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ERV
The room static pressure setpoint is entered and adjusted from the unit controller display or
provided by the BMS. The minimum and maximum values for the room static pressure setpoint
are unit dependent. An adjustable PI loop will compare the measured room static pressure to
the static pressure setpoint and adjust the exhaust fan speed. If the measured static pressure
varies from the desired static pressure by more than 0.05 inches water gauge (adjustable)
for more than 300 seconds (adjustable) a room static pressure alarm will be set to true. This
exhaust fan operation mode can be used to provide a constant room pressure for variable
exhaust systems
6.0 TEMPERING CONTROL
The secondary purpose of the ERV unit is to provide 100% outdoor air that tempered.
6.1 MODES OF OPERATION
There are three modes of operation (if applicable):
u
Heating Mode—Will run the heating to maintain a heating setpoint
u
Sensible Cooling Mode—Will run the cooling to maintain a cooling setpoint
u
Ventilation Mode—Will only run the fans for ventilation
See the following sections for more information on these modes. The mode is determined in
this order:
1. Heating: Is the unit configured for heating? Is the outdoor air temperature lower than the
heating lockout temperature?
2. Cooling: Is the unit configured for cooling? Is the outdoor air temperature higher than the
cooling lockout temperature?
3. If it in no other mode and the unit is on, it will be in Ventilation Mode.
In normal heating operation, the controller will prevent the heater from running when the
Outdoor Air temperature is above the Lockout Above setpoint. This causes the ERV unit to use
energy recovery from the RA for heating instead of firing the heat module. The Lockout Above
setpoint is assigned by the user, based on both ambient temperatures and experience with the
building being heated.
RenewAire suggests an initial Lockout Above setting of 50
°
F.
If the OA
air is at 50°F and the EA coming from the Occupied Space is at 72°F, the CA recovers enough
heat energy from the EA that it will reach about 67.6°F without any supplementary heat from
the heat module when the heat exchange core is at maximum efficiency. In every building,
there is additional heat being generated by human activity, equipment and thermal gain from
sunlight, etc. If there is very little additional heat being generated in the Occupied Space, the
Lockout Above setting may have to be raised. If there is a great deal of heat being generated,
the Lockout Above setting can actually be lowered further.
The Lockout Above function has a hysteresis band built into it to prevent short-cycling when
the OA air is near the Lockout Above setpoint. In other words, if the Lockout Above setpoint is
at 50°F, the gas heat module will be disabled whenever the OA air temperature is higher than
50°F. When the OA air temperature drops to 50°F, the controller will continue to lockout the
heat module until the OA temperature drops an additional 1.8°F, the hysteresis band.
Lockout Below performs the same function as Lockout Above, but for cooling. The factory
setpoint for Lockout Below is 70°F, meaning that if the Outdoor Air temperature is lower than
70°F, the cooling unit will be blocked from running.
RenewAire suggests an initial Lockout
Below setting of 70
°
F.
TEMPERING CONTROL
