how air con­di­tion­ing units work

Classic Car Weekly (UK) - - Living With Classics -

1 Cir­cuit di­a­gram

The di­a­gram shows that the sys­tem has high- and low-pres­sure sides. The former is be­tween the out­put of the com­pres­sor and the in­put of the ori­fice tube or ther­mal ex­pan­sion valve. It may be de­scribed as ‘hot’. The lat­ter side is from the ther­mal ex­pan­sion valve, or ori­fice tube, through to the in­put side of the com­pres­sor. It may be de­scribed as ‘cold’.

2 Ther­mo­static ex­pan­sion valve

This of­fers a vari­able rate of flow of re­frig­er­ant to the evap­o­ra­tor. A bulb and cap­il­lary con­tain­ing re­frig­er­ant acts as a tem­per­a­ture sen­sor. When the re­frig­er­ant be­ing out­put to the evap­o­ra­tor is too cold, the di­aphragm acts on the ac­tu­at­ing pin, which in turn re­stricts flow, pre­vent­ing fluid re­frig­er­ant from ex­it­ing the evap­o­ra­tor and dam­ag­ing the com­pres­sor.

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