Supply & Return Piping; Cleaning And Flushing Water System - Daikin VHF Installation And Maintenance Manual

Supply & Return Piping
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 pres-
sure drop characteristics exist in the same loop.
• To insure proper water flow, measure the temperature
differential between the supply and return connections.
The temperature differential 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.
• The piping can be steel or copper.
Note: Polyolester Oil, commonly know as POE oil is a
synthetic oil used in many refrigeration systems.
POE oil, if ever in contact with PVC/CPVC will
coat the inside wall of PVC/CPVC pipe causing
environmental stress fractures.
It is recommended that PVC/CPVC piping is not
used in the installation of the loop system, as sys-
tem failure and property damage could result.
The supply and return stub outs and the factory-provided
shutoff valves have male JIC connections and 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.
• Some flexible hose threaded fittings are supplied with sealant
compound. If not, apply Teflon tape to assure a tight seal.

Cleaning and Flushing Water System

CAUTION
Prior to first operation of any unit, the water circulating
system must be cleaned and flushed of all construction dirt
and debris or damage will occur.
1 . Prior to first operation of any unit, the water circulating
system must be cleaned and flushed of all construction dirt
and debris.
2 . If the units are equipped with water shutoff valves, either
electric or pressure operated, the supply and return
runouts must be connected together at each unit location.
This will prevent the introduction of dirt into the unit,
23).
Figure 23: Connections for flushing system piping
IM 986-11 • Vertical Stack WSHP
2 . Fill the system at the city water makeup connection with all
air vents open. After filling, close all air vents.
The contractor should start main circulator with the
pressure reducing valve open. Check vents in sequence
to bleed off any trapped air, ensuring circulation through all
components of the system.
Power to the heat rejector unit should be off, and the
supplementary heat control set at 80°F (27°C).
While circulating water, the contractor should check and
repair any leaks in the unit and surrounding piping. Drains
at the lowest point(s) in the system should be opened
for initial flush and blow-down, making sure city water fill
valves are set to make up water at the same rate. Check
the pressure gauge at pump suction and manually adjust
the makeup to hold the same positive steady pressure both
before and after opening the drain valves. Flush should
continue for at least two hours or longer until the drain
water is clean and clear.
3 . Shut off supplemental heater and circulator pump and open
all drains and vents to completely drain down the system.
Short circuited supply and return runouts should now be
connected to the unit supply and return connections. Do
not use sealers at the swivel flare connections of hoses.
4 . Flush system with water for 2 hours or longer until water is
clean.
5 . Refill the system with clean water. Test the water using
litmus paper for acidity, and treat as required to leave
the water slightly alkaline (pH 7.5 to 8.5). The specified
percentage of antifreeze may also be added at this time.
Use commercial grade antifreeze designed for HVAC
systems only. Do not use automotive grade antifreeze (See
"Antifreeze Correction Factors" on page 23).
Once the system has been filled with clean water and
antifreeze (if used), precautions should be taken to protect
the system from dirty water conditions.
It is not Daikin Applied policy to make recommendations on
water treatment. However, the general contractor or owner
should contact a local water treatment company regarding
water treatment. A fouled closed loop water system will
lead to premature component failure.
Note: Contact a local water treatment company to confirm
(Figure
water clarity prior to unit operation.
Dirty water will result in system wide degradation
of performance and solids may clog system-wide
valves, strainers, flow regulators, etc. Additionally, the
heat exchanger may become clogged which reduces
compressor service life or causes premature failure.
6 . Set the loop water controller heat add setpoint to 70°F
(21°C) and the heat rejection setpoint to 85°F (29°C).
Supply power to all motors and start the circulating pumps.
After full flow has been established through all components
including the heat rejector (regardless of season) and the
vented air and loop temperatures have been stabilized,
each of the units will be ready for check, test and start-up,
air balancing, and water balancing.
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ysteM PPliCations
NOTICE
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