Jon Klima, Owner
360 Trout Lane, PO Box 23, Guffey, CO 80820
Phone: 719 479-2281,  Email:
In business for 37 years


• Article 15 - February, 1996


Programmable Differential Temperature Controllers #2©


This is the second in a series of several articles that will summarize the programming capabilities of most of the differential temperature controllers used in the Colorado area. The previous newsletter, (May '95) presented the capabilities of the Dencor, Dynatech, HI2/Hawthorne, and Honeywell controllers. I stated then that the next newsletter would contain programming information for the Heliotrope, Independent Energy, and Johnson brands of controllers. However, as I started researching the product literature, I decided that it will take several articles just to cover the Independent Energy (IE) line of controllers. So, it will be awhile before I cover the Heliotrope and Johnson capabilities.


The information contained within this article is taken from product literature I have collected over the years and I believe it to be accurate.


Let's start first with the IE C-30. This controller uses 10 K ohm thermistor sensors and, if needed for freeze protection, GC-l, or equivalent, snap switches that open on temperature fall at 44° F ± 4° F and close on temperature rise at 54° F ± 5° F. Recirculation freeze protection (not recommended for this part of the country) can be accomplished with the C-30-1S by moving the factory installed jumper on the right side of the circuit board one position to the left, i.e., one half of the jumper on the left FREEZE terminal and the other half on the right hand collector terminal. This causes recirculation to turn on at 40° F ± 1.5° F and off at 45° F ± 1.5° F (other IE data sheets place these values at 40° F ± 2° F and 44° F ± 2° F). IE also recommends that one or more GC-l sensors be wired in series with the collector sensor as secondary freeze protection if this type of recirculation is being utilized. An alternate way to accomplish C-30-lS recirculation is to remove the jumper from the FREEZE terminals and replace it with a standard 10 K ohm sensor or several GC-l snap switches (or all wired in series). The C-30-1S-2F is a two output controller used to energize a pump and a drain-down valve.. The drain-down valve can be de-energized by the collector sensor at 44° F ± 20° F if the freeze jumper is connected between the left FREEZE terminal and the right hand collector terminal. If desired, a third 10 K ohm thermistor sensor can be connected to the FREEZE terminals in place of the freeze jumper. Secondary drain-down protection can be initiated by placing one or more GC-1 snap switches across the R-W terminals in place of the R-W jumper. This is probably a good idea as it serves as a backup to a thermistor sensor failure. Keep in mind however, that if this approach is used, when a GC-l snap switch opens at 44° F, the red power ON LED on the left side of the circuit board will go out. This happens because when the R-W circuit is opened, power to the C-30 circuitry is removed. The remaining programming available with the C-30 is the storage high limit temperature adjustment. Some units came with a 62° F to 104° F adjustable high limit range (usually used for SPA/hot tub heating) while the more commonly encountered units have a 105° F to 212° F range. The C-30-1S-2F drain-down valve is also de-energized when the storage sensor reaches the high limit adjustment set point.


Next let's look at the IE CM-30. This unit uses the same sensors as the C-30. The CM-30 has an adjustable TURN ON differential that ranges from 8° F to 240° F and an adjustable storage high limit that ranges from 110° F to 230° F. It's TURN OFF differential is set at 40° F. The unit is shipped from the factory with the recirculation feature disabled. To ENABLE recirculation, the 12 jumper, located at about the center of the circuit board, must be moved to the IN position. When enabled, the CM-30 output will turn ON when the collector sensor falls to 40° F ± 2° F or when any GC-l snap switch wired in series with the collector sensor falls to 44° F ± 2° F. Recirculation stops when the collector rises to 45° F ± 2° F AND all GC-l snap switches rise to 54° F ± 5°F. IE recommends at least one (preferably two or more) GC-l sensors be wired in series with the collector sensor. Alternately, or in combination with the above configuration, a GC-l snap switch(s) can be wired across the R-W terminals (R-W jumper removed). Differing from the C-30 here, when this option is used and activated, the left red power ON LED will not turn off.


The IE CM-33 is similar to the CM-30 except its storage high limit adjustment has a range of from 50° F to 104° F. The IE CM-50 differs from the CM-30 in that its adjustable TURN ON differential ranges from 15° F to 40° F along with a following TURN OFF differential of 4° F to 20° F. The adjustable storage high limit ranges from 60° F to 160° F. There is no provision for recirculation freeze protection with the CM-50.


One word of caution is in order for when any of the CM-XX controllers are used with the DLX-30, DM-30, or TD-CM monitors. A fault in any of these monitors can make it look as if the controller has failed. This can easily be checked by unplugging the monitor from the controller. If the controller now works, the fault is in the monitor.


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