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

Thanks,

Chris

JLMCDANIEL

See attached
Jack

Attachment:
christech

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

JLMCDANIEL

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

Timothy Miller

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

Ernie_Fergler
Timothy Miller wrote:

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.:D