Usage not matching meter readings

[chrismiller49@gmail.com]

I’m based in the uk, so single phase 240v supply.

My supply is split onto two meters, one for heating, the second for domesitc loads. I have a 200A ct clamp on the output of each meter.

I’ve downloaded the exported data and I find the sum of the measured consumed power is fairly close for the heating circuits. However for the domestic loads the difference between the meter reading and the measured power consumption by the emporia is out by about 50%. Any ideas?

One other observation, I’ve got a load of LED lights in one room, when these are swiched on the power being measured appears to go down. Clearly this isn’t the case. Any ideas? I’ve check the clamps are on the correct way round.

 

[djwakelee]

The 200A clamps are for connection to single phase, split phase (aka 2-phase), and 3-phase mains (1-3 ports and clamps used depending on electrical service).  For the UK, you are 240V (50Hz) and single phase.  That would mean you would use a single 200A clamp for your combined mains power feed (before both meters).  You can’t use another 200A clamp (on the A/B/C ports) to measure a separate circuit, such as you are trying to do with heat and other loads.  That is where you would use the 1-16 ports and the 50A clamps.

If you can’t place the single 200A clamp before the two meters (physically, etc), you can purchase a 3.5mm Y cable and combine (2) 200A clamps into the single A port.  That way you can get the combined reading for your domestic loads and heat, and clamp after those meters.  If you want to then know the individual power in each, that is where you would add the 50A clamps (connected to ports 1-16) and clamp those around the circuits you want to specifically monitor.

After you make this change, you’ll probably want to re-setup the software as it is surely confused by seeing power on something other than the A port for a UK installation.  It is probably improperly assuming split-phase currently, if you are indeed using port B (which shouldn’t be being used for single phase).

Hope that helps.

• This reply was modified 3 years ago by djwakelee.

[chrismiller49@gmail.com]

Thanks for your replay – very helpful. Does the unit assume the second input is out of phase with the first, hence why i’m seeing the power  at a lower than expected level?

i’ll adjust my clamps as you suggest.

cheers

[djwakelee]

Yes, for a split-phase setup where you’d use the A and B clamps over each 120V leg (like here in the US), it would expect those to be 180 degrees out of phase with each other.  And if 3-phase power, 120 degrees out of phase for each A/B/C clamp.

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