Want to use aircon wiring to add new circuit.

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Old 07-22-19, 08:50 AM
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Want to use aircon wiring to add new circuit.

I want to add a separate circuit for my network equipment rather than having it just plugged into the wall outlet circuit where it's located.

The problem is that a concrete framed construction means finding unused conduits that pass through the slabs would involve tearing apart ceilings.

So I had an idea, there is a conduit for the Air conditioner power which runs from a panel in the garage to the attic/roof where the A/C and the networking stuff is located.

My idea would be to disconnect the circuit from the breaker in the panel where it currently is, connect it to the mains and add a panel at the first pull at the attic (where one of the lines is currently tapped for the air handler/furnace/etc electronics) with two breakers, one for the AC circuit and one for the networking equipment.

I ran this by the AC techs and they said that the one thing to be aware of was that the cables were already fairly closely sized to the load of the A/C but that if the load was small it might be ok. They also told me not to take their word for it.

Checking the label on the A/C is somewhat confusing.

It's a Lennox 5tn compressor and the label says:

380v - 3ph
Nominal Current: 9a
Minimum circuit current: 12.6a
Locked Rotor current: 64a

(no idea what last one means)

at the pull where I'm thinking of putting a new panel we have 4 wires with a 4mm2 cross section and an uninsulated stranded ground.

The applicable norms I can find online for here in Argentina say a 4mm wire is rated for 24 amps in conduit. That's single phase I assume I'm not sure how to compare that to the load from a three phase motor.

I also can't find a label on the air handler to indicate the consumption although I assume its much less than the compressor. From the wiring I can see that it is single phase .

The network equipment is a pretty small load, less than 150w or .7A although I think the smallest breaker I can buy is 5A.

Does this pencil out?
 
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Old 07-22-19, 08:54 AM
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One more thing, there is a box with a fused disconnect near the meter which is before the panels in the house with the circuit breakers which might mean they're considered sub-panels.
 
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Old 07-22-19, 10:37 AM
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What are the clearances in the attic? Panels have specific requirements for access. Basically imagine a refrigerator box in front of the panel. That is the space you need.
 
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Old 07-22-19, 01:03 PM
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There is enough space to walk past the air handler it would go next to
 
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Old 07-22-19, 02:00 PM
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Here is a diagram I found. When you say attic I think of a space where you need to crawl around. If it is a walk up attic that is different.
Note: Panel does not need to centered in the box. It can be to one side or the other and still be compliant.

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Old 07-22-19, 11:13 PM
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Our codes don't pertain to you in Argentina.

I would not recommend attaching any computer equipment to the end of a circuit that supplies refrigeration equipment. The spike when the compressor shuts down could be damaging to electronic equipment.
 
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Old 07-23-19, 09:31 AM
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One of the benefits of conduit is that you can add additional wires inside it (depending on the existing wires and size of the conduit). So instead of installing a whole subpanel, I would consider just running 2 new wires sized for your networking equipment and run it off a new circuit in the main panel.

Pulling new wires in a conduit with existing wires can be a challenge, but is doable.
 
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Old 07-25-19, 08:31 PM
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Pjmax: does that still apply if everything on the computer circuit is low voltage DC with power bricks?
also the idea would be that they would be separate circuits with their own breaker.

as for pulling new cables, the problem is that bare ground, I havenít tried in this one but in other conduits i have pulled that ground twists itself around cables and generally makes itself much more of a pain than an insulated ground would be.

That aside id be putting 7 AWG 6 sized conductors in a 1 inch EMT which is what the internet says is the max fill is.

what does that 64amp rotor current number from the compressor mean? Thatís a huge number for the wires currently supplying it but it also says 12 as the min circuit amps.
 
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Old 07-25-19, 09:02 PM
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Maybe itíll be easier to visualize with pictures,

Here is the panel/sub panel the AC circuit is currently hooked up to. In particular the GFCi device labeled R1 and the breaker labeled R2.



Here is the pull where id like to put a sub panel. Whatís going on here is wires from the above panel enter on the left. At the bottom some wires go to and come back from the aire handler and at the top of the box are the wires that go to the compressor.


What I was thinking of doing is unpluging the wires from the top terminals of the R2 breaker and trying to fit them in the top terminals of the R1 GFCi and moving the smaller (blue) neutral from the bottom of R1 to the top, That I think would give me a circuit that is not subordinate to that GFCI breaker. Then at the pull in the second picture id get a mini panel and add another 4 pole gfci, a 25a 3 pole CB and a 5a 2 pole cb(like the ones at the bottom of the first picture) and then connect the writings in the box to new breaker and add the circuit for the networking equipment on one of the 2 phases not tapped for the air handler.
 
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