Other: Furnace tips (part 2 of 5)

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

Dehumidification wiring and logic

Goodman · Systems with Dehum input

The Dehum input reduces blower speed to 85% during a cooling plus dehum call. The dehumidistat type sets the Dehum logic.

1. Connect the dehumidistat between R and Dehum if using an external dehumidistat. It must run on 24VAC.
2. If the dehumidistat opens on a humidity rise, set Dehum logic to Low using the CoolCloud app or push buttons.
3. If the dehumidistat closes on a humidity rise, set Dehum logic to High using the CoolCloud app or push buttons.
4. If using a thermostat, set it to energize Dehum only when dehumidification is wanted.

Diagnostics: last six faults storage

Goodman · All 34.5in chassis furnaces

The diagnostics menu stores the last six faults, newest first. A fault that repeats back to back is stored no more than three times. For example, a clogged return filter tripping the limit repeatedly is stored only three times in a row.

1. Open the diagnostics menu to review the last six faults.
2. Clear the fault history during maintenance or service.

Drain pan and freeze protection

Goodman · Furnaces installed above conditioned space or exposed to freezing

If the furnace sits over a conditioned space, use a drain pan that covers the full area under the furnace and any air conditioning coil. Keep the drain trap and vent piping from freezing, and insulate vent piping that sees freezing temperatures or the outdoors with 1/2 in. closed-cell foam.

1. Install a drain pan under the full furnace footprint when installed over conditioned space.
2. Insulate vent piping exposed to temperatures below 35 F for long periods with 1/2 in. closed-cell foam.
3. Insulate vent piping run outdoors or in unheated areas past the listed terminations.
4. Check piping for leaks before insulating.

Electronic air cleaner (EAC) line voltage connection

Goodman · Furnace with integrated control module

The EAC terminal supplies line voltage to an electronic air cleaner or device that runs with the circulating fan. Maximum load is 1.0 A at 120 VAC.

1. Turn off furnace power before installing accessories.
2. Connect the hot leg to the EAC terminal and the neutral to the NEUTRAL bus or the junction box neutral.
3. Use 1/4 in quick connect terminals.
4. Make all line voltage splices inside the furnace junction box.
5. Use wire rated at least 105°C if extra line voltage wire is run inside the furnace.

Electrostatic discharge precautions for the integrated control module

Goodman · Integrated control module on all furnaces covered

Equalize your body, the furnace and the control to the same electrostatic potential before touching the control or its wiring. This protects the integrated control module from damage on installed and uninstalled furnaces.

1. Disconnect all power to the furnace.
2. Touch a clean, unpainted metal surface of the furnace near the control to discharge your body.
3. Handle the control or wiring, and avoid moving or shuffling your feet or touching ungrounded objects. If you do, touch metal again before handling the control.
4. Discharge yourself to ground before taking a new control out of its packaging, and return old or new controls to their containers before touching anything ungrounded.

Induced draft and circulator blower motors

Goodman · All 34.5in chassis gas furnaces

Bearings in the induced draft and circulator motors are permanently lubricated, so no lubrication is needed. Check motor windings for dust buildup, which can cause overheating, and clean as needed.

1. Check motor windings for dust buildup.
2. Clean the motor if dust is present.

Integrated control module diagnostic LED

Goodman · All 34.5in chassis gas furnaces

If the control detects a possible safety concern, it stops the appropriate operation and shows diagnostic information on the LED. Use the error code (letter and number) with the troubleshooting chart at the back of the manual.

1. Read the error code on the 7-segment LED.
2. Look up the code in the troubleshooting chart.

Junction box relocation and wiring rules

Goodman · Gas furnace

The junction box is shipped on the left side (right for counterflow). Line voltage can enter through either side panel after relocation.

