Drainback System Serving DHW and Swimming Pool Problem

calmech

Finishing up install consisting of 6- 4x10 Glazed panels heating one 119 gallon HTP indirect water heater (priority) then serving titanium pool heat exchanger if pool needs heating. I am using 2 pumps, one for each load with check valves upstream of pumps, Problem i am having is when pump shuts off water doesnt want to drain back quickly unless I open pressure relief valve to let back pressure out of drain back tank (20 gallon) I have a vacuum breaker and air relief at top of panels. I tried installing a normally open motorized valve between the supply and return pipes to panels that closes when either pump turns on but it still seems to have back pressure in D.B. tank that when relieved lets water quickly drain back into tank.

I removed motorized valve up high and have tried using a washing machine hose between supply and return hose bibs just below D.B. tank opening them when pump shuts off but still have back pressure inD.B. tank. Thought I might relocate motorized valve below drain back tank. Other issue is when pool is calling lot of turbulence in tank not sure if that air in that loop. Solar piping to pool equipment goes under ground over to heat exchanger. Nothing is ever easy. Oh Ya Happy Thanksgiving !

hot_rod

No place for a check valve in a drainback, get rid of that. I've never used a vacuum breaker either. Or even this crossover tube.

The drainback tanks needs to have an air space at the top, maybe 1/3. This is what breaks the siphon when the pump turns off. It is also the expansion space.

The collectors will drainback even under pressure, when the pump turns off.

Looks like a BX or MX control. It has drainback specific settings in it.

A pic of the system that is working right above me now.

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calmech

Thanks for your reply Bob, I have 2 pumps that tee off from the D.B. one for the indirect water heater and one for the pool heating circuit

I put the check valves in so when 1 pump was on it wouldn't pump thru the other circuit. I installed a drainback on my former house served just the water heater and everything worked fine. This is the first 2 load one I've done. I did see the drain back feature in the control which just let 60 seconds go by before reactivating pump. I have about 40 feet of pipe over to pool heat exchanger part of it underground. When pool pump is on I get alot of turbulence maybe still some air in loop. Maybe I should remove vacuum breaker and air vent. Or maybe lose pump to pool circuit and replace with a 3 way valve ? Then I could get rid of check valves.

hot_rod

I think you would be better with a single pump and 3 way zone valve like this arrangement

Use a 120V ac zone valve and it wires to R-2.

No air vent or vacuum breaker needed. Run 12- 15 psi or more to supress flashing to steam.

What pump are you running, what is the lift? Water level in DB tank to top of collector?

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calmech

This diagram would still work with the drainback ?

hot_rod

yes. Really all you do with a drainback is get the water out of the collectors and any piping that could freeze

calmech

Thanks Again Bob your knowledge and time are Greatly Appreciated 🔧

I will let you know how it all works out.