CONIFER SOLAR CONSULTING

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

 

• Article 16, Part 2 - March, 1996

 

Programmable Differential Temperature Controllers©

 

Let's now move on to the C-100 and C-120 programming capabilities. The older C-100s were programmed at the factory or by someone who knew which traces to cut (or re-solder) on the printed circuit board. The newer C-100s have two DIP (dual inline package) switches (each DIP contains eight switches) that allows the user to place the switches in the ON or OFF positions and accomplish the desired programming. Details of the C-100 and C-120 programming can be found in the IE C100/C120 Programming, Installation, and Application Manual, pages 4 through 21 and 34.

 

First, start with all switches in the ON position. The Al and A2 switches select the reference sensor for the Output #2 function. This reference can be either the Storage sensor or the Aux 2 sensor, i.e., the Aux 1 sensor temperature is compared to either the Storage sensor or the Aux 2 sensor. With the Al and A2 switches in the ON position, the Aux 1 sensor temperature is compared to the Storage sensor. With the Al and A2 switches in the OFF position, the Aux 1 sensor temperature is compared to the Aux 2 sensor. In this latter case, the Output #2 differential is completely independent from the Output #1 differential (Collector to Storage temperature comparison).

 

The A3 and A4 switches govern the Output #1 temperature differentials. A3 and A4 both in the ON position results in ON/OFF differentials of 20/5° F. A3 OFF and A4 ON results in ON/OFF differentials of 8/3° F. A3 ON and A4 OFF results in ON/OFF proportional differentials of 16/5° F (meaning 5° F first ON and 16° F full ON). A3 and A4 both OFF results in ON/OFF proportional differentials of 8/4° F (meaning 4° F first ON and 8° F full ON).

 

The A5, B1 and B2 switches work together to govern the type of freeze protection provided, of which six different variations are available. When the A5, B1, and B2 switches are all in the ON position, NO freeze protection is provided. With A5 ON, B1 OFF, and B2 ON, Output #1 recirculation freeze protection will result. Output #1 will turn ON when the Collector sensor temperature drops to 40° F and will turn OFF when the Collector sensor temperature rises to 45° F. If a GC-1 snap switch is wired in series with the Collector sensor, it will simulate a very cold temperature when it opens at 44° F ±4° F. This recirculation freeze protection overrides all other control logic for Output #1. With A5 ON, and B1 and B2 OFF, Output #3 drain down freeze protection (C-100 only) will take place when the Collector sensor temperature drops to 44° F, i.e., Output #3 will turn OFF and will not turn back ON until the Collector sensor temperature rises to 64° F. With A5 ON, B1 ON, and B2 OFF, the previous Output #3 drain down freeze protection (C-100 only) takes place in addition to the turning OFF of Output #3 at the Output #1 high limit (Storage equal to or greater than Aux 4 input). When Output #3 turn OFF is due to a high limit condition, it will turn back ON after the Storage sensor temperature has dropped to 3° F below the Aux 4 input AND the Collector sensor is at least 64° F. With A5, B1 and B2 OFF, Output #2 will turn OFF when the Collector sensor drops to 44° F and will not turn ON until the Collector temperature raises to 64° F. This option could be used with a drain-down system. With A5 OFF, B1 ON, and B2 OFF, the previous Output #2 drain down freeze protection takes place in addition to the turning OFF of Output #2 at the Output #1 high limit (Storage equal to or greater than Aux 4 input). When Output #2 turn OFF is due to a high limit condition, it will turn back ON after the Storage sensor temperature has dropped to 30° F below the Aux 4 input AND the Collector sensor is at least 64° F. The A6 switch simply determines whether the digital temperature readout will be displayed in degrees F or C. The ON position designates degrees F while the OFF position designates degrees C. The A7 switch applies only to the C-120 (its position is not important for the C-l00) and deals with ENABLING either direct heating or indirect heating. Outputs #3 and #4 on the C-120 are dedicated to the control of solar heat distribution. When the A7 switch is in the ON position, the C-120 controls solar space heating directly from the solar collectors (top priority) or indirectly from solar storage (second choice). Back up control must be from the second stage of the thermostat. When the A7 switch is in the OFF position, the C-120 controls space heating from storage (Output #3) and also controls the back up heat source in the event of insufficient storage temperature (Output #4, W2). If all this seems confusing, don't feel bad. Pages 19 and 20 of the Cl00/CI20 manual contain two tables and many words that go into this in the utmost detail.

 

The A8 switch applies to C-l00 controllers only and only those with the #3 output capability. In the OFF position, Output #3 is turned OFF (disabling the back up DHW electric heating element) whenever solar collection is occurring. This allows solar to have first chance of heating the tank. If solar cannot completely heat the tank, then the element can finish the job when solar heating stops. When the A8 switch is in the ON position, the above Output #3 function is disabled.

 

The B3 switch, when in the ON position, does not allow for a high limit for Output #2. When in the OFF position, the high limit is set by the Aux 3 input if the "storage reference sensor" is the Aux 2 sensor, or by the Aux 4 input if the" storage reference sensor" is the Storage sensor. When the "storage reference sensor" reaches the high limit set point, Output #2 is forced OFF regardless of its differential temperature condition. Normal operation resumes when the" storage reference sensor" falls 30° F below the high limit threshold. This switch is for C-100 controllers only since the Aux 3 and Aux 4 inputs do not exist on C-120 controllers.

 

The B4 switch, when in the ON position, does not allow for a high limit for Output #1. When in the OFF position, the high limit is set by the Aux 4 input. When the Storage sensor reaches the high limit set point, Output #1 is forced OFF regardless of its differential temperature condition. Normal operation resumes when the Storage sensor falls 30° F below the high limit threshold.

 

The B5 switch, when in the ON position, disables nocturnal cooling. Nocturnal cooling would most likely be used only with a pool or spa/hot tub system. When the B5 switch is in the OFF position, nocturnal cooling is enabled. This means when the Collector is cooler than the pool (Storage) by the previously established turn ON differential temperature AND the pool (Storage) temperature is greater than the Aux 4 high limit set point, Output #1 will turn ON. This switch is for C-100 controllers only since the Aux 4 input does not exist on C-120 controllers.

 

When a C-l00 or C-120 is used in conjunction with a woodstove, the B6 switch is used to prevent relatively cool storage water from flashing to steam when it is pumped into an overheated stove. When the B6 switch is in the OFF position, Output #2 is forced OFF when the Aux I sensor temperature exceeds 210° F. Normal operation resumes when the Aux 1 sensor temperature falls to 200° F. When the B6 switch is in the ON position, this function is disabled.

 

The B7 and B8 switches govern the Output #2 temperature differentials. B7 and B8 both in the ON position results in ON/OFF differentials of 20/5° F. B7 OFF and B8 ON results in ON/OFF differentials of 8/3° F. B7 ON and B8 OFF results in ON/OFF proportional differentials of 16/5° F (meaning 5° F first ON and 16° F full ON). B7 and B8 both OFF results in ON/OFF proportional differentials of 8/4° F (meaning 4° F first ON and 8° F full ON).

 

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