Maximum current rating of CTs and or Sense

What is the maximum current rating for the CTs and or Sense box. I have 400 amp service into two panels and am considering putting the CTs at the meter box so I can monitor whole house. I have 3 ACs, 3 children home all summer in a newer house such that hopefully dont run together that often.

Really the question might be what happens when you go over 200 Amps on the CTs and Sense box.



1 Like

I’m using a Sense with a 400A service, with 3 EVs (up to 80A charging per car) and 2 ACs. Seems to calibrate and work just fine.


Hey Greg. We’re rated up to 200A. You have find that everything works at a higher amperage, but we definitely cannot guarantee it. The most likely failure will be just seeing clipping in your power meter, but there may be failures beyond that.


In reality, even though we have a 400A panel, the max power we’ve run up to is 36kW when two cars are charging concurrently. That’s pretty balanced across both legs at 220V so that’s only 163A or so. So the reality is that a 400A service probably never needs to deliver more than 200A.

1 Like

That’s definitely fair to note. It’s rare that you’ll hit the full 400A, but once you go over 200A, it’s just hard for us to say exactly what will happen.



Here’s what the delivery mains for a 400A service look like… Note that we had to open the meter side of the box in order to install our Sense.


Question: If connecting a Sense to a 400a service like this, is there any danger of damaging the Sense unit? (I understand that it might not work properly as it might clip the inputs)

I have a friend with a house (lodge) that is at the end of the end of the power grid in the middle of nowhere. He has a 400a electrical service and is having issues with devices (electronics and such) dying. I was hoping to get him a Sense in order to monitor power quality to try to diagnose this remotely since the house is a vacation home and not occupied all the time.

I think the issue is either that their transformer is too small (25kW even though he has a single instant water heater that is 38.5kW) or that power quality at the end of the line is so horrible that they get regular spikes/surges/undervoltages.

I will have to get the utility to allow access to the metering cabinet in order to get the CT’s around it so I wanted to understand what the ramifications would be of putting a Sense on it. If the data was just inaccurate at high loads that would be one thing, but if it damages the device that is a different story.

Obviously the voltage monitoring would work which is fantastic (though seriously - can I have a graph of voltage per phase leg pretty please!!!) :wink:

This is the main service panel I am working with. No good way to get a single set of CT’s over the entire feed without getting into the metering cabinet. Sense really needs a solution for these 400/320a services.

1 Like

I know this is old but was trying to find a picture to point people to that showed how sense would be wired for 400 amp service in some situations.
What stood out to me is the wire size below the meter. Hopefully that’s solar coming in because that aluminum wire looks to be size 4 and would be very undersized for 400 amps.