Electrical FAQs

Brandmer · Dec 11, 2020

Can you advice me any books about this?

wyliesdiesels · Dec 11, 2020

Norcal said:
Here is a list of UL HP rating for attachment plugs, not sure if the link will work. If anyone wishes to edit this feel free to do so.

http://www.owwm.org/download/file.php?id=316453

Im not able to download it. says not authorized

AP514 · Dec 26, 2020

wyliesdiesels said:
Im not able to download it. says not authorized

Same here...

beelsr · Dec 26, 2020

you need a login for the forum - can't see attachments if you're not logged in - just like here.

Downloaded it and converted to jpg - the PDF was an image anyways and way oversize and converting it to text just ***** for tabular info.

wyliesdiesels · Mar 14, 2022

U/L letter regarding suitable replacement breakers for crouse-hinds panels/breakers

https://www.garagejournal.com/forum/attachments/ul-breaker-substitutions-murray-mh-t-crouse-hinds-1-pdf.899842/

wyliesdiesels · Jun 23, 2022

comprehensive chart of Pre-NEMA flat blade receptacles and plugs

Museum of Plugs and Sockets: pre-NEMA types

Pre-NEMA plugs and sockets

www.plugsocketmuseum.nl

William Payne · Mar 2, 2023

I feel this should be added somewhere in this site. You USA guys know your electrical system but get a bit confused about how things work in many other countries that are 230/400v 50HZ WYE. So maybe this may help.

wyliesdiesels · Mar 2, 2023

William Payne said:
I feel this should be added somewhere in this site. You USA guys know your electrical system but get a bit confused about how things work in many other countries that are 230/400v 50HZ WYE. So maybe this may help.

Wye connected systems dont confuse me

We have wye connected systems here.

208Y/120, which sometimes feeds residences and almost always apartment complexes.

480Y/277 which is used in industrial plants...

My shop has 208Y/120v...

William Payne · Mar 2, 2023

wyliesdiesels said:
Wye connected systems dont confuse me

We have wye connected systems here.

208Y/120, which sometimes feeds residences and almost always apartment complexes.

480Y/277 which is used in industrial plants...

My shops has 208Y/120v...

Yeah but you know what you are talking about. You haven't spent multiple pages on the internet trying to explain why USA 240 and our 240 aren't the same thing.

wyliesdiesels · Mar 3, 2023

William Payne said:
Yeah but you know what you are talking about. You haven't spent multiple pages on the internet trying to explain why USA 240 and our 240 aren't the same thing.

Looks like your systems are 230/400, so not the same as 120/240.... the problem comes up when people call your system 240v... instead of 230v...

William Payne · Mar 3, 2023

wyliesdiesels said:
Looks like your systems are 230/400, so not the same as 120/240.... the problem comes up when people call your system 240v... instead of 230v...

For us it can be 230-240 due to voltage variation. See in the old days it used to be 240/415 volts. But over time everything just got standardized to a more commonly used 230/400 which covers the allowed voltage variance

Norcal · Mar 3, 2023

William Payne said:
For us it can be 230-240 due to voltage variation. See in the old days it used to be 240/415 volts. But over time everything just got standardized to a more commonly used 230/400 which covers the allowed voltage variance

The EU chose 400/230V as the "harmonized" voltages, some EU countries were 380/220V, & others were 415/240V, so in order to harmonize things 400/230V was chosen, nothing changed but everyone was under one standard.

William Payne · Mar 3, 2023

Norcal said:
The EU chose 400/230V as the "harmonized" voltages, some EU countries were 380/220V, & others were 415/240V, so in order to harmonize things 400/230V was chosen, nothing changed but everyone was under one standard.

That is exactly it.

PCustoms · May 14, 2023

Bump, can someone add/confirm insulation ratings and what is allowed indoors?

CoronadoBruin · Aug 3, 2023

The Cobbler said:
Hope this is useful
Common Power Cords (NEMA 120V 15A)

NEMA 1-15P: Two-prong plug.
NEMA 1-15P: Two-prong plug.
The Non-polarized version has two equal straight blades.
The Polarized version features 2 blades with one being wider.

