Other: Furnace tips (part 3 of 5)

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

Do not connect a phone line to the control

Rheem · 96V and 96MDV communicating furnace control

The RJ-14 jack (J-11 / J1) is used only for factory programming. Connecting a telephone or phone line can cause irreparable damage to the furnace control, the telephone or the phone line.

Do not install in a mobile home

Rheem · 96V and 96MDV series furnaces

This furnace is not approved for mobile home installation. Installing it in one can cause fire, property damage, injury or death.

Do not share the condensate drain with an AC coil drain

Rheem · Condensate drain routing

Tying the furnace drain into a common line with an air conditioner evaporator coil drain below the furnace can block the line. A blocked line can overflow the coil pan and defeat the furnace blocked-drain shutoff.

1. Route the furnace condensate to its own drain, not into a shared line with an AC evaporator coil drain located below the furnace.

Downflow non-combustible floor base requirement

Rheem · Downflow installations

A downflow unit is certified only for a non-combustible floor. Use the special base listed on the furnace clearance label. The base is sold as an accessory. Not installing it can cause fire, property damage or injury. A base is needed when installing on a combustible floor without an air conditioning plenum.

1. Confirm the floor is non-combustible or install the special base from the clearance label.
2. Order the base as an accessory if it is not already on site.

Downflow non-zero clearance on the right side

Rheem · Downflow installations

For downflow non-zero clearance installs, the minimum right-side clearance is shown in Figure 4. If that clearance cannot be kept, a downflow zero-clearance kit RXGY-ZK must be installed.

1. Check the right-side clearance against Figure 4.
2. If the clearance cannot be met, install zero-clearance kit RXGY-ZK.

ECM blower communications are separate

Rheem · 96V and 96MDV furnaces with ECM blower

The ECM blower motor does not use the same communications bus as the furnace, condenser or thermostat. It uses a different protocol on its own peer-to-peer network at connector P4.

Electrical supply and overcurrent protection

Rheem · Furnace electrical supply

Match the voltage, frequency and phase to the rating plate. For one furnace, maximum overcurrent protection is 15 amps. Use a separate fused or breaker-protected branch circuit run to a disconnect near the furnace.

1. Confirm voltage, frequency and phase against the rating plate.
2. Protect the circuit with a maximum 15 amp fuse or breaker.
3. Run the circuit to an accessible disconnect near the furnace.
4. Keep electrical components protected from condensate.

Electronic air cleaner output

Rheem · Furnaces with EAC output

Line voltage for an electronic air cleaner comes from the EAC terminal and a neutral terminal on the control board. It runs whenever the circulating blower runs, but only above the minimum target CFM for the model. Maximum current is 1.0 amp.

1. Connect the air cleaner to the EAC terminal and control board neutral.
2. Confirm the target CFM is above the model threshold, or the output will not energize.

Factory setting and LP conversion

Rheem · Gas type conversion on all 96V furnaces

The furnace is factory set for natural gas only. Conversion to LP needs the special kit listed in the kit index that ships with the furnace. Using the wrong kit can cause fire, CO poisoning or explosion.

1. Confirm the fuel on the rating plate matches the gas supply before firing.
2. For LP, use only the conversion kit listed in the kit index supplied with the furnace.
3. Have a qualified installer, service agency or gas supplier make any conversion, using factory-specified or approved parts.

Filters and twinning

Rheem · All 96V and 96MDV furnaces

A filter is not supplied and must be field-installed and kept clean. Twinning of these furnaces is not permitted.

1. Install a field-supplied filter and keep it clean.
2. Do not twin these furnaces.

Flexible gas connector limits

Rheem · Gas connections

Do not run a flexible gas connector inside the furnace; the cabinet gas pipe gasket does not seal around it. Where codes allow one, use a new listed connector. Massachusetts requires flexible connectors under 36 in.

1. Do not run a flexible connector inside the cabinet.
2. Use only a new listed connector that has never served another gas appliance.
3. In Massachusetts keep flexible connectors under 36 in.

Freeze protection for the condensate trap and drain

Rheem · Attic, alcove, crawl space or other cold-location installs

Where the furnace may see temperatures below 32 °F (0 °C), such as an alcove or attic, protect the drain trap and drain piping from freezing. If the trap is inside the cabinet, no freeze protection is needed. A trap mounted outside or partly outside the cabinet must be protected, and exposed drain piping must be protected per local practice. A UL or CSA listed heat tape or heating cable rated 3-6 watts per foot is acceptable. Verify heat tape operation at installation.

1. Check whether the trap is inside or outside the cabinet.
2. Install listed heat tape or heating cable rated 3-6 W/ft on any exposed trap or drain piping.
3. Verify heat tape operation per its instructions at installation.

Gas detectors and LP below-grade limit

Rheem · Installations with natural gas or LP

UL or CSA recognized fuel gas and CO detectors are recommended on all applications. LP furnaces must not be installed below grade where local law prohibits it.

1. Install UL or CSA recognized fuel gas and CO detectors per the detector maker and local rules.
2. Do not install LP furnaces below grade (such as a basement) if local rules prohibit it.

Gas valve operation and gas line purging

Rheem · Gas valve

The 24-volt gas valve has inlet and outlet pressure taps and a regulator. Its control switch only sets ON or OFF. It opens slowly, taking 2 to 3 seconds. Never purge a gas line into the combustion chamber.

1. Check that the gas valve control switch is set to ON or OFF only.
2. Allow 2 to 3 seconds for the valve to fully open after it is energized.
3. Never purge a gas line into the combustion chamber.

Gas valve pressure test limit

Rheem · Gas supply piping tests

Disconnect the furnace and its manual gas stop from supply piping before any test above 1/2 PSIG (3.48 kPa). The gas valve is not rated for high line pressure.

1. Disconnect the furnace and its manual gas stop before pressure testing above 1/2 PSIG.

General condensate and conversion rules

Rheem · All field conversions

All conversions require condensate plumbing to slope in the direction of water flow. Hoses must be free of kinks. Plug or cap any unused hose taps when hose routing changes. The inducer coupling ships with a 10-20 degree tilt for upflow. When converted to downflow, rotate the inducer coupling as shown, at least 10 degrees from horizontal. The IDB coupling arrow must point in the exhaust flow direction when reinstalled.

1. Slope all condensate plumbing in the direction of water flow.
2. Remove kinks from all condensate hoses.
3. Plug or cap unused hose taps.
4. Rotate the inducer coupling for downflow, at least 10 degrees from horizontal.
5. Reinstall the IDB coupling with the arrow pointing in the exhaust flow direction.

Grounding and blower door safety switch

Rheem · Electrical installation

The cabinet needs an uninterrupted ground to the junction box ground screw. Do not use gas piping as ground. Do not disable the blower door safety switch.

1. Connect the cabinet to the junction box ground screw.
2. Do not use gas piping as the ground.
3. Do not disable the blower door safety switch.

Heat loss calculation and duct design

Rheem · 96V and 96MDV series furnaces

Perform a heat loss calculation to size the furnace BTU output for the structure. Ducts must be designed and installed for proper airflow. Inspect existing ductwork for proper size and sealing. Proper airflow affects comfort and equipment performance.

1. Run a heat loss calculation to determine the required furnace BTU size.
2. Design and install ducts for proper airflow.
3. Inspect existing ducts for correct size and sealing.

Horizontal installation: external condensate trap and clamps

Rheem · Horizontal left and right conversions

Horizontal installations require the condensate trap mounted externally below the unit. Mount the trap after the unit is at its installation point to avoid damage in transport. Hand-tighten screws when mounting the trap or drain coupling to protect the mounting flange. Allow at least 6 in. of clearance below the furnace. When horizontal, worm drive clamps on the flue transition or IDB couplings must sit above the level midline.

1. Mount the trap externally below the unit after the furnace is in place.
2. Hand-tighten the trap and drain coupling screws.
3. Keep at least 6 in. of clearance below the furnace.
4. Position worm drive clamps on the flue transition and IDB couplings above the midline.
5. Apply freeze protection if required.

Humidifier output

Rheem · Humidifier accessory

The humidifier output is a set of dry contacts. Logic and wiring diagrams are in the Humidification/Dehumidification section.

1. Wire the humidifier to the dry contacts as shown in the Humidification/Dehumidification section.

IDB coupling orientation

Rheem · Horizontal right with vertical vent conversion

If the IDB coupling is removed during conversion, it must go back in the right direction. The coupling has an arrow showing exhaust flow direction, and the arrow must point the correct way.

1. Before reinstalling the IDB coupling, find the arrow on the coupling.
2. Check that the arrow points in the direction of exhaust flow.

