Furnace Control Board; Primary Limit; Auxiliary Limit; Rollout Limit - Amana MVM97 Installation Instructions Manual

Furnace Control Board

The furnace control board is an electronic device which,
if a potential safety concern is detected, will take the
necessary precautions and provide diagnostic information
through an LED display.

Primary Limit

The primary limit control is located on the partition panel
and monitors heat exchanger compartment temperatures.
It is a normally-closed (electrically), automatic reset,
temperature-activated sensor. The limit guards against
overheating as a result of insufficient conditioned air
passing over the heat exchanger.

Auxiliary Limit

The auxiliary limit controls are located on or near the
circulator blower and monitors blower compartment
temperatures. They are a normally-closed (electrically),
auto-reset sensors. These limits guard against overheat-
ing as a result of insufficient conditioned air passing over
the heat exchanger.

Rollout Limit

The rollout limit controls are mounted on the burner/
manifold assembly and monitor the burner flame. They
are normally-closed (electrically), manual-reset sensors.
These limits guard against burner flames not being prop-
erly drawn into the heat exchanger.
• Furnace circulator blower and outdoor cooling unit
run their appropriate speeds, integrated control mod-
ule monitors safety circuits continuously.
• R and Y1/G or Y2/G thermostat contacts open, com-
pleting the call for cool.
• Outdoor fan and compressor are de-energized.
• Circulator blower continues running during a cool off
delay period. The OFF delay time and airflow level
are determined by the selected ramping profile.
• Electronic air cleaner terminal and circulator blower
are de-energized.
• Furnace awaits next call from thermostat.

Fan Only Mode

The normal operational sequence in fan only mode is as
follows:
• R and G thermostat contacts close, initiating a call for
fan.
• Integrated control module performs safety circuit
checks.
• Circulator blower is energized on continuous fan
speed (25%, 50%, 75% or 100% DIP switch selectable
when using a conventional thermostat). Electronic air
cleaner terminal is energized.
• •The furnace control board HUM dry contacts close.
• Circulator blower runs, integrated control module
monitors safety circuits continuously.
• R and G thermostat contacts open, completing the
call for fan.
• Circulator blower is de-energized. Electronic air
cleaner terminal is de-energized.
• Furnace awaits next call from thermostat.

Operational Checks

The burner flames should be inspected with the burner
compartment door installed. Flames should be stable,
quiet, soft, and blue (dust may cause orange tips but they
must not be yellow). Flames should extend directly out-
ward from the burners without curling, floating, or lifting
off. Flames must not impinge on the sides of the heat
exchanger firing tubes.
Burner Flame

Safety Circuit Description

A number of safety circuits are employed to ensure safe
and proper furnace operation. These circuits serve to
control any potential safety hazards and serve as inputs in
the monitoring and diagnosis of abnormal function. These
circuits are continuously monitored during furnace opera-
tion by the integrated control module.
Furnace Control Board
The furnace control board is an electronic device which,
if a potential safety concern is detected, will take the
necessary precautions and provide diagnostic information
through an LED display.
Primary Limit
The primary limit control is located on the partition panel
and monitors heat exchanger compartment temperatures.
It is a normally-closed (electrically), automatic reset,
temperature-activated sensor. The limit guards against
overheating as a result of insufficient conditioned air
passing over the heat exchanger.
Check the
Burner Flames for:
1. Stable, soft and blue.
2. Not curling, floating
or lifting off.
Figure 54