Outside Sub-panel for AC units

[yeldogt]

I have three AC compressors going into the same spot. Does it not make sense to have a small sub-panel vs all these wires and boxes?

was going to talk about running one feeder wire to the panel and then whips out to each unit ....have the courtesy outlet from the panel. I could use it for my outside tree light feed as well.

was thinking it could be on a wood post (Maybe metal is code?) .. can't the panel be the disconnect for the AC units this way?

 

[alfredeneuman]

Does it not make sense to have a small sub-panel vs all these wires and boxes?
.. can't the panel be the disconnect for the AC units this way?

Yes it makes perfect sense.
If the nameplates on the units give a Max Fuse or Circuit Breaker size you can use the breakers in the panel as disconnects.
If it says only Max Fuse size you can't

 

[yeldogt]

Yes it makes perfect sense.
If the nameplates on the units give a Max Fuse or Circuit Breaker size you can use the breakers in the panel as disconnects.
If it says only Max Fuse size you can't

That's interesting .... Why not ? What's the significance/ distinction?

It's a residential Carrier Condenser and two Mitsubishi Mini-split condensers.

 

[wyliesdiesels]

That's interesting .... Why not ? What's the significance/ distinction?

It's a residential Carrier Condenser and two Mitsubishi Mini-split condensers.

Because if it says Fuse only, then you will need a fusible disconnect in addition to the breakers in the subpanel.

Some types of fuses react differently to overloads and short circuits than breakers do and some condensers require fuses only. Check the nameplate.

 

[snorky18]

I've considered the same.

The main thing I haven't looked into... I believe with a dedicated HVAC circuit the OCPD can be higher ampacity than a given conductor would typically allow. So would my subpanel then need to be fed with the size conductor to support that higher OCPD continuously?

 

[jeepxj]

I'd do external panel sized for all 3, then your standard AC disconnects at each unit location. at the fuse disconnect you can transfer over to liquid tight. it'll look real clean.

 

[alfredeneuman]

The 3 are going "in the same spot" according to yeldogt (right next to one another).
The sealtite whips can come right out of the panel if it meets the nameplate breaker requirement, which would look even cleaner

 

[wyliesdiesels]

I'd do external panel sized for all 3, then your standard AC disconnects at each unit location. at the fuse disconnect you can transfer over to liquid tight. it'll look real clean.

why bother with individual disconnects? just adds unneeded complexity when the breaker is right there....

 

[jeepxj]

why bother with individual disconnects? just adds unneeded complexity when the breaker is right there....

because I like complexity.

 

[Norcal]

why bother with individual disconnects? just adds unneeded complexity when the breaker is right there....

Have agree, cleaner & more economical, the KISS principle comes to mind.

Keep

It

Simple

Sir

 

[yeldogt]

The two mini split compressors will be end to end (9k and 18k) with the Carrier sitting behind them ... So they are all together. Having the whips direct to the units would be ideal.

 

[pattenp]

Unless my memory fails me, but won't all the units need to be within 6ft of the sub panel to meet the 6ft limit of LFNC?

 

[Bert_]

Unless my memory fails me, but won't all the units need to be within 6ft of the sub panel to meet the 6ft limit of LFNC?

Where do people get this stuff?

It's only limited to six foot when unsupported. You can run it as far as you want if you put some straps on it.

 

[alfredeneuman]

The only time seal tight would be limited to 6' would be if you are using it for the ground.

LFNC is non metallic. Thinking of LFMC?

 

[pattenp]

Where do people get this stuff?

The only time seal tight would be limited to 6' would be if you are using it for the ground. If you pull a ground you can run the stuff as far as you want.

I get it from NEC 356.12(3) LFNC, you're thinking of FMC used for grounding.

 

[Aceman]

A subpanel would also be convenient for adding the code required service receptacle within 25 feet of the units, if you don't already have one.

 

[Bert_]

I get it from NEC 356.12(3) LFNC, you're thinking of FMC used for grounding.

Ok so put a ******** it.

 

[nadogail]

Please correct me if I am wrong, as long as the disconnects are within sight of the AC Units and within wrench throwing distance, IMHO an exterior sub panel would be OK.

 

[Bert_]

LFNC is non metallic. Thinking of LFMC?

Yes my bad.

 

[pattenp]

Ok so put a ******** it.

I was just commenting about want I recalled about LFNC. The a/c whips at the big box stores are normally 6' LFNC, so that's what made me think about it.
I just didn't appreciate your comment starting off with an insult.

 

[pattenp]

Please correct me if I am wrong, as long as the disconnects are within sight of the AC Units and within wrench throwing distance, IMHO an exterior sub panel would be OK.

Within sight and readily accessible is the requirement.

 

[yeldogt]

What type of wire has to come out of the wall ?

I'm doing this because the property is very tight on mechanical space -- and it's a stone building. I want the units a few feet from the building and I don't want boxes in the building.

I'm thinking a conduit to the sub on some type of post ... the whips to the units. We are going to design a screen to obscure the units.

Can you run some type of wire through the house and keep this same wire in the conduit to the sub?

 

[Norcal]

Any conduit outdoors or underground is a wet location so the wire must be rated for wet location use like THWN.

 

[yeldogt]

Any conduit outdoors or underground is a wet location so the wire must be rated for wet location use like THWN.

But -- How do you do that all the way back to the panel of you can't run conduit all the way back to the panel ?

 

[Norcal]

Going to have to transition from NM cable to a wiring method suitable for a wet location.

 

[sberry]

Or use uf all the way. But let's calculate the wire size.

 

[yeldogt]

Or use uf all the way. But let's calculate the wire size.

This is not DIY ..... I'm thinking.

I went the the property Wednesday as they were prepping the spot for the units with a backhoe .... was also looking at the very limited space for wires. The panel and most of the mechanicals are housed in the new addition and the wires have to go through the old stone building. Getting through 2' of stone wall is not easy and we only have so many points through.

My guess is where the panel would be ideal is 3' ..maybe 4' from the wall of the old stone building.

 

[sberry]

I would likely be done before I could get someone else involved. Some part might be hard, duh, that's why they don't get old women and children to do it.

 

[yeldogt]

I would likely be done before I could get someone else involved. Some part might be hard, duh, that's why they don't get old women and children to do it.

Don't follow ...sorry.

My builder was on it -- I'm glad my generator is a 22k -- as the 3T is not going to pose a problem. Was planning on using a load control on the 3T ..

May need to control the shop.

 

[dcg9381]

I'm adding Siemens Talon (subpanels with 50A, 30A, 20A GFCI outlets) to HVAC compressor installs.. It's just a flexibility thing for me. The panel breakers serve as readily accessible disconnects and because the panel has 20A, it meets that requirement also.

 

[yeldogt]

I'm adding Siemens Talon (subpanels with 50A, 30A, 20A GFCI outlets) to HVAC compressor installs.. It's just a flexibility thing for me. The panel breakers serve as readily accessible disconnects and because the panel has 20A, it meets that requirement also.

That's the way it's going ... they are at the house now. The builder put in a temp post and sparky is going to run the wire from the main and mount a box.

We need to get some of the AC working so the inside can be conditioned for the stairs and other millwork.

He many just use a temp box and loop some extra wire -- we only need to get the one going. When the AC guys are ready to set the other units we will have a better idea of the proper placement. Sparky mentioned we need 3' ... so that may change location.

Naturally, this is a very space challenged project ... And I need to hide 4 compressors. It always works that way!