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


• Article 20 - November, 1996


Programmable Differential Temperature Controllers©


This is the seventh in a series of articles that will summarize the programming capabilities of most of the differential temperature controllers used in the Colorado area. This article will examine the Independent Energy SP-30, -32, -33, and -34 series of set point controllers. All use 10 k ohm sensors and can be powered from 120 VAC, 240 VAC, or 24 VAC. The differences between these controllers are their set point ranges which are SP-30 (-26° F to 200° F), SP-32 (-26°F to 90° F), SP-33 (40°F to 104° F), and SP-34 (50° F to 200° F).


These units differ from the C-30 and CM-30 in that there is no power at the SPDT relay contacts, i.e., they are isolated contacts and you must provide whatever power you need switched to the common terminal (R) on the output terminal board. The R to B circuit opens on a temperature rise while the R to W closes on a temperature rise. The factory installed jumper on the sensor terminal board must be left in place if the internal adjustable set point knob is to be effective. This internal set point adjustment can be disabled by removing the jumper and installing, in its place, either a fixed resistor, a 10 k ohm sensor, a remote adjustable 10 k ohm pot (a higher value pot will allow an adjustment lower than 77° F). Also, the T1 adjust knob on a DLX-30, when interfaced with the SP-3X, will override the SP-3X internal adjustment (the SP-3X internal adjustment must still be disabled by removing the terminal board jumper). If over time, the internal set point becomes erratic, Independent Energy suggests removing the sensor terminal board jumper and installing a remote adjustable pot.


The SP-3X output is ON (relay energized and indicated by the LED) whenever the temperature of the sensor wired to terminals 3 and 4 is equal to or greater than the set point temperature. The output turns OFF whenever the SP-3X sensor temperature drops to the set point temperature, minus the differential setting. This turn OFF differential is adjustable from 1.5° F to 25° F.


This concludes the group of articles dealing with the Independent Energy series of controllers. Next time we will look at the Novan 2011 and DLP-20 controllers. Although they don't have a lot of programming capabilities, the sequences of operation are interesting and can cause a lot of confusion.


I've taken all of the above information from the manufacturer's product literature which I assume to be correct. If I've made a mistake or have left out some important information, or you otherwise take exception to what I have written, please write to me (c/o CoSEIA or to my address listed in the CoSEIA membership directory) and we will include your comments in the next newsletter.


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