ADVICE SOUGHT: Residential Steam Boiler cycles when door is applied


Old 02-23-14, 12:28 PM
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ADVICE SOUGHT: Residential Steam Boiler cycles when door is applied

I have a large residential steam boiler that has two sets of controls, and has 8 burner pipes on one side and 6 on the other side that normally work in tandem... when heat is called for, both sides fire up to heat the boiler, and both sides stop when no more heat is called for.

Recently, the smaller of the sides began to cycle every few minutes. I replaced the intermittent pilot device, the cable for spark, and even the Honeywell Ignition module S8600F IID to be sure that it wasn't contributing to the cycling.

As I can disable the working side of the boiler furnace to focus on the problem side, I troubleshot to determine that the newly replaced parts provided good spark, good gas, good pilot, and the burners fire right up. No problems until I replace the small metal door that allows access to the burners, and within 30 seconds the system starts cycling. When the door is removed, the system fires right up and does not cycle. There is no apparent blockage in the exhaust vents, which run together and out through a chimney.

The larger of the two sides of the burners has no issues and works fine despite the problems with the smaller side.

An insights would be much appreciated. THANK YOU.
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Old 02-23-14, 01:04 PM
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Hi Tom,

Make and model of the boiler please?
Old 02-25-14, 05:00 AM
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is there a flame roll out switch on the burner door ?
Check for intermittent short to ground, bad connection, finally temporarily jump it out to see if it short cycles when you put the door back on.
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