Commissioning: Furnace tips (part 1 of 3)

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

Check gas connections for leaks

Allied · Gas piping

Test every factory and field gas joint after piping is finished.

1. Use a commercial leak-detection soap solution.
2. Never use an open flame to find leaks.
3. Rinse the piping after the test is done.
4. Isolate the furnace from the supply during any test at or above 1/2 psig.

Combustion check

Allied · All sizes

Check combustion only after the furnace has run at least 15 minutes with correct manifold pressure and gas flow. The maximum carbon monoxide reading should not exceed 50 ppm.

1. Run the furnace at least 15 minutes with correct manifold pressure and gas flow.
2. Take the combustion sample beyond the flue outlet.
3. Compare the CO2 reading with the CO2 table for the fuel type.
4. Confirm CO is no higher than 50 ppm.

Duct static limit for heating mode

Allied · All 92G1UH installations

The furnace is not certified for heating mode (blower on heating speed) when external static pressure is above 0.5 in. w.c. Higher static can cause improper limit operation.

1. Measure external static pressure with the blower on heating speed.
2. If it is above 0.5 in. w.c., correct the duct system before commissioning.

Gas valve lighting procedure

Allied · First start and relighting after gas shut-off

The furnace uses a hot surface ignitor and must not be lit by hand. Do not use this furnace if any part was underwater.

1. Set the thermostat to the lowest setting.
2. Turn off all electrical power to the unit.
3. Remove the upper access panel.
4. Move the gas valve switch to OFF. Use only your hand on the lever.
5. Wait five minutes to clear any gas. If gas is smelled, stop and call the gas supplier from a neighbor's phone.
6. Move the gas valve switch to ON.
7. Replace the upper access panel.
8. Turn electrical power on and set the thermostat to the desired setting.
9. Repeat these steps if needed to purge air from the gas line on first start.
10. If the unit will not operate, turn off the gas and call a service technician or gas supplier.

Gas valve pressure testing

Allied · Gas valve

The gas valve can be damaged by test pressure.

1. Disconnect and isolate the gas valve before pressure testing the line.
2. Do not test above 1/2 psig (3.48 kPa) at the valve.
3. Use the 1/8 in NPT plugged tap on the valve for gauge connection.
4. If the manual main shut-off valve will not hold test pressure, use the isolation method shown in Figure 48.

Let solvent fumes clear before startup

Allied · After cementing vent joints

Fumes from PVC cement can ignite during the system check.

1. Allow fumes to dissipate for at least 5 minutes before placing the unit into operation.
2. Keep solvent cement away from ignition sources and keep the area ventilated.

Priming the condensate trap

Allied · First start-up

The trap must hold water before the first run so condensate drains properly. Pour 10 fl oz (300 ml) of water into the trap, or prime it by firing the burners.

1. Light the unit following the lighting procedure.
2. Set the thermostat to call for heat and let the burners fire for about 3 minutes.
3. Set the thermostat to end the heat call.
4. Wait for the combustion air inducer to stop.
5. Call for heat again and let the burners fire for about 3 minutes.
6. End the heat call and wait for the combustion air inducer to stop.

Remove the bottom panel for bottom or side return

Allied · Upflow with bottom return or horizontal installs

The furnace ships with the bottom panel in place. It must come out for horizontal or upflow bottom-return installs.

1. Remove the two screws holding the bottom cap.
2. Pivot the bottom cap down to release the bottom panel.
3. Remove the bottom panel.
4. Reinstall the bottom cap when done.

Remove the shipping bolt on 1/2 HP blower units

Allied · 1/2 HP blower motor units

Units with a 1/2 HP blower have one rigid leg with a shipping bolt and white plastic washer. Remove them before start-up.

1. Check the blower motor size. This procedure applies to 1/2 HP units only.
2. Remove the shipping bolt and flat white plastic washer from the rigid leg.
3. Confirm the rigid leg does not touch the blower housing after removal.
4. Do not run the furnace until the bolt and washer are removed.

Start-up and performance check list

Allied · 92G1UH furnace

Checklist to complete at commissioning and record on the sheet.

1. Record the model and serial number.
2. Check gas supply pressure and gas manifold pressure.
3. Check line voltage and supply voltage, and confirm electrical connections are tight.
4. Confirm gas piping connections are tight and leak tested.
5. Confirm intake and exhaust joints are primed and glued, terminations are correct, pipes are supported and horizontal runs are sloped.
6. Confirm the condensate trap is primed and the line is sloped; check heat cable if fitted.
7. Confirm the supply and return ducts are sealed, insulated if needed, and the filter is installed and clean with grilles unobstructed.
8. In heating mode, measure combustion CO2 and CO (ppm), indoor blower amps, supply and return duct temperatures, and total external static.
9. Calculate the temperature rise from the supply and return duct readings.
10. In cooling mode, measure indoor blower amps, supply and return duct temperatures, and total external static on a dry coil, then calculate the temperature drop.
11. Check the condensate and drain lines and vent pipe for leaks.
12. Confirm the thermostat is adjusted and programmed, and explain operation to the owner.

