Hi guys, I am new here and need some help.
I have a nine panel solar hot water heating system that works great for the fall, winter, and spring months, but the system is oversized for for the summer months and quickly gets too hot and shuts down. This was somewhat prepared for when the system was designed, and the plan was to use excess energy to heat the hot tub, however the hot tub receives enough solar energy just from the sun shining on it that using it as a heat dump would make it unusable! Instead I was thinking of installing a recirculating stream type thing in the backyard in which I could place a heat exchanger and pump glycol through to absorb some of the excess heat.
The plumbing is all there to do this, all I need is a controller that will signal the pump to turn on when the storage tanks reach a certain temperature. All I have been able to find are differential controllers. If anybody has an idea of a pump controller that would work for this application please let me know. Thanks in advance.

Sorry for the long post.
Cliff Notes: Need a controller that will signal pump to turn on when solar tanks reach a certain temperature (150-180 degrees Farenheit)

Also, I should mention that I have an unused TACO SR 501 unit. Is there anyway to have a thermistor communicate with the TACO controller?

What temps are you looking to dump at? A simple pool or hot tub controller would likely do the trick. Or what about a water heater element and reverse the contacts? So its set for say 150F, normally it would open, but wire it to a relay and once it opens, it would turn the pump on? Once the temp fell below your set point and the water heater element turned back on it would shut the pump off.

Thanks for the suggestions. I really like the idea of just using the water heater controller. Seems like a simple and cost effective way of accomplishing what I want.
Thanks again.

There are a variety of differential controllers with two or more relays and a thermostatic function. I bought the Resol Delta Sol BS Plus from Frank at www.sssolar.com. I believe the Steca TR0603mcU also has this capability, but it is much more expensive than the Resol controller.

GoGreenMachine,
Look into this valve. Plumbed on hot side of collectors on the roof to something with finned elements such as Apricus HD-25 heat dump, this valve uses not controller or electricity. A 190°F valve begins opening to send fluid to dump at 185°F and is fully open at 195°F. I use this in my Solar Installation business. No wires or sensors, just works. TempmatiX from Independent Energy Center in New Mexico. Made in USA, too.
Good luck,
Raysun
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