Aquastat High Limit temp not working for Honeywell L8148A


Old 01-23-16, 07:59 PM
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Aquastat High Limit temp not working for Honeywell L8148A

Hello everyone. I have been reading these forums for awhile and love all of the information and help everyone provides. I have an issue that I didn't see addressed in other threads.

My family room, which is on it's own zone, struggles to get above 68 degrees on cold days when it is 20 degrees or below outside. I have had this issue ever since my boiler was replaced about 10 years ago. I tried vacuuming the fins and removing obstructions in front of the baseboards but that didn't help. I was hoping to squeeze a little more heat by increasing the boiler temp.

I have a Durham boiler with a Honeywell L8148A aqua stat (oil). My boiler kicks on at 160 degrees and shuts off at 180 degrees. I adjusted the high limit setting to 190 degrees and nothing changed (still cycles at 160/180). Am I missing something painfully obvious? Any suggestions?
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Old 01-23-16, 09:10 PM
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Is it only the family room that gets cold? If so, you might not have enough radiation in that particular room.
Old 01-24-16, 06:17 AM
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To be clear, what you are saying is that even with the circulator running 100% of the time, the family room doesn't get warm enough? And family room has it's own thermostat, correct?

If the circulator is not running 100% of the time under this condition, they you have a thermostat, wiring, or control problem.

If the circ is running 100% then increasing water temp will help, but as Rockledge points out, real answer may be adding convector area to that zone.

OK, you adjusted the aquastat setting to 190 but burner is still shutting down at 180, correct?
If the circ is still running but burner shuts down at 180 then you may have an second high limit safety switch that's also set at 180. You should be able to trace the wiring to the gas valve to see if this is the case.

If there's no second safety, and the circ is running, then it seems like an aquastat problem, although they are pretty reliable.
Old 01-24-16, 06:21 AM
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Yes, family room is the only one that can't reach thermostat temp setting on colder days. I am definitely light on baseboard heating in the room (bigger room w/ cathedral ceiling). Since it was never an issue with the old boiler, I am assuming it likely was set at a higher boiler temp. I am hoping setting the new boiler at a higher temp than 160/180 will at least help a little bit.

Everything appears to be working properly as the circulator will continue to run 100% of time while the thermostat calls for heat. Yes, I adjusted aqua stat to 190 degrees and boiler continues to cycle off/on at 160/180. I tried to follow the wiring and couldn't find any other safety switch. Is it possible that the module that controls start/up timing (the one with the reset button) has it's own hard coded temperature range? I read the Burnham installation guide and my install set up appears to be the same (using correct aqua stat), and those instructions say adjust boiler temp with the high limit dial on the aqua stat.

I checked return piping in the zone loop and it gets hot while circulator is on so I don't think it is an air/blockage problem.

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