49
Unit is capable of operating with Entering
Water Temperatures (EWT) as low as 50°F
during heat pump heating mode 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.
Table 3 - Glycol Freezing Points
% Glycol
Ethylene
Glycol
Propylene
Glycol
20
18°F
19°F
30
7°F
9°F
40
-7°F
-6°F
50
-28°F
-27°F
Water loop piping runs through unheated
areas or outside the building should be
insulated.
Water Piping
All
water-source
heat pump
units are built
with a water flow switch. Some
water-
cooled
units may not have a water flow
switch. This sensor provides a signal to the
unit controller that water flow is present in
the heat exchanger and the compressors can
operate without damaging unit components.
Installing
contractor
must
ensure
a
differential pressure switch is installed
between the condenser water supply and
return connections if the unit does not have a
water flow switch installed at the factory.
The water connections will differ depending
on whether the unit is water-cooled only or
if it is water-source heat pump. The water-
source heat pump units have water supply to
the top of the heat exchanger and the return
to the bottom.
Figure 21 - Water-Source Heat Pump Water
Piping
WATER FREEZING
Failure of the condenser due to
freezing will allow water to enter the
refrigerant circuit and will cause
extensive damage to the refrigerant
circuit components. Any damage to
the equipment as a result of water
freezing in the condenser is excluded
from
coverage
under
AAON
warranties and the heat exchanger
manufacturer warranties.
WARNING
Summary of Contents for M2 Series
Page 2: ......
Page 5: ...5 Split System Piping Diagrams 98 M2 Series Startup Form 115 Maintenance Log 121 ...
Page 35: ...35 Table 1 Electric and Gas Heating Capacities ...
Page 38: ...38 Figure 5 M2 Series Unit Four Point Lifting ...
Page 39: ...39 Figure 6 M2 Series Unit Eight Point Lifting ...
Page 58: ...58 Figure 32 Supply Fan Banding ...
Page 95: ...95 Figure 52 Filter Layout Viewed from the Upstream Side of the Cooling Coil ...
Page 98: ...98 Split System Piping Diagrams Figure 53 A C Split System Piping Suction Down ...
Page 99: ...99 Figure 54 A C Split System Piping Suction Up ...
Page 100: ...100 Figure 55 A C with LAC Split System Piping Suction Up ...
Page 101: ...101 Figure 56 A C with Modulating Hot Gas Reheat Split System Piping Suction Down ...
Page 102: ...102 Figure 57 A C with Modulating Hot Gas Reheat Split System Piping Suction Up ...
Page 103: ...103 Figure 58 A C with Hot Gas Bypass Split System Piping Suction Down ...
Page 104: ...104 Figure 59 A C with Hot Gas Bypass Split System Piping Suction Up ...
Page 107: ...107 Figure 62 Heat Pump Split System Piping Suction Down ...
Page 108: ...108 Figure 63 Heat Pump Split System Piping Suction Up ...
Page 109: ...109 Figure 64 Heat Pump with Modulating Hot Gas Reheat Split System Piping Suction Down ...
Page 110: ...110 Figure 65 Heat Pump with Modulating Hot Gas Reheat Split System Piping Suction Up ...
Page 111: ...111 Figure 66 Heat Pump with Hot Gas Bypass Split System Piping Suction Down ...
Page 112: ...112 Figure 67 Heat Pump with Hot Gas Bypass Split System Piping Suction Up ...