15
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. 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 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 1:
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.
Water loop
applications
Applications
