Ground-Water Heat Pump Applications - Johnson Controls JMW Series Installation Operation & Maintenance

WAT E R - S O U R C E H E AT P U M P S
JMW-Series
R e v . : F e b r u a r y 2 8 , 2 0 2 3

Ground-Water Heat Pump Applications

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 materials should be limited to copper, PE, or similar
material. PVC or CPVC should never be used as they
are incompatible with the POE oils used in HFC-410A
products and piping system failure and property damage
may result.
Water quantity should be plentiful and of good quality.
Consult Table 1 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. It is
recommended to install an intermediate heat exchanger
to isolate an open loop from the heat pump loop on
open well systems. Heat exchangers 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.
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. 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.
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WARNING! Polyolester Oil, commonly known as POE oil, is
a synthetic oil used in many refrigeration systems including
those with HFC-410A refrigerant. POE oil, if it ever comes
in contact with PVC or CPVC piping, may cause failure of
the PVC/CPVC. PVC/CPVC piping should never be used
as supply or return water piping with water source heat
pump products containing HFC-410A as system failures and
property damage may result.
WARNING! Never jumper terminal "A" from CXM2 or
DXM2.5 board #1 to CXM2 or DXM2.5 board #2 on multi-
compressor/control bound units. See Figure 5 in electrical
section of this document for motorized valve wiring.
Low Water Temperature Cut-Out Setting - For all open
loop systems the 35°F [1.7°C] LT1 setting (factory setting-
water) should be used to avoid freeze damage to the unit.
See Figure 4: "Low Water Temperature Cutout - LT1".
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.
I n s t a l l a t i o n , O p e r a t i o n , M a i n t e n a n c e
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WARNING!
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