branching off existing 230V disconnect

[strobes]

Hi, everyone. This is related to my mini split project but getting 230V different way by placing condenser by garage.
So I thought may be a good idea to start a different thread.

Any way I have a disconnect on garage external wall for central AC and one option is to place Mini split condenser near by.
Is it OK per NEC to take that branch and terminate with two disconnects : one for Central AC and second for Mini split?
If yes I'll start collecting information for existing wire branch wire rating to see if it can handle this additional load.
Thank you.

 

[wyliesdiesels]

I cant think of a code prohibition on this. However You would need fusible disconnects for both as the higher breaker rating needed wont match the MOCP rating on the units

Also, the existing wire is probably too small… so youd have to run a new circuit either way…

 

[strobes]

Ok, let me start with requirements:
Mini Split: Min Ampacity 13A; Max fuse 15A
Central AC: Min Ampacity 24 A Max fuse 40A

The panel currently has 40A fuse. It was 50A fuse installed by the builder fore previous central AC.
Unfortunately I do not see any markings on wire in relation to GA or temperature rating.
The cooper core measured between .18"-.2" picture attached.

Not sure why information vary so mach from different sources. But even if it is 6ga this may be OK if insulation is rated for 90C. But how to find temp. rating? (wires are in conduit. the run is about 5')
it is 4ga or 5ga

American Wire Gauge Conversion Chart | AWG Sizes

Refer to this American wire gauge (AWG) conversion chart when determining the correct wire size of molybdenum, tungsten, tantalum, or niobium.

www.rembar.com

or 6ga

https://alabamawire.com/technical-information/wire-gauge-chart/

 

[mm08822]

Looks like the same size as the blue #8. Read the print on the conductor. It will indicate the insulation type. From that the temp rating can easily be determined. Easier to just remove it and replace.

I would run #6 Copper THHN/THWN and use a 60A cb in the panel.

You will need 2 fused disconnects and a junction box to split the feed between the 2.
On the load side of the fuses you can reduce the conductor size to each unit.

 

[sparky 1971]

It's romex and that means you have 60°C wire. It looks to me like it's #8, but there is a slim chance it's #6. It's not #4, and there's no such thing as 5.

 

[strobes]

It's romex and that means you have 60°C wire. It looks to me like it's #8, but there is a slim chance it's #6. It's not #4, and there's no such thing as 5.

I think I got it - no rating on wires because it's romex. The rest of the house done with romex too.
Based on diameter of the wire and that this circuit was protected by 50A breaker at the time of inspection, the wire is 6ga. Which does not help me. It's still to small.

 

[mm08822]

I think I got it - no rating on wires because it's romex. The rest of the house done with romex too.
Based on diameter of the wire and that this circuit was protected by 50A breaker at the time of inspection, the wire is 6ga. Which does not help me. It's still to small.

Not necessarily. The 50A cb was protecting a dedicated circuit ......the ac unit. The original unit may not have spec'd a MCA or MOP, but reading the nameplate on the unit and applying general motor circuit sizing rules and over-current protection, 50A could easily apply to the #8's.

If it's only 5' of conduit, just yank it out and the nm-b jacket should be legible. What size conduit?

 

[sparky 1971]

(wires are in conduit. the run is about 5')

How do you know it's in conduit? It looks like a flush mounted panel to me and you might be looking at a 3/4" romex connector. It and an EMT connector look awfully similar when all you can see are the threads and a lock nut. If, in fact, it is in conduit, just change it to #6 THHN/THWN and a #10 ground and you will be good to go for up to 65 amps.

 

[nadogail]

The 10’ tap rule is my friend.

My garage heater is tapped off my welder supply circuit.

 

[strobes]

How do you know it's in conduit? It looks like a flush mounted panel to me and you might be looking at a 3/4" romex connector. It and an EMT connector look awfully similar when all you can see are the threads and a lock nut. If, in fact, it is in conduit, just change it to #6 THHN/THWN and a #10 ground and you will be good to go for up to 65 amps.

yes, you are correct. I made incorrect assumptions (no experience).
So I removed a receptacle mounted right under panel to see how this wire installed. There is no conduit. It is NM-B 6/2 with ground. And 55A only

 

[mm08822]

Ok, so that is good. Now you need to plan the other end. Might want to consider a weatherproof double gang box surface mounted and locate it where the cable comes out of the wall. Then ****** in to a fused disconnect on each side of it, one for each unit. Good time to add a surge suppressor ...two birds with one stone.