Flushing; Electrical-Power Supply Wiring; High-Voltage Wiring - Bosch QV Series Installation, Operation And Maintenance Manual

14 | Electrical—power Supply Wiring

Flushing

WARNING: If equipped with a disconnect
switch, de-energize unit by opening line
voltage at disconnect switch or If no
disconnect switch is present, de-energize
by opening line voltage at the service panel
before flushing the system.
Once the piping is complete, units require final
purging and loop charging. A flush cart pump of at
least 1.5 hp is needed to achieve adequate flow
velocity in the loop to purge air and dirt particles
from the loop. Flush the loop to purge air and dirt
particles from the loop. Flush the loop in both
directions with a high volume of water at a high
velocity.
Follow the steps below to properly flush the loop:
1. Verify that the power is off.
2. Fill loop with water from the hose through
flush cart before using flush cart pump to
ensure an even fill. Do not allow the water level
in the flush cart tank to drop below the pump
inlet line to prevent air from filling the line.
3. Maintain a fluid level in the tank above the
return tee to avoid entering back into the fluid.
4. Shutting off the return valve that connects into
the flush cart reservoir it will allow 50 psig
surges to help purge air pockets. This
maintains the pump at 50 psig.
5. To purge, keep the pump at 50 psig until
maximum pumping pressure is reached.
6. Open the return valve to send a pressure surge
through the loop to purge any air pockets in
the piping system.
7. A noticeable drop in fluid level will be seen in
the flush cart tank. This is the only indication of
air in the loop.
If air is purged from the system while using
a 10 inch PVC flush tank, the level drop will
only be 1 to 2 inches, since liquids are
incompressible. If the level drops more than
this, flushing should continue since air is
still being compressed in the loop. If level is
less than 1 to 2 inches, reverse the flow.
8. Repeat this procedure until all air is purged.
9. Restore power.
8733829041 (2021/07)
Antifreeze may be added before, during, or after
the flushing process. Refer to the Antifreeze
section below for more detail.
Loop static pressure will fluctuate with the
seasons. Pressures will be higher in the winter
months than during the warmer months. this
fluctuation is normal and should be considered
when charging the system initially. Run the unit in
either heating or cooling for several minutes to
condition the loop to a homogeneous temperature.
When complete, perform a final flush and
pressurize the loop to a static pressure of 40 to 50
psig for winter months or 15 to 20 psig for summer
months.
After pressurization, be sure to remove the plug
from the end of the loop pump motor to allow
trapped air to be discharged and to ensure the
motor housing has been flooded. Be sure the loop
flow center provides adequate flow through the
unit by checking pressure drop across the heat
exchanger.
Antifreeze
In areas where entering loop temperatures drop
below 40°F or where piping will be routed through
areas subject to freezing, antifreeze is needed.
Alcohols and glycols are commonly used as
antifreeze agents. Freeze protection must be
maintained to 15°F below the lowest expected
entering loop temperature. For example, if the
lowest expected entering loop temperature is
30°F, the leaving loop temperature would be 22°F
to 25°F. Therefore, the freeze protection must be
at 15°F (30°F-15°F=15°F).
ELECTRICAL—POWER SUPPLY WIRING

High-Voltage Wiring

WARNING: PERSONAL INJURY HAZARD
Field wiring must be installed by qualified
and trained personnel.
All field-installed wiring must comply with the
National Electric Code as well as all applicable
local codes. Refer to the unit electrical data on the
unit nameplate for wire and branch circuit
protection sizing. Supply power voltage and
phasing must match the required voltage and
phasing shown on the unit nameplate. Operating
Subject to change without prior notice
QV Series Heat Pumps
QV Series Heat Pumps