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





The Independent Energy C-120-1S-3I(adj)-4B is a programmable digital differential temperature controller from the early 1980s that is used for solar space heating systems. It has a six station digital readout that monitors the Collector and Storage temperatures along with two Auxiliary sensor temperatures. Two additional readouts display the Storage Minimum and Maximum settings used for the Space Heating operation. This controller operates the heat collection loop and interfaces with a thermostat and furnace to provide space heating from either solar storage or a furnace back up. Click here to see a general sensor and thermostat/furnace hook ups view or here for a more detailed view.


Only one controller is available. It uses a 1 HP relay as the final output device for the heat collection loop.


This C120 controller uses up to four readily available standard 10 K ohm thermistor sensors, one for the collector, one for the storage, and one each for the two Auxiliary sensor inputs.


If you would like more information about the C120 controller go to the Tech Manual Index on this web site and scroll down to the Independent Energy C-100/120 Programming, Installation, Application Manual section and download the entire manual.


If you are looking to replace your defective C-120-1S-3I(adj)-4B controller or just want one as a backup, order this one today as it is the only one left. Prices shown do 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 11-16-2018