Adjusting aquastat


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Old 01-22-03, 10:25 AM
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Adjusting aquastat

I have a Burnham FR 147 oil fired boiler with a tankless water heater and a 4 zone setup. The hot water is just too hot. The aquastat is set at 180 high 160 low with diff at 15. Can I lower the high limit to 170 or lower to lower the domestic hot water. I expect this will slow the house heating down some. If I am willing to accept, or at least expirement with this, are there any other factors to consider. And is it necessary to keep the low limit 20 degrees below the high limit. And what does the diff setting do?Do I change this or leave alone no matter what?

Thanks in advance for your help!
 
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Old 01-22-03, 11:54 AM
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The low limit is the temperature that the boiler will reach at any time there is no call for heat. The low limit minus 10 degrees is the temp. the burner will start up at when there is no call for heat. The differential controls the circulator-off section of the low limit control and I always set that as low as possible. It is not a critical adjustment. The high limit is the temperature that the burner will stop at when there IS a call for heat. If you don't separate the high and low by 20 degrees, you can get into a circulator lockout situation where the circulator won't come on because the temp is not high enough for it to activate and the burner is off on high limit.

You can set the high at 170 and the low at 150 for starters. You might consider installing a tempering valve on the hot water coil. It is now called an extending valve. It measures the temp of the hot water and adds a small amount of cold to achieve a desired temperature to the faucets. They can be troublesome at times, but if installed correctly, solve problems such as yours.
 
 

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