GMW GMW16571 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 whether the control of the compressor cycling (clutch control), variable displacement mechanism (Electronic Variable Displacement Control (EVDC)), or compressor speed (Electric Compressor) adequately protects the evaporator from condensate freeze.

Note: The refrigerant charge variation included in this test is not sufficient to evaluate condensate freeze below a critical refrigerant charge (as defined by GMW7022), (i.e., GMW16571 is not a low refrigerant charge evaluation test).

Foreword. This test procedure is intended to be used to collect data for vehicle climate control decisions during Heating Ventilation and Air Conditioning (HVAC) system development.

• As a test technique to develop and verify the optimal location of the refrigerant control sensors (Evaporator Air or Fin Temperatures). A refrigeration bench is required for this evaluation and a clear plastic window or camera to view frost formation on the evaporator (inside the HVAC Module) is required.

• 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 applicable conditions expected to be encountered for the vehicles intended usage.

• As a system development test to define an appropriate factor of safety necessary for a robust system calibration. During system development, it is necessary to modify the intended capacity control system and to lower the control set point to the cause of condensate freeze formation. This frost formation data along with component variation analysis is used to predict expected customer satisfaction.

Note: GMW15775 is a complementary vehicle level 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.

Applicability. This test procedure is intended for use on HVAC systems with temperature based control systems on a climatic test bench. These conditions must be met for valid results of the testing.

Tests 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).

Tests 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).

Tests must be conducted with production intent compressor and refrigerant expansion device(s).

Tests must be conducted with refrigerant control software and calibrations as well as representative refrigerant control sensing devices (Evaporator Air or Fin Temperature Sensors, High Pressure Transducers, Low Pressure Switches or Transducers, etc.)

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 will enable a more robust frost control system. Ambient variation will require additional test conditions as the transition points must also be evaluated.

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