Max CT mA output - readme says 33mA peak max, but recommended models sold by your company go all the way up to 100mA. about expandable-6-channel-esp32-energy-meter HOT 3 CLOSED

Hi Alex,

I realize the documentation is a bit confusing. It does need to be updated.

For dual pole circuits, each hot is going to carry half of that load (assuming the thing on that circuit isn't using 1 hot for 120V power only). See here on the different ways you can monitor 2 pole circuits.

So, depending on how you would like to set this up determines what CTs you will need. Likely either 4 80A CTs or 2 100A (also depends on the wire size).

from expandable-6-channel-esp32-energy-meter.

Hi John,

The confusing bit is regarding the output of the CTs. The documentation says:

Current Transformers (any combination of the following, or any current transformer that does not exceed 720mV RMS, or 33mA output)

However several of the CTs you recommend have 40, 50 and 100mA outputs. I found some YHDC CTs that are 50A and have either a 50mA or 100mA output (not specified on amazon product page) so based on the CTs you recommend I figured they would be compatible. I should get a tad bit of added resolution since the CTs' measured current range is closer to what may flow on those breakers compared to using the 80/100A CTs.

I plan on measuring:

200A main breaker
2 x 200A CTs (Edit: 100 to 200. Just confirmed that each split phase is the full 200A)

40A Oven breaker
2 x 50A CTs

30A Dryer breaker
2 x 50A CTs

When the addon boards are back in stock, I may expand the system to also measure the 2 HVAC systems.

from expandable-6-channel-esp32-energy-meter.

Hello,
For the records : the max voltage ATM90E32 can measure is 720mV (with gain=1). Considering the 6-channel have 22Ω burden resistors, that means the maximum current you can flow through the burden is I=U/R=0.720/22 = 32.7mA

Using a 5Ω burden would allow to use SCT up to 144mA but with a lower resolution.

Did I miss something ?

from expandable-6-channel-esp32-energy-meter.