# CT wire and jack diameters to estimate knockout and conduit size needed

I was searching the forums before buying trying to estimate what size conduit I would need, and found a few discussions but no measurements. I thought I would post some measurements here so if anyone else searches for this they can find it.

I have the AccuCT 50A and 200A currently sold in the store. I didn’t find any difference in the size of the cable or jack between the 50 A and 200 A versions, but all the measurements include two 200 A CTs and then the rest are 50 A. I measured with digital calipers, and I tried to err on the side of over estimating when it came to bundles where it was hard to measure the diameter without squeezing the bundle. Consider these the absolute minimums, and remember conduits shouldn’t be 100% filled.

``````1 cable           =  3.5 mm
1 jack            =  9 mm
4 cables          =  9 mm
3 wires + 1 jack  = 13 mm
5 wires + 1 jack  = 17 mm
14 wires          = 19 mm
13 wires + 1 jack = 25 mm
``````
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So it sounds like 14 wires is the most that can fit in a 1” conduit?

Well since you’d need to pass the cables through one by one you’d care about the 13 cables + 1 jack number so 25 mm, which is 0.984 inches. So technically seems like it’d fit, but I don’t know what the actual internal diameter of 1" conduit is, it may be slightly less than 1". Also, it’d be super difficult to fish through, so I wouldn’t even try it unless you were only going like 1 foot.

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``````The NEC specifications are:

One wire: maximum fill is 53% of the space inside a conduit
Two wires: maximum fill is 31%
Three wires or more: maximum fill is 40% of the conduit’s total available space
Using the wire cross-sectional areas you’ve already calculated, you can now determine the minimum conduit size that you need.conduit
``````

Those specs are there because the wires the NEC usually deals with are carrying a lot current and heat up, so need space to dissipate. If your work is inspected it will likely need to meet code. Even if it isn’t, it is a good idea to make sure it does.

I went with 1-1/4" PVC conduit, and it fit my 14 CT’s plus 14/2 power cable easily.