the cad cell is operational, replace the primary control.
4.If the LED continues to fl ash at the interval listed above, verify that the control is not in restricted mode. If in restricted mode, reset it. If not in restricted mode, replace the control.
5.If the (LED indicator for R7184 control; green LED for 7505 control) stays off while the fl ame is on, check the cad cell sighting for view of the fl ame.
6.If the burner locks out, check the cad cell resistance. (See Table 8)
7.If the burner stays running, the system is operational.
8.If the (LED indicator for R7184 control; green
LED for 7505 control) is off, check the cad cell assembly after disconnecting the line voltage.
Burner will not start and the LED indicator is
flashing at 2 seconds on, 2 seconds off for R7184 (or the green LED is fl ashing for 7505).
•Hold the reset button down for 1 - 2 seconds. If LED indicator continues to fl ash, wait for 60 - 70 seconds. If it still continues to fl ash, replace the primary control.
•Honeywell R7184 control: To check cad cell resistance, press and release the button during the run mode, with the igniter off.The LED will
flash to indicate the cad cell resistance. For proper burner operation, it is important that the cad cell resistance is under 1600 Ohms. For cad cell resistance, see Table 8.
•Beckett 7505 control: To check cad cell resistance, unplug the cad cell leads (yellow wires) from the control.Measure the resistance with a meter in the conventional way (when a
flame is present).For proper burner operation, it is important that the cad cell resistance is under 1,600 Ohms.
OPTIONAL ACCESSORIES
Necessary when the Furnace is Used with Some Central Air Conditioners
If an air conditioner is installed that does not use the furnace blower for air distribution and operates independently of the furnace, the thermostat system must have an interlock to prevent the furnace and air conditioner from operating at the same time. This interlock system usually contains either a
The furnace must also be equipped with an automatic damper to prevent cold air from being discharged up around the heat exchanger (NORDYNE p/n 901996 for furnaces without coil cavity, or p/n 901083 with coil cavity). See Figure 36 or 37.Cold air may cause condensation inside the heat exchanger which can rust and lead to early failure.
Figure 36. Coil Cavity Damper
LED Flashes (Ohms) | Cad Cell Resistance |
|
|
1 | |
2 | |
3 | |
4 | >1600 |
Table 8. Cad Cell Resistance when
sensing flame
Figure 37. Damper without Coil Cavity
28
