Install current sensing switch?

Old 01-03-12, 07:45 PM
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Join Date: Feb 2007
Location: Northeast PA
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Install current sensing switch?

I have an in-line booster fan to try to get better air supply yo a bedroom on a long run. It currently has a pressure sensing switch on it, but it's the second one that has gone bad:

To reduce failures, I want to install a current sensing switch, probably a split core, to the HVAC - so the fan only runs when the system does. What is a good brand to get? I saw Greystone and Setra brands. Info on these two or other recommendations will help.

It appears I need to put the switch on the electrical supply to the HVAC unit. Is it best to attach the switch inside the unit or at the breaker box? I looks like it will be easier at the unit.

Any information that helps with the install will be greatly appreciated.
Old 01-03-12, 08:38 PM
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Join Date: Jan 2011
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how many amps is the inline booster fan? If it is low amp draw (.42A or less) you could use an Aprilaire #51 relay. If it higher amp draw then you could use Aprilaire #50 relay with an additional relay to switch on the fan. Or depending upon your HVAC equipment if you have an EAC terminal on the control board you could use that to power a relay. The EAC terminal sends power every time the fan runs. There are a number of options. I guess we need more info on the Booster and the HVAC equipment.

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