Fenwal 05-212225-107 Ignition Control Board

Silicon Carbide Ignition System

GENERAL INFORMATION

Utilizing a high energy ignition source and the principals of flame rectification, the 05-21 combines an interrupted means of ignition and monitoring of main burner flame. Specifically designed for use in residential gas heating applications, the 05-21 can provide positive ignition over a wide range of air/gas mixtures.

PRINCIPLE OF OPERATION

The system utilizes a silicon carbide element that performs a dual function of ignition and flame detection. The ignitor is on electrically heated resistance element which thermally ignites the gas. The flame detecfor circuit utilizes flame rectification far monitoring the gas flame.

The ignitor serves two functions. Upon a call for heat, the element is powered from the 120VAC line and allowed to heat for 45 seconds (typical). Then the main valve is powered, permitting gas to flow to the burner for the trial-for-ignition period which is typically seven seconds long, although other timings are available. At the end of this period, the ignitor is switched from its heating function to that of a flame probe which checks for the presence of flame. If flame is present, the system will monitor it and hold the main valve energized. If flame is not established within the trial-for-ignition period the system will lock out, de-energizing the main valve and shutting off power to the ignitor. If, during the heating cycle a loss of flame occurs, the system will recycle through the ignition sequence.

MOUNTING

The Series 05-21 is not position sensitive and can be mounted vertically or horizontally. The case, or printed circuit board, may be mounted with #6 hardware, Integral standoffs on the bottom of the PC board provide proper electrical and thermal isolation between the board and the mounting surface.

INITIAL OPERATION

1. Check installation, mounting and position of ignitor in the flame envelope.
2. Apply 120VAC power to the system_ Manually shut off the gas supply and apply 24VAC power to the system by advancing the thermostat.
3. Check to insure that the ignitor glows during the trial-for-ignition period specified for the unit. The system should lock out after the trial-for-Ignition period. Set thermostat to the lowest setting.
4. Manually open the gas supply line and advance the thermostat to recycle the system.
5. Check that ignition has been accomplished within the trial period. The ignitor glow will diminish after the trial-for? ignition period.
6. If the system ignites but foils to hold in, check for 5 microamps minimum flame sense current using a Fenwal Test adapter, P/N 05-080223-001 and a 0-SODC moving coil microammeter per Figure 46. Also, insure that the system is. properly grounded per Figure 4A and 4B.

WIRING

CABLE ASSEMBLY
Fenwal P/N 05-128070-0XX (Last two digits indicate length of wire in inches.)
Insert plastic connector onto edge of PC board as shown in Figure 1_ (connector will not fit if reversed.) Connect leads as shown in Figures 4A and 4B.
CAUTION: 120 Volts
Black wire to hot-side 120VAC line.
Gray wire to silicon carbide ignitor
Blue wire to silicon carbide ignitor Non-polarized
White wire to neutral side of 120VAC tine Brown wire to gas valve (24VAC)
Red wire to 24VAC supply
Green wire to ground (Control module, burner, and gas valve must have common ground)
NOTE: lr the cable assembly is not ordered from fenwtri, component parts may be procured using Table 1 below.