EM with 50A and 120A clamps

1. offizieller Beitrag
    • Autor

    Is it possible to have an EM with one 120A clamp and one 50A? I'd like to monitor the whole house and separately the feed to my home office.

    The main breaker is 100A so I guess I need a 120A for the main feed, although I can't imagine ever drawing that much! It's a 4 bedroom house but 100A! I can easily get to the MCB output that feeds the office and one other room but that's close enough, that's a 32A ring main breaker so 50A is plenty.

    Maybe I should risk it and get 2x 50A, especially as the 120's seem to be out of stock right now.

    Does anyone have experience of how much is really drawn by a house with only two people in it? We have gas heating but an electric oven, I have a lot of power hungry network equipment in the office, which is why I want to measure the usage.

    Even 50A seems a lot, I am an Electronics Engineer so I do know what 50A means. ;-)

    According to my knowledge, the difference between a 50A and a 120A clamp is primarily the size of its core and its point of maximum magnetic saturation. The clamp won't be destroyed if you measure i.e. 70A with a 50A clamp - but its reading will be heavily distorted.

    • Offizieller Beitrag

    Hello AndreNewman ,

    The Shelly EM is designed for one phase only! Two measuring contact outputs means 2 measurements over 2 loads of one and the same phase!

    The Shelly 3EM is better suited for this! Measurement phase 1, 2 and 3.

    The measuring transducers (120A) of the 3EM are connected via plugs, the EM has open cable ends.

    Separate measuring transducers (120A) are not available in the store, contact the support here.

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    • Autor

    Thanks for the comments, I ordered two 50A clamps in the end and they arrived yesterday, I decided I could always order a 120A one later if it was required. The UK store lists the clamps separately but is out of stock of the 120's.

    I'm measuring only one phase just two different loads within a few inches of each other, I'll risk it with the loading, pretty certain it won't ever get anywhere near 50A.

    I was more interested to know the setup and limitations of the Shelly EM

    Hopefully get it installed this weekend.

    • Autor

    Answering my own question in case someone else looks for the info:

    The em has separate setting for each clamp so it's possible to set one to 50A and one to 120A completely independent.

    I installed it earlier today and found that the 50A clamp wasn't physically big enough to fit around the 100A input cable so that's another factor, I hadn't though of. I was able to fit it around the cable from the utility before it goes in to the meter, not sure why that's smaller but it fits exactly and will be measuring the same thing.

    The second clamp on the feeds to the upstairs ring main works perfectly, both on the same phase as pointed out by SparkyMaster. That has two cables wired to the breaker, feed and return for the ring main I expect. Current reads correctly with both through the clamp.

    About to cook sunday dinner so will see how much juice that uses :-)

  • SparkyMaster 20. September 2020 um 16:11

    Hat das Label Shelly EM hinzugefügt.