Feeding surface mount enclosure from recessed panel + shorting CTs during service

Preparing to install my IotaWatt and have a few questions.

What is the recommended, code-compliant (NEC) way to run the CTs from a flush-mount main panel to a surface mount enclosure? I want to use a surface mount for IotaWatt to avoid disrupting the fireblock and insulation. I purchased the Orbit enclosure, however I need to mount this at the entrance from my garage, so this is going to be pretty obstrusive. So I would prefer a small enclosure. I have an outlet nearby from which I can supply voltage reference and power supply, which obviates the need for a built-in outlet (have to think about whether this looks better or not).

My understanding is that conduit is only needed to facilitate feeding of CTs. Off hand, maybe it is better to go through the stud on the side of the flush-mount, since the top and bottom bays are filled with wires that I’d rather not have to be careful about, however I’m open to any suggestions. It’s not clear to me how to elegantly transition from the flush mount box to the surface mount box. Would straight conduit + LB fitting work nicely?

What is the spec/schematic for shorting CTs? Is it just a dead-short from TS, or do I need to use a resistor / other pins?

Are there off-the-shelf gadgets for shorting the CTs during servicing? It would be great to get a pack of 10-20 so I just have them sitting around. Or do users usually just buy 3.5mm female → screw terminal adapters and DIY? I have a few on order from Amazon – I assume it’s OK to use non-listed components if I’m only going to have them in place during service?

It’s always ok to dead-short, however the AccuCTs have diodes to protect them while disconnected.

Code compliance is whatever the local jurisdiction says is compliant. Local electricians usually have a sense of what the inspector will approve.


Hmm, OK. Can I rely on the TVS diodes for an extended period of time (EG 1-2 weeks) if I run into a problem with the installation? I’ll also keep the parts on hand to make dead short for double the safety, just in case.

I’ll ask the inspector what they’ll accept here, and write up the plan very explicitly in how I’ll install it. Are there similar devices I can research to see how people do this flush → surface integration? (want to get ideas for how to do it neatly)

Going through the stud side will likely be hard. You have to drill through the stud and you have remove the knockout, assuming there is one.

Using an LB connector could work, if it is big enough that you can pull through it without needing to use the opening that allows for straight pulls.

Make sure you account for wire fill and pulling the wire. There is unlikely to be a real safety with wire fill, since there is very little current flowing in normal conditions. But, the inspector will probably care. The pull is likely short, but will still be hard with the extreme angle.

I was faced with the issue of a flush mount panel. I went with opening up the drywall to mount a deep (12x12x6) electrical enclosure/wiring box. That allowed me to use Smurf tube for the connections. I used 1/2" trade size, which was fine for my original CTs that have very fine wires with no ends. It doesn’t work well for the thicker wires and plugs on the newer ones. I can only fit 2 or 3 in each, so need more tubes for all my CTs.

I will probably mount the IotaWatts on the outside of the box, but haven’t gotten around to it yet.

Thanks, appreciate the info. Do you have a picture that you can share of how to go out of the 12x12x6? I don’t think that size is needed for the wire gauge of the CT cables, but it would be needed if you use large diameter nipples and the CT cables are considered big enough.

I spent a little more time thinking about the studs approach. There are knockouts on that side, and I’ve read about ways to get the knockout from either side. However it would require coming through the back of a surface mount panel for there to be an advantage in terms of installation neatness. I think that would be hard to do with smurf tubing in an insulated firewall. I might be able to use very tight 90 degree fittings, but those would be pretty hard to pull through.

Yeah, I’ll account for wirefill, I think pulling is the bigger issue if I only have data cables in there, I plan to pull in power via an extension cord. However I’m not sure what the inspector would say, I think technically it’s held to Class1 scrutiny because it goes into the panel. Might have to guesstimate on the cross section of the CT probes.

If you were to do it again, would you use a bigger trade size, or is there an advantage in your situation to use 1/2" still? I have a ton of 1/2" smurf tube sitting around from another project, but i’d rather just have one conduit. Split loom would probably be a lot easier to work with, however that will run in to the Classification issue. I doubt the inspector would appreciate split loom going straight out of the panel.

I’m planning on using a media cabinet or smaller NEMA1 box instead of the orbit, since the NEMA3 (or whatever) is overkill and leads to the orbit box being massive.

The 1/2" is really too small and not an advantage. A bigger conduit is better. The box is PVC so easy to drill.

I didn’t have to deal with fire stopping, since my panel is not in a garage.

I haven’t cut holes in the top yet, so no pictures.

This is what I did:
Those studs are NOT load bearing so I was able to pass two 1" conduits and 1/2" for electrical.
The idea is that I will have 3 IoTaWatts in total. In one conduit I was able to pass 1 1/2 CT wires.

I will have an inspector in the next 2 weeks come and look at my install…

Thanks. How did you plumb the power (voltage reference and USB PSU) into the box?

On the left, I have space for 3 USB adapters. You can see on the right a distribution block.

I am trying to use some chassis mounted transformers:

I am yet to figure out if I will get good results…
Right now I am monitoring the phase and each split (2 120V transformers, and 1 240V transformer). Most likely I won’t need all but I am experimenting a bit this round.