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How do I wire a PEARL to control a separate supply and return damper actuator?

Type of actuator:

The PEARL can control an HVAC unit’s outside and return damper to provide economization, ventilation, and demand ventilation sequences. The type of actuator required on the outside and return dampers is a modulating type; one that accepts a 2-10VDC input. An example actuator would be a Belimo LMB24-SR.

Wiring the PEARL to the supply and return damper actuators:

When wiring an outside and return damper for economizer, ventilation, and demand ventilation sequences: you will us the (A1) output from the PEARL to control these actuators. The (A1) output will send DC voltages to both actuators to change the actuator’s positions.

  1. Use a standard 18G unshielded thermostat wire and wire the (A1) output from the PEARL to the 2-10VDC position input of both the outside and return damper actuators. 
  2. Use a second 18G unshielded thermostat wire and wire the common (C) terminal from the PEARL to the common (-) terminal from both the outside and return damper actuators. You will also need to connect the common (-) terminal from both the outside and return damper actuators to the actuator’s power source.
  3. Use a third 18G unshielded thermostat wire and wire power, normally either 24VAC or 120VAC, to both the outside and return actuators (+) terminal. Follow the actuator manufacturer’s recommended instructions for providing the correct power source to both the outside and return actuators. Make sure not to wire any form of external power to the (A1) or (A2) terminals on the PEARL. This can damage the PEARL’s internal hardware.
  4. If your outside actuator provides a feedback signal, use a fourth 18G unshielded thermostat wire to connect the (S1) terminal from the PEARL to the 2-10VDC feedback output at the outside damper actuator. Do not wire the feedback to the return damper actuator, this is not needed.

Test the dampers:

You will need to set the return and outside actuators to move opposite of each other. For example, if the PEARL outputs 10VDC the outside dampers will be at 100% open and the return damper would be at 100% closed.

If you installed the feedback signal (step 4 above) to the PEARL, you can use the auto-test sequence to verify your dampers are moving correctly. This is explained in the PEARL’s installation guide.

If you do not have the feedback signal, you will want to finish configuring the PEARL through the Pelican App. Then you can turn the Fan to On and the PEARL will open the outside damper to the Minimum Damper Configuration. If you temporarily set the Minimum Damper Configuration to 100%, then the outside damper should go to 100% open and the return damper should go to 100% closed.

During testing if one of the actuators is not moving in the correct direction, the actuator will normally have a toggle on it that allows you to change the direction it is moving.

What about a modulating exhaust damper actuator?

Yes, you can also wire a modulating exhaust damper’s actuator to the PEARL. Follow steps 1 through 3 above, but do the same for the exhaust damper actuator. The exhaust damper will need to move in the same direction as the outside damper. For example, if the outside damper is 100% open, the exhaust damper should be 100% open.