Single-Wire Twinning Operation
Heating - On a call for heat (W signal) from the wall thermostat, both furnaces will start the ignition sequence and the burners on both fur- naces will light. About thirty seconds after the burners light, the blowers on both furnaces will come on in heating speed. When the thermostat is satisfied, the burners will all shut off and, after the selected blower off delay time, both blowers will shut off at the same time. The twinning control ensures that both blowers come on and shut off at the same time.
Cooling - On a call for cooling (Y signal) from the wall thermostat, both furnace blowers will come on at the same time in cooling speed. When the thermostat is satisfied, both blowers will stay on for 60 seconds, then will shut off at the same time.
Continuous Fan - On a thermostat call for continuous fan (G signal), both furnace blowers will come on at the same time in cooling speed and will stay on until the G signal is removed.
| FURNACE 1 |
|
|
| FURNACE 2 |
| CONTROL BOARD |
|
|
| CONTROL BOARD |
| W |
|
|
| W |
| G |
|
|
| G |
| C |
|
|
| C |
| R TWIN |
|
|
| R TWIN |
| Y |
| ISOLATION | Y | |
|
|
|
| ||
|
|
|
| RELAY |
|
TO A/C | W | G | R | Y |
|
| WALL THERMOSTAT |
|
FIGURE 21: Single Stage Twinning Wiring Diagram
STAGING
This control can also be used along with a
Single-Wire Staging
The
Single-Wire Staging Instructions
Connect the control wiring as shown in Figure 22,
1.Connect the low voltage wiring from the wall thermostat to the ter- minal strip on the control board of Furnace #1. For staging applica- tions, the wire from thermostat W1 is connected to the W connection on the board on Furnace #1. The wire from thermostat W2 is connected to Furnace #2 through a separate relay, as described below.
2.Connect a wire from the TWIN terminal of Furnace #1 to the TWIN terminal of Furnace #2.
3.Install a separate 24V relay as shown in the diagram below. Use of this relay is required, as it ensures that the transformers of the two furnaces are isolated, thus preventing the possibility of any safety devices being bypassed.
Single-Wire Staging Operation
Heating - On a call for
Cooling - On a call for cooling (Y signal) from the wall thermostat, both furnace blowers will come on at the same time. When the thermostat is satisfied, both blowers will stay on for 60 seconds, then will shut off at the same time.
Continuous Fan - On a thermostat call for continuous fan (G signal), both furnace blowers will come on at the same time in cooling speed and will stay on until the G signal is removed.
| FURNACE 1 |
|
| FURNACE 2 | |
| CONTROL BOARD |
|
| CONTROL BOARD | |
| W |
|
| W |
|
| G |
|
| G |
|
| C |
|
| C |
|
| R TWIN |
|
| R | TWIN |
| Y | ISOLATION | Y |
| |
|
|
| RELAY |
|
|
TO A/C | W1 G | R | Y W2 |
|
|
| WALL THERMOSTAT |
|
|
FIGURE 22:
Johnson Controls Unitary Products | 15 |