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How do I wire a PEARL to control my economizer?

Note:

There is a detailed diagram for this installation in the PEARL’s installation guide.

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 economizer damper assembly is a modulating type; one that accepts a 2-10VDC input. An example actuator would be a Belimo LMB24-SR.

If you are replacing a third-party economizer controller, you will need to verify that the actuator on the economizer assembly is compatible with the PEARL. There are actuators that are proprietary and only work with the same manufacturer’s equipment. If you run into a proprietary actuator, you will want to replace that actuator with a modulating (2-10VDC) alternative.

Wiring the PEARL to the economizer damper actuator:

When wiring an actuator for economizer, ventilation, and demand ventilation sequences: you will us the (A1) output from the PEARL to control the actuator. The (A1) output will send DC voltages to the 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 the economizer actuator. 
  2. Use a second 18G unshielded thermostat wire and connect the common (C) terminal from the PEARL to the common (-) terminal of the economizer actuator. You will also need to connect the common (-) terminal from the actuator to its power source.
  3. Use a third 18G unshielded thermostat wire and connect it to power. This is normally 24VAC or 120VAC. Follow the actuator manufacturer’s recommended instructions for providing the correct power. 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 economizer actuator provides a feedback signal, use a fourth 18G unshielded thermostat wire and connect the (S1) terminal from the PEARL to the 2-10VDC feedback output at the economizer actuator.

Test the dampers:

On single actuated economizer assemblies you will normally have mechanically linked return, outside and sometimes exhaust dampers. The return damper should be opposite of the outside and exhaust dampers. For example, if the PEARL outputs 10VDC the outside and exhaust dampers will be at 100% open and the return damper should be at 100% closed.

If you installed the feedback signal to the PEARL (step 4 above), 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 the actuator 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.