Caleffi solar pump station

EricAune

check valves are really not relevant to the suction/discharge side of the pump. The pump should be sized for head loss and gpm's. If I read Dan's book and understand it properly, the placement of that pump in relation to the expansion tank is critical to the proper performance of the pump. Check valves play no role in this situation at all; its a given that they are open during pump operation.


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Big D_2

Caleffi solar pump station

Doesn't the Caleffi pump station pump toward the expansion tank(point of no pressure change). It seems to me all of the advantages of pumping away would apply to a solar loop as well as a typical hydronic heating system. If you were going to build a solar pumping station (with individual parts), would you pump away from the expansion tank?

Jim Plaugher

Solar station

Dave,
The expansion tank has to "open" to the Solar collectors which is the heat source. Most of the expansion happens when the pump is off. There are check valves in the solar station to prevent heat migration . They close when the pump is off, and would be "in the way" if the tank was on the other side of the pump.
Jim Plaugher

Jim Plaugher

Eric, I agree, pumping away is great for hydronic heating system pumps. It works well without fancy calculations. With the Solar Station, pumping towards the expansion tank is not ideal for the pump, but can work, if there is adequate
pressure on the suction side of the pump. The higher pressures usually recommended with solar systems seem to work OK.
With Solar it is not so much about pressure in the system while the pump is running, its about the expansion potential of the fluid when the system is at a standstill. The Caleffi Solar Station, Viessmann and others, have 2 check valves(supply and return) to prevent night time heat migration, so the tank has to be toward the collector. This is also a reason to not have a shut off valve for the expansion tank.

Paul Pollets

Valve on solar expansion tank

If the solar expansion tank is not valved, the tank cannot be charged, or checked for proper pressure without draining anitfreeze. The isolation ball valves on all pump modules is below the expansion tank port.

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Jim Plaugher

Valve on expansion tank

I saw the suggestion for not having a shut off valve, on the Reflex website. They make the expansion tanks for Viessmann. Yes, it would mean dealing with the fluid at the same time. It suggests having a high quality, long lasting tank would be a good idea. Or replacing the tank at the same time as the fluid replacement. If there was a shut off valve, you would not want to shut it when the sun's energy was increasing,right?

rt_3

I have a shut off valve going to my tank but I've lockwired it open to prevent anyone from shutting it by mistake.

RT