split systems

[JRCJ]

I have a situation where there is an existing accu that is being replaced with 3 new mitsubishi split systems. The existing breaker for the existing accu is a 2P60A breaker and a 2P15A breaker for the fcu. The panel is 100A main 208/120v, 1Phase with no spare breakers or PFB spaces.
My question is if I can combine the 3 new split systems onto one 2 pole breaker for the ACCU since there are no spare spaces in the panel to individually provide seperate breakers for each new ACCU?
The ratings of the new split system.
ACCU #1: Compresssor 11.5RLA, Fan: 0.65FLA.
ACCU #2: compressor 8.9RLA, Fan: 0.65FLA.
ACCU #3: Compressor 8.9RLA, Fan 0.65FLA.
208V, 1Phase
If so, how do you size the breaker for the 3 ACCU's?

 

[electricman2]

I believe I would set a sub panel and feed it from the main. One breaker would likely be oversized for one unit based on nameplate data. Also a problem with one unit that trips the breaker would also shut down the other two

 

[augie47]

Accu

Accu

agree. I see three choices: (a)subpanel, or (b) change existing to panel with more spaces, or (c) use a feeder breaker in the existing panel, apply tap rules and provide individual OCP at each unit.. The realtive location of the panel and the units and costs would determine which is best.
Each unit must be protected per its nameplate data.

 

[Pierre C Belarge]

Each unit must be protected per its nameplate data.

As Augie has mentioned, what does the nameplate state as maximum overcurrent protection for the different units? You most likely will need a subpanel.

 

[necnotevenclose]

JRJC- Great question here is a link to an article posted by Mike Holt describing how to properly size equipment:
http://ecmweb.com/mag/electric_motors_motor_circuits/index.html
This article has helped me many of times.

If I were you I would verify that since these units are split systems that the voltage is the same. The fan load seems so small that it makes me think that they could be seperate 120/1ph loads. For this I would just group the smaller loads and homerun them together.

But based on what you mention if you take your largest load 11.9 x 2.5 (for your circuit breaker) then add in the additional loads your total is:48.5 so in theory you could replace the 60A/2P breaker with a 50A/2p. Your wire size should stay the same for the homerun #10.

 

[JRCJ]

Thank you all for your reply.
necnotevenclose you are correct, I checked and the fcu's are at 115V, 1Phase. Thank you also for the great web link. It was very helpful.