Originally Posted by Acuario (Post 63443)

Have you measured the entry/exit temperatures of the water passing through the tank? And the temperature at the lowest point of the heat exchanger?

What is the delta across the heat exchanger? The water from the panels should enter at the top of the tank heat exchanger (I assume this is what you have).

If the exit temperature is the same as the temperature at the lowest point of the heat exchanger then you have removed all the heat somewhere in the heat exchanger. Try increasing the pump speed until the exit temperature is slightly higher, then reduce it a little, then you know that you have the maximum possible flow rate to get the maximum transfer from the heat exchanger.

Originally Posted by Acuario (Post 63445)

If your connections are as you say then they are the wrong way around.
Heat always travels from hot to cold, never the reverse.

You need to feed the hottest water to the hottest point of the tank for it to transfer otherwise you will find the water leaving the top of the heat exchanger may well be the temperature of the hottest water in the tank.

Originally Posted by dremd (Post 63480)

I’m in no way an expert here, but my guess is you are drawing max out of your collectors by keeping them cooled by your tank thus maximizing collection, maybe some math involving tank outlet / inlet temp and electric cost to run pump is in order. That way you are also taking into account losses in plumbing. Again, I’m no expert.