Thomas & Betts UDAP - Manual (Page 17)

Form RZ-NA I-UDA, Mfg #195673 Rev 5, Page 17
Make sure that the heat anticipator setting on the thermostat is 0.6 amps (or in
accordance with the amperage value noted on the wiring diagram of your heater).
Make thermostat connections at the terminal strip on the back of the heater. The
strip has four terminals, R, G, W1, and W2; refer to the wiring diagram.
FIGURE 13 - Terminal
Strip for 24-volt wiring
is on the outside rear
of the heater
NOTE: The size of heater
illustrated has a vertical
terminal strip. Some sizes
have a horizontal terminal
strip.
Unit Mounted
Thermostat -
Option CM3
Multiple Heater
Control - Option
CL31 and Option
CL32
If the heater was ordered with Option CM3, a kit for mounting the thermostat on
the rear of the heater is shipped separately. Follow the instructions in the option
package to attach the bracket.
Select a snap-action thermostat when using the unit mounted thermostat bracket.
Do not use a mercury switch thermostat because the vibration may cause exces-
sive unit cycling. Be careful with the thermostat leads; shorting the thermostat
wires to a metal surface will cause the transformer to fail.
If the heater was ordered with a multiple heater control option, one thermostat can
be used to control up to six heaters. The option includes a 40VA transformer that
replaces the standard transformer in the “master” unit and a relay assembly that
attaches to the “slave” unit. Option CL31 provides for control of two heaters. If
control of additional heaters is desired (up to six total), Option CL32 which is the
relay assembly only must be added to each of the “slave” heaters.
The option packages are shipped separately and include complete instructions on
installation and wiring.
16. Combustion
Air Proving
Switch
(Pressure
Switch)
The combustion air proving switch is a pressure sensitive switch that monitors air
pressure to ensure that proper combustion airflow is available. On Model UDAP,
the switch is a single pole/normally open device which closes when a negative
pressure is sensed in the venter housing. On Model UDAS, the switch senses the
differential pressure between the negative pressure in the venter housing and the
pressure in the cabinet. (For switch location, see FIGURE 18, page 31.)
On startup when the heater is cold, the sensing pressure is at the most negative
level, and as the heater and flue system warm up, the sensing pressure becomes
less negative. After the system has reached equilibrium (about 20 minutes), the
sensing pressure levels off.
If a restriction or excessive flue length or turns cause the sensing pressure to be
outside the switch setpoint, the pressure switch will function to shutoff the main
burner. The main burner will remain off until the system has cooled and/or the flue
system resistance is reduced.
Supply
Wiring
Entrance
R
G
W1
W2
R
G
W1
W2
Supply
Wiring
Entrance
Terminal
Strip
Terminal
Strip
Built-in
Disconnect
Switch
Rear View - Model UDAP
Rear View - Model UDAS