How to correctly set Honeywell Triple Aquastat L8124A


Old 02-16-07, 05:41 PM
Thread Starter
Join Date: Feb 2007
Posts: 3
How to correctly set Honeywell Triple Aquastat L8124A


I'm trying to figure out how to get my Hot water (domestic water) to be hotter than it is today....A have a CROWN Boiler model BD-120 WC (Bahama), oil fired cast iron with tankless domestic Heater coil for hot water use.
The oil burner is Beckett model AFG

The Honeywell Triple Aquastat relay for temp. control is L8124A, C

The HI setting on the Honeywell control panels is set to 200F and the LOW setting is at 180F. The DIFF (I don't know exactly what that control supposed to do) looks to be set at 13 degrees (between 10 and 15 degrees). The DIFF control has a low setting of 10 and a high setting of 45.

I have two heating zones (one upstairs and one downstairs) with one circulator....When the heat comes on the upstairs zone seems to heat better than the downstairs zone although both valves are wide open just the same....That's not a real problem for me as the heat seems to be working well in heating the house when need to.

My real probelem has to do with setting the domestic hot water correctly (ie hotter water)....I don't have a manual for the Honeywell Aquastat and how to set it correctly.

Any advice is welcome.....Also an explanation of what the DIFF control is used for will be appreciated.

Regards - VK
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Old 02-17-07, 08:23 AM
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For starters, you probably could learn about your control by reading this:

You already have the settings on your unit "maxed out" (too high IMHO).

It's likely that your problem is related to the tankless coil, and not the settings on the aquastat. Is there a mixing valve on the domestic piping to the boiler ?
Old 02-17-07, 04:49 PM
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Join Date: Feb 2007
Posts: 3
Okay, thanks for the info

I lowered the HIGH and LOW settings on the Honeywell Aquastat to 190F (high) and 170F (low)....I also set the DIFF to 15 (instead of 12 that it used to be) and it made a difference already...The domestic water is hotter.

To answer your other question, YES there is a valve for MIXED water on the piping to the boiler...I have not touched it. I'm not sure what it supposed to do (my guess is it controls the mixing of Hot and Cold water).

Anyway, like I said the water is hotter now that the DIFF setting is set to a higher number....Thanks again for your help and info.


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