Boiler with domestic hot water preheating for water heater.


Old 09-28-09, 10:52 AM
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Join Date: Sep 2009
Location: Pennsylvania
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Boiler with domestic hot water preheating for water heater.

We have a Thermo-Dynamics boiler with domestic hot water. We are installing a heat pump water heater. This water heater has an EF of 2.3. We still want the boiler to preheat water during the winter when the boiler is operating, however not operate when the home is not calling for heat. We would like to avoid having the boiler run just to heat the domestic water. Is there a control I should be looking at that will shut down the demand for the oil gun to run to heat the water in the coil in the boiler but still function properly for home heat? Here is the link to the manual for the boiler:
Thanks for any advice.
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Old 10-06-09, 05:26 PM
Join Date: Oct 2009
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In short, you want the boiler only to work when the boiler calls for heat right?

looks like you have an aquastat with a low and high setting. If wired correctly, when the thermostat calls for heat, it should be working from the high setting. When the thermostat is not calling for heat, the boiler should come on with the low setting. An easy fix is just lower the low all the way down, and put the differential to 20. If the low is 100 degrees, the boiler will only come on when the temperature of the water reaches 80 degrees or thermostat calls for heat.

This is the easiest fix. Otherwise, you have to install a switching relay from the thermostat 24v to give power to the aquastat when thermostat is calling for heat.

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