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Prewiring 240V Outlets

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Forum topic by Steinbierz posted 09-14-2020 09:13 PM 449 views 0 times favorited 34 replies Add to Favorites Watch
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Steinbierz

132 posts in 984 days


09-14-2020 09:13 PM

Hello,

I am in the process of wiring my 1500 sq. ft. wood shop and want to install a fair number of 240v outlets throughout. I have a couple of pieces of equipment where I already know what the recommended breaker and receptacle/plug size is but not certain how to size all of the rest that are just waiting for my wife to let new equipment be plugged into them. One buddy of mine said to make them all 30 amps (breaker/wire/receptacle) and good to go…change plugs later if you have equipment with 20 amp plugs on them. I’ve read varying degrees of answers to this with some saying that my buddy is correct but others saying that the breaker also needs to be changed to 20 amps.

I have a whole bunch of 8 ga. so that is what I will be pulling in the conduits. Instead of installing the 240v receptacles now, I am somewhat inclined to coil the wires in the receptacle boxes and put blank covers on them and maybe coil the wires in the circuit panel as well until I have a specific need (I’m not real crazy about the circuit panel idea and not certain it is to code either). Thoughts?

-- Larry ~ Alvin, TX (Home of Nolan Ryan)


34 replies so far

View LeeRoyMan's profile

LeeRoyMan

1399 posts in 574 days


#1 posted 09-14-2020 09:40 PM

Are they all going to be on dedicated circuits?
Run all your conduit and boxes, then wait to pull wire when you get the machines you want.
That way you can size the breaker and wire accordingly.
Probably only takes about 1/2 hour to pull wire and hook up plug and breaker.

-- I only know... what I know....

View squazo's profile

squazo

185 posts in 2493 days


#2 posted 09-14-2020 09:57 PM

I would make them all 20 amps for the 120volt circuits, nothing really takes more than 20 apms.

View controlfreak's profile

controlfreak

1217 posts in 449 days


#3 posted 09-14-2020 10:04 PM

I would pull the No. 8 and blank the unused. that way you have the right wire and can match the breakers to the outlets later.

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Steinbierz

132 posts in 984 days


#4 posted 09-14-2020 11:15 PM



Are they all going to be on dedicated circuits?
Run all your conduit and boxes, then wait to pull wire when you get the machines you want.
That way you can size the breaker and wire accordingly.
Probably only takes about 1/2 hour to pull wire and hook up plug and breaker.

- LeeRoyMan

All dedicated! Most, but not all, will be pulled in the same conduit as 120 circuits so would rather do the pull together rather than trying to pull wires later. There might be some spots though where your idea would work.

-- Larry ~ Alvin, TX (Home of Nolan Ryan)

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Steinbierz

132 posts in 984 days


#5 posted 09-14-2020 11:16 PM



I would make them all 20 amps for the 120volt circuits, nothing really takes more than 20 apms.

- squazo

Thanks…that’s my plan but my questions was about 240v circuits.

-- Larry ~ Alvin, TX (Home of Nolan Ryan)

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Steinbierz

132 posts in 984 days


#6 posted 09-14-2020 11:20 PM



I would pull the No. 8 and blank the unused. that way you have the right wire and can match the breakers to the outlets later.

- controlfreak

Thanks…that’s kind of how I’m leaning right now.

-- Larry ~ Alvin, TX (Home of Nolan Ryan)

View Mario's profile

Mario

201 posts in 4244 days


#7 posted 09-14-2020 11:48 PM

My shop is roughly the same size, all circuits 120 & 220 run on 30 amp breakers, that way I limit resetting breakers while performing heavy machining, 30 amp is still safe in case you have a mayor malfunction and 8 ga. wire is dead on for keeping your machines going.

View pottz's profile

pottz

11215 posts in 1832 days


#8 posted 09-15-2020 12:16 AM

well i just checked the 220v in my shop and everyone is 20amp,i run 2 -3 machines at once sometimes and never blow a breaker.im no electrician so dont hold me too it,i just know what i have and it works fine.

-- working with my hands is a joy,it gives me a sense of fulfillment,somthing so many seek and so few find.-SAM MALOOF.

View CaptainKlutz's profile

CaptainKlutz

3586 posts in 2342 days


#9 posted 09-15-2020 01:09 AM

Power planning is frustrating. It is really easy to do much and never use it all. :-(

Also hard to recommend another man’s shop setup?

Suggest you think about your current and future tools by motor sizes, and then consider the special cases:

2-3HP – 20A
4-5HP – 30A
7.5HP – 50A

IME – For average hobby work shop, 30A for 5HP motor everywhere usually works.
But if you plan to install a large wide belt sander, then you might need 50A.
Do you have a welder that needs 50A?
If you plan to use phase convertor for 3 phase tools, that changes the plan too.

With 8AWG wire, assuming THHN can run any 230v tool up to 7.5 HP.

