Comfort-Aire HWW120 - Manual (Page 12)

11
Installation & Operation WATER-TO-WATER (HWW) SERIES Heat Controller, Inc.
Ground-Water Heat Pump Applications
In areas with extremely hard water, the owner should be
informed that the heat exchanger may require occasional acid
flushing.
Expansion Tank and Pump
Use a closed, bladder-type expansion tank to minimize mineral
formation due to air exposure, as shown in Figure 3. The
expansion tank should be sized to handle at least one minute
run time of the pump to prevent premature pump failure using
its drawdown capacity rating. Discharge water from the unit
is not contaminated in any manner and can be disposed of in
various ways depending on local building codes; i.e. recharge
well, storm sewer, drain field, adjacent stream or pond, etc.
Most local codes forbid the use of sanitary sewer for disposal.
Consult your local building and zoning department to assure
compliance in your area.
Low Water Temperature Cut-Out Setting
For all open loop systems the 35°F [1.7°C] FP1 setting (factory
setting-water) should be used to avoid freeze damage to the unit.
See Figure 4 [Page 14]: “Low Water Temperature Cutout - FP1”.
Water Control Valve
Note the placement of the water control valve in Figure 3.
Always maintain water pressure in the heat exchanger by
placing water control valves at the outlet of the unit to prevent
mineral precipitation. Pilot operated or Taco slow closing
valve’s solenoid valves are recommended to reduce water
hammer. If water hammer persists, a mini-expansion tank can
be mounted on the piping to help absorb the excess hammer
shock. Insure that the total ‘VA’ draw of the valve can be
supplied by the unit transformer. For instance the Taco slow
closing valve can draw up to 35VA. This can overload smaller
40 or 50 VA transformers depending on the other controls
employed. A typical pilot operated solenoid valve draws
approximately 15VA.
Flow Regulation
Flow regulation can be accomplished by two methods. First,
most water control valves have a built in flow adjustment. By
measuring the pressure drop through the unit heat exchanger,
flow rate can be determined and compared to Table 8 [Page
28]. Since the pressure is constantly varying, two pressure
gauges might be needed. Simply adjust the water control
valve until the desired flow of 1.5 to 2 gpm per ton is achieved.
Secondly, a flow control device may be installed [see Figure
3]. The devices are typically an orifice of plastic material that is
designed to allow a specified flow rate. These are mounted on
the outlet of the water control valve. On occasion, these valves
can produce a velocity noise that can be reduced by applying
some back pressure. This is accomplished by slightly closing
the leaving isolation valve of the well water setup.
� WARNING! �
� CAUTION! �
Never jumper terminal “A” from CXM board #1 to CXM
board #2 on multi-compressor/control bound units. See
Figure 5 [Page 15] in electrical section of this document
for motorized valve wiring.
CAUTION! Many units are installed with a factory or field
supplied manual or electric shut-off valve. DAMAGE WILL
OCCUR if shut-off valve is closed during unit operation.
A high pressure switch must be installed on the heat
pump side of any field provided shut-off valves and
connected to the heat pump controls in series with the
built-in refrigerant circuit high pressure switch to disable
compressor operation if water pressure exceeds pressure
switch setting. The field installed high pressure switch
shall have a cut-out pressure of 300 psig and a cut-in
pressure of 250 psig.
� CAUTION! �
Low temperature limit system will not allow leaving load
water temperature (cooling mode) or leaving source water
temperature (heating mode) to be below 42°F [5.6°C].
Air Pad or
Extruded
polystyrene
insulation board
Unit Power
Disconnect
Pressure
Tank
Flow
Regulator
Water
Control
Valve
P/T Plugs
Water Out
Shut-Off
Valve
Boiler
Drains
Water In
Optional
Filter
Thermostat Wiring
Figure 3: Typical Open
Loop/Well Application