Access to the wiring terminals of the primary control illustrated in Figure 5-4 is obtained by loosening the screws that secure the chassis to the base. When remounting the chassis, be sure to tighten all mounting screws because they also serve as electrical connections.
No attempt should be made to repair a primary control except for tube replacement. Vacuum tubes are used in Honeywell primary controls. Never replace them with radio tubes. If a primary control is defective, the entire chassis should be replaced with a good one.
Operating controls located in the T/T circuit (see Figure 5-6) should be of the low-voltage, two-wire type. A low-voltage transformer for this purpose is built into a Honeywell Protectorelay. Safety controls located in 1–6 terminals must be two-wire, line voltage type. With the exception of the line switch, no controls should ever be placed in the line ahead of the 1–2 terminals of the primary control.
Before assuming that the primary control is defective, be sure to check the pilot, pilot adjustment, flame detector circuit, and all operating and safety controls; proper operation is also dependent on these external factors. The flame circuit can be more accurately checked by the use of a microammeter to read flame current. Normal operation requires a current of 2 microamperes or more.
Never push relays in manually because it can result in accidental opening of the main diaphragm valve. Be sure to turn off the electrical power before removing the primary control chassis from the base.