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Rick Mather
Rick Mather, HVAC Technician
Category: HVAC
Satisfied Customers: 3634
Experience:  35 years experience, HVAC
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I have a Honeywell L8124a, c Aquastat and I was wondering what

Customer Question

I have a Honeywell L8124a, c Aquastat and I was wondering what adjustments of the high, low and differential settings would be in my best intrest as far as efficiancy is concerned. As of now I have the High set at 185 and the low at 165. The differential is set at 23. I have read several forums on the subject and all of them seem to suggest that the differential should be set quite a bit lower. From my understanding this should make the burner fire up more frequently but stay on for shorter intervels. I also would like to clearly understand what the point of the differential is if there is a low setting also. It seems that if the differential is set at 10 and there is a variance of 20 degrees between the low and the high, the temp would not ever go below 10 degrees of the high so whats the point of having the low setting? maybe Im not understanding it correctly so any information that would help clear things up would be greatly appreciated!                   Thanks Eddie
Submitted: 7 years ago.
Category: HVAC
Expert:  Rick Mather replied 7 years ago.
I would only change the differential to 10 degrees this would allow your hot water to be more stable because at 23 degrees your boiler has to see a drop from low limit setting of 23 degrees which means the boiler would be around 140 range really not enough to satisfy hot requirements
Customer: replied 7 years ago.

Can you explain the basics of what the 3 adjustments are for and what is best for the burner to operate at peak efficiency in different climates. For instance, right now the average temp for my area is in the mid 20's. what would be the best high and low settings and how should I adjust these settings in the warmer months? From what you have told me so far the differential alows the temp to drop the designated amount below the low setting? what is the point of having the differential? why wouldnt a high and low setting be enough?

Expert:  Rick Mather replied 7 years ago.
The boiler works off the low limit setting with no call of heat. When it calls for heat it will run up to the high limit. and when it calls for heat and the boiler temp is between low and high boiler will fire. when no call for heat the boiler temp will fall below low limit setting by the number of degrees the diff setting is before the boiler will fire. hope this helps
Expert:  Rick Mather replied 7 years ago.



Page 7 fig 12 will explain this in greater detail

Customer: replied 7 years ago.

When you set the diff setting at say 10 it will fall 10 degrees below the low setting and fire up even if it is not calling for heat to maintain the water temp? so is setting the diff at larger intervals such as 20 better in certain instances? My main reason for these questions is I want to set the settings at the appropriate numbers durning different seasons so that my burner operates as efficent as possible and uses the least amount of fuel oil. I am not concerned with having to wait a minute for my hot water to heat up.

For instance it may make sense for me to set the diff at 10 durning the winter but adjust it during the summer when the heat isnt on in the house so that the burner isnt firing all the time just to heat the water that I am only using once a day.

Expert:  Rick Mather replied 7 years ago.
I agree with your above statements

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