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My GEM installation - part 1, main panel

published, Aug 28, 2012 3:59am
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I received a few request to describe the installation of my Brultech GreenEye Monitor (GEM for short). My house has an old main panel, and I recently added a sub panel as part of a major house rewiring. My intent was to monitor both panels using the Brultech GreenEye Monitor.

I plan to cover this in a few installments: main panel wiring, sub panel wiring, Brultech wiring, Brultech config, software setup.

Main panel

This is the main panel. It has two 2-phase groups (for the sub panel and the dryer), and several 15A and 20A circuits. Two of the circuits are currently not used.

Main panel


The CT installation in the old main panel. You can see I used the (much cheaper) "donut" CTs for everything, including the main service. This is not a trivial operation, and you have to be very comfortable with electrical systems before you attempt this yourself. When in doubt, get an electrician to do it. It takes about 30 minutes. Don't even think about doing this with the power on the panel. You can kill yourself.

Main panel CTs


All CT connections are zip-tied together, and exit the panel through a nippel on the left. The nippel is critical to avoid chafe on the CT cables. The nippel is connected to a square box.

Main panel CT detail 2


The CT splices in progress. Since I have two panels, and the monitoring unit is about 20 feet away, I decided to simply use CAT5 cables for the signals. CAT5 is typically 24 AWG, which is the same as the leads of the CT themselves. As you can see I used multiple CAT5 cables, each named A-F (one spare). The CAT5 and the CT leads are spliced using 3M telecom crimp connectors. It's still a little messy, but the cables will later be grouped together by CAT5 cable and bundled with two zip ties. Every CT lead is labeled with the circuit number to reduce time-consuming troubleshooting later on.

Main panel CT splice in progress


The finished splice box. The 6 CAT5 cables go up to the joists, and run inside ceiling bays to the monitoring panel. The Square box received an extension ring to avoid having to jam the bundles into the box. Cover plate and straigforward labeling finishes the job.

Main panel CT finished


Part 2 will cover the sub panel installation.

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Ooo, switchboards.  Love em.

Nice post!

Sam, @samotage

More to come Sam :).

Hi Sandeen,

I did.

in more detail: after I ran the cat5 cables to the splice box and separated the pairs, I cut the CT leads and each cat5 twisted pair to the same length as I was wiring them up. I ligned them up, zip tied them when they would meet in the back of the box, then cut them so the lead and cat5 pair would stick outside of the box evenly, about 10cm. The 3m splice connectors were crimped on, then one more zip tie near the connector to keep the wires together and avoid a tangle, and finally a label for future identification.

I consider this installation permanent, in the same way that a breaker or panel is permanent. Perhaps in the future you make a modification, in that case you can possibly reuse the CT in that position, or add amother one. Since the splice box is right next to the panel, it's easy to fish another CT lead into the splice box.

Hi Sandeen,

officially that's a question for your AHJ (Authority Having Jurisdiction), but in my case (in the USA), I reasoned that the cat5 carries low voltage, and conduit is typically required when line voltage is exposed and can be subject to damage. So it should be fine without conduit. 

My rule of thumb is to use materials for the purpose or context they are intended for, since it all is designed to go together, and you won't have problems where things don't fit well. Hence my use of metal boxes, nippels and metal connectors, since that's what's made for connecting wiring (which would typically be line voltage) to a panel.

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