Recetly, I am in the process of installing a nema 14-50R (receptacle) which is rated for up to 50Amps. The double pole circuit breaker itself is rated for 45amps. The cable is nominally rated for up to 55amps (6/3).
I am mostly familiar with nm-b (romex) cable, bx, thhn, etc. In a nec publication, the table 310.15 shows the ampacity for current carrying conductors (in cables, raceways, conduits) but this tables does not mention nm-b (or romex).
The cables I bought has 3 current carrying conductors (and ground) and is rated for up to 55 amps. It is made by Southwire, and is named Romex Simpull . Looking in the aforementioned table, the best fit would likely be the first column and seventh row: which shows 55 amps, thus likely the TW type of cable. UF probably means some type of underground rated cable. Is that a correct assumption? In other words, TW = nm-b?
Below is the aforementioned table:
Also, the nema 14-50R receptacle will used in the garage whereby the load center is located. So, the installation is very straightforward. Codes and regulations can be finicky sometimes; so, I was wondering if there would be any problem in installing the receptacle right below the panel (rectangle pointed by arrow) besides the other regular receptacle, as shown in the pic below:
In the nec, nm is stated to use the 60deg.C column for sizing even though nm is not a conductor type listed in the table.
See NEC 334.80. TW is not nm.
You can use that plastic snap-in fitting, or use the NM clamp and simply clamp it to the wire before feeding it into the panel. Then attach the locknut like usual. Both are code-acceptable methods.
NEC requires 6" extending out from the front of the box, but I'm sure no one is going to take a measuring tape to confirm you are accurate. IMO, on such a short run, it's not like it's a huge issue if you need to make changes. If it were across the house, I'd be more concerned about a few extra inches for future changes.
Also, technically the way you're exiting that box isn't compliant with the way the box is listed. It should be exiting through the existing wire clamps as you're not allowed to drill boxes in general. But, similar to the above statement, I personally wouldn't have much heartburn with it as the clamp is securing the cable safely.
I believe that the side of the clamp with screws should face down, but even if it faces up (inside the panel) if I was to tighten the screw it would not fit. With screws side facing down, it would imply removing more drywall (what I really don't want to do).
Install the cable clamp on the cable first before inserting it into the panel with the locknut taken off. Slide the wire into the panel and secure the cable clamp using the locknut. Loosen the screws in the plastic box and remove any slack as needed. Retighten the plastic box cable clamp.
In a detached structure subpanel with an isolated neutral bar the grounding electrode conductor from the ground rods connects to the ground bar, not to the isolated neutral bar.
NM-b cable has THHN wires in it but is limited to the 60-degree column for ampacity. At the 60-degree column #6 is rated for 55 amps. Code allows to go up to the next size breaker as 55 amps is not a standard size breaker. However, a 50 amp (or your 45) breaker is fine as well.
Yes, you can install the receptacle under the panel. You should use a 2 gang plastic remodel box unless you want to open the drywall. Make sure to use the proper NM cable connectors to attach the cable to the panel.
Also, just on a side note. Looking at the panel the bar of the left side which is the ground bar. The bar is on insulators which separates it from the metal panel. I can't see because of the wires in the way but is there a grounding screw or grounding strap connecting from the ground bar to the metal cabinet?
Good to know that. But they should at least allude somewhere in the table or footnotes that the 60 degrees columns would apply to nm-b/romex since that is what is used in the vast majority of the cases nowadays.
I am using a 45amps breaker because it was easier to find and had a better price point. Besides, it is very unlikely to there be a need for more than 40 amps. The cable is so short in this cases that I went with 6/3.
I am planning on installing a new work electrical box (not a retrofit type) due to the fact that the spot for the electrical box is right beside a stud. It is a dual gang pvc box with depth adjustment, 34 cu inches and about 3 inches of depth. I don't feel confortable installing a high voltage receptacle in something as flimsy and weak as sheetrock. Below is a pic of the box:
My understanding is that about 3 inches of wires should be protruding from the opening of the box. I am having a hard time fitting (or cramming) an extra 3 inches of wire of such gauge (6 awg) inside that box.
On another issue related to securing the cable to the panel:
I believe that the side of the clamp with screws should face down, but even if it faces up (inside the panel) if I was to tighten the screw it would not fit. With screws side facing down, it would imply removing more drywall (what I really don't want to do). Would the following type of cable clamp be adequate for that type of installation?
The ground bar is connected to the panel encasement via screws. And it is connected to a ground rod and bonded to the neutral.
If the main service panel the ground rod should be connected through the Grounding Electrode Conductor to the neutral bus, not the ground bar. And then the neutral bus should be bonded to the panel box and ground bar.
If the main service panel the ground rod should be connected through the Grounding Electrode Conductor to the neutral bus, not the ground bar. And then the neutral bus should be bonded to the panel box and ground bar.
