valent VX Series, Installation, Operation And Maintenance Manual

Page: 12 / 72

Dedicated Outdoor Air Unit 12
Optional Coil Piping
Factory-installed cooling and heating components are
mounted in the coil section of the unit. The coil section
is downstream of the energy wheel on the supply air
side of the unit. Note the coil connection locations on
the picture. Coil connections are located external to the
unit.
Note: DX coil liquid connection is internal to units.
Water Coils
1. Piping should be in accordance with accepted
industry standards. Pipework should be supported
independently of the coils. When installing couplings,
do not apply undue stress to the connection
extending through the unit. Use a backup pipe
wrench to avoid breaking the weld between coil
connection and header.
2. Connect the water supply to the bottom connection
on the air leaving side and the water return to the
top connection on the air entering side. Connecting
the supply and/or return in any other manner will
result in very poor performance. Be sure to replace
factory-installed grommets around coil connections
if removed for piping. Failure to replace grommets
will result in water leakage into the unit and altered
performance.
3. Water coils are not normally recommended for
use with entering air temperatures below 40 ° F. No
control system can be depended on to be 100% safe
against freeze-up with water coils. Glycol solutions
or brines are the only safe media for operation of
water coils with low entering air conditions. If glycol
or brine solutions are not used, coils must be drained
when freezing conditions are expected.
If required,
vent and drain connections must be field-
piped, external to the unit.
4. Pipe sizes for the system must be selected on
the basis of the head (pressure) available from the
circulation pump. The velocity should not exceed
6 feet per second and the friction loss should be
approximately 3 feet of water column per 100 feet
of pipe.
5. For chilled water coils, the condensate drain
pipe should be sized adequately to ensure the
condensate drains properly. Refer to Drain Trap
section.
Direct Expansion (DX) Coils (Split DX)
1. Piping should be in accordance with accepted
industry standards. Pipework should be supported
independently of the coils. Undue stress should not
be applied at the connection to coil headers.
2. The condensate drain pipe should be sized
adequately to ensure the condensate drains properly.
Refer to Condensate Drain Trap section.
3. When connecting suction and liquid connections
make sure the coil is free from all foreign material.
Make sure all joints are tight and free of leakage. Be
sure to replace factory-installed grommets around
coil connections if removed for piping.
4. Manufacturer does not supply compressor,
condensing units, or thermal expansion valve (TXV)
with standard models. For further instruction on
DX coil installation and operation contact your
compressor and/or condenser manufacturer.
Condensate Drain Trap
This unit is equipped with a stainless steel condensate
pan with a stainless steel connection. It is important
that the drain connection be fitted with a P trap to
ensure proper drainage of condensate while maintaining
internal static pressures and to prevent migration of
sewer gas back into the unit.
A P trap assembly (kit) is
supplied with each unit and is
to be assembled and installed
as local conditions require and
according to the assembly
instructions provided with
the P trap. If local and area
codes permit, the condensate
may be drained back onto the
roof, but a drip pad should
be provided beneath the outlet. If local and area codes
require a permanent drain line, it should be fabricated
and installed in accordance with Best Practices and all
codes.
In some climates, it will be necessary to provide freeze
protection for the P trap and drain line. The P trap
should be kept filled with water or glycol solution at all
times and it should be protected from freezing to protect
the P trap from damage. If severe weather conditions
occur, it may be necessary to fabricate a P trap and
drain line of metal and install a heat tape to prevent
freezing.
Condensate Overflow Switch
This unit is equipped with an optional factory-mounted
condensate overflow switch. In the event that a high
level of condensate is detected, a dry contact will be
powered (24 VAC). This dry contact can be used for
field monitoring of condensate levels. All monitoring and
control shall be provided by others.
Piping Installation