Manual 2100-738C
Page
54 of 73
Circulation System Design
Equipment room piping design is based on years of
experience with earth coupled heat pump systems. The
design eliminates most causes of system failure.
Surprisingly, the heat pump itself is rarely the cause.
Most problems occur because designers and installers
forget that a closed loop earth coupled heat pump
system is
not
like a household plumbing system.
Most household water systems have more than enough
water pressure either from the well pump or the
municipal water system to overcome the pressure of
head loss in 1/2" or 3/4" household plumbing. A closed
loop earth coupled heat pump system, however, is
separated from the pressure of the household supply
and relies on a small, low wattage pump to circulate
the water and antifreeze solution through the earth
coupling, heat pump and equipment room components.
The small circulator keeps the operating costs of the
system to a minimum. However, the performance of the
circulator
must
be closely matched with the pressure
of head loss of the entire system in order to provide the
required flow through the heat pump. Insufficient flow
through the heat exchanger is one of the most common
causes of system failure. Proper system piping design
and circulator selection will eliminate this problem.
Bard supplies a work sheet to simplify head loss
calculations and circulator selection. Refer to
“Circulating Pump Work sheet” section in manual
2100-099.
Copper Water Coil Application
Copper water coils are available as a factory-installed
option. The unit model number will indicate the coil
option as the next to last character; “C” represents
a water coil constructed of copper material and “N”
represents a water coil constructed of cupronickel.
The cupronickel coil is suitable for all applications.
The
copper coil is suitable for applications using ground
loop and cooling tower only and is not recommended
for open well application.
Start Up Procedure for Closed Loop
System
1. Be sure main power to the unit is OFF at
disconnect.
2. Set thermostat system switch to OFF and fan
switch to AUTO.
3. Move main power disconnect to ON. Except as
required for safety while servicing,
do not open the
unit disconnect switch.
4. Check system air flow for obstructions.
A. Move thermostat fan switch to ON. Blower
runs.
B. Be sure all registers and grilles are open.
C. Move thermostat fan switch to AUTO. Blowing
should stop.
5. Flush, fill and pressurize the closed loop system as
outlined in manual 2100-099.
6. Fully open the manual inlet and outlet valves. Start
the loop pump module circulator(s) and check for
proper operation. If circulator(s) are not operating,
turn off power and diagnose the problem.
7. Check fluid flow using a direct reading flow meter
or a single water pressure gauge; measure the
pressure drop at the pressure/temperature plugs
across the water coil. Compare the measurement
with flow versus pressure drop table to determine
the actual flow rate. If the flow rate is too low,
recheck the selection of the loop pump module
model for sufficient capacity. If the module
selection is correct, there is probably trapped air or
a restriction in the piping circuit.
8. Start the unit in cooling mode by moving the
thermostat switch to cool. Fan should be set for
AUTO.
9. Check the system refrigerant pressures against the
cooling refrigerant pressure table in the installation
manual for rated water flow and entering water
temperatures. If the refrigerant pressures do not
match, check for airflow problem then refrigeration
system problem.
10. Switch the unit to the heating mode by moving the
thermostat switch to heat. Fan should be set for
AUTO.
11. Check the refrigerant system pressures against the
heating refrigerant pressure table in installation
manual. Once again, if they do not match, check
for airflow problems and then refrigeration system
problems.
CLOSED LOOP
(Earth Coupled Ground Loop Applications)
