Teledyne EHE warranty 4E-2c.Fireman Switch and External Interlocks, 4E-2d.Limit Switches

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4E-2c. Fireman Switch and External Interlocks

Probe for voltage at point 3, the other connection of the terminal block, which has a white wire connected to it. If there is no voltage, the time clock switch or other external interlock may be mis-adjusted, mis-connected or defective. Correct this external problem.

4E-2d. Limit Switches

Probe for voltage at point 4, which is the water pressure switch terminal with the white wire connected to it. This switch is mounted on the end of a copper tube and is about 2” in diameter. Absence of voltage at this point indicates that one of the limit switches is open. This is normally due to excessive water temperature, which should be thoroughly investigated before replacement of limit switches. Water flow deficiency may be due to obvious problems such as a defective pump or blocked water filter. Alternatively, it may be due to overfiring, or to a problem with the water piping or the heater's internal bypass control. Overfiring might be a result of an incorrect gas orifice or supply of propane gas to a heater intended for natural gas. If there are no such fundamental problems, identify which of the switches is open by temporarily connecting a jumper wire across its terminals. Replace a defective limit switch. Limit switch access is through the side cover panel on the side of the heater to which water pipes are connected.

Note that the limit switches have different trip points, and it is important that replacements are correct. The 150°F switch has a red dot on the side of the brass fitting, and must be installed closest to the combustion chamber. The 135°F switch has no dot and must be installed in the tapping closest to the water piping connections.

4E-2e. Water Pressure Switch

Touch the voltage probe to point 5, which is the other terminal of the water pressure switch having a black wire is connected to it.

If there is no voltage, the pressure switch contacts are open. This is almost always due to a water flow deficiency, the most common one being a blocked water filter. It may be due to causes cited in the previous paragraph, however, and sometimes is due to blockage of the copper tube or mis-adjustment of the switch. Investigate thoroughly, referring to the earlier section on “Adjustment of Pressure Switch”. If there is no problem with the pool system or pressure switch adjustment, replace the pressure switch.

4E-2f. Temperature Control

Probe for voltage at point 6, which is the terminal of the venturi pressure switch having a yellow & black wire connected to it. This is the switch mounted on the frame above the blower between the vent diffuser and the venturi tailpipe. It is about 4” in diameter.

Absence of voltage at point 6 indicates that the Flex Temp control is not calling for heat. Be sure that knobs are set to call for heat as indicated earlier and as described in the Operating Instructions section of this manual. Verify that the thermistor sensor wires are not severed or shorted. Check wiring connections by removing the temperature control through the front of the bezel. If the control is properly set and all wiring and connections are correct, replace the Flex Temp control.

4E-2g. Venturi Pressure Switch

Touch the voltmeter probe to point 7, which is the terminal of the venturi pressure switch having a purple wire connected to it. If there is no voltage at point 7, the venturi pressure switch is open, indicating inadequate flow through the combustion system. The venturi pressure switch is a differential type switch which is activated by the pressure difference created when air flows through the venturi. When the combustion blower is not operating, the venturi pressure switch must be open and voltage will not be present. See following sections on ignition control "lockout" and combustion blower operation for possible remedies.

Check for blockage at the combustion air inlet, a dirty air filter or blockage at the vent exhaust or in the vent. In improperly installed vent may trap condensate water, for example, restricting flow. If there is no obvious problem, analyze venturi operation as outlined in a later section of this manual. If flow is normal, replace the Venturi pressure switch.

4E-2h. Ignition Control

There will be voltage at point 8, which is the “MVP” terminal of the ignition control, only when there is an attempt to ignite the burner or when the ignition control’s flame sensing system has determined that it is OK to allow burner operation. Even if voltage has been confirmed at point 7, the “trial for ignition” sequence is imposed by the ignition control. This sequence consists of a 15 second period of pre-purge blower operation, a 20 second period for heatup of the igniter and a 7 second trial for ignition, during which there is voltage at point 8. If satisfactory ignition is not achieved, the igniter is turned off and the blower is operated for a 45 second post-purge. The system may go through this cycle as many as three times, but thereafter it is “locked out” by the ignition control. Additional attempts will be made only if the call for heat is interrupted by turning off electrical power or setting the Flex Temp control to “Off”.

To trouble shoot the ignition control, connect the voltmeter probe at point 8 and set the Flex Temp control to call for heat. Observe that the normal sequence takes place by noting blower operation, the glow of the igniter through the combustion chamber sight glass and then voltage at point 8. If the blower