Flow Controller 3
R e v. : F e b u r a r y 9 , 2 0 1 6
16
G e o t h e r m a l H e a t P u m p S y s t e m s
Antifreeze Charging
Figure 11: Low Temperature Cutout Selection
LT1
LT2
LT1
LT1
LT2
LT2
CXM PCB
JW3-FP1 jumper
should be clipped
for low temperature
operation
Pressure/Temperature Ports
The pressure/temperature ports (P/T ports) supplied with
the earth loop connector kit are provided as a means of
measuring flow and temperature. The water flow through
the unit can be checked by measuring the incoming water
pressure at the supply water P/T port and subtracting
the leaving water pressure at the return water P/T port.
Comparing the pressure differential to the pressure drop
table/flow rate in the unit installation manual will determine
the flow rate through the unit. Ground loop required flow
rates are 2.25 to 3 U.S. gpm per nominal cooling ton [2.41 to
3.23 l/m per kW]. Note: Minimum flow for units is 2.25 gpm
per ton [2.41 l/m per kW].
Example: Model 036 has a 50°F entering water temperature
(EWT) and 50 psi entering water pressure (EWP). The leaving
water pressure (LWP) is 46 psi. Pressure Drop (PD) = EWP
- LWP = 50 - 46 = 4 psi. In the unit Installation manual, a 3.9
PSI pressure drop is equivalent to 9 GPM at 50°F EWT on
the chart. More flow will not hurt the performance. However,
insufficient flow can significantly reduce capacity and
possibly even cause damage to the heat pump in extreme
conditions. Digital thermometers and pressure gauges
are needed for the P/T ports, which are available in the
residential price list.
NOTICE
: Pressure/temperature gauges should be pushed
gently into P/T ports to prevent internal damage to the
port. Use same gauge and thermometer to determine the
differential in pressure and temperature
Earth Loop Pressure
The earth loop must have a slight positive pressure to
operate the pumps [>3 psi, >20.7 kPa]. The system pressure
will drop as the earth loop pipe relaxes, and will fluctuate as
the fluid temperature changes. Typical earth loop pressures
range from approximately 15-50 psi [103-345 kPa]. At the
start-up of a system, the earth loops should have a (static)
holding pressure of approximately 50-75 psi [345-517 kPa].
Maximum operating pressure should never exceed 100 psi
[689 kPa] under any circumstance.
NOTICE
: It is recommended to run the unit in the cooling,
then heating mode for 15-20 minutes each to ‘temper’ the
fluid temperature and prepare it for pressurization. This
procedure helps prevent the periodic “flat” loop condition of
no pressure.
After pressurization, be sure the loop Flow Controller
provides adequate flow through the unit by checking
pressure drop across the heat exchanger and comparing it
to the pressure drop/flow rate tables in the unit Installation
manual. Flow Controller pump performance is shown in
Chart 2.
Start-Up of Flow Controller
1) Check to make sure that the loop and unit isolation
valves (if applicable) are completely open and the flush
ports are closed and sealed.
2) Check and record the earth loop pressure via the P/T
ports. Loop Pressure = In_______ Out_______.
3) Check and record the flow rate.
Flow Rate = _______gpm.
4) Check performance of unit. Refer to unit installation
manual. Replace all caps to prevent pressure loss.
When replacing a pump, isolate the pump from loop as in
Figure 12. Always disable power to the pumps and remove
pump power wiring if needed. The five steps below outline
the detailed procedure.
