Roberts Gorden POP-ECA/PGP-ECA 015 to 0100 Control - Gas-Fired Heaters, Sequence of Operation

SECTION 10: COMMISSIONING

3. Check gas flow rate at gas meter.

10.3 Control - Gas-Fired Heaters

For High/Low and modulating burners, follow the general sequence as described below and also have extra functional stages related to air damper positions. Refer to the burner manufacturers instructions for further detail. Gas burners have only one pressure switch, which is configured to cover combustion air and reaction to increases in combustion chamber pressure.

10.3.1 Description of Gas-Fired Heater Control

The gas fired burner fitted to all COMBAT® cabinet heaters is controlled by a full sequence plug-in control. This control ensures the safe start and stop sequence and also monitors the safe presence of a flame and burner air pressure.

Models 015 - 030 are wired for direct ignition of the main flame. All other models are wired for ignition of a start gas flame as the first stage and then the main gas flame as the second stage.

10.3.2 Sequence of Operation

1.With the external controls on calling for heat, and the pressure switch at rest, the burner fan will switch on after the control does a "self check".

NOTE: If the pressure switch contacts (normally closed) are open, the heater will not start.

2.The combustion air fan turns on and the pres- sure switch contacts close within the next 5 seconds to indicate sufficient combustion air or lockout will occur.

3.The sequence continues with a purge period with the burner fan running.

4.The electrical ignition switches ON at the end of the purge period.

5.The start gas valve opens (main gas valve for 015 - 030) and once a flame has been estab- lished, this remains open until close down. The flame probe is now continuously monitoring for the safe presence of flame.

6.Five seconds later, the electric ignition turns off, leaving the start gas flame to be proved as sta- ble.

7.The start gas runs for ten seconds, then the main gas valve opens. The control is now in its normal run position

Figure 14: Gas-Fired Heater Control Box Sequence

Thermostat

Motor

Pressure Switch

Transformer

Gas Valve

Ionization Probe

+	30 s	3 s
+
	2 s

Necessary Input Signal

Output Signal of the Device

10.3.3 Motor Starter and Thermal Overload

On belt-driven models, the motor is controlled by a direct on-line contactor starter fitted with thermal overload protection. If the thermal overload operates, the main fan will not run. To reset, press the reset button on the overload unit.

NOTE: For models with a 5.5 kW motor or larger, the direct on-line starter will be replaced by a automatic starter.

The overload should be set to indicate approximately 0.2 A above the normal running current of the heater. See Page 8, Section 4.4.

10.3.4 Burners

For details of the packaged burners, see the manufacturer’s instructions and Page 8, Section 4.5 through Page 9, Section 4.6. When reading the data tables, ensure that the correct table for the burner and gas valve installed is being used. The data tables are listed under a burner reference letter which can be found on the heater data plate.

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