DUALAIR® HEATING AND COOLING UNITS INSTALLATION OPERATION AND SERVICE MANUAL
16.6Cooling Coil Safety Devices 16.6.1 Cooling Coil Frost Thermostat
The sensing element for this device is inserted into the pocket of the cooling coil situated through the access hole in the coil cover.
The frost thermostat has two settings marked as set point with an arrow head and "diff". The control should be set at 5° C with a 1° C differential.
To replace, remove screw and pull off knob. Remove cover. Disconnect wires.
Pull the sensing element out of the pocket in the coil. Replace in reverse order.
16.6.2 Pressure Switches
The coil and dirty filter pressure switches are preset and different. They are differential pressure switches measuring the pressure loss across the coil or filter.
Coil Pressure Switch
(Normally open contact) used to prove adequate air flow for safe operation of cooling coil.
Filter Pressure Switch
(Normally open contact) used to give indication of filter becoming blocked.
To replace, remove coil compartment cover. Disconnect wires noting their position. Remove the flexible tubing noting the position of the tube connection. Replace in reverse order and check operation.
Figure 18: Cooling Coil Safety Devices.
Red
Coil Frost Thermostat set at 5°C with 1°C diff.
Coil Pressure Switch
set at 0.57 mbar (.23 in wc)
Filter Pressure Switch
set at 1.17 mbar (.47 in wc)
Red
N.O
Connections Negative
Pressure
White
White
Filter
Set | Positive |
Pressure | |
Point |
|
Description | Part Number |
Coil Pressure Switch | 90439801 |
Filter Pressure Switch | 90439804 |
Coil Frost Thermostat | K018 |
40