1. Disconnect all power before relocating the junction box.
2. Remove the burner compartment door.
3. Remove and keep the two screws securing the junction box to the side panel.
4. Move the junction box, plugs and grommets to the opposite side panel and secure with the saved screws.
5. Use copper replacement wire rated at least 105°C if original harness wire is replaced.
6. Label all wires before disconnecting them when servicing controls.

Learn menu (communication network reset)

Goodman · Communicating systems

The Learn menu resets the ClimateTalk communication network so the furnace finds the devices on it again. The menu does not appear when the control is connected to a non-communicating outdoor unit.

1. Use the Learn menu only when the furnace must rediscover the connected devices.

Line voltage electronic air cleaner (EAC) connection

Goodman · All 34.5in chassis furnaces with EAC accessory

The EAC terminal switches line voltage to an electronic air cleaner or other device that runs with the circulator. Maximum accessory load is 1.0 A at 120 VAC. Use 1/4 in quick connects. Hot goes to the EAC terminal and neutral goes to the NEUTRAL bus or the furnace junction box neutral. Any field line voltage splices must be inside the junction box, and added wire must have a minimum 105 C rating.

1. Turn off furnace power before installing the accessory.
2. Connect the accessory hot to the EAC terminal and the neutral to the NEUTRAL bus or junction box neutral.
3. Make all line voltage splices inside the furnace junction box.
4. Follow local codes and the air cleaner maker's mounting and grounding instructions.

Propane and high altitude conversion notes

Goodman · Propane and high altitude installations

For propane, an orifice change is needed. The LPLP03 kit is strongly recommended so the furnace will not fire when LP supply pressure is too low. At high altitude, a pressure switch and/or orifice and spring change may be needed. Above 7000 ft, use the specification sheets. In Canada, furnaces are certified only to 4500 ft.

1. Change the orifice for propane operation.
2. Install the LPLP03 kit on LP conversions.
3. At high altitude, check whether the pressure switch and/or orifice/spring kit is required.
4. Above 7000 ft, use the specification sheet kits. Canada: certified only to 4500 ft.

Reading the furnace model number

Goodman · ACVC96, AMVC96, GCVC96, GMVC96 furnaces

The 14-character model number identifies the brand (A = Amana, G = Goodman), configuration (M = upflow/horizontal, C = downflow/horizontal, K = dedicated upflow, D = dedicated downflow), gas valve type (M = modulating, C = 2 stage, H = convertible 2 stage, S = single stage), AFUE rating (80, 92, 96 or 97), input capacity in MBtu/h (030 to 120), and maximum CFM (3 = 1200, 4 = 1600, 5 = 2000). Cabinet width is coded A = 14 in, B = 17.5 in, C = 21 in, D = 24.5 in. The nomenclature layout on the page is jumbled, so confirm any position not listed here against the rating plate.

1. Locate the 14-digit model number on the rating plate.
2. Match the brand, configuration, gas valve and AFUE characters to the nomenclature key.
3. Use the model number, not the file name, when ordering parts or service information.

Safety circuit overview

Goodman · All 34.5in chassis gas furnaces

Primary limit: on the partition panel, normally closed, auto reset, watches heat exchanger temperature. Auxiliary limit: near the circulator, normally closed, manual reset, watches blower compartment temperature. Rollout limit: on the burner manifold, normally closed, manual reset, trips if flame is not drawn into the heat exchanger. Pressure switches: normally open (closed in operation), watch induced draft and coil front pressure taps for insufficient airflow or blocked condensate drain. Flame sensor: probe on the burner manifold that uses flame rectification to detect flame.

Status Menu rotation

Goodman · All 34.5in chassis furnaces

The Status Menu cycles through the operation mode, blower CFM (when running), humidification or dehumidification mode (when active), ventilator operation (when active), and any active fault codes. Each item shows for 2 seconds, then is off for 1 second, then the next item shows.

