Electrical - 240v outlet installation

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njohnston924

New User
Nate
[FONT=&quot]I am installing a heater in my garage and have run wiring to the new receptacle (240v). I have some electrical experience, but I want to make sure this is correct before i connect to the main panel and give power to the circuit. some details:[/FONT]

  • [FONT=&quot]30 amp, double pole breaker will be installed[/FONT]
  • [FONT=&quot]10 gauge wire (10/2 romex, white and black wires with bare grounding wire)[/FONT]
  • [FONT=&quot]30 amp switch[/FONT]
  • [FONT=&quot]wiring route: from the breaker it runs to the switch, then runs to the outlet. grounding wires are tethered together at the switch junction.[/FONT]
[FONT=&quot]
I'm having an experienced buddy check it to make sure in the next couple days, but just trying to get most of the work done up front. Any one with electrical experience that can confirm this?[/FONT]
 

Gofor

Mark
Corporate Member
Not an electrician, but that needs to be 10/3 romex. (Black, red, white, + ground). I suggest you do a little more research because it appears you are unfamiliar with 220v circuits.

If your friend is a licensed electrician, I suggest you check with him before buying/installing anything.

In NC, I believe you require a permit for that work. The inspection dept can advise you on what is required, and if ground-fault protection will be required beings it is in a garage.


Go
 

njohnston924

New User
Nate
the outlet is a nema 6-30r. from my research there is no neutral wire for this type of plug, only the 2 hots (black/red) and grounding.
How-to-wire-outlets-4-750.jpg
 

Jpalumbo

New User
Jon Palumbo
Hard to answer completely without knowing the heater info. 10-2 for 30 amp is correct and your wiring for this type of outlet is correct. there are two hot and the ground. There is no neutral on this type of plug.

I am going to stop there because you do need a permit to add work to the electrical panel and I don't want to be responsible should your house / garage catch fire.
 

ehpoole

Administrator
Ethan
Not an electrician, but that needs to be 10/3 romex. (Black, red, white, + ground). I suggest you do a little more research because it appears you are unfamiliar with 220v circuits.

If your friend is a licensed electrician, I suggest you check with him before buying/installing anything.

In NC, I believe you require a permit for that work. The inspection dept can advise you on what is required, and if ground-fault protection will be required beings it is in a garage.


Go

Note that if it is electric strip heating then there will be no neutral since it is likely 240 exclusively (no 120V circuit requiring neutral), so just the two hot legs plus ground. That said, in a shop environment it is better to encase the wiring in conduit for physical protection of the conductors (I'm not a big fan of exposed Romex).

If your heater amperage is anywhere near the actual 30A (say 24+A) and the run is of any significant length then consider upping the gauge to #8 if your outlet and switch will accept the larger gauge conductor as that will reduce the voltage drop ensuring your heater puts out closer to its full rated BTUs as excess voltage drop can significantly influence the efficiency of your heater (especially if resistive heat).

Edit: It is OK to use 10/2 Romex, you just wrap red electrical tape around the white "neutral' conductor at each end to signify it is a hot leg in a 240V circuit -- if you do not want to buy red tape then black will also suffice to indicate that the white conductor is hot (red is just harder to mistake later on). This is the same as is done when using a black conductor as either neutral (white tape) or ground (green tape) in a feeder to signify that these are not the hot legs that black would otherwise have signified, but it should be done at each end of each run length.
 

Skymaster

New User
Jack
so 8/2 with grnd for 150' run to a sub panel, pull 220v for heater/30a, the 1 0r 2 110 outlets? es ho k?
 

Bear Republic

Steve
Corporate Member
Jack beat me to it... Be careful on your run distance. The farther you go the lower gauge that is required
 

ehpoole

Administrator
Ethan
so 8/2 with grnd for 150' run to a sub panel, pull 220v for heater/30a, the 1 0r 2 110 outlets? es ho k?

We seem to be getting two competing sets of questions going on within the same thread as there was no reference to running 120V outlets in the original question?

But 8/2 should be fine to run a 240V receptacle (or hardwired) for a 30A heating accessory load with a 150ft run, but not if you also want to add a pair of 20A 120V outlet circuits as well as those loads are going to be another 20A above and beyond your 25-30A heater circuit plus they will require a neutral to get 120V (none of which is covered by the 8/2 heater circuit, they would be entirely separate runs of their own).

For that setup you may as well go ahead and consider adding another small subpanel provided the heater and outlets are all going to be in your shop area. So you would want to go for #6 copper for the two hot legs and neutral plus I would prefer at least a #8 copper for the ground and run all this into a 50A subpanel with at least four spaces in it -- two for the 30A 240V heater breaker plus one each for both 20A 120V outlet circuit breakers, taking care to ensure that each 20A 120V outlet circuit is on a different 120V leg (one on leg A, the other on leg B). This will give you a balanced 50A across both legs, worst case, and the #6 copper will be adequate to limit voltage drop to reasonable levels (particularly since you will not normally be drawing the full 50A at 240V...probably closer to 40A on average since the heater will not actually draw 30A).

