16
Model RT Energy Recovery Unit
Plumbing
Coil Application Recommendations
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 airside of the unit.
Note the coil connection locations on the picture.
Airside coil connections are located internal to the
unit as shown.
Water Coils
Water coils are a design option that must be specified
for factory installation. A water coil may be used
for further tempering of the outdoor air. If used, the
optional hot water coil would be located vertically on
the internal cabinet partition that separates the airside
coil from the supply air blower compartment of the RT.
See also Subassemblies/Coils.
1. Piping should be in accordance with accepted
industry standards. Pipework should be supported
independently of the RT unit. Water connections
are male NPT iron pipe. 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. To ensure proper venting, an external air
vent in the piping is recommended. 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. The air vent at the uppermost point should be
temporarily opened during system start-up to
release all of the air from the coil. To maintain heat
transfer capacity, periodically vent any air in coil.
Hot
water coil
connections
Coil access door
4. Water coils are not normally recommended for
use with entering air temperatures below 40ºF;
however, the energy wheel maintains a pre-coil
temperature higher than 40ºF. 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.
Continuous water circulation through the coil at all
times is highly recommended.
5. 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.
Heat Pump Airside Coils
Outdoor air entering the RT is first tempered by the
energy wheel and then passes through the heat pump
airside coil for further heating or cooling. Refrigerant
in a vapor state will circulate through the airside
coil whenever the heat pump is operating, but the
direction of flow will change, depending on whether
the unit is in cooling or heating mode. When the unit
is operated in the cooling mode, a significant amount
of condensate will be produced and then collected in
the stainless steel condensate drain pan.
The condensate drain pipe should be sized
adequately to ensure the condensate drains properly.
Refer to Drain Trap section.
