Use and Care Manual
12
Table 12.1
Propeller Unit Heaters – PDP Model
Single-Stage, Standing Pilot, 100% Shut-Off – Utilizes a single-stage combination gas
control and thermocouple. Pilot needs to be manually lit initially and stays lit.
Single-Stage, Intermittent Pilot Ignition, 100% Shut-Off with Continuous Retry – Utilizes a
single-stage combination gas control and an ignition control (continuous retry). Pilot is
automatically lit on call for heat.
Two-Stage, Intermittent Pilot Ignition, 100% Shut-Off with Continuous Retry – Utilizes a
two-stage combination gas control (which fires at 50% or 100% of full rated input) and an
ignition control (continuous retry). Pilot is automatically lit only on call for heat. Available on
model sizes 50-400.
Mechanical Modulation with Automatic Pilot Ignition, 100% Shut-Off with Continuous
Retry – Utilizes a modulating combination gas control and an ignition control (continuous retry).
Pilot is automatically lit whenever there is power to the unit. Modulation range is between 50% and
100% fire; gas control shuts off below 50% fire. Available on blower models only.
11
12
81
82
30
31
85
86
63
64
87
88
59
60
89
90
115V
200/230V
115V
200/230V
115V
200/230V
115V
200/230V
115V
200/230V
115V
200/230V
115V
200/230V
115V
200/230V
25V
25V
25V
25V
25V
25V
25V
25V
25V
25V
25V
25V
25V
25V
25V
25v
natural
natural
propane
propane
natural
natural
propane
propane
natural
natural
propane
propane
natural
natural
propane
propane
Control System Description
Control
Code No.
Service
Voltage
Thermostat
Voltage
Type of
Gas
Two-Stage Gas Controls (intermittent pilot)
Utilizes a two-stage combination gas control, an ignition
control, and a two-stage low voltage thermostat. The unit fires
at 50% fire on low stage and 100% fire on high stage.
1. The thermostat calls for low stage heat.
2. The power exhauster relay is energized starting the power
exhauster motor. Once the motor has reached full speed,
the differential pressure switch closes.
3. The pilot valve opens and the spark ignitor sparks in an
attempt to light the pilot.
4. Once the pilot is lit, the flame sensor proves the pilot and
stops the spark ignitor from sparking.
5. The main gas valve is opened and the main burner is lit to
50% fire.
6. The air mover starts after 30 to 90 seconds.
7. If the temperature at the thermostat continues to fall, the
thermostat will call for high stage heat.
8. The main gas valve is opened completely and the main
burner is lit to 100% full fire.
9. The unit continues to operate until the high stage of the
thermostat is satisfied, at which time the main valve closes
to 50% fire.
10. The air mover stops after 30 to 90 seconds.
START-UP PROCEDURE