Appendix I: Water Source Heat Pump Water Line Piping
Requirements and Field Mounted Options and Accessories
Functional Descriptions
Head Pressure Control
A three-way modulating head pressure control valve is re-
quired to maintain stable operation of the refrigeration sys-
tems when operated on ground loop water systems when
the design water temperature is below 65°F in the cooling
mode. A refrigerant pressure sensor on the compres-
sor discharge is used to modulate the water flow to the
condenser using a 2 to 10 VDC signal to artificially keep
the compressor discharge pressure at a high enough op-
erating condition to prevent the low pressure refrigerant
switch from tripping.
The three-way modulating head pressure control valve
consists of a 24 VAC NEMA 1 or 2 modulating actua-
tor with a temperature rating of −22°F to 122°F [−30°C
to 50°C], nickel plated forged brass valve with stainless
steel ball, stem and replaceable valve cartridge assembly
which is an option and must be externally field mounted.
For outdoor applications a NEMA 4x rated actuator must
be installed. The hydronic valves are intended for use in a
normal indoor/outdoor environment for hot or cold water
or glycol solutions to 60% concentration with a medium
temperature rating of 0°F to 212°F [−18°C to 100°C].
The valve and actuator are pre-assembled for 100% flow
to the coil with minimum of 2 VDC signal. The refrigerant
pressure sensor is internally factory mounted, pre-wired
and programmed for the DDC to control the three-way
valve. A 6 foot coiled wiring harness is factory supplied
with the unit, located in the compressor compartment for
field extension and wiring to the actuator.
See Table I2 for three-way valve sizing and performance
data. Dimensions, technical and installation data follow.
See the wiring schematic for connection and the VHC-36,
-42 and -50 DDC Controls Package Manual for sequenc-
ing information.
Water Shut-off
A two-way motorized on/off water shut-off valve is re-
quired to isolate water flowing through both the econo-
mizer coil (if equipped) and water-to-refrigerant condenser
for conservation when the unit is off. The water shut-off
valve must be placed upstream of the economizer coil
and three-way economizer control valve and the three-
way modulating head pressure control valve (if equipped).
The motorized water valve must open 90 seconds prior to
compressor start-up and remain open five seconds after
the compressor is shut off.
IMPORTANT
• Water source heat pump external water supply and return piping shall be in accordance with national and local codes.
Line sizing, pressure limiting devices, backflow preventers, strainers, valves, flow temperature and pressure measuring,
freeze protection and all other safety or control piping requirements for system operation are the sole responsibility of the
Installing Contractor and/or Design Engineer.
• Some external piping components and control interlocks are offered as an option or accessory for partly field and fac-
tory installation and are summarized in Table I1. A detailed functional description follows.
• On open loop systems, a field supplied and installed water strainer (16–20 mesh minimum, 20–40 mesh best) is rec-
ommended in the water inlet or supply line to the unit to eliminate contaminants and must be used for 14, 16 and 21
ton dual circuit WSHP units which utilize a brazed plate heat exchanger condenser. Warranty will be voided without the
presence of the proper strainer.
• Air vents must be field installed on the high side of the water supply or inlet line to discharge the non-condensable air in
order to avoid unexpected high head pressure and poor cooling/heating performance.
• Manual shut-off valves in supply and return water lines are recommended to be field installed for isolation and service.
• A circuit balancing valve with pressure and temperature gauge connections is recommended to be field supplied and
installed for balancing and service. The water supply must be sized for the minimum flow as indicated on the submittals.
• Prior to connection of condensing water supply, verify water pressure is less than the maximum pressure for com-
ponents in the water line. To prevent injury or death due to instantaneous release of high pressure water, relief valves
should be field supplied and installed in system water piping.
• Maximum working pressure, pressure drop or C
v
factors for condenser and optional or accessory components are
given in tables below.
Table I1: WSHP Water Line Option or Accessory
Function
Field Installed
Factory Installed
Head
pressure
control
Three-way water control
valve with modulating
actuator
Head pressure control
DDC program logic
Refrigerant pressure
transducer
Water
shut-off
Two-way water shut-off
valve with on/off actuator
Water on/off control
DDC program logic
Freeze
protection
Water flow switch
Unit on/off control DDC
program logic
Water outlet temperature
sensor
VCES-VHC-IOM-1F – VHC-36, -42 & -50
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