But if you are going to the trouble of adding another subpanel and think you may want even more circuits down the road, then you may as well consider installing a 100A subpanel and feeding it with #2 copper feeders for the two hots plus neutral and at least a #6 copper ground. With the subpanel covering most of the run length, you can then go ahead and use ordinary #10 copper for the 30A heater circuit and #12 copper for the 20A 120V receptacle circuits within your shop space since the run length to the new subpanel will be much shorter than going all the way back to your main panel (or an existing subpanel, wherever you are tapping in). But do make sure whatever existing panel you are wishing to tap into has sufficient capacity to accept the anticipated new subpanel load since it will present a new load on that panel that did not previously exist as you do not want to be routinely tripping you rmain or subpanel circuit breakers.

If you do not wish to run another subpanel then you would run #8/2 copper all the way back to the existing panel for the 30A heater circuit plus two additional #10/2 copper runs for each of the two new 20A 120V receptacle circuits.

That said, if one has any doubts in their abilities or does not fully understand what needs to be done and why then it is really best to either hire a good licensed electrician or find a friend who is qualified (*really* qualified, not kinda qualified) to help you out as you do need to ensure that adequate capacity exists within an existing main or subpanel before adding a major new load and/or subpanel onto it. After all, if you add a 50A load to a panel that no longer has at least 50A of remaining capacity to spare then you are just going to end up with a lot of nuisance breaker trips every time you try to take advantage of that nonexistent capacity. Determining available capacity is ultimately a function of panel's feed ampacity (its "main" breaker) minus the typical and expected worst case loads (plus any upstream loads that may cut into available ampacity resulting in an effective ampacity lower than the circuit breaker feeding the panel), it is not just a matter of adding up the totals of all the circuit breakers unless it is a likelihood that all those breakers would be delivering their full rated output simultaneously -- for the proposed 50A subpanel the effective calculated load may well be in in the 40A range since the heater likely draws around 25A and you may very well have a 15A router, shop vac, or circular saw (as examples) all running off that subpanel at the same time since heat will cycle on at will whenever needed and we will often run a shop vac on one circuit and a another corded tool (hooked to the same shop vac) on another outlet circuit all at the same time. But for household circuits we rarely have every light turned on simultaneously and every outlet circuit loaded up to the max at all times plus every appliance running simultaneously, that is why you may well have upwards of 40 circuit breakers ranging in value from 15-20A to as great as 50A, or more, all fed from a single 200A service and main breaker...your effective load is the sum of everything you are likely to have running concurrently at the same time. That is a really hard thing to tell someone unfamiliar with electrical how to gauge since it is partly based upon measurement (using a clamp-on ammeter on each 120V leg) and art (educated guess to an extent) short of actually recording actual usage over an extended period (which then requires logging equipment), which is why it is good to get help when adding major new circuits where none previously existed so that you do not overload anything. Few things are more frustrating than a lot of unexpected nuisance breaker trips if a panel becomes overloaded!
 

bowman

Board of Directors, Webmaster
Neal
Staff member
Corporate Member
Thanks for the details Ethan. Where did 150' run come in? I don't see it in the OP message? I am also assuming his garage is already equipped with electricity, and I also do not see any requirements for additional 120V circuits.

What did i miss?
 

Skymaster

New User
Jack
:gar-Bi I added that comment since the original thread was very similar to what I was considering. I am between a rock and a hard place trying to find a temporary solution. Permanent solution, and the best, would be separate service but that's a lot of money right now
 

bowman

Board of Directors, Webmaster
Neal
Staff member
Corporate Member
Understood Jack.

I wound up running underground wiring from my main panel and mounted a 100A panel in my building. I think it was #2 direct burial 3 conductors plus the ground wire if memory serves. About 2 months after having it installed, I noticed one leg of my circuits only had 20V AC, the other was 120V. The contractors had nicked the insulation and water got inside the jacket and caused corrosion. They had to come back on their dime to replace the wiring. It was no small wonder my 240V DC had not burned out...

I had considered using Duke Energy to run another meter from the outside, but driveway construction and other right-of-way issues ruled that out of consideration. I would have had to pay a contractor to bury conduit from the pole for more than I paid to have the run buried from the house panel.
 

Skymaster

New User
Jack
Wake electric wants 350 bucks to run 10 ft from the transformer. Plus meter pan, inside panel ,permits, insp etc. I can find better things for 1000 bucks
 

mkepke

Mark
Senior User
:gar-Bi I added that comment since the original thread was very similar to what I was considering. I am between a rock and a hard place trying to find a temporary solution. Permanent solution, and the best, would be separate service but that's a lot of money right now
Politely..best to start your own thread as the OP has neither a 150' run, nor a need for a subpanel/separate service.

My standalone shop is 100+ feet away from the main panel..let me tell you all about it in a separate thread.

-Mark
 
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