Johnson Controls TGLS*MP, TG8S*MP Section Vii Vent System, Single-WireTwinning Operation, Staging

356485-UIM-G-1211

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

Single-Wire Staging Operation

Heating - On a call for first-stage heat (W1 signal) from the wall thermo- stat, Furnace #1 will start the ignition sequence and the burners will light. About thirty seconds after the burners light, the blowers on both furnaces will come on in heating speed. When the thermostat is satis- fied, the burners will shut off and, after the selected blower off delay time, both blowers will shut off at the same time. On a call for second stage of heat, the burners of Furnace #2 will also light and both blowers will run. 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. 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.

W

G

W G

FURNACE 1	FURNACE 2
CONTROL BOARD	CONTROL BOARD

C
R	TWIN
Y	ISOLATION
	RELAY

C

R TWIN Y

W
G
C
R	TWIN
Y	ISOLATION
	RELAY

W

G

C

R TWIN Y

TO A/C		W G R Y
	WALL THERMOSTAT

FIGURE 20: Single Wire Twinning Wiring Diagram

STAGING

This control can also be used along with a two-stage wall thermostat to stage two twinned furnaces, making them operate like a single two- stage furnace. This allows only one furnace to supply heat during times when the heat output from one furnace is sufficient to satisfy the demand. When one duct system is used for two furnaces, it is neces- sary that the two blowers operate in unison. The twinning function of this board ensures that both blowers turn on and off simultaneously, and operate on the same blower speed. Even when only one furnace is supplying heat, both furnace blowers must run.

Single-Wire Staging

The single-wire twinning feature of this board can also be used for stag- ing of two furnaces. With this feature, a single wire is connected between the TWIN terminal on one furnace board to the TWIN terminal on the second furnace board. The board then communicates the blower status from one furnace to the other along this wire. This communica- tion makes the second furnace blower come on at the same time, and on the same speed, as the first furnace blower. To ensure stable com- munication, the common terminal of each control must be connected.

Single-Wire Staging Instructions

TO A/C
		W1 G R Y W2
	WALL THERMOSTAT

FIGURE 21: Single Wire Staging Wiring Diagram

SECTION VII: VENT SYSTEM

VENT CONNECTIONS

All models are provided with a flue transition that is sized for 4” diame- ter vent connections. If a larger size vent connector is required, that connection must be installed external to the furnace. Figure 22 shows the furnace as it is shipped from the factory. To convert to a horizontal or downflow position, remove the four screws that secure the inducer assembly and rotate 90° being careful not to damage the gasket. Rein- stall screws. Remove cap from appropriate vent outlet location on the cabinet, cut insulation in cabinet to same size as the hole provided and reinstall cap in the hole in the top panel.

In downflow applications, do not block the combustion air inlet. The furnace must be installed on a coil cabinet or subbase to allow com- bustion air to enter the burner compartment.

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.

4.Connect the common between furnace #1 and furnace #2.

COMBUSTION AIR INDUCER

90°	Mounting Screw	90°
	(Remove)

Pressure Switch
Tube Routing	Flue Transition
	(Do Not Remove)

Pressure

Switch

Mounting Screw (Remove)

FIGURE 22: Combustion Air Inducer

16 Johnson Controls Unitary Products