button again to return to the main screen. Replace the user con- trol cover.
387.eps Fig. 19 — Exhaust Air Offset Screen
Modulating CO2 with Balanced Air Option (Fig. 20) — This option allows the user to enter minimum and maximum outside airflow levels. The user will then be allowed to enter minimum and maximum CO2 levels. The EzERV program will modulate the cfm of the ERV based on the building CO2 level. To enter the user settings press the pushbutton once to display the minimum cfm screen. Adjust the knob clockwise to increase and counterclockwise to decrease the minimum cfm level.
a62-388.epsFig. 20 — Modulating Cfm
Press the push button again to display the maximum cfm screen. Adjust the knob clockwise to increase and counter- clockwise to decrease the maximum cfm level. See Fig. 21.
Fig. 21 — Maximum Cfm Screen a62-389.eps
Press the push button again to display the minimum CO2 level screen. Adjust the knob clockwise to increase and coun- terclockwise to decrease the minimum CO2 level. See Fig. 22.
Fig. 22 — Minimum CO2 Screen a62-390.eps
Press the push button again to display the maximum CO2 level screen. Adjust the knob clockwise to increase and coun- terclockwise to decrease the maximum CO2 level. See Fig. 23.
Fig. 23 — Maximum CO2 Screen a62-391.eps
The exhaust airflow will automatically adjust to equal the supply airflow. Press the button again to return to the main screen. Replace the user control cover.
NOTE: The scale for the cfm vs. CO2 level is based on a CO2 sensor that outputs 0-vdc at 0 ppm CO2 and 10-vdc at 2000 ppm CO2. For example, using the figures above, the air- flow would modulate linearly from 1458 L/s (3090 cfm) at 3vdc to 2336 L/s (4950 cfm) at 5-vdc. A signal below 3-vdc would result in a constant 1458 L/s (3090 cfm) while a signal above 5-vdc would result in a constant 2336 L/s (4950 cfm).
Modulating CO2 with Offset Air Option — Follow the steps above for modulating CO2 with balanced air. After setting the maximum CO2 level press the push button again to display the
exhaust air offset screen. A negative exhaust air offset would equate to a smaller amount of air being exhausted from the building when compared to the outside air being supplied to the building. Adjust the knob clockwise to increase and counter- clockwise to decrease the exhaust offset cfm level. Press the button again to return to the main screen. Replace the user con- trol cover.
Building Pressure Control Option — This option will hold the outside air cfm level constant and will modulate the exhaust airflow to maintain the building pressure set point. Press the push button once to bring up the ERV cfm screen. Turn the knob clockwise to increase or counterclockwise to decrease the amount of outside air coming into the building. Press the push button again to display the "Building Pressure Set Point" screen. Adjust the knob clockwise to increase and counter- clockwise to decrease the desired building pressure level. Press the button again to return to the main screen. Replace the user control cover.
Modulating CO2 with Building Pressure Control Option — This option will modulate the supply fan of the ERV based on the building CO2 level, and will modulate the exhaust airflow to maintain the building pressure set point. Follow the proce- dure outlined above to configure the minimum and maximum outside airflow and CO2 levels. After setting the maximum CO2 level press the push button once more to display the build- ing pressure set point screen. Adjust the knob clockwise to increase and counterclockwise to decrease the desired building pressure level. Press the button again to return to the main screen. Replace the user control cover.
Operating Sequence — When operation is called for by the rooftop supply fan interlock or remote timer option, the ERV supply blower(s), exhaust blower(s) and wheel motor will be energized. The supply and exhaust blowers will provide the adjusted/programmed airflow and the ERV wheel will rotate at a constant speed unless influenced by one of the following con- ditions. The sequence of operation is shown in Fig. 24.
LOW TEMPERATURE LOCKOUT — The optional low temperature lockout function locks out the 62E ERV if the out- door-air temperature entering the wheel is below the set point. The low temperature lockout is factory set at –23.3 C (–10 F), and can be field adjusted from –34.4 C to 37.8 C (–30 F to 100 F).
FROST PROTECTION — The frost protection option moni- tors the pressure drop across the ERV wheel. If the pressure drop rises above an adjustable limit, the outside air fan will be de-energized for a 5-minute period. The setting must be field set at 50% above (1.5 times) the pressure drop measured at the maximum adjusted airflow and a clean, dry wheel.
ERV WHEEL VARIABLE FREQUENCY DRIVE (VFD) — The ERV wheel VFD option monitors the pressure drop across the ERV wheel. If the pressure drop rises above an adjustable limit, the ERV wheel rotational speed will be re- duced for a minimum of 5 minutes to defrost the wheel. The setting must be field set at 50% above (1.5 times) the pressure drop measured at the maximum adjusted airflow and a clean, dry wheel.
PRE-HEATERS — Units may be equipped with electric pre- heaters to prevent frost build-up on the wheel by slightly warming the outdoor air. This feature monitors the pressure drop across the ERV wheel and the outdoor-air temperature. If the pressure drop rises above an adjustable limit and the out- door-air temperature is below an adjustable set point, the heat- ers will be energized. The wheel pressure drop setting must be field set at 50% above (1.5 times) the pressure drop measured at the maximum adjusted airflow and a clean, dry wheel. The outdoor air thermostat is factory set to activate at –20.6 C (–5 F), and can be field adjusted from –34.4 C to 37.8 C (–30 F to 100 F).
