Service manual

ManualsBrandsModine Manufacturing ManualsGas HeaterBD

Table 14.1

Propeller and Blower Unit Heaters – PD and BD Models

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, Standing Pilot, 100% Shut-Off – Utilizes a two-stage gas control (which fires at 50% or 100% of

full rated input) and thermocouple. Pilot needs to be manually lit initially and stays lit.

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.

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.

➀➀

115V

200/230V

460V

575V

115V

200/230V

460V

575V

115V

200/230V

460V

575V

115V

200/230V

460V

575V

115V

200/230V

115V

200/230V

115V

200/230V

115V

200/230V

115V

200/230V

115V

200/230V

25V

natural

propane

natural

propane

natural

propane

natural

propane

natural

propane

Control System Description

Control

Code No.

Service

Voltage

Thermostat

Voltage

Type of

Gas

Two-Stage Gas Controls (standing pilot)

Utilizes a two-stage combination gas control with a standing pilot

operator and a two-stage low voltage thermostat. The unit fires at

50% fire on low stage and 100% fire on high stage.

1. Pilot is lit continuously.

2. Thermostat calls for heat.

3. The main gas valve is opened and the main burner is lit to

50% fire.

4. The air mover starts after 30 to 90 seconds.

5. If the temperature at the thermostat continues to fall, the

thermostat will call for high stage heat.

6. The main gas valve is opened completely and the main burner

is lit to 100% full fire.

7. The unit continues to operate until the high stage of the

thermostat is satisfied, at which time the main valve closes to

50% fire.

8. The unit continues to operate until the low stage thermostat is

satisfied, at which time the main valve closes 100%.

9. The air mover stops after 30 to 90 seconds.

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 pilot valve opens and the spark ignitor sparks in an

attempt to light the pilot.

3. Once the pilot is lit, the flame sensor proves the pilot and

stops the spark ignitor from sparking.

4. The main gas valve is opened and the main burner is lit to

50% fire.

5. The air mover starts after 30 to 90 seconds.

6. If the temperature at the thermostat continues to fall, the

thermostat will call for high stage heat.

7. The main gas valve is opened completely and the main burner

is lit to 100% full fire.

8. The unit continues to operate until the high stage of the

thermostat is satisfied, at which time the main valve closes to

50% fire.

9. The unit continues to operate until the low stage thermostat is

satisfied, at which time both the main and pilot valves close 100%.

10. The air mover stops after 30 to 90 seconds.

Mechanical Modulating Gas Controls

Utilizes a mechanical modulating gas control and an ignition

control. The mechanical modulating gas control is designed for use

in constant blower applications. The discharge air temperature is

maintained by setting the control dial of the modulating gas valve

in one of ten positions. A hydrostatic sensing bulb located in the

discharge air stream controls the gas flow between 50% through

100% full fire. When the discharge air hydrostatic sensing bulb is

satisfied, the modulating valve closes completely, but the pilot

remains lit. This control cannot be used with a room override

thermostat.

1. Power is supplied to the unit through either an exhaust fan

interlock contact or a start/stop switch.

2. The pilot valve opens and the spark ignitor sparks in an

attempt to light the pilot. The blower starts at this time.

3. Once the pilot is lit, the flame sensor proves the pilot and

stops the spark ignitor from sparking.

4. The hydrostatic sensing bulb, integral to the mechanical

modulating gas valve, calls for heat. The main gas valve is

opened and the main burner is lit. The burner modulates

between 50% through 100% fire based on the call for heat.

5. The unit continues to operate until the hydrostatic sensing

bulb is satisfied, at which time the main valve closes 100%,

but the pilot remains lit.

6. The unit blower (and pilot) continues to operate until either an

exhaust fan interlock contact or a start/stop switch is opened.

Dial Number

Lo12345 678Hi

Discharge

Air Temp. 58 62 65 69 72 76 79 83 86 90

(°F)

START-UP PROCEDURE

➀ Factory wired 460/575 available on blower models. Field installed step down transformer may be used for 460/575 propeller applications.