Piping system
cleaning and flushing
Cleaning and flushing the WLHP
piping system is the single most
important step to ensure proper
start-up and continued efficient
operation of the system.
Follow the instructions below
to properly clean and flush the
system:
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Ensure that electrical power to
the unit is disconnected.
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Install the system with the
supply hose connected directly
to the return riser valve. Use a
single length of flexible hose.
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Open all air vents. Fill the
system with water.
Do not
allow system to overflow.
Bleed all air from the system.
Pressurize and check the
system for leaks and repair as
appropriate.
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Verify that all strainers are
in place (Zehnder Rittling
recommends a strainer with
a #20 stainless steel wire
mesh). Start the pumps, and
systematically check each vent
to ensure that all air is bled
from the system.
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Verify that make-up water is
available. Adjust make-up
water as required to replace
the air which was bled from the
system. Check and adjust the
water/air level in the expansion
tank.
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Set the boiler to raise the loop
temperature to approximately
85 °F (29 °C). Open a drain at
the lowest point in the system.
Adjust the make-up water
replacement rate to equal the
rate of bleed.
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Refill the system and
add trisodium phosphate
substitute in a proportion of
approximately one pound per
150 gallons (0.8 kg per 1000 l)
of water (or other equivalent
approved cleaning agent).
Reset the boiler to raise the
loop temperature to 100 °F
(38 °C). Circulate the solution
for a minimum of 8 to 24 hours.
At the end of this period, shut
off the circulating pump and
drain the solution. Repeat
system cleaning if desired.
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When the cleaning process is
complete, remove the short-
circuited hoses. Reconnect
the hoses to the proper supply,
and return the connections
to each of the units. Refill the
system and bleed off all air.
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Test the system pH with litmus
paper. The system water
pH should be in the range
indicated in Table 6. Add
chemicals, as appropriate to
maintain neutral pH levels.
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When the system is
successfully cleaned, flushed,
refilled and bled, check the
main system panels, safety
cutouts and alarms. Set the
controls to properly maintain
loop temperatures.
Do not
use “Stop Leak” or
similar chemical agent in this
system. Addition of chemicals
of this type to the loop water
will foul the heat exchanger and
inhibit unit operation.
Notes:
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The manufacturer strongly recommends
all piping connections, both internal and
external to the unit, be pressure tested by
an appropriate method prior to any finishing
of the interior space or before access to all
connections is limited. Test pressure may
not exceed the maximum allowable pressure
for the unit and all components within the
water system.
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The manufacturer will not be responsible
or liable for damages from water leaks due
to inadequate or lack of a pressurized leak
test, or damages caused by exceeding the
maximum pressure rating during installation.
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