Why two circuits?

zepfan

I am curious why ever geo manufacture on their equipment requires two electrical circuits? One specifically for the compressor, and one that does the controls, fan motor, and heat kit if there is one. It seems that it would make more sense to make the unit a single point connection. I used to think this was done by just one manufacturer, but every geothermal unit I see is made this way

109A_5

Are you referring to the building's electrical supply wiring or inside the equipment ? Ultimately both ?

Many reasons, (probably forgetting some);

NEC rules (maybe) or influence and/or other rules from another authority.

Building's electrical supply wiring;

Construction cost, larger wires and wiring methods needed.

Smaller more manageable building wire.

Better protection of the equipment (better application of over-current devices).

The loads may be in different locations.

Minimizing Arc Flash exposure hazard (personal and to the equipment).

Less cost of the components inside the equipment. Higher current components get bigger and cost more.

Compressors can be from 120 VAC, 240 VAC single phase to 480 VAC 3 Phase depending on the application. The control and lower power loads may only need 120 VAC single phase.

Troubleshooting benefits.

Inside the equipment;

Independent control of otherwise unique functionality.

A Relay, Contactor, SCR, TRIAC, IGBT or other switching device may be less expensive for a lower current device.

Circuit board and equipment real estate.

Wiring cost and management. Larger wires may cost more, termination methods and their cost is higher and harder to deal with.

Kaos

You can't connect a 25A compressor directly to a 50A circuit. You now need to add in power distribution and fusing. That cost money which either increases your price or reduces your profit, manufacturers don't like either.

Also not all people need resistance heat backup, so for them installing a single larger circuit would just add cost.