CONDENSER APPROACH
On a chiller with water cooled condensing, this is the difference
between the saturated temperature of the discharge pressure and the
leaving condenser water temperature. On a high efficiency
chiller with flooded type condenser, this should normally be no more
than 1 to 2 degrees C (1.8 to 3.6 degrees F). Where historical
information is available, it is always good to compare previous
approach readings with the current Reading.
High condenser approach will cause loss of chiller efficiency and
capacity.
The most likely case of increasing condenser approach is fouling
of the waterside of the condensing tubes. Looking at the
quality of the condenser water itself can give an indication of the
probability of condenser tube waterside fouling.
High condenser approach may also be due to ¨drift¨ in the
pressure reading of the compressor discharge pressure/ temperature
sensor or the reading of the leaving condenser water
temperature sensor. These items can be verified by comparing
against a refrigerant manifold reading or temperature meter reading,
as appropriate.
On a chiller with air cooled condenser, the approach is the
difference between the saturated temperature of the discharge pressure
and the ambient air temperature. Normally, this will be 10 to
15 degrees C.
Possible
causes of high approach on air cooled chillers can be error in the
compressor discharge pressure sensor Reading. A likely cause is
dirty coils. This can easily be discerned with a visual
inspection.
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