Water Piping; Chilled Water Piping; Hot Water Piping; Field Installed Txv - Bosch DX Series Installation And Maintenance Manual

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18 Unitary Air Handler DX and Hydronic Series
Pressure drop in liquid must not exceed 30 psi
or erratic operation and thermostatic expan-
sion damage will occur.


All piping must be supported independent of coils
to prevent vibration and stress on coil headers.
Swing joints or flexible fittings must be provided to
absorb expansion and contraction strains. Rig id
piping reduces the effectiveness of vibration
isolators. Water piping should always be connected
so that the entering water is on the bottom
connection of the water coil. Coils must be
adequately vented in order to prevent air binding.
Units are provided with manual air vents mounted
through the manifold panel.


Supply and return chilled water piping to the coil
should be ¾ inch ID up to 42,000 BTUs, 1 inch on
units greater than 42,000 BTUs. Water piping must
always be connected so that the entering water is
on the leaving side of the coil.


If a residential water heater is used for space
heating water, do not exceed a distance of 70 feet
between the air handler and the water heater. The
water heater should be the quick recovery type. Air
handler and water heater must be located indoors
and not subject to freezing temperatures.
Air handler must be located so that if any
connections should leak, water will not cause
damage to the adjacent area. When such
locations can't be avoided, a suitable drain
pan should be installed under the air handler,
not over 1-1/2" deep, with minimum length and
width at least 2" greater than the air handler
dimensions and connected to an adequate
drain. Under no circumstances is the manu-
facturer to be held libel for any water damage
in connection with this air handler.
Total piping should not exceed 140 feet. All piping
should be ¾" ID (7/8" OD) copper. CPVC piping
may be used in applications where the water
temperature does not exceed 150°F. It is
recommended that the water shut-off valve for the
water heater be located close to the water heater.
Isolation valves are also recommended.
It is recommended that any devices installed,
which could create a closed system, have a by-
pass and/or the system have an expansion tank to
relieve the pressure built up by thermal expansion
in the water system.
After piping has been installed, allow the system
to fill with water and check connections for leaks.
To insure complete filling of the system, follow
start-up procedure.


Thermal expansion valve (TXV) can be used on
both heat pump and air conditioning applications.
All TXVs have a built in check valve making them
heat pump capable. All are externally equalized
with non-adjustable superheat and are available
with 15% bleed construction. Hard start capability
for outdoor units is not normally required when
15% bleed valve is used. The external equalizer
line attached to the TXV has a female flare nut with
built in Schrader valve depressor that attaches to
the Schrader valve port provided on coils.
Subject to change without prior notice
Water Piping
Toxic chemicals such as used for treatment of
boilers or non-potable water heating appli-
ances shall never be introduced into a potable
water space heating system.
When the system required water at tempera-
tures higher than required for other uses, a
means such as a mixing valve shall be
installed to temper the water for those uses in
order to reduce the scald hazard potential.
With reference to the figure 9, the TXV
assembly is to be installed between the
flowrator distributor and the existing liquid line
attached to the flowrator distributor.
Revised 11-11

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