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Old 09-27-21, 05:14 AM   #2
Solar Mike
Helper EcoRenovator
 
Join Date: Apr 2010
Location: Wellington, New Zealand
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Quote:
Originally Posted by Daox View Post
Is it simply a differential temperature controller? Is there any new tech or features I should be looking for in this area? Variable speed pump control?
Have built a few of these controllers over the years, you need a min. of 2 sensors for differential control, plus a setting for the min. pump on differential, usually about 3-4 degrees Celsius, as there is no point in running the pump when the difference is only a few degrees or less.

For water flow through the panel array: needs to be fast enough for turbulent flow in the pipes to get best heat transfer. Pump size depends a lot on length of your pipes to the array and array size; you want enough flow to get approx a 10 degree Celsius temperature rise out of the array; any higher (less water flow) will loose efficiency through heat radiation.

Last controller I built used a Picaxe 8 pin CPU (program in basic) and a couple of 1-wire temperature sensors DS18B20.

Also have one using a couple of Op Amps, will have a look for the schematic.

Edit: found it, I published this in Silicon Chip many years ago https://www.eeweb.com/solar-hot-wate...mp-controller/

Cheers
Mike

Last edited by Solar Mike; 09-27-21 at 05:49 AM..
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