It has been a long time since I installed an electrical panel. My understanding is that the ground conductor coming from the ground rod needs to be connected to the ground bus. And the chassis/panel is grounded.
My understanding is that AFJES was concerned about the panel/chassis itself not being grounded. But it is grounded.
Last edited by tk3000; 11-28-22 at 09:17 PM.
Reason: complement the info
You can use that plastic snap-in fitting, or use the NM clamp and simply clamp it to the wire before feeding it into the panel. Then attach the locknut like usual. Both are code-acceptable methods.
NEC requires 6" extending out from the front of the box, but I'm sure no one is going to take a measuring tape to confirm you are accurate. IMO, on such a short run, it's not like it's a huge issue if you need to make changes. If it were across the house, I'd be more concerned about a few extra inches for future changes.
Also, technically the way you're exiting that box isn't compliant with the way the box is listed. It should be exiting through the existing wire clamps as you're not allowed to drill boxes in general. But, similar to the above statement, I personally wouldn't have much heartburn with it as the clamp is securing the cable safely.
Good to know that plastic snap-in fitting would be acceptable. Clamping to the cable first sounds like a good approach, I will give it a try.
I used to get confused about whether the 6" of wire would extend from the point of entry in the box (raceway or cable sheathing) or would be measured from the opening in the box. It seems that the 6" is as measured from the point of entry, but at least 3" should extend from the opening of the box. If 6" is as measured from the opening of the box, I would be screwed in this case considering how difficult it would be to fit that amount and type of wire inside the box.
The hole and clamp on the side of the box as shown in the pic are part of the box design. I did not drill the hole there.
My understanding is that the ground conductor coming from the ground rod needs to be connected to the ground bus. And the chassis/panel is grounded.
Nope. The idea is to solidly ground the neutral conductor so the Grounding Electrode Conductor should be terminated on the neutral bus. There is a lug just for this. The green neutral bonding screw that is usually shipped loose then gets installed to bond the grounded neutral bus to the panel box thus grounding it. When a ground bar is used at the main service panel (which isn't required) only the Equipment Grounding Conductors are terminated on that ground bar. This is the procedure for the main service panel, subpanels are slightly different.
In a detached structure subpanel with an isolated neutral bar the grounding electrode conductor from the ground rods connects to the ground bar, not to the isolated neutral bar.
This is not a sub-panel, but the main panel.
In this case, neutral and ground interconnected. The main difference between neutral and ground is that the neutral is alive -- connected to the center-tap of the secondary transformer. Current does alternate between the hot and the neutral. Also, the resistance to the passage of current to the ground and neutral differs.
I went to install a new cabinet wall oven. The original owner had installed the old oven with a 240v plug at the base of the cabinet. The installation was not right and the oven was not grounded. The new oven installation guide says it needs to be hard wired. The new install requires the junction box at about the 4 foot level. The conduit is not long enough on the new oven to reach the junction box at the base and still allow the oven to be slid out. Can I run a conduit connection to a 2nd box at the 4 foot level and hard wire both boxes? The base box is behind a drawer in the wall. To raise the junction box to the 4 foot level would require uninstalling a number of cabinets.
The old breaker is 50 amps. The new oven only requires 20 amps. I need to downgrade the breaker, correct?
I have a few questions if someone can help me understand.
First, is it normal that in the picture with the yellow tester, OPEN GROUND is lit instead of CORRECT? Keep in mind it is a LIFEPO4 battery connected to an inverter. I guess this would make sense because there is no ground wire in the battery. Still, just want to run this by the experts.
Second, If I buy a few more of these LIFEPO4 batteries and Parallel connect them to the inverter, what is the best connectors to do this as well as FAST and SECURE? Right now, I am using SPADEs for the battery terminals and I am using RINGs for the inverter terminals. I prefer not to use Alligator clips. I really don't like the RINGs either. Anything else I can use for FAST and SECURE connections?
Third, any thoughts on how I have used the 5.5mm connectors? Should I avoid using them and maybe stick something like EC5?
Fourth, the wires/cables are 18 AWG.
[b]A few reasons for the sudden interest in this setup:[/b]
Last time when I traveled for vacation, TSA was not going to let me proceed forward with my car battery jumper since it is more than 100Wh. My alternative is to buy a LIFEPO4 6-8 Ah.
**I want to run my hedge trimmer but it has been a hassle to run the extension cords. So setting this up with an inverter has helped me make my current electric hedger into a portable one. LOL, "the poor man portable".
**I want a backup battery system for my cameras, routers and a bunch of other stuffs in the case if the power goes out at my house.
[b]NOTE:[/b]
**This maybe ignored since the LIFEPO4 Power Station that I bought on Black Friday may have resolved this interest.
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11-21-22, 03:57 PM
