TIA,

Ryan

Reply to
Ryan
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two possibilities. One is that the flame sensor is bad, and is not telling the safety control that the flame has lit. The other possibility is that the over temperature sensor on the boiler has gone bad, and is telling the control to turn off the flame. Ahh, the draft sensor! I haven't worked with those, but that really sounds like it might require a 15 second timeout before the draft starts pulling. Maybe it requires more time, or the sensor mechanism is dirty. Since it has a Honeywell control, you should be able to get in touch with somebody at Honeywell to tell you how to diagnose the problem.

Jon

Reply to
Jon Elson

does this use a thermostat? sometimes the unit will go bad and not call for heat properly

Reply to
Jran

Oil burners with intermittent ignition have flame sensors. Photoelectric cells, basically. You might have one and it being faulty would give your symptoms.

Bob

Reply to
Bob Engelhardt

My bet too. You can just clean the sensor with fine emery cloth and try it again. Greg

Reply to
Greg O

Is the flame pulsating? We had this problem with the boiler at work, and the problem was a faulty gas pressure regulator.

If the flame seems to be burning normally, then it is probably a sensor. The optical flame sensor may be covered with soot, or the stack temperature sensor may be faulty.

Gary

Reply to
Gary Coffman

Thanks to everyone who has posted so far... I will have a close look at it this morning and see if I can find some literature...

RB

Reply to
Ryan

I had some time to look at the boiler today. I was wrong on the time it takes before the unit shuts off the gas flow.

When the unit is powered up, the piezo fires and the boiler lites for 2 - 3 seconds. Then it shuts off. It will continue to re-lite, but the time it runs is the same. Sure sounds like a sensor, as you folks have indicated. Now I will search for some paperwork on troubleshooting it.

Ryan

Reply to
Ryan

The problem was a plugged heat exchanger in the boiler, which was not allowing the boiler to vent the exhaust properly thru the chimney. A thorough (read NASTY) cleaning was in order, and it now works 100%. Thanks to all who lent a hand...

Ryan

Reply to
Ryan

Hey Ryan,

I hesitated to reply earlier, but now your trouble is solved, I'll tell you that I was having a somewhat similar problem. My furnace is a "mid-efficiency" gas forced air and uses a programmable thermostat. The program allows the house to be cooler at night, and then at

6:00AM, a warmer "daytime" temp is selected. I noticed that quite often the ignition sequence would start, but about 30 seconds later the "noises" wou,ld stop. Then about a minute later, it would cycle like that again. Eventually, it seemed to get warm enough to bring the blower on-line, and then would seem OK through-out the balance of the day. I suspected a bad heat sensor that was not turning on the blower, and then when a "high heat" sensor tripped, it would shut down. But as usual, I was wrong. I had a furnace tech come in, and after my description he reached inside and pulled out a flame sensor rod. He cleaned a build-up of carbon from it, and replaced it. Runs great now.

Take care.

Brian Laws>The problem was a plugged heat exchanger in the boiler, which was not

Reply to
Brian Lawson

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