5 pilot ignition systems – Reznor SC Duct Furnace Unit Installation Manual User Manual

Page 31

Form I-SC, P/N 207696 R11, Page 31

Is there 24 volts

between Terminal 2 on #1

Time Delay Relay and

Terminal 7?

Go to

Troubleshooting

Chart for heater.

Is there 24 volts

between Terminal 84 and

Terminal 7?

Is the

damper open?

Is there voltage

between Terminal 88 and

Terminal 7?

Is there voltage

between Terminal 4 on

ignition permissive relay and

Terminal 7?

Replace #1 time delay relay.

Replace ignition

permissive

relay.

Check combustion

damper lower end switch

adjustment. If necessary,

replace end switch.

Is there voltage

between Terminal 87 and

Terminal 7?

Check combustion

damper lower end switch

adjustment. Replace end

switch if necessary.

Place a jumper

across Terminal

86 and Terminal 7.

Did the

damper close?

Replace motor run

time delay relay.

Replace combustion

damper gear motor.

Replace primary

manifold

pressure switch.

YES

FIGURE 31- Troubleshooting Guide

for Checking Bypass Combustion Air

Damper Safety Circuit on Model SC

with Option AG39 or AG40

General Instructions: For each step,

check to ensure that the wiring is not

defective and that the wiring connections

are secure.

Symptom - Part 1:
Main burners are

inoperative.
Assumes that 24

volts is available

between Terminal 2

and Terminal 7.

Measure manifold

pressure

during burner cycling.

When the

manifold pressure is

BELOW 1.0" w.c., is there a steady

voltage between Terminal 95

and Terminal 7?

Replace secondary

manifold pressure

switch.

While the

burner is cycling, is

there a steady voltage

between Terminal 84 and

Terminal 2?

Replace the primary

manifold pressure switch.

When the

manifold pressure is

ABOVE 1.5" w.c., is there a steady

voltage between Terminal 95

and Terminal 7?

Replace secondary

manifold pressure

switch.

Is there voltage

between Terminal 4 of the

ignition premissive relay and

Terminal 7?

Replace ignition

permissive relay.

YES

Symptom - Part 2: Steady call for heat - burner cycles.

Assumes

that 24 volts

is available

between

Terminals 11

and 7 and

Terminals 2

and 7.

Ignition System - Natural gas units are equipped with a spark ignited intermittent

safety pilot system that shuts off the pilot gas flow between heat cycles. Propane units

(or as an option on natural gas units) require a lockout device that stops the gas flow to

the pilot if the pilot fails to light in 120 seconds. The lockout device has a 1-hour retry

or can be manually reset by interruption of the thermostat circuit. Refer to the wiring

diagram supplied with the unit for pilot system identification and proper wiring. Pilot

with lockout is Option AH3; spark pilot without lockout is Option AH2.
Ignition Controller - As part of the intermittent safety pilot systems, the ignition con-

troller provides the high voltage spark to ignite the pilot gas and also acts as the flame

safety device. After ignition of the pilot gas, the ignition controller electronically senses

the pilot flame. A low voltage DC electrical signal is imposed on the separate metal

probe in the pilot assembly. The metal probe is electrically insulated from ground. The

pilot flame acts as a conduction path to ground completing the DC circuit and proving

pilot flame. Proper operation of the electronic spark ignition system requires a mini-

mum flame signal of .2 microamps as measured by a microampmeter. With pilot flame

proven, the ignition controller energizes the main gas valve.
Pilot - All pilots are vertical, target type with lint-free feature. Pilot flame should be

approximately 1-1/4" in length. Pilot gas pressure should be the same as the supply

line pressure. Pilot gas is supplied through the combination valve; the pilot gas flow

is controlled by an adjustment screw located in the valve body. For maintenance, see

Paragraph 10.2.

CAUTION: Due to

high voltage on

pilot spark wire

and pilot electrode,

do not touch when

energized.

8.5 Pilot Ignition

Systems