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ALTHOUGH THE GT-S IS COMPATIBLE WITH
OPEN LOOP APPLICATIONS, IT HAS BEEN
DESIGNED FOR OUTDOOR EARTH LOOP
APPLICATIONS. THE GT-G INDOOR SPLIT
WOULD BE A BETTER CHOICE FOR THIS INDOOR
APPLICATION.
Open loop applications should always be located in a
conditioned space that will prevent freezing pipes.
Typical open loop piping is shown in Figure 6. Shut off
valves should be included in case of servicing. Boiler
drains or other valves should be ‘tee’d’ in 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. The water freezestat
should be wired. Piping materials should be limited to
PVC SCH80 or copper.
Due to the pressure and
temperature extremes, PVC SCH40 is not
recommended.
Water Quantity should be plentiful and of good quality.
Consult CM 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.
Desuperheater
coils can likewise become scaled and possibly plugged.
In areas with extremely hard water, the homeowner
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. 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) 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 17.
Flow Regulation
Flow regulation can be accomplished by two methods.
Most water control valves have a flow adjustment built
in. By measuring the pressure drop through the unit heat
exchanger flow rate can be determined and compared to
Table 13. 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. The devices are typically an orifice of plastic
material that are 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.
Freeze Protection
The high temperature freeze protection setpoint (water)
should be activated to avoid freeze damage to the unit.
Consult the freeze protection section of the controls
description for instructions.
OPEN LOOP - GROUND WATER SYSTEMS
Figure 6. Typical Well Installation Detail
Pressure Ports
Pilot Operated or
Slow Closing Valve
Flow Regulator
Isolation Valves
Flush Ports
Paradigm Unit
1-1/4” FPT
From Domestic
Supply
To Disposal
