GMW GMW15775 PDF

Note: Nothing in this standard supercedes applicable laws and regulations.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose. Evaporator Core freeze results in reduced compressor oil circulation and can result in compressor damage. The purpose of this test is to determine:

In the case of the variable capacity compressor, whether the Pneumatic Control Valve adequately protects the evaporator from condensate freeze (with worst case control variation comprehend).

In the case of fixed capacity compressor systems, whether the control of the compressor cycling (clutch control) adequately protects the evaporator from condensate freeze with production variation in the control system comprehended.

In the case of an Electronically Variable Displacement Control (EVDC) or electrically driven compressor systems, whether the capacity control (either displacement command or compressor speed command) adequately protects the evaporator from condensate freeze with system variation comprehended.

Note: The refrigerant charge variation included in this test is not sufficient to evaluate condensate freeze below Operational refrigerant charge. (i.e., GMW15775 is not a low refrigerant charge evaluation test).

Foreword. This Test Procedure is intended to be used to collect data during Heating Ventilation and Air Conditioning (HVAC) system validation.

GMW15775 is a vehicle-level or bench test to perform final system verification around evaporator condensate freeze with production intent sensor designs/placements, controller, software and calibrations under a robust set of vehicle operating conditions while comprehending control system variation

GMW16571 shall be used as a test technique to determine the optimal location of the refrigerant control sensors (Evaporator Air or Fin Temperatures, refrigerant temperature probes or refrigerant pressure transducers).

GMW16571 shall be used during system development testing to define an appropriate factor of safety necessary for a robust system calibration. Frost formation data along with a system variation analysis is used to predict expected production variation.

GMW16571 shall be used as a test technique to develop initial calibrations with a proposed sensor placement and production intent control design that will provide robust protection from evaporator condensate freeze under most applicable conditions expected to be encountered for the vehicles intended usage.

Applicability. This test procedure is intended for use on either a HVAC system test bench or full vehicle tests in Climate tunnels. The following conditions must be met for valid results of the testing.

Test must be conducted with representative Air Handling conditions at the Evaporator Air Inlet and Exit (typically this means testing with a complete and representative HVAC Module).

Test must be conducted with representative Air Flow conditions at the Condenser Air Inlet and Exit. Typically this means testing with a complete and representative Condenser Radiator Fan Module (CRFM).

Test must be conducted with production intent Compressor and Refrigerant Expansion Devices.

Test must be conducted with production intent refrigerant control software and calibrations as well as representative refrigerant control sensing devices (Evaporator Air Temperature Sensors, High Pressure transducers, Low Pressure Switches or transducers, etc.) See paragraph 4.1.7.

Note: Consideration should be applied where the production intent control points change with ambient temperature. The matrix included in this procedure does not comprehend the impact of variable control points in terms of the effective evaporator loading in regards to determining worst case frosting conditions. Using a fixed control point regarding ambient change during system frost control development may enable a more robust frost control system.

Test shall be conducted with representative refrigerant plumbing (length, diameters and bends production representative).