Thermostat heat anticipator setting

Allied · Heating thermostat setup

If the thermostat heat anticipator is adjustable, set it to the amp draw listed on the wiring diagram attached to the unit.

1. Read the amp draw on the unit wiring diagram.
2. Set the thermostat heat anticipator to that value.

Airflow setup for communicating and non-communicating outdoor units

Goodman · Communicating and non-communicating outdoor units

A communicating outdoor unit sets indoor airflow itself. A non-communicating outdoor unit needs airflow set by tonnage.

1. Communicating outdoor unit: no main airflow adjustment is needed. Airflow trims can be made if wanted.
2. Non-communicating outdoor unit: find the desired airflow, using 350 to 450 CFM per ton with 400 CFM per ton as the standard.
3. Select the tonnage closest to the desired airflow in the tonnage menu. Trim is available for fine adjustment.

Allowed installation positions

Goodman · Upflow and counterflow models

The furnace can be installed upright or horizontal on the left or right side panel. Never install it on its back. Return ductwork goes to the side panels and/or basepan on upright upflow units, and to the basepan on horizontal upflow and counterflow units. Never attach ductwork to the back of the furnace.

1. Select an upright or horizontal position per the recommended positions figure.
2. Attach return ductwork only to the allowed panels or basepan.
3. Do not attach any duct to the rear of the cabinet.

Dual certification: non-direct and direct vent

Goodman · Dual-certified MVC96/CVC96 models

The furnace can be installed as non-direct vent (one pipe, vent only) or direct vent (two pipes, vent plus combustion air intake). Use the section for the chosen type for pipe size, length, elbows and terminations.

1. Decide between non-direct vent (single pipe) and direct vent (dual pipe).
2. Follow the matching section for piping size, length, elbows and terminations.

High altitude application (USA)

Goodman · High altitude installs

Install the correct high altitude orifice or pressure switch kit for the altitude and gas type. Kits are chosen by installation altitude and natural or propane use. Do not derate by lowering manifold pressure below the rating plate.

1. Select the orifice or pressure switch kit using the altitude range table in the technical manual or spec sheet.
2. Choose the kit for natural or propane gas.
3. If the gas supplier derates the gas, size the orifice from the derated BTU/ft³ and altitude per NFPA 54 / ANSI Z223.1 and supplier data.
4. Do not lower manifold pressure below the rating plate value to compensate.

Minimum clearances and service access

Goodman · CVC96 and MVC96 furnaces, all positions

Keep the printed clearances to combustible materials on the unit label, and always allow 24 in. of front service clearance. Pipe and wiring connections can need more room than the minimum. Where accessibility clearance is larger than an enclosure clearance, the larger one wins. The clearance table on this page has jumbled column alignment in this file, so take the exact numbers from the unit label or the printed clearance figure.

1. Check the unit clearance label for the position (upflow, counterflow or horizontal).
2. Confirm 24 in. of front clearance for servicing.
3. Allow room for gas, electrical, drain trap and vent/intake connections.

Non-direct vent: intake elbow requirement

Goodman · Non-direct vent installations

Non-direct vent needs no intake pipe, but put at least one 90-degree elbow on the combustion air intake to guard against blockage. This applies to upright units on the standard intake or horizontal units on the alternate intake.

1. Install at least one 90-degree elbow on the combustion air intake coupling.

Pipe slope, support and transitions

Goodman · Vent/flue piping

Support horizontal vent runs every three to five feet with a 1/4 in. per foot downward slope back to the furnace so condensate drains. Avoid a horizontal transition, which creates a water trap. Do not change from 2 in. to 3 in. pipe in a horizontal run. Leave room for expansion, and secure piping well if a long run is followed by an offset under 40 in.

1. Support horizontal vent runs every 3 to 5 ft.
2. Slope horizontal runs 1/4 in. per foot back toward the furnace.
3. Use a transition of no less than 45 degrees to the horizontal plane.
4. Do not make a horizontal 2 in. to 3 in. transition.
5. Secure piping tightly where a long run ends in an offset under 40 in.

