General Description, Dual HVAC System
The Dual HVAC system replaces the standard sleeper HVAC when optioned. Vehicles with a Dual HVAC system have a larger alternator, additional batteries, and premium insulation. The Dual HVAC system operates both when the engine is running and when the engine is off.
The Dual HVAC system controls temperature differently than the standard sleeper HVAC system. The standard sleeper HVAC (without Optimized Idle) attempts to maintain vent discharge temperature at the sleeper vents, much like the main HVAC in the dash. The Dual HVAC system is a zone control system which attempts to hold the bunk at a constant temperature.
The Dual HVAC system has two evaporators for cooling, one supported by the engine-driven A/C system, and the other on a separate battery-powered A/C loop with a back wall-mounted condenser. When the engine is running, the Dual HVAC system uses the traditional engine-supported systems for heating and cooling. When the engine is turned off, the vehicle batteries power the separate electric air conditioner loop or support a fuel-operated heater.
Operation of the Dual HVAC system is regulated by the cab Progressive Low Voltage Disconnect (PLVD). The PLVD must be enabled for the Dual HVAC system to be started. The PLVD will stop operation of the Dual HVAC system when the voltage gets below a pre-determined threshold. Before operating the Dual HVAC system, bring the sleeper interior temperature to the desired temperature with the engine running and the bunk curtain open. The Dual HVAC system is designed to maintain an established comfortable bunk temperature in parked mode for up to 12 hours with the bunk curtain closed.
Note: The condition and charge of the vehicle batteries will directly affect the run time of the Dual HVAC system. If the vehicle run time between discharges is less than eight hours, or if additional loads are added to the vehicle batteries, the Dual HVAC system run time will be less than expected.