Commercial water loop
Commercial systems typically
include a number of units
connected to a common piping
system. Any unit plumbing
maintenance work can
introduce air into the piping
system; therefore air elimination
equipment is a major component
of the mechanical room
plumbing. Consideration should
be given to insulating the piping
surfaces to avoid condensation.
Zehnder Rittling recommends
unit insulation any time the water
temperature is expected to be
below 60 ºF (15.6 ºC). Metal-to-
plastic threaded joints should
never be used due to their
tendency to leak over time.
Piping installation
Teflon
®
tape thread sealant
is recommended to minimize
internal fouling of the heat
exchanger. Do not over tighten
connections and route piping so
as not to interfere with service
or maintenance access. Hose
kits are available from Zehnder
Rittling in different configurations
as shown in Figure 10 for
connection between the unit
and the piping system. Depending
upon selection, hose kits may
include shut-off valves, P/T plugs
for performance measurement, high
pressure stainless steel braided
hose, “Y” type strainer with blow
down valve, balancing valve, and/or
“J” type swivel connection. Balancing
valves and an external low pressure
drop solenoid valve for use in
variable speed pumping systems may
also be included in the hose kit.
The piping system should be
flushed to remove dirt, piping chips,
and other foreign material prior
to operation (see “Piping System
Cleaning and Flushing Procedures”
in this manual). The flow rate is
usually set between 2.25 and 3.5
gpm per ton (2.9 and 4.5 l/m per kW)
of cooling capacity. Zehnder Rittling
recommends 3.3 gpm per ton (4.3
l/m per kW) for most applications of
water loop heat pumps. To ensure
proper maintenance and servicing,
P/T ports are imperative for
temperature and flow verification, as
well as performance checks.
Loop conditions
Water loop heat pump (cooling
tower/boiler) systems typically
utilize a common loop, maintained
Note
n
n
Refer to page 11 for horizontal duct
system details.
n
n
Note: Low water temperature operation
requires extended range equipment.
Figure 10: Typical water loop application
Applications
Return air
Supply air
Flex hose
Out
In
Building loop
Ball valve with PT port
Control valve
Flow regulator
Water loop applications
between 60-90 °F (16-32 °C).
The use of a closed circuit
evaporative cooling tower with
a secondary heat exchanger
between the tower and the
water loop is recommended. If an
open type cooling tower is used
continuously, chemical treatment
and filtering will be necessary. For
low entering water temperature
applications, Zehnder Rittling
recommends following the water
limit guidelines:
Table 2:
Water limit guidelines
EWT
min.
(°F)
Min. flow
rate
(GPM/ton)
Antifreeze
required?
50
1.5
No
40-50
3
No
40-50
1.5
Yes
20-40
3
Yes
Low water temperature
cutout setting
Zehnder Rittling’s heat pump
controller includes a user
configurable switch (DIP switch 2
on the PCB controller) to change
the low water temperature cutout
(FP1) setting between water
(30 °F) and Glycol (10 °F). When
loop conditions allow (antifreeze is
used), the FP1 DIP switch should
be set to the Glycol (10 °F) setting
to avoid nuisance faults.
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