Midco Unipower MPG Series - Manual (Page 12)

Part 1 Installation
PRE-PURGE ("POWER" LED is lit).
The RM7895 in this application features a pre-purge time of 30-seconds for On-Off, 90-
seconds for 2-Step or Modulating burners.
Once the STANDBY sequence has a "CALL FOR HEAT" input, normal start-up pre-purge will
be initiated.
A. The blower motor is powered to start the pre-purge sequence.
B. The airflow interlock switch must close in ten seconds of pre-purge or within the
specified purge card timing. Otherwise a recycle to the beginning of pre-purge or
lockout will occur, depending on how the airflow switch selectable jumper is
configured. Refer to Honeywell RM7895 literature for configuration requirements.
IGNITION TRIAL
1. PILOT FLAME ESTABLISHING PERIOD (PFEP)
A. The pilot valve and spark generator are energized.
B. Flame must be proven by the end of the 4 or 10-second PFEP to allow the sequence to
continue. If flame is not proven by the end of PFEP, a safety shutdown occurs.
2. MAIN FLAME ESTABLISHING PERIOD (MFEP)
After the ignition trials, and with the presence of flame, the main valve is energized.
("MAIN" LED will be lit.) If a flame-out occurs, the RM7895 will lockout or recycle within 3-
seconds, depending on "jumper" configuration. Refer to Honeywell literature for proper
configuration.
RUN
The RM7895 is now in RUN mode and will remain in run mode until the controller input opens,
indicating that the call for heat has been satisfied or a limit has opened. Once this occurs the
RM7895 will sequence back to the STANDBY mode.
Notes:1. During STANDBY and during RM7895 sequencing the "POWER" LED will blink
every four seconds. This is normal.
2. The "ALARM" LED will be lit in the event of any flame failure.
3. To maintain proper operation of this device it MUST be electrically grounded. Refer
to Honeywell RM7895 literature for grounding requirements.
___________________________
Special equipment, either factory or field installed, can cause variations in the procedures and
descriptions given in this manual. Generally, any burner ordered with special factory installed
equipment will be supplied with the appropriate wiring diagram and related instruction manuals
from the special equipment manufacturer. Consult these manuals to identify any differences in
construction, operation and testing. Field installed special equipment is the responsibility of the
installing contractor.
For example, when a high/low gas pressure switch is used, the high gas pressure setting must
be higher than the maximum manifold pressure during initial start-up and the low pressure setting
must be set below the normal minimum inlet pressure to prevent nuisance shutdowns during the
start-up procedure.
After the burner is started, the low pressure setting should be raised until the burner shuts off.
Reduce the setting and set the low pressure switch to restart the burner. Reduce the high
pressure setting until the burner shuts off. Then raise the setting slightly and reset the high
pressure switch to restart the burner. Do not make the adjustments too close to trip points or
nuisance shut downs may occur. Anytime the burner gas supply is shut off with the main manual
valve, the low pressure switch will require resetting.
If any doubt exists concerning burner operation when special equipment is involved, contact
the installing contractor or MIDCO INTERNATIONAL INC. (front cover).
___________________________
Note: These Instructions are designed for experienced combustion contractors/
technicians.
1) Check the gas piping for leaks. If a leak is detected, it should be repaired.
2) Make sure that the burner main and pilot gas lines are both completely purged of air.
Do not purge into the combustion chamber. Purge outside the building.
3) Make sure the burner power On-Off switch is OFF, manual main gas valve and manual
pilot gas valves are closed and the motor is free to rotate.
4) Make the proper settings on all limit controls and set the operating controller (by others)
to call for heat.
12
XVI Initial
Start Up
Instructions
2-Stage and Full
Modulating Burner
XV Special
Equipment
(OEM Versions)
XIV Flame
Safeguard
Continued