25
Model PV
e
Heat Recovery Unit
Parts List
1. Supply blower
• Forward curved fan
• Adjustable motor mount for belt tensioning
• Adjustable sheaves for speed control
2. Vibration isolators (quantity 4 per blower)
• Neoprene
3. Aluminum plate heat exchanger
4. Supply weatherhood with 2-inch aluminum mesh
filter
5. Exhaust weatherhood with birdscreen
6. Supply and exhaust air filter racks for
2-inch pleated, 30% efficient filters
7. Electrical control box (standard features)
• Single point power
• Disconnect interlocked with access door
• Motor starters for the supply and exhaust
blower
• 24 VAC, control circuit with terminal strip
Not depicted on this image
8. Exhaust blower
• Forward curved fan
• Adjustable motor mount for belt tensioning
• Adjustable sheaves for speed control
Sequence of Operation
Basic Unit
The PVe units are prewired such that when a call for
outside air is made (via field supplied 24 VAC control
signal wired to unit control center), the supply and
exhaust fan are energized and optional motorized
dampers open. The PVe is normally slaved (24 volt) to
the roof top air handler. When the roof top air handler
starts, the auxiliary contactor in the air handler closes
to start the PVe.
Summer Operation
Outdoor air is preconditioned (temperature is
decreased) by the transfer of energy from the cooler,
drier, exhaust air via the aluminum heat exchanger.
The preconditioned air is typically mixed with return
air going back to the air handler for final conditioning.
Economizer Operation:
Refer to Economizer
Application/Operation section.
Winter Operation
Outdoor air is preconditioned (temperature is
increased) by the transfer of energy from the warmer,
more humid exhaust air via the aluminum heat
exchanger. The preconditioned air is typically mixed
with return air going back to the air handler for final
conditioning.
Frost Control Operation:
Refer to Frost Control
Application/Operation section.
Other Accessories:
Dirty Filter Sensor
: Refer to Optional Accessories
section
CO
2
Sensor:
Refer to Optional Accessories section
VFD on Blowers:
VFDs on blowers are often used
as part of a demand control ventilation system. This
type of system takes advantage of varying occupancy
through the use of CO
2
sensors to monitor space CO
2
levels. If CO
2
levels are low in the space, the VFD will
operate the blowers at minimum airflow required by
code. As the space occupancy increases and CO
2
levels increase, the VFD will increase the amount
of fresh outdoor air being brought in to offset the
CO
2
levels in the space (exhaust airflow is increased
proportionally as outdoor airflow increases). As CO
2
levels come back down, the airflow will decrease
back to minimum requirements.
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