Reload model data with the memory card

Goodman · GMVC95/AMVC95 upflow and *CVC9 counterflow two-stage furnaces

Used for d0 / d4 or after a control swap.

1. Use the memory card for this exact model.
2. Power off, insert the card, power on. Data loads at power-up.
3. Power off before removing the card.

Set heat anticipator on room thermostat

Goodman · ACVC96/AMVC96/GCVC96/GMVC96 furnaces

The room thermostat heat anticipator must match the wiring diagram note for this furnace.

1. Set the heat anticipator on the room thermostat to 0.7 amps.

Sharp sheet metal edges

Goodman · All cabinets

Holes in the cabinet can have sharp edges. Wear gloves when removing hole plugs.

1. Wear gloves when removing hole plugs from the cabinet.

Standard furnace vent and intake connections

Goodman · Vent/flue connections

The vent outlet takes 2 in. pipe and is glued into the furnace fitting, or a short 2 in. section can be glued in with a rubber coupling for service removal. Route piping away from refrigerant lines, metering devices and condensate lines. Two 45-degree long-sweep elbows make an offset that counts as one 90-degree elbow.

1. Glue the vent pipe into the furnace fitting, or use a short glued section and rubber coupling.
2. Route vent and intake pipe clear of refrigerant lines, metering devices and condensate drains.
3. Use two 45-degree long-sweep elbows if extra clearance is needed; count as one 90-degree elbow.

Thermostat setup: single stage heat and cool

Goodman · All systems with this control

The furnace needs only Y for cooling and W for heating. Set the thermostat to single stage heat / single stage cool and do not use multi stage mode.

1. Set the thermostat to single stage heat / single stage cool.
2. Confirm 24VAC on Y for cool calls and on W for heat calls.
3. Do not set the thermostat to heat pump mode. The only exception is a non-communicating single stage heat pump, which needs heat pump mode with the reversing valve on in cooling.
4. Do not use an O wire; this system has no reversing valve input.

Program the unit size code on a replacement furnace control

Lennox · All EL296UHV models: EL296UH045XV36B, 070XV36B, 090XV36C, 090XV48C, 090XV60C, 110XV48C, 110XV60C, 135XV60D

A replacement control needs the furnace size code stored; three bars then E203 at power-up means no valid code.

1. Thermostat OFF and control idle.
2. Hold the button until a solid P shows, then release.
3. Hold the button again and release when the right size code shows.
4. Within 10 s hold the button for 5 s to store it.
5. Cycle 24 V power to confirm the code was saved.

Auxiliary drain pan over finished ceilings and living areas

Rheem · Installations over finished ceilings or living space

If the unit is installed over a finished ceiling or living area, put an auxiliary condensate drain pan under the entire unit. The pan must extend under any evaporator coil installed with the furnace and under the open portion of the condensate drain assembly.

Bend the supply and return flanges before install

Rheem · All 96V and 96MDV series furnaces

Both flanges on the supply and return openings ship flat and must be bent up or down. They cannot be left flat.

1. Bend each supply and return flange up or down with duck-billed (folding) pliers along the perforations.

Check the IDB coupling arrow before reinstalling

Rheem · All 96V and 96MDV field conversions that remove the IDB coupling

If the IDB coupling is removed during conversion, it must go back in the correct orientation. An arrow on the coupling shows the direction of exhaust flow.

1. Find the arrow on the IDB coupling.
2. Confirm the arrow points in the direction of exhaust flow before tightening the clamps.

Clean the furnace and ducts after construction

Rheem · 96V and 96MDV series furnaces

After construction is substantially complete, clean the furnace, ductwork and components before final verification.

1. Clean the furnace, duct work and components.
2. Re-verify ignition, input, temperature rise and venting afterward.

Combustion air in confined and unconfined spaces

Rheem · All 96V and 96MDV series furnaces

An unconfined space needs at least 50 cubic feet of volume for each 1,000 BTUH of total input of all appliances in that space. Tight modern construction may still need outside air. Outside air openings for a confined space are sized the same way. Do not reduce the combustion air supplied to other gas appliances in the same space.

1. Calculate the total BTUH input of all gas appliances in the space.
2. Confirm at least 50 cubic feet per 1,000 BTUH is available for an unconfined space.
3. If the space is tight or confined, size outside air openings for a confined space.
4. Check that other gas appliances keep their combustion air supply.

Communicating systems use the thermostat for setup

Rheem · 96V and 96MDV communicating furnaces

On communicating systems the dipswitches are not used. Configuration changes are made at the thermostat. The dipswitch settings apply only in legacy (non-communicating) mode.

1. Make configuration changes at the thermostat on communicating systems