Intertherm M1B Series, Installation Instructions Manual

25

Figure 32

5/32” GAP

ELECTRODE

NOZZLE

0-1/16”

5/16” ABOVE CL

1 1/8”

Figure 32. oil Gun electrode Position

Gas Gun (M1B Models)

Combustion air box adjustment is made to the main burner 

by loosening the two lock nuts on the plastic air shutter, 

located on the left side of the burner blower housing. Air 

shutter adjustment line is located on the same side of 

the blower housing. Turn the plastic shutter to a smaller 

number (counter clockwise) for less air to a larger number 

(clockwise) for more air. Gently tighten the lock nuts after 

completing the adjustment. For best results, use instrument 

to measure between 8 - 9% CO

2

, after the combustion air 

has been adjusted. 

notE:

 Do not over-tighten the lock 

nuts. This may damage the plastic air shutter.

Oil Gun Only (M5S Models)

It is recommended that the CO

2

 and Smoke levels be 

measured for maximum performance. CO

2

 readings should 

be 10 - 11% for 66,000 BTUH furnaces and 12 - 13% for 

86,000 BTUH furnaces. The Smoke should be N0. 0 on 

the Bacharach Scale, and 0 to 0.02 negative draft over fire.

Electrode setting (oil Gun only)

Poor ignition of the oil spray may result if the electrodes 
are not adjusted as shown in 

Figure 32

. Do not permit 

any electrodes to be grounded to any surface.

switching  Ignition  control  between 

Interrupted and Intermittent Duty

(oil Gun only)

Honeywell and Beckett oil primary controls can be switched 

between interrupted and intermittent ignition control. To 

switch from interrupted duty (Factory set) to intermittent 

duty, remove the blue wire from the quick-connect terminal. 

Attach the burner motor and igniter wire to the burner 

motor (orange) control terminal by splicing or adding tab 

adapters. Seal and isolate any bare wires.

oPERatInG sEQuEncE

Direct Ignition Furnaces (M1M Models)

1. On a call for heat, the thermostat contacts close, 

supplying 24 VAC between terminals 

C

 and 

W

 of the 

control module.

2. When the inducer starts, the air pressure switch closes 

at -0.20 W.C. differential pressure and energizes the 

gas valve.

3. After a 45 second purge, the ignitor is energized for a 30 

second warm-up period. After warm up, the gas valve 

opens. 

notE: 

The time for ignition is approximately 6 

seconds, after which the gas valve either remains open 

if flame is sensed, or closes if flame is not sensed.

5. If flame is not sensed, the sequence repeats four more 

times before a lockout occurs. To reset, wait 30 seconds 

and then interrupt the 24 VAC power by turning the room 

thermostat below room temperature, then returning it 

to the original set point.

6. If flame does not establish on the 5th attempt (initial 

fire + 4 re-tries), the control de-energizes the gas valve, 

the 

red LED flashes 4 times, and the furnace locks out 

heat operation for 1 hour. See 

Table 9, (page 29)

.

7. If a flame is present, the control energizes the main 

blower on heat speed 30 seconds after the gas valve 

opens.

8. When call for heat is satisfied the thermostat contacts 

open, the gas valve shuts off gas flow and the combustion 

blower remains on for a 30 second post-purge period.

9. The main blower is de-energized after a 120 second 

blower off delay.

Oil Gun Furnaces (M5S Models)

With Honeywell R7184 / Beckett 7505 Control

1. When a call for heat is initiated, there is a 2 to 6 second 

delay while the control performs a safe start check.

2. The  ignition  and  motor  are  turned  on  and  a  flame 

should establish within a 15-second lockout time.  

notE: 

Burner will prepurge for 15 seconds if equipped 

with Honeywell R7184B or Beckett 7505B Control.

3. If  flame  is  not  sensed  within  the  15-second  lockout 

time, the control shuts down on safety lockout and must 

be manually reset by pushing the reset button on the 

control. If control locks over three times in a row, the 

control enters restricted lockout. To reset Honeywell 

R7184: Hold down the reset button for 45 seconds until 

the LED flashes once. Beckett 7505: Hold down reset 

button for 15 seconds until the 

red

 LED turns off and 

the 

yellow

 LED turns on.

 WaRnInG:

If furnace still doesn’t light, turn the furnace off 

as described above and call your technician. In 

the event of flashback or explosion, immediately 

shut off furnace and call your service technician.

4. After flame is established, the ignition remains on for 

10 seconds to ensure flame stability. It then turns off.