AAON M2-036 - Manual (Page 47)

47
Before connection to the unit the condenser
water system should be flushed to remove
foreign material that could cause condenser
fouling. Install a screen strainer with a
minimum of 20 Mesh ahead of the
condenser inlet to prevent condenser fouling
and internal tube damage.
Mineral content of the condenser water must
be controlled. All make-up water has
minerals in it and as the water is evaporated
in the cooling tower, these minerals remain.
As the mineral content of the water
increases, the conductivity of the water
increases.
Field provided and installed water treatment
program must be compatible with stainless
steel, copper, aluminum, ABS plastic, and
PVC. Batch feed processes should never be
used as concentrated chemicals can cause
corrosion. Never use hydrochloric acid
(muriatic acid) or chlorine as it will corrode
stainless steel.
Unit is capable of operating with Entering
Water Temperatures (EWT) as low as 50°F
without the need for head pressure control.
If the EWT is expected to be lower than
50°F or more stable operation is desired, a
field provided water regulating valve may be
used.
Glycol solution should be used if ambient
temperatures are expected to fall below
freezing or if the loop water temperature is
below 50°F while operating in the heating
mode (heat pump units only). Adding glycol
to condenser water causes an increase in
pressure drop resulting in a decrease in unit
performance. A minimum concentration of
20% glycol solution is recommended.
WATER PIPING
Follow national and local codes when
installing water piping. Connections
to the unit should incorporate
vibration eliminators to reduce noise
and vibration and shutoff valves to
facilitate servicing. Supply and return
water piping must be at least as large
as the unit connections and larger
depending on length of runs, rise and
bends.
CAUTION
Each heat exchanger is equipped
with a refrigerant pressure relief
device to relieve pressure should
excessive condensing pressures
(>675 psig) occur. Codes may
require installing contractor to
connect and route relief piping
outdoors. The relief valve has a 5/8”
male flare outlet connection.
CAUTION
PVC (Polyvinyl Chloride) and CPVC
(Chlorinated Polyvinyl Chloride) are
vulnerable to attack by certain
chemicals. Polyolester (POE) oils
used with R-410A and other
refrigerants, even in trace amounts,
in a PVC or CPVC piping system will
result in stress cracking of the piping
and fittings and complete piping
system failure.
CAUTION