Thermostat mounting location

Goodman · All ACVC96/AMVC96/GCVC96/GMVC96 installations

Mount the thermostat about five feet off the floor on an inside wall, away from vibration and with good air circulation. Keep it away from drafts, registers, sun, lights, other appliances, fireplaces, hidden pipes or chimneys, and cold outside walls.

1. Pick an inside wall about five feet above the floor.
2. Avoid drafts, dead spots, registers, sunlight and heat from fixtures or fireplaces.
3. Avoid hidden water pipes, chimneys and unconditioned walls behind the thermostat.
4. Follow the thermostat maker's mounting instructions.

Thermostat placement

Goodman · Thermostat installation with the furnace

Mount the thermostat about five feet above the floor on a vibration-free inside wall with good air circulation. Keep it away from drafts, dead spots behind doors, corners, and areas under supply registers or in direct sun.

1. Pick an inside wall with good air movement and no vibration.
2. Mount the thermostat about five feet above the floor.
3. Keep it clear of drafts, dead air spots, direct sunlight and heat sources.

Valid equipment combinations

Goodman · Furnace system matching

The furnace can be paired with: a furnace alone; a 1-stage or 2-stage non-communicating A/C or heat pump; a communicating A/C or heat pump; or a communicating A/C or heat pump inverter. All combinations assume a non-communicating single stage thermostat and AHRI matched equipment.

Venting restrictions and vent system check

Goodman · All vented installations

This furnace cannot connect to Type B, BW or L vent or vent connector, and cannot enter any part of a factory-built or masonry chimney, except as a pathway for PVC. Never common-vent it with another appliance or a solid-fuel vent. Use only the no-hub connectors shipped with the unit. Before leaving, check the whole flue system inside and out for sealing, because leaks can cause carbon monoxide exposure.

1. Confirm the vent is not Type B, BW or L and is not common-vented.
2. Confirm the vent does not run through a chimney except as a PVC pathway.
3. Use only the supplied no-hub connectors.
4. Inspect the full flue system inside and out for leaks before startup.

Wiring replacement and grounding requirements

Goodman · ACVC96/AMVC96/GCVC96/GMVC96 furnaces

Wiring and grounding notes from the wiring diagram page that apply when servicing the furnace.

1. Use copper conductors only.
2. If any original wire supplied with the furnace must be replaced, use wiring rated for the temperature shown on the diagram note (the number is cut off in the text, so check the unit's own wiring label).
3. Use the manufacturer's specified replacement parts when servicing.
4. Permanently ground the unit in accordance with the National Electrical Code and local codes.
5. Disconnect all power before servicing or installing the unit, since multiple power sources may be present.

Alternate horizontal termination

Rheem · Alternate horizontal non-direct vent termination

The vent terminal sits 8 to 12 in from the wall. The vent tip portion must remain vertical. The vent may be rotated up to 45° left or right from vertical as long as the tip stays vertical. Maximum length shown is 60 in.

1. Set the terminal 8 to 12 in from the wall.
2. Keep the tip portion vertical.
3. Rotate the vent no more than 45° left or right if needed.

Avoid chemicals that contaminate combustion air

Rheem · All 96V and 96MDV series furnaces

Combustion air must not come from a corrosive atmosphere. Acid-forming chemicals such as sulfur, fluorine and chlorine can turn into corrosive acids when burned. Common sources include aerosol sprays, bleaches, cleaning solvents, paint removers, refrigerants, pool chemicals, and cements. Areas like laundry rooms, hobby rooms, indoor pools and chemical storage may need direct vent with outside air.

1. Check the combustion air area for chemical exposures listed in the manual.
2. If exposure exists, switch to direct vent with outside air.

Blower and induced draft motor lubrication

Rheem · R96V furnace motors

Do not add lubricant to the blower motor or induced draft blower motor bearings. Both motors are permanently lubricated. Adding lubricant can shorten motor life and void the warranty. Clean the motors periodically to prevent overheating from dust buildup on windings or housing.

