Typical open loop piping is shown in Figure 3. Shut off valves
should be included in case of servicing. Boiler drains or other
valves should be ‘tee’d’ into the line to allow acid flushing of
just the heat exchanger. Pressure temperature plugs should
be used so that flow and temperature can be measured.
Supply and return water piping should be limited to copper,
HPDE, or other acceptable high temperature material. Note
that PVC or CPVC material is not recommended as they
are not compatible with the polyolester oil used in HFC-
410A products. Water quantity should be plentiful and of
good quality. Consult Table 2 for water quality guidelines.
The unit can be ordered with either a copper or cupro-nickel
water heat exchanger. Copper is recommended for closed
loop systems and open loop ground water systems that are
not high in mineral content or corrosiveness. In conditions
anticipating heavy scale formation or in brackish water, a
cupro-nickel heat exchanger is recommended. In ground
water situations where scaling could be heavy or where
biological growth such as iron bacteria will be present, a
closed loop system is recommended. Heat exchanger coils
may over time lose heat exchange capabilities due to a build
up of mineral deposits inside. These can be cleaned only by
a qualified service mechanic as acid and special pumping
equipment are required.
Expansion Tank and Pump
Use a closed, bladder-type expansion tank to minimize
mineral formation due to air exposure. 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. The pump should be sized to
the home’s domestic water load (5-9 gpm [19-34 l/m]) plus
the heat pump water load. 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.
Water Control Valve
Note the placement of the water control valve. 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. Note the special wiring diagram of the
AVM valve (Figure 8).
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. Simply adjust the water control valve until the
desired flow is achieved. Secondly, a flow control device may
be installed. 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.
Low Temperature Cutout
The water low temperature cutout setpoint should be
activated to avoid freeze damage to the unit. Consult the
low temperature cutout section of the controls description for
instructions.
CAUTION!
CAUTION! Many units are installed with a factory or field
supplied manual or electric shut-offvalve. DAMAGE
WILL OCCUR if shut-offvalve is closed during unit
operation. A high pressure switch must be installed on the
heat pump side of any field provided shut-offvalves 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 235 psig [1620 kPa] and a cut-in
pressure of 190 psig [1310 kPa]. This pressure switch can
be ordered with a 1/4” internal flare connection as part
number 39B0005N01.
CAUTION!
CAUTION! Refrigerant pressure activated water regulating
valves should never be used with this equipment.
Ground-Water Heat Pump Systems
9
Tranquility®High Temperature Water-to-Water (THW) Series
Rev.: 28 Aug., 2014
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