Other: Furnace tips (part 1 of 5)

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

Canadian installations: combustion air to other appliance clearance

Allied · Canadian installations

CSA B149 requires a minimum distance between the combustion air intake inlet and the exhaust outlet of other appliances.

1. Keep at least 12 in. (305 mm) between this unit's combustion air intake inlet and another appliance's exhaust outlet.

Conditions for using the furnace as a construction heater

Allied · Furnace used for heating during construction

The manual discourages construction heating. Allowed only when every condition below is met.

1. Install the vent system permanently per these instructions.
2. Control the furnace with a room thermostat. No fixed jumpers for continuous heating.
3. Provide and seal the return air duct to the furnace.
4. Keep return air between 60°F (16°C) and 80°F (27°C).
5. Keep air filters in place during construction and replace them at completion.
6. Set input rate and temperature rise to the nameplate.
7. Provide 100% outdoor combustion air through temporary ducting, not connected directly to the furnace.
8. Clean the heat exchanger, components, duct system, filters and evaporator coil after final cleanup.
9. Verify ignition, input rate, temperature rise and venting per these instructions.

Do not vent into an existing stack or use screens

Allied · Exhaust and intake terminations

Exhaust must not discharge into a stack that serves another gas appliance. Screens or perforated metal in exhaust or intake terminations cause freeze-ups and can block them.

1. If a vertical discharge through an unused stack is required, insert PVC pipe into the stack until its end is even with the top of the metal stack.
2. Do not install screens or perforated metal on exhaust or intake terminations.

EAC and HUM accessory terminals on the control board

Allied · Accessory wiring on the integrated control

The EAC terminal is a 120 V output that is energized whenever the indoor blower runs. The HUM terminal is a 120 V output that is energized in heating mode when the combustion air inducer runs. Each takes up to 1 amp; larger loads need an external relay.

1. Connect an accessory rated up to 1 amp directly to EAC or HUM, with its neutral on a provided neutral terminal.
2. For a load above 1 amp, use an external relay and do not connect it directly to the terminal.

Electrostatic discharge (ESD) precautions

Allied · Installation and service of the integrated control

Electrostatic discharge can damage the furnace electronic controls. Put the furnace, the control and the technician at the same static potential before service.

1. Touch bare metal on an unpainted part of the unit, such as the gas valve or blower deck, before any service work.
2. Touch all tools to the same unpainted surface before using them near the control.

Exhaust tee and direction notes

Allied · Sidewall exhaust terminations with optional tee

Figure 32 shows the exhaust tee termination. Do not use an accelerator with the tee. The exhaust must never point toward the combustion air inlet.

1. Connect the exhaust termination tee to the 2 in. or 3 in. PVC flue pipe as shown.
2. Do not install an accelerator when an exhaust termination tee is used.
3. Rotate the exhaust 45 degree elbow to the side away from the combustion air inlet if needed to keep exhaust away from neighbors.
4. Never direct exhaust toward the combustion air inlet.

Field electrical connections and overcurrent protection

Allied · Power supply and thermostat wiring

Wiring must meet Class I limits and be protected by a fuse or breaker matched to the unit nameplate. Maximum overcurrent protection allowed is 15 A.

1. Use a fuse or breaker sized from the nameplate maximum current, never above 15 A.
2. Install a separate properly sized disconnect near the furnace.
3. Use at least 18 gauge wire rated Class II for thermostat connections.
4. Ground the unit per local code, or the NEC (ANSI/NFPA 70) in the USA or CSA C22.1 in Canada. A green ground wire is in the field makeup box.
5. Check polarity and ground, because the integrated control is polarity sensitive.
6. Leave enough thermostat wire to remove the blower for future service.
7. If the makeup box is moved to the right side, plug the unused left side opening after removing the plug from the right side.

Gas piping layout (left side, right side, horizontal)

Allied · Gas piping, all sizes in this manual

Gas piping can enter from the left side (standard), the right side (alternate), or run for horizontal applications. Only black iron pipe may be routed inside the cabinet. A drip leg, ground joint union and manual main shut-off valve go in the supply line.