Another factor to consider is 3 wire or 4 wire power at each outlet. Most tools need only 3 wire. But I like running a couple 4 wire boxes when planning future possibilities, especially on the long runs away from panel?
It brings the neutral and allows 120v lamp on tool or small sub-panel. But then I over engineer stuff often. :)

FWIW – All my tools are mobile and get moved around a lot.
I put in several L14-30 and a 14-50 receptacle in last couple shops. For some tools I use smallest 4 circuit breaker box with a 120 & 240 plug on side, so I can power my band saw and the overhead light with one power cord. Did same for TS work station. Have 240v plug for TS, and 120V 20A for router table, leaving only one power cord to trip over. :-)

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

View Fred Hargis's profile

Fred Hargis

6415 posts in 3341 days


#10 posted 09-15-2020 10:28 AM

The breaker wouldn’t need to be 20 amps in your description. The breakers are to protect the wiring and the building, not the device plugged onto it. So using a 30 amp circuit on a 20 amp tool isn’t against any code. That said, I wouldn’t be afraid to do as you suggested, coil the wires in the box, but I would probably not put them in the panel, maybe make a hatch above/below the panel to access the wires when need…and label them of course. Good luck coiling 8 gauge wire, it’s tough enough with 10 gauge.

-- Our village hasn't lost it's idiot, he was elected to congress.

View bmerrill's profile

bmerrill

118 posts in 921 days


#11 posted 09-15-2020 01:19 PM

This may help.

Ampacity of THWN Copper wire size, 75C° for circuit runs up to 100 feet. Over 100 feet use next wire size.
14 Gauge = 15 AMPs
12 Gauge = 20 AMPS
10 Gauge = 30 AMPS 8 Gauge = 50 AMPS
Match breakers to the wire size.

Search for Conduit max wire fill. Don’t want to over fill the conduit.
ROMEX is also a good choice.

-- You are not told the truth, you have to learn the truth.

View Steinbierz's profile

Steinbierz

132 posts in 984 days


#12 posted 09-15-2020 01:35 PM


Power planning is frustrating. It is really easy to do much and never use it all. :-(

Also hard to recommend another man s shop setup?

Suggest you think about your current and future tools by motor sizes, and then consider the special cases:

2-3HP – 20A
4-5HP – 30A
7.5HP – 50A

IME – For average hobby work shop, 30A for 5HP motor everywhere usually works.
But if you plan to install a large wide belt sander, then you might need 50A.
Do you have a welder that needs 50A?
If you plan to use phase convertor for 3 phase tools, that changes the plan too.

I have a Phase Perfect 30 HP unit for the four pieces of 230V, 3 phase equipment that I have: 7.5 HP table saw, 7.5 HP band saw, 5 HP DC, and 5 HP Jointer/Planer. I am planning for future growth for my three phase equipment as well but this is a little more predictable e.g. 5 HP air compressor.


Another factor to consider is 3 wire or 4 wire power at each outlet. Most tools need only 3 wire. But I like running a couple 4 wire boxes when planning future possibilities, especially on the long runs away from panel?
It brings the neutral and allows 120v lamp on tool or small sub-panel. But then I over engineer stuff often. :)

i hadn’t put a lot of thought to this but it makes sense to maybe run some 4 wire circuits!


FWIW – All my tools are mobile and get moved around a lot.
I put in several L14-30 and a 14-50 receptacle in last couple shops. For some tools I use smallest 4 circuit breaker box with a 120 & 240 plug on side, so I can power my band saw and the overhead light with one power cord. Did same for TS work station. Have 240v plug for TS, and 120V 20A for router table, leaving only one power cord to trip over. :-)

Very little of my equipment will be mobile although that doesn’t mean that I have exactly nailed down where each piece is going to go…have a reasonable idea though considering how my work flow will work given the layout of the building. I like the combo plug that you linked above…what wires do you have to pull for that?

BTW…great reply! Thank you!

-- Larry ~ Alvin, TX (Home of Nolan Ryan)

View Robert's profile

Robert

3932 posts in 2328 days


#13 posted 09-15-2020 01:37 PM

8 gauge wire requires a 50A breaker. That might run your whole shop! Unless you’ve got a 10HP machine somewhere.

Plus, how are you going to wire a 220V outlet? You would need a dryer plug.

12ga/20A 240V circuits will run any machine 3HP or less. For a hobby shop you can run them all on one 20A circuit.

The exception is a dust collector or a big compressor, they need dedicated circuits.

-- Everything is a prototype thats why its one of a kind!!

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Steinbierz

132 posts in 984 days


#14 posted 09-15-2020 01:50 PM



8 gauge wire requires a 50A breaker. That might run your whole shop! Unless you ve got a 10HP machine somewhere.

Sorry but this is no more true than to say that if I ran 12 ga. I HAVE to install 20 amp breakers.


Plus, how are you going to wire a 220V outlet? You would need a dryer plug.

Not certain I get your point. Granted, a NEMA 6-20R won’t take any higher than 10 ga. but a NEMA L6-20R can take 8 ga. All 30 amp devices will take 8 ga.


-- Larry ~ Alvin, TX (Home of Nolan Ryan)

View pottz's profile

pottz

11215 posts in 1832 days


#15 posted 09-15-2020 02:20 PM


8 gauge wire requires a 50A breaker. That might run your whole shop! Unless you ve got a 10HP machine somewhere.

Plus, how are you going to wire a 220V outlet? You would need a dryer plug.

12ga/20A 240V circuits will run any machine 3HP or less. For a hobby shop you can run them all on one 20A circuit.

The exception is a dust collector or a big compressor, they need dedicated circuits.

- Robert


i agree 8ga. is pretty heavy are you gonna be running a business in this shop.hell my whole shop is all 12ga.never had a problem in 28 years.most of my machines are 220v sometimes im running 3 at a time with dust collection.i agree do more than you think youll ever need but sounds like your goin way over.

-- working with my hands is a joy,it gives me a sense of fulfillment,somthing so many seek and so few find.-SAM MALOOF.

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