Piping Considerations - Daikin ARQ Installation And Maintenance Manual

Piping Considerations

1. All units should be connected to supply and return piping
in a two-pipe reverse return configuration. A reverse return
system is inherently self-balancing and requires only trim
balancing where multiple quantities of units with different
flow and pressure drop characteristics exist in the same
loop. Check for proper water balance by measuring
differential temperature reading across the water
connections. To insure proper water flow, the differential
flow should be 10°F to 14°F (5°C to 8°C) for units in
cooling mode.
A direct return system may also work acceptably, but
proper water flow balancing is more difficult to achieve and
maintain.
2. The condenser water or loop piping can be steel or
copper.
3. Supply and return runouts usually join the unit via short
lengths of high pressure flexible hose which are sound
attenuators for both unit operating noise and hydraulic
pumping noise. One end of the hose should have a swivel
fitting to facilitate removal for service. Hard piping can
also be brought directly to the unit. This option is not
recommended since no vibration or noise attenuation can
be accomplished. The hard piping must have unions to
facilitate unit removal.
4. Some flexible hose threaded fittings are supplied with
sealant compound. If not, apply Teflon tape to assure a
tight seal.
Note: Do not over-torque fittings. The maximum torque
without damage to fittings is 30 foot pounds. If a torque
wrench is not available, use as a rule of thumb, finger-
tight plus one quarter turn.
5. Supply and return shutoff valves are required at each
conditioner. The return valve is used for balancing and
should have a "memory stop" so that it can always be
closed off but can only be reopened to the proper position
for the flow required.
6. No unit should be connected to the supply and return
piping until the water system has been cleaned and
flushed completely. After the cleaning and flushing has
taken place, the initial connection should have all valves
wide open in preparation for water system flushing.
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7. Condensate drain piping can be steel, copper or PVC or
CPVC.
8. The condensate drain hose must be trapped. The hose
must be pitched away from the unit not less than 1⁄4"
per foot. The unit drain pan has a 7/8 inch O.D. drain
connection to accommodate the condensate drain hose.
Figure 33: Condensate disposal trapping detail
Drain Pan (Left End)
A
B
Table 9: Condensate drain trap & static pressure
Standard Static Pressure
High Static
9. Do not locate any point in the drain system above the
drain connection of any unit.
10. Automatic flow controlled devices must not be installed
prior to system cleaning and flushing.
11. A high point of the piping system must be vented.
12. Check local code for the need for dielectric fittings.
19
C
7/8" I.D. Clear Plastic
A B
1¼" 5/8" 2¾"
1½" 3/4" 3⅛"
IM 1083-3
C