Bard ERVF-A3, Installation Instructions Manual, Page: 12 / 15

Manual 2100-512B
Page
12 of 15
Control Wiring
The ERVF-*3/CHERV-*3 comes from the factory with
the low voltage control wires not wired into the wall
mount low voltage terminal strip. Care must be taken
when deciding how to control the operation of the
ventilator. When designing the control circuit for the
ventilator the following requirements must be met.
Control Requirements
1. Indoor blower motor must be run whenever the
ERVF-*3/CHERV-*3 is run.
2. Select the correct motor speed tap in the
ERVF-*3/CHERV-*3. Using Table 1 to determine
the motor speed needed to get the desired amount
of ventilation air needed. For instance, do not use
the high speed tap on a ERVF-A3 if only 250 CFM
of ventilation air is needed; use the low speed
tap. Using the high speed tap would serve no
useful purpose and significantly affect the overall
efficiency of the air conditioning system. System
operating cost would also increase.
3. Run the ERVF-*3/CHERV-*3 only during periods
when the conditioned space is occupied. Running
the ERVF-*3/CHERV-*3 during unoccupied periods
wastes energy, decreases the expected life of
the ERVF-*3/CHERV-*3 and can result in a large
moisture buildup in the structure. The ERVF-*3/
CHERV-*3 removes 60 to 70% of the moisture
in the incoming air, not 100% of it. Running
the ERVF-*3/CHERV-*3 when the structure is
unoccupied allows moisture to build up in the
structure because there is little or no cooling load.
Thus, the air conditioner is not running enough to
remove the excess moisture being brought in. Use
a control system that in some way can control the
system based on occupancy.
Recommended Control Sequences
Several possible control scenarios are listed below:
1. Use a programmable electronic thermostat
with auxiliary terminal to control the ERVF-*3/
CHERV-*3 based on daily programmed occupance
periods. Bard markets and recommends the Bard
Part No. 8403-060 programmable electronic
thermostat for air conditioner and heat pump
applications.
The units are set from the factory with the exhaust
blower on the low speed and the intake blower on
medium speed. Moving the speed taps located in the
control panel can change the blower speed of the
intake and exhaust. See Figure 6A on page 11.
TABLE 1
2. Use a motion sensor in conjunction with a
mechanical thermostat to determine occupancy in
the structure. Bard markets the CS2000A for this
use.
3. Use a DDC control system to control the ERVF-*3/
CHERV-*3 based on a room occupancy schedule to
control the ERVF-*3/CHERV-*3.
4. Tie the operation of the ERVF-*3/CHERV-*3 into
the light switch. The lights in a room are usually on
only when occupied.
5. Use a manual timer that the occupants turn to
energize the ERVF-*3/CHERV-*3 for a specific
number of hours.
6. Use a programmable mechanical timer to energize
the ERVF-*3/CHERV-*3 and indoor blower during
occupied periods of the day.
Ventilation Airflow
The ERVF-*3 and CHERV-*3 are equipped with a
3-speed motor to provide the capability of adjusting
the ventilation rates to the requirements of the specific
application by simply changing motor speeds.
IMPORTANT
Operating the ERVF-*3/CHERV-*3 during
unoccupied periods can result in a build up of
moisture in the structure.
!
WARNING
Open disconnect to shut all power OFF before
making adjustments to the speed taps. Failure
to do so could result in injury or death due to
electric shock.
Ventilation Air (CFM)
Model
High
Speed
(Black)
Medium
Speed
(Blue)
Low
Speed
(Red)
ERVF-A3
CHERV-A3
ERVF-C3
CHERV-C3
400 325 250