Help - Settings on my oil burner

Old 10-30-04, 02:01 PM
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Help - Settings on my oil burner

I have a oil burner which heats hot water that runs through the house into room radiators. We also use the same oil burner for heating our tap/shower water. There is no traditional hot water tank however.

As I understand, the dials on our (Honeywell Triple Aquastat L8124A & Valiant Oil Burner) controller mean :

High - oil burner shuts off when the water heats up to this temp
Low - oil burner fires on when the water gets down to this temp
Diff - this I don't understand.

Could you please give me a quick definition of this "Diff" Setting, and approximately what temp these dials should be set?

Thank you,

Tristan Fiedler
Long Island, NY
Old 10-31-04, 06:01 AM
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You are not correct about the high or the low. The high is the temperature that the burner will shut off at DURING A CALL FOR HEAT from the thermostat. It has a fixed 10 degree differential.
The low is the temperature that the burner will shut off at WHEN THERE IS NO CALL FOR HEAT. (like all summer) It also has a fixed 10 degree differential. There is also a third control, the reverse (which stops the circulator if water gets below this temp. That temperature is determined by subtracting the variable differential from the low limit setting. It does sound a little complicated but if you have a domestic hot water coil, set the adjustable differential at 10 degrees and leave it alone. Set the low limit at 160 and the high limit at 180. If you have a shortage of domestic hot water, you can push them both up 20 degrees to 180 and 200. Keep them 20 degrees apart or you can lock out the circulator and not have heat. If the real issue is not enough domestic hot water, you might look into an indirect water heater. Then you can run the boiler at a lower temperature and have more hot water than a coil will give you.


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