Second Loop and Circulator on Zone Valve System

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    • #279753

      I am adding a Superstor SSU-80 indirect fired water heater to an existing Burnham LE-1 oil fired boiler and Runtal radiant/convection radiators. The Burnham is controlled by a Burnham EC-5000 Outdoor Reset controller hooked up to zone valves. Because of the low mass of the boiler, it is necessary to run the bypass wide open and the return throttled way down. This is fine for the Runtals because much of the heating season the boiler is just sitting there at 135 degrees, with return water at 100-110 degrees. Now, I want to install this SuperStor water heater. Under DHW Priority, the EC-5000 controller will want to crank up the boiler to 180 degrees and above. However, with the bypass wide open, not much of that heated water is going to get to the SuperStor.

      To solve the problem. I want to add a SECOND 007 circulator in a SECOND loop with its own bypass, exclusively serving the SuperStor. There will be the existing loop for the radiators, including the existing bypass and zone valves for the heating zones. The heating loop and the DHW loop will each have a Watts Flow Chek to prevent backflows into the other loop.

      I have been told that it is not conventional to add a second circulator circuit to a zone valve system and that I risk unexpected difficulties because of interactions between the two 007 circulators. It seems to me that with Flow Chek valves on each circuit there should be no problems. The Flow Chek on the heating circuit would be ahead of the expansion tank to avoid the possibility of negative pressure on that component.

      I would appreciate hearing from experienced hydronics installers and engineers about my proposed solution for getting enough hot water to the SuperStor. Is there an alternative approach that I should be considering?


    • #301612

      Before zone valves became popular any multizone installation had multiple circulators with flow checks to prevent one zone from influencing the others. Adding a circulator should not cause a problem as the zone valves will prevent flow from the new circulator.

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