I'm just installing a solar heating system and need some advice please.
I have an Intex pump 2000GPH and have the solar T'd off and back in from the pump outlet, into 1 1/2" poly pipe
for a distance there and back of about 160' total with a rise in ground level of about 4', with 5 coils of 3/4" poly pipe each of 160' all linked from a central manifold also of 3/4".
At the moment I have 4 coils connected to see what the flow would be like with this pump (which is about 1/2 to 3/4 hp).
I am surprised to see that the flow is strong even after going through 4 coils.
Now, I have read conflicting opinions on flow v temp. Some people seem to say that flow should be slow but not so slow that the coils are able to warm up to the touch.
Others say flow should be fast and that even a slight temp difference is better from larger flow than a greater temperature from a smaller flow.
I have also read that only a small flow should be diverted to the solar coils whilst allowing the pump to move the majority of the water in the normal way so as to
reduce back pressure on the pump and therefore not shorten its life.
This would require a non return valve on the return line otherwise the water would not circulate in the solar system (ie if the main valve is open).
I have a Jandy non return which I could fit, but the spring on it is probably too strong for such a small flow to push it open.
As the pump seems to be functioning near normally on full flow through the solar system (at least with 4 coils at the moment), should I worry about back pressure and reducing the flow
to increase the temp?