Nordyne M3RL Sequence of Operation, Shut Down Procedure, Verifying Firing Rate

5.After the furnace has run for approximately five minutes, set the thermostat below room temperature and verify steps 9 - 11 of the

SEQUENCE OF OPERATION.

Shut Down Procedure

In the event that the furnace must be shut down, follow this procedure:

1.Set the room thermostat to "OFF" or its lowest temperature setting.

2.Turn OFF the main gas supply to the appli- ance at the manual valve outside of the appliance casing.

3.Remove the control access panel / lou- vered door.

4.Move the appliance gas valve lever/knob to the “OFF” position.

5.Turn OFF the electrical power to the appliance.

Verifying Firing Rate

The firing rate must be verified for each instal- lation to prevent over-firing the furnace.

NOTE: The firing rate must not exceed the rate shown on the furnace rating plate. At altitudes above 4000 ft. it must not exceed that on the rating plate less 4% for each 1000 ft.

Use the following procedure to determine the firing rate:

1.Shut off all other gas fired appliances.

2.Start the furnace and allow it to run for at least three minutes.

3.Measure the time (in seconds) required for the gas meter to complete one revolution.

4.Convert the time per revolution to cubic feet of gas per hour using Table 11.

5.Multiply the gas flow rate in cubic feet per hour by the heating value of the gas in Btu per cubic foot to obtain the firing rate in Btuh. Example:

•Time for 1 revolution of a gas meter with a 1 cubic foot dial = 60 seconds.

•From Table 11 read 60 cubic feet per hour of gas.

•Heating value of the gas (obtained from gas supplier) = 1000 Btu per cubic foot.

•Firing rate = 1000 x 60 = 60,000 Btuh.

6.See the "High Altitude Derate" section for additional information on firing rate at eleva- tions above 4,000 ft.

The gas valve regulator is set at a nominal value of 3.5 in. water column for use with natural gas. The manifold pressure must be set at 10.0 in. water column for use with LP gas.

Verifying and Adjusting Temperature Rise Verify that the temperature rise through the furnace is within the range specified on the fur- nace rating plate. Temperature rises outside the specified range could result in premature heat exchanger failure.

Place thermometers in the return and supply air stream as close to the furnace as possible. The thermometer on the supply air side must be shielded from direct radiation from the heat exchanger to avoid false readings. Adjust all registers and duct dampers to the desired position and run the furnace for fifteen minutes before taking any temperature readings. The temperature rise is the difference between the supply and return air temperatures.

For typical duct systems, the temperature rise will fall within the range specified on the rating plate with the blower speed at the factory recommended setting. If the temperature rise measured is outside the range specified, it may be necessary to change the blower speed. Lower blower speeds will increase the tem- perature rise and higher blower speeds will decrease the temperature rise.

The furnace is equipped with a multispeed motor. Heating and cooling speed selection is made by moving the leads on the integrated control board located in the furnace. The wiring diagram on the furnace and Figure 30 show the speed taps for adjusting motor speed.

If it is desired that the blower operate at the same speed for heating and cooling, tape off the terminal of the unused blower wire. Install the jumper wire, found in the plastic instruction bag, across the HEAT and COOL taps on the control board. Reconnect the desired blower tap to the piggyback quick connect.

The blower control is designed to start the circulating air blower 30 seconds after the gas valve is opened. The blower control is factory wired to turn the blower motor off 120 seconds

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