Is This 400A Split Service Install Correct?

We have a 400A service into our home, and I am looking for guidance on how if at all to monitor it using Sense (or possibly two Sense accounts if needed). The local electrician installed the Sense, I believe incorrectly, wrapping 2 CTs around a pair of 2 big wires on each side, i.e. 4 wires total, 2 wires inside each CT going down into what is a 400 Amp disconnect swtich. As installed now, I don’t think the Sense reads properly, I think it is reading a higher amount of electricity than I am really using. Any tips would be welcome, or even a referral to an Electrician I could pay to do a zoom-based inspection (this home is in Puerto Rico). Do I have a parallel feed? I am wondering if there is any way to make sense work with our setup.

This one probably deserves a few pictures if you took them when your box was open. I have a 400A service, where the two panel feeds split immediately after the meter, and go through two separate 200A shutoffs.

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Sure, here is a photo of what I have, 4 wires (2 on each side) coming into a 400 Amp Disconnect Switch. Below that, are some smaller amperage breakers feeding several sub-panels.

That panel looks positively “industrial” compared to mine. A few more questions - where does the meter live in relation to the buses that the CTs are on (are both sets of pairs coming out of your meter)? Do you have solar ? Why do you think Sense is reporting too much usage ? If those really are the buses coming out of the meter, it looks to me like your CTs are correctly placed, but others might have additional questions.

One more thing that might be interesting is a screenshot of your Settings > System > Signals section.

Thank you, the meter is to the left of the 400 AMP disconnect, in the prior photos the door to it is closed with a little padlock, this shows where it is. I do not have Solar.

I did not think you could wrap 2 wires with a single CT. I am not sure what my setup is called - is this a parallel feed? Sense says they don’t support a parallel feed. When I emailed Sense my photos earlier in the year / late last year, they told me this configuration was not supported. So I was curious to learn from others who may have a similar 400A setup where they put their CTs and whether they used the second pair of CTs offered on the Solar version in some fashion. I was wondering if it would be better for me to get a second set of CTs (4 in total) and perhaps just use Sense to measure two of my sub-feeds which are each 200A. There are 4 disconnect switches lower down on my system, 2 are 200A, 2 are 100A, but only one of the 100A switches is in use I think. Maybe I am overthinking it.

@amd, a few answers:

  • You have something close to a parallel feed, but your branch doesn’t happen until after the big 400A breaker, based on what you have described. I have a true parallel feed, that doesn’t let me put CTs around the combined split output of the meter (so my CTs on the 2 single main buses before the meter).

  • You can clip multiple wires within a CT as long as the current flow direction and phase are the same. In your configuration, that is absolutely true. The red tape at the bottom distinguishes one phase from the other.

  • With no solar, you could get a second sensor and do the split 200A approach. Unless you are actually using more than 200A at any one time, that approach probably won’t improve things, and will preclude monitoring Solar or a generator in the future. If you do have regular usage over 200A (for the whole house), then Sense might show clipping where the monitored current/power flattens out because the measurements are out of the calibrated range.

Thank you, this is so helpful, you are a well of knowledge!

Upon closer review, I think the readings I am seeing on Sense on my total electrical usage are accurate. I was thrown off a bit when the Sense Tech folks told me late last year that my setup wasn’t supported.

However, it is struggling to identify devices and more importantly, shows a significant always-on load, which I will need to investigate further to try to trouble-shoot or narrow down. I will also look into enhancing its smarts by investing in some dedicated smart plugs that are compatible with Sense for known larger loads.

I do have a generator, however, my generator is located pretty far away from my main electrical panel. When installing a Sense to monitor both generator and utility electric supply, is the Sense typically installed in the Automatic Transfer Switch?

Edit: I am attaching a screen shot of my Settings > System > Signals

That’s great that you think it is accurate.

Device identification takes time and repetitions, plus works far better for some kinds of devices vs. others. I wrote the following to help people better understand which devices are likely to be identified and not, plus why:

Smart plugs are a good way to go. Just be careful when purchasing. TP-Link Kasa’s have worked best for me, but Kasa is moving to a new standard for communications, Matter, which is incompatible with their installed base of smart plugs that work with Sense. Buy KP125s or HS300s. AVOID incompatible KP125Ms (note the M) and EP25s (there are some older EP25s that are compatible, but it’s impossible to tell from the packaging of model #). Also watch out if using Amazon - it often offers alternate Kasa smart plugs that don’t even measure power, so look at the model numbers carefully.

Smart plugs can help with figuring out Always On because they separate out Always On vs dynamic power for each device you plug them into once they are on the plug for 48 hours or so. I recommend using one of two Traveller smart plugs before deploying more broadly. The whole methodology is described here:

As far the Generator is concerned, you want your Sense in your main panel, then run generator CTs to wherever the feed-in is to the main circuits. Sense offers extensions for the CTs if the existing ones aren’t long enough. More information on generators here: