Rules regarding field installation or modification of electric heaters in Trane light commercial split system air handlers and package units: 

Rules:

• Increasing Heater kW Size - DO NOT increase the electric heat kW size without changing the entire electric heater assembly (Control Panel and Elements).   
• Units without factory installed electric heat, and with UDC/UCB - On a unit with a factory installed unit disconnect switch (UDC) or unit circuit breaker (UCB) and without a factory installed electric heater, DO NOT install an electric heater accessory.
• Units with factory installed electric heat, and with UDC/UCB - On a unit with a factory installed unit disconnect switch (UDC) or unit circuit breaker (UCB) and with a factory installed electric heater, DO NOT replace the electric heater assembly model with one having a larger kW size than that of the original factory installed electric heater.

Detailed rule explanation:

• Increasing Heater kW Size - Increasing heater element kW size alone is NOT feasible.  The number, size, and type of the electric heater control components and wiring are based on the element kW size and number of stages.  The electric heater assembly models are agency-approved only as an entire assembly (Control Panel and Elements).  Always refer to the official Trane heater kit tables available in product data or installation documentation.  If unsure, please contact your local Trane sales office.
• Units without factory installed electric heat, and with UDC/UCB - For units with a factory-installed unit disconnect switch (UDC) or unit circuit breaker (UCB), and without a factory installed electric heater, a heater assembly model replacement with a larger one is NOT feasible without reworking the unit or installing a new, separate power supply circuit for the heater.  This separate circuit would require separate over current protection, disconnecting means, wire and conduit (above-base conduit connection only), all sized and installed in accordance with NEC and local codes.   The reason a separate circuit is required is that models with a factory-installed unit disconnect switch (UDC) or unit circuit breaker (UCB) also contain corresponding agency-approved internal factory wiring for a single point power supply circuit.  The types and sizes of these components, as well as the unit nameplate ratings are based on the combination load of the unit model and the factory installed heater assembly model, if any.  Therefore, if a larger heater is installed in the field, these components could be too small to handle the load.
• Units with factory installed electric heat, and with UDC/UCB - For units with a factory-installed unit disconnect switch (UDC) or unit circuit breaker (UCB), and with a factory installed electric heater, replacing the electric heater assembly model with one having a kW larger than that of the original factory installed electric heater is NOT feasible without reworking the unit or installing a new, separate power supply circuit for the heater.  This separate circuit would require separate over current protection, disconnecting means, wire and conduit (above-base conduit connection only), all sized and installed in accordance with NEC and local codes.   The reason a separate circuit is required is that models with a factory-installed unit disconnect switch (UDC) or unit circuit breaker (UCB) also contain corresponding agency-approved internal factory wiring for a single point power supply circuit.  The types and sizes of these components, as well as the unit nameplate ratings are based on the combination load of the unit model and the factory installed heater assembly model, if any.  Therefore, if a larger heater is installed in the field, these components could be too small to handle the load.

Electrical Service Requirements:

Changing electric heat kW can directly affect:

• Minimum circuit ampacity (MCA)
• Maximum overcurrent protection (MOP)

Higher kW = higher current draw

Lower kW = lower current draw

You must ensure:

• The building's electrical infrastructure can support the change.
• Conductors and circuit breakers match the MCA/MOP listed for the heater kit used.

Unit Compatibility:

Trane light commercial split system air handlers and package units, like Odyssey, Foundation, and Precedent units, accept only specific heater kits designed for:

• The unit model (size/tonnage)
• The supply voltage (208-230V, 460V, 575V)
• The control scheme
• The physical cabinet size

Using an incompatible heater can cause:

• Improper airflow/temperature rise
• Control issues
• Electrical safety hazards

Always refer to the official Trane heater kit tables available in product data or installation documentation.   If unsure, please contact your local Trane sales office.

Temperature Rise and Airflow:

Considerations include:

• Ensuring airflow (CFM) matches the heater's required temperature rise range.
• Avoiding high discharge temperatures that may trip safety limits.

More electric heat kW increases leaving air temperature.

Reducing kW lowers heat output and may reduce the unit's ability to meet heating loads.

Unit UL Listing and Nameplate:

UL Listing: 

• Heater kits are certified as part of the unit system.  Changing heater size must be done only with Trane approved kits where applicable to keep the safety listing valid.
• When there are field electric heat installations or modifications (including modifications that reduce the heater KW) the original unit nameplate may not correctly indicate the electrical data for those field installations or modifications.   
• After electric heater installation or modification, and until a new UL on-site field evaluation can be performed, the UL Listing on the original unit nameplate label must be removed.
• How can the unit become UL Listed again?   Contact UL to schedule an on-site field evaluation to regain compliance and a new UL Listing.

Replacement unit nameplate: 

• A new replacement nameplate to indicate field changes to electric heat (including modifications that reduce the heater KW) CANNOT be printed by the factory.  
• Only an original "as shipped" unit nameplate label can be reprinted which WILL NOT reflect the new electrical data for the unit after modifying the electric heat or changing the electric heat kW.