RLC-SVX19J_SHORT-GB
18
Optional Free-Cooling
Figure 9 – Total and Partial Free-Cooling option
a.Total Free Cooling, Direct free cooling version
b.Partial Free Cooling, Direct free cooling version
If there is a need to get a defi nition for partial heat recovery coil distribution, please contact the Trane Sales offi ce.
Free-Cooling Enabling Conditions
To get the free cooling active, condition is to have unit in
active cooling mode and that Outdoor temperature low
enough according to fi gure below.
The free cooling function is enabled when outdoor air
temperature is below Active chilled water cooling set
point minus FC_offset.
A hysteresis should also apply to avoid short cycling of
Free Cooling enabling logic. The Free Cooling offset is an
adjustable parameter to make free cooling active.
If free cooling function is enabled, free cooling becomes
the 1st stage of cooling. Free cooling is the fi rst stage to
engage for cooling capacity loading and the last stage to
consider in capacity unloading.
In order to maximize tandem operation of free cooling
with compressor the following logic is applied:
When unit is confi gured in “Partial free cooling”, when
free cooling reaches its full capacity and there is a call
for compressor start, then the fi rst circuit to start shall
be circuit 2 (if available).This also means compressor
balancing function is disabled in these conditions.
Note: UC800 will not lockout compressor below free
cooling change over point, but the compressor is locked
out when outdoor air is below “low ambient limit”
set at -10°C. So FC will be the only source of cooling
below -10°C.
Figure 10 – Free-cooling enabling conditions
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