1. Install a manual main shut-off valve and a drip leg in the supply line.
2. Install a ground joint union in the supply piping.
3. Route only black iron pipe inside the cabinet and seal the cabinet opening with the bellows grommet.
4. Plug the unused side of the gas valve when piping from the other side.

Gas type approval and LP conversion

Allied · All A95UH, A93UH, 95G1UH and 92G1UH units

The furnace is set up for natural gas only. Use only the gas type listed on the unit nameplate. LP/propane needs a separate conversion kit, which is ordered separately.

1. Check the nameplate for the approved gas type.
2. Install the LP conversion kit before operating on propane/LP gas.

Gas valve connection torque

Allied · Gas valve

Do not overtighten the gas piping at the valve.

1. Use two wrenches so the valve is not twisted.
2. Do not exceed 600 in-lbs (50 ft-lbs) when attaching gas piping to the valve.

High altitude installation

Allied · Installations above 4,500 ft

In Canada, installations above 4,500 ft are under local authority jurisdiction. At 4,501 to 10,000 ft a pressure switch change may be needed, and orifice conversion kits may apply. Combustion air pressure switches are factory set and need no adjustment.

1. Check the altitude of the installation against the altitude tables.
2. Order and install the required pressure switch and orifice kit for the unit size and altitude.
3. Do not adjust the combustion air pressure switch.

Limits and switches that are factory set

Allied · Furnace safety controls

Primary limit, pressure switch and the two flame rollout switches are factory set and should not be adjusted. The primary limit is on the vestibule panel. The pressure switch sits on the cold end header box and proves combustion air inducer operation before ignition. The two rollout switches are manual reset and are on the front of the burner box.

1. Do not adjust the primary limit or pressure switch.
2. If a rollout switch has opened, check for an exhaust or intake obstruction before pressing its manual reset.

LP/propane leak detector

Allied · LP/propane installations

LP/propane odorant can fade, and LP gas settles near the floor, so it can be hard to smell. An LP leak detector should be installed in every LP application.

1. Install an LP/propane leak detector in all LP installations.

Massachusetts carbon monoxide detector and venting requirements

Allied · 92G1UH furnace installed in Massachusetts

Requirements for side wall, horizontally vented gas equipment in Massachusetts dwellings where the vent termination is under 7 feet above grade.

1. Confirm a hard-wired CO detector with alarm and battery backup is on the floor level where the equipment is installed, and a battery or hard-wired CO detector with alarm is on each additional level.
2. If the equipment is in a crawl space or attic, the hard-wired detector may be on the next adjacent floor.
3. If the requirement cannot be met at completion, the owner has 30 days to comply, and a battery-operated CO detector with alarm must be installed during that time.
4. Detectors must meet NFPA 720 and be ANSI/UL 2034 listed and IAS certified.
5. Install a metal or plastic sign on the exterior at least 8 feet above grade, directly in line with the vent terminal, reading GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS. Lettering must be at least 1/2 inch.
6. Leave the installation instructions and venting instructions with the appliance.

Preventing exhaust icing in extreme cold

Allied · Exhaust terminations in cold climates

Long vent runs through unconditioned space can form ice at the termination below about 20 F (6.7 C) and stop the unit from running.

1. Make sure run times are at least 5 minutes, which clears most icing problems.
2. If icing persists, install heating cable on the exhaust piping and termination. Heating cable kits are available; check the unit spec sheet for part numbers.

PVC versus ABS connections at the furnace

Allied · Vent pipe material selection

Intake and exhaust connections on 92G1UH are PVC. ABS pipe needs transition solvent to join the PVC fitting in the unit.

1. Use PVC primer and PVC solvent cement when running PVC vent pipe.
2. When using ABS vent, bond to the unit's PVC fitting with transition solvent cement.
3. Use all-purpose cement only when fittings and pipe are the same material.
4. Use low-temperature solvent cement in cold weather.
5. Do not use hammer blows to insert pipe.

Return air must not come from a room with a gas appliance

Allied · Return air plenum installations

Pulling return air from a room with a gas water heater, gas appliance or wood fireplace creates negative pressure. Flue gases can then be drawn back down the vent and produce carbon monoxide that is spread through the duct system.

1. Do not draw return air from a room that contains another gas appliance or combustion device.
2. Seal the plenum to the furnace cabinet with fiberglass strips, caulk or equivalent when using bottom or side return.

