36
Enertech Global
IOM, ZS/ZT Models
Open Loop Piping
Placement of the components for an open
loop system are important when considering
water quality and long term maintenance. The
water solenoid valve should always be placed
on the outlet of the heat pump, which will keep
the heat exchanger under pressure when the
unit is not operating. If the heat exchanger is
under pressure, minerals will stay in suspension.
Water solenoid valves are also designed to
close against the pressure, not with the pressure.
Otherwise, they tend to be noisy when closing.
A flow regulator should be placed after the
water solenoid valve. Always check the product
specification catalog for proper flow rate. A
calculation must be made to determine the
flow rate, so that the leaving water temperature
does not have the possibility of freezing.
Other necessary components include a strainer,
boiler drains for heat exchanger flushing, P/T
ports and ball valves. Ball valves allow the
water to be shut off for service, and also help
when velocity noise is noticeable through the
flow regulator. Spreading some of the pressure
drop across the ball valves will lessen the
velocity noise. Always double check flow rate
at the P/T ports to make sure the ball valve
adjustments have not lowered water flow too
much, and essentially taken the flow regulator
out of the equation. It’s a good idea to remove
the ball valve handles once the system is
completed to avoid nuisance service calls.
Hose kits are optional, but make for an easier
installation, since the P/T ports and connections
are included. The hose also helps to isolate the
heat pump from the piping system.
Two-stage units typically include two water
solenoid valves, since the heat pump can
operate at lower water flow on first stage,
saving water. The flow regulators should be
sized so that when one valve is open the unit
operates at part load flow rate, and when
both valves are open, the unit operates at
full load flow rate. For example, a 4 ton unit
needs approximately 4 GPM on part load, and
approximately 7 GPM at full load. The flow
regulator after the first valve should be 4 GPM,
and the flow regulator after the second valve
should be 3 GPM. When both valves are open,
the unit will operate at 7 GPM.
SECTION 5: UNIT PIPING INSTALLATION
Figure 3: Open Loop Piping Example
IN
OUT
S
HEAT
PUMP
Single
Speed
Units
S
S
Two-
Stage
Units
Boiler Drain
for Heat
Exchanger
Maintenance
(2 required)
P/T Port
(2 required)
WYE Strainer
Ball Valve
(2 required)
Flow Regulator**
Water
Solenoid
Valve
Optional
Hose Kit*
*Hose kit used for unit isolation, includes fittings for P/T ports.
**See product specifications for flow rates.
From Well
Discharge Line
TYPICAL OPEN LOOP PLUMBING
AND VALVE INSTALLATION EXAMPLE
Note:
• When sizing the first stage
flow regulator, be sure to
allow enough flow to close
the flow switch. If takes a
minimum of 3.5 GPM to
close the flow switch.
• Smaller tonnage two-stage
units may only utilize one
solenoid valve and flow
regulator.