3 phase resistance calculation

[Thermatech]

Frank

You are completely right lots of modern 3 ph splits do include some phase rotation protection but often it is to ensure scroll compressors rotate in the correct direction.

My little story pre dates 407c equipment by quite a few years though & lots of engineers looking on this site still working on basic R22 kit.

The point I tried to make was that nobody tends to think about this issue until its to late & some one has to pay.

[frank]

The point I tried to make was that nobody tends to think about this issue until its to late & some one has to pay.

Thermatech
It's not just the reverse phase protection though. If the phase imbalance goes over 10% the electronics shuts down the equipment under fault conditions to prevent damage.
I agree that not all manufacturers include this but most of the 'better' ones do.
I've worked on lots of old 22 units where this is so. Chillers especially (OK I know that's not splits)

[Peter_1]

Frank


The point I tried to make was that nobody tends to think about this issue until its to late & some one has to pay.

I do, always a overcurrent relay on a 3 phase motor.
Besides this, many hermetic compressors have a clixon in the starpoint of the windings.
Most semi hermetics have an additional Kriwan protection and together with the overcurrent, you almost have a perfect motor protection.
If you have a phase loss on a 2 phase motor, then it simply will stop to run.

The electronic devices in splits and VRV/VRF's not only control phase rotation but also phase loss, it's incoporated in teh same enclosure.