Bimetal basics

Generic

Copper expands more than steel so the strip bends with heat. Bimetal discs snap over and are used as furnace high-limit and rollout switches.

Condensate pumps (Code Alert / Pro Tip)

Generic

Local code dictates condensate disposal, materials and piping. Pumps are self-priming with a float switch, vents must stay uncovered; many have two inlets — one for the evaporator drain, one for the acidic high-efficiency furnace condensate. Clean coils, pans and drains often to stop mold/algae.

Makeup air inlet placement

Generic

Outdoor intake needs clearance from appliance exhaust terminations and may need to be within a set distance of the furnace; check mfr sheet.

Active alarm display

Goodman · All 34.5in chassis furnaces

An active alarm appears in the Status Menu as E followed by a two-digit alarm code. Look up the two-digit code in the troubleshooting chart.

1. Read the E and two-digit code in the Status Menu.
2. Look up the code in the troubleshooting chart at the back of the manual.

Air filter maintenance

Goodman · All 34.5in chassis gas furnaces

Never run the furnace without a filter. Dust and lint can build up on internal parts and cause lost efficiency, damage and possible fire. Filters are not shipped with the furnace and must be supplied by the installer. Clean permanent filters or replace disposable ones every two months or as needed, using the same type and size.

1. Turn off power to the furnace before removing an upflow or counterflow filter.
2. Replace the filter with one of the same type and size.
3. Vacuum the blower compartment when the filter is removed, if needed.

Airflow display in the Status Menu

Goodman · All 34.5in chassis furnaces

When the blower runs, the first 7-segment character shows A. The next two show the CFM divided by 100, rounded to the nearest 100 CFM. For example, 550 to 649 CFM shows A06 and 1150 to 1249 CFM shows A12.

Alternate electrical, gas and vent connections

Goodman · Upflow and horizontal models

Electrical and gas lines can enter through either side panel, and on horizontal units through the top or bottom. Horizontal alternate vent setups need the RF000142 vent drain kit.

1. Choose the side or top/bottom entry for electrical and gas lines.
2. If using the horizontal alternate vent, install the RF000142 vent drain kit.

Auxiliary alarm (condensate) switch wiring

Goodman · All 34.5in chassis furnaces

The control has a 24VAC Aux Alarm input labeled Condensate for a condensate switch. It can also take compatible CO2 sensors or fire alarm contacts. The default AUX switch is normally closed and opens when the evaporator base pan water level is too high.

1. Wire the condensate switch to the Condensate (AUX) input on the control.
2. Verify the switch is normally closed when the pan is dry.

Blower door interlock

Goodman · Gas furnace

The blower door interlock cuts unit voltage when the door is opened. Do not defeat it.

Bypass the inductor to test an ECM motor

Goodman · 3/4 and 1 HP ECM motors with inductor

The inductor is in the line power supply to the motor. If it has failed, the motor will not run.

1. Disconnect the black line wire from the inductor.
2. Connect that wire directly to the motor.
3. If the motor runs, replace the inductor.

Combustion and ventilation air

Goodman · All furnace installations

Most homes need outside air supplied to the furnace area through grilles or ducts open to the outdoors, an attic or a crawl space. Exhaust fans, dryers and fireplaces that pull air out of the house can cause backdrafting. If other gas appliances share the room, size their combustion air as well.

1. Confirm the furnace room has adequate outside combustion and ventilation air.
2. Check house depressurization with exhaust appliances running.
3. Size air for other gas appliances in the same space per NFPA 54/ANSI Z223.1 or CAN/CSA B149.1-15.

ComfortBridge memory chip (last resort)

Goodman · ComfortBridge furnaces

Use the shared data memory chip only as a last resort. The preferred method is the CoolCloudHVAC app.

1. Populate shared data using the CoolCloudHVAC app, Shared Data menu under the Furnace tab.
2. Use the memory chip only if the app method is not possible.

Counterflow drain trap clearance

Goodman · Counterflow model installed horizontally with left side down

A horizontal counterflow installation needs a minimum clearance under the drain trap.

1. Keep at least 5 1/2 in of clearance beneath the drain trap.