Electrician Questions

I want to disconnect my Central air in my house and run window a/c units. I only have a 100amp main breaker in the house to run everything off of.
The breaker I want to plug all the grow lights into is only a 15amp breaker, and I plan on running two 600w HPS (Flower) and one 400 8 bulb t5's. That alone is to much for that breaker. I will have 3 window units on 3 different breakers to spread the load so really I can plug the lights in and the window units.
So heres my question... My electric that hooks up the central AC runs off the main panel outside and then runs to the Ac unit where it has a service location w/ Fuse.
I want to tap into the lines that supply my AC and run wires into the grow room so that way I wont have a problem tripping breakers inside of my house.
Would this be a bad idea? any advice? I plan on buying a voltage meter to test the lines and all that. I know its a long shot, but can you tell whether the ac runs on 120v or 240v?

It's a bad idea and your risk of death is high, IMO
That main panel is no joke man. At the VERY least, have your power company shut you off completely while you do the work ... But I don't recommend you do this yourself.
I am not an electrician but I have wired a couple buildings. Main outside electrical feed panels, I will not touch.

If I go to the main panel and shut off the main breaker there should be no power running to the a/c and I would be able to check w/ voltage meter to make sure nothing is live.

how would you tap off the ac disconect? you could potentially run a pony panel off of the disconnect. and then you could have multiple 15 amp circuits to wire up your grow room. Its not the right way but it could potentially work. you need to find out the amperage and voltage running to your unit before you do any crazy shit like that.

003n1gm400 said:

If I go to the main panel and shut off the main breaker there should be no power running to the a/c and I would be able to check w/ voltage meter to make sure nothing is live.

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So you're talking about a panel with breakers feeding the ac unit, not a branch from the main feed line into the structure? Maybe I was just picturing this wrong.
If you can kill it completely and you feel good about that, I would just offer these points then...

Proper wire size is essential. 15A=14ga, 20A=12ga, etc.
Wire per NEC, local code. Take the time to look it up, it's not that difficult even though getting info from electricians can be a pain sometimes. Just don't rush
Never run more than 80% of your amp rating. 15 amp breaker = 12 amps, etc.
Everything on a breaker, GFCIs aren't a bad idea where applicable. If you end up installing a sub panel, there is a "whole house" arc fault option for Homelite boxes I think is worth the extra $60 or so.
Look over EVERYTHING a second or third time, then have a friend look it over too before you flip the power back on.

All that said. I would assume the central AC has a double pole breaker in the main box, indicating it is 220v (240v, whatever). Knowing the amperage rating on those breakers would help

I just can't take a post serious when it has grey text on white background.

I copied and pasted the thread from another on reddit, thats why its grey text sorry.

Yea Jerry you got it. Its a main panel outside w/ a breaker feeding the AC. A couple years ago a guy my uncle knew who is an electrician installed the breaker and line going to the ac (see pic) because the house did not have enough juice before. Now I want to take that line and bring it in the house for the lights etc. Theoretically if I did get it wired correctly it should be more than enough to run my lights right?

Ha I didn't realize there was a link up there. I got one of these new fancy iPads but I don't know how to work the damn thing.
Anyway it's hard to tell from the picture. He's what I know: 2x600w=12 amps. Plus the 400 watt light and we're at 18 amps, assuming you'll run your lights on 120v. This of course doesn't account for your new window AC units, presumably also on 120v? I have no idea how much amperage yours draw, but a cursory search of Amazon tells me a standard 5,000btu window air conditioner uses about 5 amps.
So if you split that up 3 ways (3 breakers), were looking at 6 amps for the light and 5 amps for the window ac for 2 of the 3 breakers, with the 3rd being 4 amps for the light and 5 for the ac.

In that scenario, your first 2 breakers would already have an 11 amp load, meaning a 15 amp circuit on proper 14/2 would have one amp to spare...remember, 80% so 12 amps total.
Breaker 3 would have a "preexisting" draw of 9 amps for the light and ac, so a proper 15 amp breaker there would have 3 remaining amps to use for fans, etc.

A sub panel could be run and 3 15A breakers using 14/2 could be used to power outlets IF the power that feeds this box is sufficient.

We need to know the amperage rating of that breaker feeding the existing AC unit, as well as the AWG used.

where the disconect for the ac is replace it with a sub panel sized to the feed wires that are in the pic. ie. 10awg 30 amp 8awg 50 ect. then runacs and lights from that sub panel there are two hot lines so it would be a 220 circuit.

H R Puff N Stuff said:

...there are two hot lines so it would be a 220 circuit.

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To clarify, each of those hots are 110v.

If those two hots are 10awg, that means each of those wires can handle 30 amps (max) at 110v. Your new breaker box (sub panel) would have those two hot wires come in at the top, one to each hot side (exact nomenclature eludes me). That gives you 24 amps of useable 110v power from each side. The total amperage rating of your breakers may exceed 24 amps per side, your actual power draw from appliances may not.

As for neutral and ground, that depends a little. Mine have all been detached structures and the protocol for wiring those is a bit different regarding the neutral and ground, so know your code requirement and do it safely.

If you want your end appliances to run on 220v instead of 110, you'll just need double pole breakers instead of single pole in your new sub panel.

The picture shown is just a fused disconnect outside by the ac unit.

If the unit has no purpose
anymore you could cut the feed and just add a sub panel and tie it in. Sizing the panel based on the feed size (#8,10 or 12) it's important you take a look at the wire's insulation rating because that will tell you exactly what you can load it with, based on no derating applicable.

The ac unit is 220-240v (2 ungrounded conductors.)

IMO better off running new circuits from the existing panel instead you cutting the wires on the ac. You cannot tap off that disconnect and go back inside. No no!

120v lights @ 1600w = 13.33A (20amp circuit)

240v lights @ 1600w = 6.66A (2p 15A cct)

Assuming not continuous load.