NEMA 1-15R: Two-prong receptacle.
NEMA 1-15R: Two-prong receptacle.
'receptacle' connectors would have holes that would accept a plug with prongs to be inserted.

NEMA 5-15P: Three-prong plug.
NEMA 5-15P: Three-prong plug.
Features 2 straight blades with a third round or U-shaped ground pin. The ground pin is longer than the two blades which ensures the device is grounded before the power is connected.

NEMA 5-15R: Three-prong receptacle.
NEMA 5-15R: Three-prong receptacle.
This will be what you would typically see in your home (USA & Canada) as a power outlet or on the female end of a power extension cord. You would also see this as the receptacles on a surge strip.

Laptop

C7: Figure Eight.
C7: Figure Eight.
Non-Polarized connector featuring a 'figure eight' shape with two holes.
Although we list as a notebook power cord, the C7 connection is used in many devices.

C7PW: Polarized connector.
C7PW: Polarized connector.
Has basically the same shape as C7, but instead of rounded 'figure 8' style, one of the sides is flat, allowing the connector to only be inserted one way.

C5: Three-pin connector.
C5: Three-pin connector.
Typically connects a laptop power brick to a wall outlet.
Polarized connector. The shape of the connector prevents shocks. Sometimes called a 'Mickey Mouse' cable due to the resemblance to a certain cartoon character's silhouette. Also called "cloverleaf."

Computer/Monitor

C13: Three slot connectors.
C13: Three slot connectors.
Features a dog-ear shape and the three slots are in a staggered vertical orientation.

C14: Three prong inlet receptacle.
C14: Three prong inlet receptacle.
Features the same dog-ear shape as the c13 with 3 blades in a staggered vertical position.

Server/Appliance

C19: Three-slot connector.
C19: Three-slot connector.
Used in Enterprise-class servers and data center rack-mounted PDUs.
Rectangular with four rounded corners, and three staggered blades in the same orientation (horizontal).

C20: Three-prong Inlet receptacle.
C20: Three-prong Inlet receptacle.
Rectangular with four rounded corners, and three staggered slots in a recessed receptacle (horizontal).

Four years late, but...

From Generator Joe https://www.generatorjoe.net/html/web/outlet/quailplug.html#60

This helped me when installing the garage a/c

Screen Shot 2023-08-03 at 10.29.20 AM.png

Norcal · Dec 25, 2023

Here is a FAQ from Schneider Electric regarding SQ D Homeline breakers being used in competitive panels . BTW, they can't be used and be code compliant.

Are the Homeline Branch Breakers Classified (or does Square D authorize them) to be used in competitors load centers? | Schneider Electric USA

wyliesdiesels · Mar 28, 2025

another topic that often comes up on this forum is load calcs. Theres many calculators online but unfortunately we have no way of knowing how they are programmed and how accurate they are.

Mike Holt had a spreadsheet on his website years ago (I think it was made by one of his students) that is easy to understand. unfortunately, it seems he removed it from his website in place of an app.

here is a link to Mike Holts apps and calcs

Mike Holt Enterprises - the leader in electrical training.

Mike Holt worked his way up through the electrical trade from apprentice electrician through electrical contractor, to become one of the most recognized experts in the world as it relates to electrical power installations. He was a Journeyman Electrician, Master Electrician, and Electrical...

www.mikeholt.com

EDIT: I have attached several versions of the spreadsheet that used to be on Mike Holt's website, made by one of his students. I also found another load calc sheet on another website. All are attached in zip file that you can download.

I also found another website with a PDF formatted spreadsheet here

https://www.ladbs.org/docs/default-source/forms/inspection-forms/sfd-electrical-vehicle-charger-service-load-calculation-form-in-form-00.pdf

Disclaimer: I have not used any of these yet so I dont know how they line up.... use them at your own risk...

wyliesdiesels · Jun 21, 2025

load calc worksheets have been attached in previous post

Carchie · Apr 25, 2026

Great idea starting a sticky for the basics. It’ll definitely help clear up the common NEC questions that pop up every week for those of us in the US.

mm08822 · May 5, 2026

Letter from Siemens regarding Siemens CBs in Murray panels.......

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