VFD & TEMP CONTROL

[Therealcrt]

I’m on a remodel job and there are Fan Box Controllers the HVAC guys took down and moved to a new location and I’m just reusing the existing circuits. I traced down the home run back to the panel so I could label it correctly and it went through a 277/480 panel and into a cabinet on a contactor loads side. The line side was obviously fed from that panel, but the feed for the coil of the contactor I traced all the way across the electrical room into a temperature control panel, that was tied into a VFD. It’s a 3 phase VFD. How can does the contact close via the VFD or temp control?

 

[Jraef]

Hard to say from just that description. It might be that the fan boxes were used circulating air fans that just turned on whenever the VFD ran.

 

[ptonsparky]

There are small 'output' relays on the VFD that can be assigned to change state for about any imagined reason.