# Thread: Calculating Wires Allowed in Electrical Boxes

#### Hybrid View

1. Junior Member
Join Date
Jun 2009
Posts
19

## Calculating Wires Allowed in Electrical Boxes

Hello All,

I'm trying to determine if any the boxes I've wired have too many wires. I am using all plastic boxes and 12 gauge NM wire with no clamps. This is how I'm calculating the allowed number of insulated wires allowed for the boxes I'm using. Please let me know if my method of calculating allowed insulated wires is correct??

Example 1:
=========
Double Gang Switch Box (34 CUI) --> 34/2.25 = 15 wires allowed. Now subtract 1 wire for the ground & 2 wires for each switch (2*2 = 4) = 10 insulated wires allowed.

Example 2:
=========
Single Gang Switch Box (22 CUI) --> 22/2.25 = 9 wires allowed. Subtract 1 ground - 2 wires for the switch = 6 insulated wires allowed.

Example 3:
=========
Ceiling Box (25 CUI) --> 25/2.25 = 11 wires allowed. Subtract 1 for ground = 10 insulated wires allowed.

Thanks,

Chris

2. ## Re: Calculating Wires Allowed in Electrical Boxes

See attached
Jack

3. Junior Member
Join Date
Jun 2009
Posts
19

## Re: Calculating Wires Allowed in Electrical Boxes

JLMCDANIEL,

None of my boxes in the table you posted correspond to the box CI's I have installed. Is my calculation based on the box CI correct?

Regards,

Chris

4. ## Re: Calculating Wires Allowed in Electrical Boxes

Yes, your calculations appear to be correct for the CUI you listed.
Jack

5. Senior Member Rank 2
Join Date
Mar 2009
Posts
1,387

## Re: Calculating Wires Allowed in Electrical Boxes

Howdy, Are you including the ground wires in your rule of thumb? And are ya counting the wire nuts?

6. Banned Rank 2
Join Date
Jun 2007
Location
Shamokin, Pa.
Posts
645

## Re: Calculating Wires Allowed in Electrical Boxes

Originally Posted by Timothy Miller
Howdy, Are you including the ground wires in your rule of thumb? And are ya counting the wire nuts?
Remember to include the devices when you calculate your total.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•