300 Volt wire vs 600 Volt wire

Old 10-04-18, 04:03 PM
Thread Starter
Join Date: Oct 2018
Location: USA
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
300 Volt wire vs 600 Volt wire

Hi, looking for some electrical insights.

I am replacing my forced air AC and gas furnace with three ductless heat pump split systems.

Each system has multiple air handlers and runs on 20 amp circuits. So in other words, I need to have four 20 amp circuits.

I am hoping to re-use the cable and breaker for the existing AC circuit. It is comprised of a 50 amp breaker connected by a 6 awg AL cable that is rated for 300 volts (not 600 volts).

I had planned to run the existing circuit to a new sub-panel, where I would install three 20 amp breakers. From that sub panel I would run 12 awg copper to each system.

Here is my question:
1) Is the existing cable, rated for 300 volts, sufficient - or do I need to replace with a 600 volts cable? (each system runs on 230 volts)
2) Can I run three systems with MFA of 20 amps on a 50 amp breaker?

Thanks, Mike
Old 10-04-18, 05:08 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,640
Received 3,898 Upvotes on 3,494 Posts
Welcome to the forums.

Can I run three systems with MFA of 20 amps on a 50 amp breaker?
Hmmmm....... that would be close. If that was copper I'd say fine. Being aluminum.... it may be borderline. As long as two didn't try to start at the same time.... it should be ok.
300v rated wire is fine.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: