? test pumps & ctrl valves?

seekerseeker Registered Users Posts: 8
New guy here! Thanks for having me.

I have an open-loop, active, solar water heater system pumping into an 80 gal electric tank (unplugged). It's all commercially-built stuff, and about 15 years old. I think it might-used to have worked, but now I'm wondering. (Grundfos pumps, Goldline controller, Erie motorized check valve, 4' x 8' sealed collector.)

(I also have a second recirculating pump in a loop to get hot water to the farthest location quickly. This works well with electric heater 'on', but heat losses keep the tank running.... very expensive, so I keep the tank electric unplugged most of the time.)

There are three parts I have to ask about...
1) Even tho I hear my Grundfos UP15-42sf recirculating pump running, how do I know it's actually pumping water? It's a sweat-fit, so I don't really want to remove it for testing.

2) Erie motorized check valve: had to remove the synchronous motor to see if the check valve was opening and closing. It was, but noticed the un-mounted motor runs constantly whenever the recirculating pump is running. The motor is a gear motor, and the final gear runs a sector gear attached to the valve shaft, and this rotates the valve open and closed. (The valve also has a spring-return-to-closed when the unit is powered off.) So, is this motor really supposed to run all the time, even after the gears have hit their mechanical stops? I think this is called 'stall'? Can this be bad for the motor, or is it normal?

3) Water-flow question.... what happens when two different pumps run water thru the same 'tee' junction?
House recirc pump pulls hot water from top of tank, hot output, thru house loop, and is then supposed to push the cooled-off water back IN the bottom of the tank for re-heating.

The solar recirc pump is supposed to pull cooler water OUT from the bottom of the tank, get it hot on the roof, then push it back into the top of the tank, cold inlet.

Picture the letter 'T'. Bottom leg goes to tank bottom. Left arm gets water shoved IN to it by house recirc pump. Right arm gets water sucked OUT of it by solar pump. Is ALL the water from house pump loop (left arm of 't') pulled up by the solar pump (right arm of 't')? Does anything go in or out of the tank bottom while both pumps are running? Does it matter?

Looks like when solar system is 'on' and both pumps are running, water circulates out of house loop, up to solar loop, and back into top of tank, then back to house loop, missing the part where anything passes thru the bottom of the tank in either direction. What's going on here?

Can you see why I'm confused????

Any ideas on 1, 2, 3 or any combo thereof will be graciously accepted and probably commented upon. Might even help me get it working again!



  • FL SUNFL SUN Solar Expert Posts: 94 ✭✭✭✭
    Re: ? test pumps & ctrl valves?

    #1 - That is an 85 watt pump and should be very quiet when running. If you don't have a way to check entering and leaving pressure of your pump, you can check your temperature difference across your inlet and outlet temperature of your collector on a sunny day. Another way to check for pumping is to shut off the inlet supply (make-up, not your solar loop) to your tank, drain the tank partially, you will hear the return water trickling inside the tank with the pump on. Make sure your water level in the tank is above the pump inlet and below the loop discharge.

    #2 - Those motorized valves are impedance protected and designed to dead head against a stop without damage.

    #3 - I usually don't like or design multiple process through a single tube. Pipe separate flow circuits separately to your tank for best efficient operation. There are enough ports on your tank for that.

    Check your return from your collector entering in the cold water inlet? Make sure that the dip tube does not go to the bottom if this is your solar discharge. Discharge from the solar loop is better at the upper third of the tank. You lose a lot of hot water on cold morning solar start-ups if you dump straight in the top, and you short circuit your tank if you draw and discharge from the bottom.

    One other note: Recirculating pumps for "instant hot water" that are always on are very inefficient due to heavy loss as you stated, and electric consumption. The designs have come a long way in the past 20 years. They have timers that only circulate water when you need it, or a manual switch for pump operation, then a thermostat turns off the pump when the temperature is satisfactory.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,508 ✭✭✭✭✭
    Re: ? test pumps & ctrl valves?

    On your question #1 you should feel the heat with you hands. Peel back the insulation and when the system starts there should be a difference "felt".
    Sorry no time for the rest.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
    E-mail [email protected]

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