Lochinvar 497 - 2067 service manual Hot surface ignition system, C, Remote mounting of a sensor

Installation & Service Manual

5 Electrical connections

Remote mounting of a sensor

You must mount the outside air temperature sensor outside the building. To mount remote sensors, follow the guidelines below. Take care to correctly wire sensors to the unit. Erratic temperature readings can be caused by poor wiring practices. Twist the wires between the unit and the remote sensor. Turn wires at least three or four turns per linear foot of wiring. This provides common mode rejection of some types of electrical interferences.

1.Do not route temperature sensor wiring with building power wiring.

2.Do not locate temperature sensor wiring next to control contactors.

3.Do not locate temperature sensor wiring near electric motors.

4.Do not locate temperature sensor wiring near welding equipment.

5.Make sure good mechanical connections are made to the sensor, any interconnecting wiring and the controller.

6.Do not mount sensor with leadwire end pointing up in an area where condensation can occur.

7.Use shielded wiring to connect the sensor to the control when the possibility of an electrically noisy environment exists. Shielded cable is recommended on all cable runs of more than 25 feet in length.

Ground the cable shield at the connection

NOTICE to the boiler temperature control only. Do not ground the shielded cable at the sensor end.

To maintain temperature accuracy, sensor wires should be at least 18 AWG, see Table 5C.

TABLE 5C

Remote Wire Connection

Wire Gauge	Max. Allowable Length
12 GA	100 FT
14 GA	75 FT
16 GA	50 FT
18 GA	30 FT

Hot surface ignition system

Hot surface igniter and ignition control module

This unit has one ignition module and one hot surface igniter.

Figure 5-11_Hot surface igniter

CAUTION The igniter is extremely fragile, be very careful when removing. A faulty or damaged

hot surface igniter MUST BE replaced with a Lochinvar PLT3400 igniter. Do not use general purpose field replacement igniters.

Hot surface ignition control module

Ignition Module Lockout Functions

The ignition module may lockout in either a hard-lockout condition, requiring pushing of the reset button to recycle the control, or a soft-lockout condition which may recycle after an approximate five-minute waiting period. This soft- lockout condition is intended to allow self-correcting faults to correct themselves and permit normal operation. A typical hard-lockout fault is a flame failure condition. An ignition module that is in a hard-lockout condition may only be reset by pushing the reset button next to the ignition control or the “RESET” button on the diagnostic panel on the left end of the unit. Upon a flame failure, the reset button is only active after the control module has completed its post-purge cycle. Turning main power “OFF” and then “ON” or cycling the thermostat will not reset a hard-lockout condition. Wait five seconds after turning on main power before pushing the reset button when the ignition module is in a hard lockout. The ignition module will go into a soft lockout if conditions of low air, low voltage or low hot surface igniter current are present. A soft-lockout condition will operate the combustion air fans for the post purge cycle and then the ignition module will pause for approximately five minutes. At the end of this timed pause, the ignition module will attempt a new trial for ignition sequence. If the soft-lockout fault condition has subsided or has been corrected at the end of the timed pause, main burner ignition should be achieved with the resumption of the normal trial for ignition sequence. If the control sensed fault is not corrected, the ignition module will continue in the soft-lockout condition. If the electronic thermostat opens during the soft- lockout period, the ignition module will exit soft lockout and wait for a new call for heat from the thermostat. A soft-lockout condition may also be reset by manually cycling the thermostat or turning the main power switch “OFF” and then “ON” after the control sensed fault has been corrected.

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