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SuperCoop · Jan 5, 2009, 09:54 PM

I have a gas boiler that from a cold start (first calls for heat) it will fire correctly, circulator will start running, and the burners stay lit until the set temp is reached. When the burners shut down the circulator will continue to run for several minutes. What I have noticed however, is that if it is really cold outside (usually at night) that the initial cycle will run but then the boiler apparently calls for the burners to fire again. They fire up correctly and then there is a click and they shut down. Five minutes later they fire again, another click and they once again shut down. This repeats several times. The circualtor continues to run during all of this.

I had a local heat and A/C guy look at it and he could find nothing wrong. He said sometimes parts have to fail completely before the fault can be found. My concern is that this seems to be adding $$$ to my gas bill.

Anybody have any ideas?

I also figured out that I have a Honeywell Type L8148E Aquastat relay, and a Taco cartridge type circulator 007-F5. I have 7 radiant baseboard heaters upstairs and 3 downstairs. Most of them are around 8' long.

Boiler info:

CAC / BDP
Series: PWB - 4D
Boiler Model No: BW2AAN000105ABAA

CGA Output 84000 BTU/HR

Cerified by: DUNKIRK

hvac1000 · Jan 5, 2009, 11:40 PM

Boilers do turn on and shut down but usually they run for a little bit once fired over even when the call for heat is not that severe.

It is possible that the heat anticipator in the thermostat is not properly set for boiler/hot water usage and that could cause the thermostat to call for heat more often than the boiler system needs.

It could be a flame sensor problem if the unit has one.

It could be the Aquastat if the settings are not correct like having the differential to close causing the unit to cycle to often due to small variations in the water temperature.

Gas bills are high and going higher and the only true way to find out if the boiler is causing the gas bill to go up is with degree day calculations and usage of cubic feet of gas NOT the dollar amount of the bill.

fencewriter · Dec 18, 2009, 12:46 PM

We have this exact boiler... and the exact problem, I think. We solve the problem only by cleaning the pilot light. The service technician saw the dust/debris/dirt that falls all over the bottom of the heater under the burners and pilot light. He said the dust clogs the pilot light, so we vacuum the pilot light after shutting the power to the unit off.

THis is very awkward. The pilot light cannot even be seen, so it is like guesswork to get a vacuum attachment anywhere near where it needs to go. Even worse, the dirt can clog the pilot light anytime, day or night, so the heat just fails to operate until we freeze enough to get down to the basement and clean it again.

hvac1000 · Dec 18, 2009, 07:37 PM

The dirt and dust should not accumulate so soon and what you probably need to do is remove the boiler jacket and use a round boiler brush to clean it real good between the sections if possible. Then your pilot should not have a problem for a few years. If too much debris is falling down it could also be a sign of another problem and professional service at that time would be recommended.

Mike Grieff · Jan 30, 2010, 07:32 PM

I jus', went through this episode with my Weil-Mclain VHE boiler. One, or all, or any combination, of the three B&G Little Red Booster pumps would get the call for heat and, if and when the water temp was at or below 170 degrees, the blower would start. Sometimes the pilot / ignitor / burners would never come on and blower would jus', switch off. Sometimes the pilot / ignitor would start and the burners would ignite and then go off in a few seconds while the Intermittent pilot / ignitor would keep trying and trying, and the burners would go on then go out, again and again, most of the time they would eventually, ignite. The 190 degree Limit would be reached and the system would shut down. I researched, and read about it being the Honeywell SM86 module being at fault or the Ignitor / Flame Sensor needing cleaning. What it turned out to be was a bad 'Pressure Differential Switch'. Once that was replaced the blower would start at 170, about 3 - 5 seconds and the pilot would come on and the ignitor would begin sparking and about another 5 seconds and the burners would ignite first time every time.