Transformers

ADAPTABLE FRAME TRANSFORMERS

UNIVERSAL MOUNTED TYPE TRANSFORMER

3C101

CAT. NO. MFG. NO. VOLTAGE PRIMARY 120V

S84-11

Plate, foot or hub mount. Not adaptable frame. VA CAPACITY EACH

VOLTAGE SECONDARY 25V

40 $48.34

Economical and stripped-down “skel- eton” type universal mount 40VA

transformer 24 volt system control power. Movable channel frame mounts allow for direct, horizontal or vertical foot mounting. Meets NEMA standards for “Class D” transformer.

CAT. NO. MFG. NO.

1C910 1C911

AT40A1121 AT40A1139

3C101M S84Z-401

VOLTAGE PRIMARY 120 240

VOLTAGE SECONDARY 26.5 26.5

120/208/240 24 VA CAPACITY EACH

40 40 40

$38.33 $40.67 $40.03

FURNACE ELECTRONIC CONTROL BOARDS

Furnace electronic boards are not as complicated as they may appear. They are actually relatively simple controls with multiple preprogrammed functions. They use inputs and send outputs based on their programs. The programs are sequential and the board will always proceed in the sequential programmed order. Deviation from the program only occurs when input is changed, or the board malfunctions. In the instance of a fan control board, the board receives an input (Call for heat on the R-W terminals from the thermostat) to begin its’ programmed process.

In the heat mode, a typical sequence might be: Close a circuit to send power to the inducer motor, determine a closed input circuit thru the limits, go thru a timed period and close a circuit to the space blower motor. In this instance, we have two inputs and two outputs. The inputs are from the thermostat, and from the limits connected to the board. A change in the inputs will result in a change in the outputs. Interrupt the input from the thermostat and the board will interrupt the outputs. Interrupt the input from the limit string and the board will respond by keeping the output circuits to the inducer and space blower closed, continuously running the inducer and space blower. (Logic being, an open limit normally means excessive temperature build up, let’s run the inducer and space blower to reduce the temperature at the equipment)

How would we “check the board” to determine if it is OK? Assuming the board has been wired correctly and is powered, we know it only has two inputs. Let’s remove the wires from those two inputs at the board and simply place a jumper on each pair of input terminals. Remember, the programs are sequential and the board must always proceed in the sequential programmed order. If the board closes the output circuit to the inducer, and space blower motor, it is functioning in it’s sequential order. (Should the board not react the same way when the inputs devices are reconnected, check the input devices and the connecting wiring, as the board is functioning normally) Conversely, should the board not close the outputs to the inducer motor and space blower motor, the board is malfunctioning and needs be replaced.

754

CONTROLS