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Old 12-30-13, 11:27 PM   #13
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Trouble is, this unit only adds a couple/few degree rise to the water, requiring multiple passes. Dialing back the flow would overcome this, but that sounds like quite a balancing act (perhaps only suited to a such mentioned ECM pump with temperature feedback). Not sure how that would effect my COP as well, since a depleted tank has a much lower condensing temperature, than trying to maintain 115-120*f outlet temperatures. Something to mull over, maybe up for experimentation.

Still need to decide an optimal way to tap the tank. I dont Want to tap the tank drain as thats a sure source of sediment. I could pull the water from the inlet dip tube, but there will be conductive heat gain on its way up. I considered removing the lower element and install a short dip tube to the bottom, or possibly a coax'd tube in through the drain with a slight rise to get it off the bottom. Im going to push the heated water in through a Tee with the T&P valve in the top. That will ensure that cold water cant bypass the tank through the heatpump. The budget for this unit is about at its limit for feasible returns, so the ECM pump is out of the picture for this round... (and I got the taco for 25$ lol)

I'm not quite clear on the adapting strategy of these ecm circulators. Are they constant head/constant flow, or are they temperature feedback? Building a simple pwm dc drive with temp feedback for a DC pump wouldn't be too difficult. Not sure I want to try to venture into driving a split capacitor ac motor with a scr drive. But I guess that will depend on what kind of returns I get out of multipass vs constant control output.

Last edited by RB855; 12-30-13 at 11:44 PM..
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