Install Instructions

Table Of Contents
26
I-UBX-UBZ-UDX-UDZ (04-21) 1034344-0
CONTROLS—CONTINUED
Thermostat Options
NOTES:
IMPORTANT: all units MUST be operated by a 24V thermostat. Never use a line voltage disconnect
switch as a means of operating the heater.
The operation of unit sizes 030–125 by means other than by a 24V thermostat may result in the
flame rollout switch tripping.
For all availaible thermostat and thermostat accessory options, contact contact an authorized
Factory Distributor.
Install an optional thermostat (available with the heater) or a field-supplied 24V thermostat in accordance with the
thermostat manufacturer’s instructions. Pay particular attention to the requirements regarding the location of the
thermostat.
Ensure that if there is a heat anticipator setting on the thermostat, it is set at 0.6 amps or in accordance with the
amperage value noted on the heater wiring diagram.
Make thermostat connections at the terminal strip on the back of the heater (see Figure 10). The strip has five
terminals: C, R, G, W1, and W2. Refer to the wiring diagram provided with the heater.
If the heater was ordered with a multiple heater control option, one thermostat can be used to control up to six
heaters. This option includes a 40VA transformer that replaces the standard transformer in the control unit and a
relay assembly that attaches to the additional 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
additional heater. The option packages are shipped separately and include complete instructions on installation
and wiring.
Circuit Board (DSI Control Module)
The heater’s ignition system is controlled by a circuit board (Direct-Spark Integrated (DSI) control module, see Figure
11) that monitors the safety devices and controls the operation of the fan and venter motors and the gas valve
between heat cycles. The module’s seven-segment display is visible through a viewport on UBZ and UDZ models.
To view the seven-segment display on UBX and UDX models, the door panel requires removal. In addition, there
is a status LED on the bottom of the heater. Its status indications are off (heater is not powered or control board
fault), steady on (heater is on with no faults), or flashing (heater is on with fault(s)). Additional status indications
appear on the display at the bottom of the control module (labeled as DSP1, see Figure 11). The display’s codes
are listed and described in Table 17.
Table 17. Circuit Board (DSI Control Module) Display Codes
Display Code Status Display Code Indication
Steady
Normal operation—no call for heat
0 Ignition sequence active
H Normal operation—call for heat (strong flame)
Flashing
2 Normal operation—call for heat (weak flame)
L Lockout from failed ignition or flame loss
3 Pressure switch is not closed within 30 seconds of venter motor energizing
4 Pressure switch is closed before venter motor is energized
5 Limit switch or rollout open
6 Undesired flame
7 Polarity reversed
Steady Off Internal fault/power failure
NOTE: Remove and reapply power to the control module to view the last five fault codes stored
in its memory. The most recent to least recent fault codes will be displayed.