Jon Klima, Owner
360 Trout Lane, PO Box 23, Guffey, CO 80820
Phone: 719 479-2281,  Email:
In business for 39 years





This Independent Energy C-30 is a basic ON/OFF differential temperature controller from the early 1980s and provides the basic "ON" and "OFF" differential functions along with a high limit tank protection which de-activates the pump when the storage tank temperature is above and adjustable high limit set point. This controller uses a relay rated at 120 VAC, 1/3 HP, as the final output device that switches power to the pump. The controller incorporates a solid state operational amplifier to determine when the pump should be turned ON and OFF.


I rescued this C-30 controller from a Grumman Sunstream DHW solar system that was being removed from a friend's house. I've converted it to a standard C-30 by removing and replacing the remote switch umbilical that the Grumman Sunstream DHW module uses with a standard OFF-AUTO-ON switch.


The Independent Energy product sheet shows this C-30 solar thermal controller as having fixed turn ON and OFF differential temperatures of 20 ºF and 5 ºF. I've tested these differentials and found them to range from 18 1/2 ºF to 22 1/2 ºF for the turn ON differential and from 6 ºF to 6 1/2 ºF for the turn OFF differential.


The adjustable HIGH LIMIT is presently set at 175 ºF and can be easily adjusted up or down from that level.


This controller was designed to operate with two 10 K ohm thermistor sensors for the ON/OFF differential and high limit functions. This unit that I am selling comes with only one of those required sensors.


If you are looking to replace your defective C-30 controller or just want one as a backup, order this one today as it is the only one I have. The price shown does not include postage.  Colorado sales will be charged the appropriate sales tax. Yes, I accept credit card payments through PayPal, checks, and money orders.  For questions or to place an order, send me an email (see top of this page) stating what you are interested in along with your zip code.  I'll check the postage to your zip code and send you a return email with the total cost.



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This page was last changed on 4-28-2018