GMW GMW16571 PDF

Introduction

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 events result 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 (clutch control, variable displacement mechanism, or compressor speed) adequately protects the system from condensate freeze. A secondary purpose while collecting data is to demonstrate refrigerant superheat control under a variety of conditions. This procedure has the required instrumentation and test sequence for a superheat analysis without additional testing.

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

Note: A change in the refrigerant used in a vehicle HVAC system has a significant impact on system performance and will require revalidation of evaporator freeze testing.

Applicability. This test procedure is intended for use on HVAC systems with temperature based control systems on a climatic test bench.

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

• As a test technique to develop and verify the optimal location of the refrigerant control sensors (evaporator air or fin temperatures). A clear plastic window and/or camera to view and record 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 control design that will provide robust protection from evaporator condensate freeze under applicable conditions expected to be encountered for a customer vehicle intended usage.

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.

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 production intent refrigeration components including the condenser, compressor and refrigerant expansion device(s). The compressor and expansion device control the flow of refrigerant and impact the location of the coldest location on the evaporator outlet face.

Tests must be conducted with functional 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.)