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Thermistor location on collectors

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Posted by kcg on January 14, 2007, 4:12 pm
I am using a goldline gl-30 controller on a domestic solar hot water
heating system. I am wondering where the 10k thermistor should be
located on the collectors.

It would seem that if the thermistor is attached to the circulating
line at the collectors,  the circulating water would tend to maintain
the thermistor temperature above the collector temperature.

This would keep the circulating pumps running after the temperature
differential between the tank and collectors reverses.

Thanks for the help!

Posted by Gary on January 14, 2007, 4:53 pm
kcg wrote:

I believe that the conventional arrangement is to put the collector sensor on
the return pipe from the collector and very close to the collector.  It should
have some insulation over it.  The tank sensor should be near the bottom (cooler
part) of the tank.

If your controller is set to turn on at (say) a 12F differential, then when the
collector sensor is 12F higher than the tank sensor it will turn the pump on.
After flow is established, the sensor on the collector will be whatever the tank
temperature is plus however much the collector heats (or cools) the water as it
goes through the collector.  When the sensor on the collector gets down to 4F
more than the tank sensor, the controller shuts the pump off.  So, if all the
sensors are placed correctly the controller won't let the collector add water to
the storage tank unless its at least 4F warmer than the tank.

On the Goldline, the turn on differential is adjustable via a little dial under
the cover -- I think from about 8F up to 24F.  The turn off differential of 4F
can't be adjusted.


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Posted by kcg on January 17, 2007, 1:29 pm
 That makes sense. Thanks for the info!

Gary wrote:



Posted by kcg on January 17, 2007, 1:30 pm
 That makes sense. Thanks for the info!

Gary wrote:



Posted by KDV on January 20, 2007, 12:32 pm
I put my sensor on the upper collector pipe, see the pictures
http://users.telenet.be/hagim/zonne_energie/Installation.htm . When the water
is warmed up by the sun the heatest water will be always at the top of the
collector. I think if you place the sensor on the collector plate near a
vertical pipe on the top it wil work too. I think its not a good idee to
place the sensor on the outlet pipe of the collectors outside the collector
The other sensor on the solar boiler: if your system works with a heat
exchanger the best place is on the outlet pipe of the heat exchanger (water
to the collectors) and not on the solar boiler himself! The raison: you
never know how mutch cold and hot water is in the solar boiler. The water
outlet temperture from the heat exchanger is the best indication to know if
you can store more heat in your solar boiler or not.

Kris De Voecht
Homepage: www.devoecht.com

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