c l i m a t e m a s t e r.c o m
35
TSM/TSL Vertical Stack
R e v. : J a n u a r y 1 8 , 2 0 2 1
T H E S M A R T S O L U T I O N F O R E N E R G Y E F F I C I E N C Y
Ground-Water Heat Pump Applications
Open Loop -
Ground Water Systems - Shut off valves
should be included for ease of servicing. Boiler drains or
other valves should be “tee’d” into the lines to allow acid
flushing of the heat exchanger. Shut off valves should be
positioned to allow flow through the coax via the boiler
drains without allowing flow into the piping system. P/T
plugs should be used so that pressure drop 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 3 for water quality guidelines. The unit can
be ordered with either a copper or cupro-nickel water
heat exchanger. Consult Table 3 for recommendations.
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, an open loop system
is not recommended. Heat exchanger coils may over time
lose heat exchange capabilities due to build up of mineral
deposits. Heat exchangers must only be serviced by a
qualified technician, as acid and special pumping equipment
is required. Desuperheater coils can likewise become scaled
and possibly plugged. In areas with extremely hard water,
the owner should be informed that the heat exchanger
may require occasional acid flushing. In some cases, the
desuperheater option should not be recommended due to
hard water conditions and additional maintenance required.
Water Quality Standards -
Table 3 should be consulted
for water quality requirements. Scaling potential should
be assessed using the pH/Calcium hardness method. If
the pH <7.5 and the calcium hardness is less than 100
ppm, scaling potential is low. If this method yields numbers
out of range of those listed, the Ryznar Stability and
Langelier Saturation indecies should be calculated. Use the
appropriate scaling surface temperature for the application,
150°F [66°C] for direct use (well water/open loop) and
DHW (desuperheater); 90°F [32°F] for indirect use. A
monitoring plan should be implemented in these probable
scaling situations. Other water quality issues such as iron
fouling, corrosion prevention and erosion and clogging
should be referenced in Table 3.
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 provide
at least one minute continuous run time of the pump
using its drawdown capacity rating to prevent pump short
cycling. Discharge water from the unit is not contaminated
in any manner and can be disposed of in various ways,
depending on local building codes (e.g. 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. Units equipped with any of the two
vFlow configurations have built in Schrader ports. Water
temperature may be viewed on the iGate communicating
thermostat or service tool.
Water Control Valve -
Always maintain water pressure in
the heat exchanger by placing the water control valve(s)
on the return line to prevent mineral precipitation during
the off-cycle. Pilot operated slow closing 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. Ensure
that the total ‘VA’ draw of the valve can be supplied by
the unit transformer. For instance, a slow closing valve can
draw up to 35VA. This can overload smaller 40 or 50 VA
transformers depending on the other controls in the circuit.
A typical pilot operated solenoid valve draws approximately
15VA.
Flow Regulation -
Flow regulation can be accomplished
by two methods. One method of flow regulation involves
simply adjusting the ball valve or water control valve on the
return line. Measure the pressure drop through the unit heat
exchanger, and determine flow rate from. Since the pressure
is constantly varying, two pressure gauges may be needed.
Adjust the valve until the desired flow of 1.5 to 2 gpm per
ton [2.0 to 2.6 l/m per kW] is achieved. A second method
of flow control requires a flow control device mounted on
the outlet of the water control valve. The device is typically
a brass fitting with an orifice of rubber or plastic material
that is designed to allow a specified flow rate. On occasion,
flow control devices may produce velocity noise that can be
reduced by applying some back pressure from the ball valve
located on the discharge line. Slightly closing the valve will
spread the pressure drop over both devices, lessening the
velocity noise.
Note: When EWT is below 50°F [10°C], 2
gpm per ton (2.6 l/m per kW) is required.