Indoor combustion air protection and exhaust fans

Rheem · Non-direct vent installations using indoor air

When indoor air is used for combustion, the inlet opening at the furnace must be protected from accidental blockage. Do not take air from a heated space with a fireplace, exhaust fan or other device that may cause negative pressure. If an exhaust fan is installed, provide enough ventilation to prevent negative pressure.

1. Protect the furnace combustion air inlet from blockage.
2. Do not draw indoor combustion air from spaces with fireplaces or exhaust fans.
3. Provide enough ventilation to stop negative pressure from exhaust fans.

Install an auxiliary drain pan where damage could occur

Rheem · 96V and 96MDV series furnaces

Recognized codes recommend an auxiliary drain pan under the furnace and under any evaporator coil located where an overflow or blocked primary drain could damage the building or its contents.

1. Install an auxiliary drain pan under the furnace and any evaporator coil in areas where water damage is possible.

Installation warnings for the cabinet and jacket

Rheem · All installations

Do not install the furnace on its back with access doors facing up. Do not lift the unit by the heat exchanger tubes, as this can damage the heat exchanger. Keep combustible materials, gasoline and other flammable vapors and liquids away from the furnace jacket. Do not use the furnace area as a storage or broom closet.

1. Do not install the furnace on its back with access doors up.
2. Lift the unit by the cabinet, not the heat exchanger tubes.
3. Keep the area around the furnace clear of combustibles and flammable liquids.

Insulate vent in freezing spaces

Rheem · Vents through unconditioned spaces

Vents through unconditioned spaces where below-freezing temperatures are expected must be insulated with approved insulation. Armaflex or Rubatex may be used. Do not apply heat tape to the vent pipe. Un-insulated pipe can freeze and block the vent, preventing furnace operation.

1. Insulate the vent through unconditioned space with approved insulation.
2. Do not install heat tape on the vent pipe.

Integrated furnace control layout and key connections

Rheem · R96V two-stage communicating furnace control

Key items on the integrated furnace control: P1, P2 and P5 are factory-wired low-voltage harness connections. J1 (RJ-14) is for factory programming only. T1 is the spark ignition transformer (about 60 Hz, minimum 12 kV). P3 is the inducer output (120 VAC, high and low speed). T3 is the EAC output. P4 is the ECM blower communications connection. S1, S2 and S3 are dipswitch banks. S4 is the bias/termination dipswitch bank. U38 holds the TX (red) and RX (green) communications LEDs. S8 is the pushbutton. U38 also drives the dual 7-segment display. P6 is the memory card connector. Humidifier relay contacts are labeled HUM.

L1 and L2 polarity

Rheem · Line voltage connections

L1 (hot) and L2 (neutral) polarity must be correct. If they are reversed, the ignition control may not sense flame.

1. Confirm L1 and L2 are not reversed when making field connections.
2. If flame sensing faults after install, check line polarity first.

Leak checking gas connections

Rheem · All gas connections

Never use matches, flame or any ignition source to find leaks. Use an approved chloride-free soap and water solution or another approved detector. Repair any leak and check again.

1. Apply approved chloride-free soap and water solution to each joint.
2. Repair any leak and repeat the check.
3. Never use a flame to check for leaks.

LP tank contamination warning

Rheem · LP gas supply

LP tanks, trucks and other delivery vessels must not hold anything but LP gas, such as fertilizer. Contamination can damage the furnace and voids the warranty. Confirm with the supplier.

1. Confirm with the LP supplier that the tanks and vessels are used only for LP gas.

Massachusetts side-wall vent: CO detectors and warning sign

Rheem · Side-wall horizontally vented installations in Massachusetts

For side-wall horizontal vent terminations less than 7 ft above grade in Massachusetts homes, a hard-wired CO detector with battery backup must be on the floor where the furnace is installed, and a battery or hard-wired CO detector on each additional level. Detectors must meet NFPA 720 and ANSI/UL 2034 and be IAS certified. A metal or plastic sign at least 8 ft above grade, in line with the vent, must read GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS, with letters at least 1/2 inch. If the detectors cannot be installed at completion, the owner has 30 days, and a battery-operated CO detector must be installed in the meantime.

1. Confirm a hard-wired CO detector with battery backup is on the furnace floor level.
2. Confirm a CO detector is installed on each additional level served.
3. Confirm the warning sign is mounted at least 8 ft above grade, in line with the vent terminal.
4. Leave the installation manual and venting parts list with the appliance.