Commissioning: Furnace tips (part 3 of 3)

Short, practical technician tips on commissioning for furnace. Check each one against the manual for your exact model before acting.

Electrical connections and polarity

Trane · Furnace wiring

The integrated control is polarity sensitive.

1. Connect the hot leg of the 120 V supply to the black power lead as shown on the wiring diagram.
2. Provide a permanently live circuit with a separate circuit protection device.
3. Ground the furnace per local code or the National Electrical Code.
4. Electronic air cleaner and humidifier connections are provided on the integrated control.

Location, access and clearance checks

Trane · All furnaces

Confirm these before setting the furnace.

1. Locate the furnace as close to the vent as practical and central to the heat distribution.
2. Keep at least 24 inches of front access for service. Any access door must allow removal of the largest component.
3. Keep at least 3 inches between the furnace front panel and any closed panel or door.
4. Keep combustion and ventilation openings large enough and unobstructed. If outside air is used, set the openings at least 12 inches above the highest snow level.
5. Leave enough supply plenum height above or below the furnace for a cooling coil if the coil is not yet installed.
6. Install so electrical components are protected from water.
7. Install the furnace level. Upflow units may tilt slightly left and/or forward; horizontal units may tilt slightly forward, for condensate drainage.

Minimum front and door clearances

Trane · All UH1/DH1 furnaces

Front access and door clearance requirements for servicing.

1. Confirm at least 24 in of front service access.
2. Confirm at least 3 in between the furnace front panel and any closed panel or door.

Minimum return air temperature

Trane · UH1/DH1 furnaces

Return air must not fall below 55 F.

1. Check return air temperature is at least 55 F before operating the furnace.

Preliminary inspections before lighting

Trane · Furnace startup

Check these items with gas and electrical power off.

1. Confirm duct connections are sealed.
2. Confirm filters are in place.
3. Confirm venting is properly assembled.
4. Confirm the blower door is in place.
5. Set the gas valve switch to OFF, open the external gas valve, and purge air from the lines.
6. Leak check all gas connections with soapy solution, then wait 5 minutes for any gas to clear. LP gas is heavier than air and may need forced ventilation.
7. Set the gas valve switch to ON.

Prime the condensate trap at start-up

Trane · Downward venting with condensate trap

The condensate trap must be filled before the first heating season.

1. Prime the condensate trap during initial start-up, before heating season operation.

Residential garage installation

Trane · Furnaces in residential garages

A furnace in a residential garage needs extra protection.

1. Mount the furnace so the burners and ignition source are at least 18 inches (46 cm) above the floor.
2. Locate or protect the furnace from physical damage by vehicles.

Set thermostat heat anticipator

Trane · AUH1B furnaces

Set the heat anticipator to the measured current flow, or to the value listed in the notes on the wiring diagram.

1. Measure the current flow, or find the value in the notes on the wiring diagram.
2. Set the thermostat heat anticipator to that value.

Upflow cased coil installation

Trane · Upflow furnaces with cased coil

The cooling coil always sits downstream of the furnace airflow.

1. Attach the cased coil with the supplied standoffs and drill screws.
2. Insert each standoff into the cabinet alignment hole, run the drill screws through the standoffs, and screw them into the furnace top flange.
3. Use the clearance alignment holes near the bottom of the coil wrapper.

Upflow return air openings for high-airflow models

Trane · Upflow 5 or 6 ton models above 1800 CFM

Applies to 5 or 6 ton upflow models where airflow exceeds 1800 CFM.

1. Provide return air openings and filters on both sides, or on one side and the bottom, or on the bottom only.