1. Clean blower and induced draft motors periodically, including windings and exterior.
2. Keep filters clean so the motor has adequate airflow for cooling.
3. Never add lubricant to motor bearings.

Check vent run against maximum equivalent length

Rheem · All 96V and 96MDV series furnaces

Add the actual pipe length and the equivalent length of all elbows. The total must not exceed the maximum equivalent vent length for the model. Example from the manual: a 60 KBTU direct-vent run of 31 ft of 2 in pipe with 5 long-sweep elbows gives 56 equivalent ft, which is acceptable against a 65 ft maximum. The same run with standard elbows gives 81 ft and is not acceptable.

1. Measure the straight pipe length.
2. Add 5 ft per long-sweep elbow or 10 ft per standard elbow.
3. Compare the total with the model maximum in the vent length table.

Communications LED behavior

Rheem · Communicating furnace control

The TX (red) and RX (green) LEDs light in an undefined pattern when other communicating components are attached and talking to the furnace control. A steady pattern alone does not confirm a fault.

Condensate drain connection options

Rheem · All conversions

Condensate drain has options for 3/4 in. or 1/2 in. PVC connections. The trap also accepts a 5/8 in. rubber hose with a hose clamp when mounted inside the unit. Improper hose connections will stop condensate from draining and may damage the furnace. The trap has two sides, so note the inlet and outlet locations when converting.

1. Select 3/4 in. or 1/2 in. PVC, or a 5/8 in. hose with clamp for an internal trap.
2. Confirm the trap inlet and outlet sides match the conversion.
3. Confirm the drain connection allows condensate to drain freely.

Condensate neutralizer and overflow line

Rheem · Condensate drain with optional neutralizer

A neutralizer cartridge is needed only where local codes require it. The overflow line is required only when the neutralizer is used and the drain runs to a floor drain.

1. Install the neutralizer cartridge in the horizontal position only.
2. When routing to a floor drain, also install an overflow line.
3. If no floor drain is available, use a condensate pump.

Condensate pump requirements

Rheem · Condensate pump installs

The pump must resist acidic water, or a neutralizer must go ahead of it. The pump needs an auxiliary safety switch to stop the furnace if the pump fails.

1. Use an acid-resistant condensate pump, or install a neutralizer ahead of the pump.
2. Install an auxiliary safety switch on the pump to prevent furnace operation and overflow if the pump fails.
3. Wire the safety switch through the R (low voltage) circuit only so the furnace runs in heating or cooling.

Conversion configurations and kit requirements

Rheem · All field conversions

Field conversions are possible from upflow (as shipped) to downflow, horizontal left or horizontal right. Each configuration lists a kit requirement. Upflow with vertical vent uses only the parts bag. The other configurations need kit RXGY-CK, and some also need zero-clearance kit RXGY-ZK. The page layout links kit labels to sections; verify on page 14.

1. Select the configuration (upflow, downflow or horizontal, left or right vent).
2. Check whether conversion kit RXGY-CK is required.
3. Check whether zero-clearance kit RXGY-ZK is also required.
4. Follow the page listed for that configuration.

Dehumidification dipswitch S2-8 warning

Rheem · 96V and 96MDV furnaces with humidification or dehumidification

S2-8 (labeled ODD) turns dehumidification on or off. It does not affect humidification. If it is ON with no humidistat installed, cooling airflow is permanently reduced by about 15 percent.

1. Set S2-8 OFF unless a humidistat is installed and dehumidification is needed.

Do not bypass or jumper safety switches

Rheem · All 96V and 96MDV series furnaces

Do not bypass, jumper or remove any safety switch. If a safety switch shuts the furnace down or makes it cycle, that is a safety hazard for a qualified technician to fix. Do not reset safety controls without corrective action and verification. Replace safety control parts only with identical OEM parts.

1. Find and fix the cause of any safety switch trip.
2. Verify safe operation before resetting.
3. Replace safety components only with identical OEM parts.