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RCBO Energy Consumption/Losses

Just refitted a large consumer unit with Wylex miniature RCBOs.  Looks like a decent compact product.  When energised on no load the metal CU casing ran about 5 degrees C above immediate surrounding ambient (in a very large cupboard).  Wylex spec says full load losses are 1.5 to 2.6W per pole and these are two pole devices.  I think this would break down between no load loss and a loss that varied with current (along the lines of copper and iron losses with a t/f).

Given the temperature rise I observed (which so far as I can tell with my cheap IR thermometer) is uniform across 20 devices the standing no loss dissipation is likely around 0.5W plus each.  Whilst this will keep consumer units warm it will also add to bills.  A 20 device CU with 0.5W per device will use 87kWh costing about £13 pa.  

I haven't got the kit to measure the losses accurately but this is certainly something to think about when specifying larger installations.

Looking across other manufacturers I see Hager quoting 3W for a single pole RCBO at full load so the Wylex unit does well by comparison.

Has anyone measured the standing losses on these and other 'electronic' devices? 

I expect we will see a new section in the Regs on losses before long given the increasing focus on energy efficiency.
  • I wonder how much of that is down to the electronics. I can understand that resistive losses will be there (and increase with load), but I would have hoped that the electronic "standby" use had been minimised (along the lines of reducing standby current for things like TVs). However, this probably won't happen if there is no legislative drive for it.


    Of course, the "standby" use will be a very low percentage if the circuit has a significant load most of the time, but I can see a lot of domestic installations where that won't be true (your figures would add about 3.5% on to my house bill).
  • Has anyone measured the standing losses on these and other 'electronic' devices? 


    I've posted several times about parasitic USB outlets built into double sockets which in a typical domestic, probably exceed your figures..................


    Regards


    BOD
  • Part of the problem is that there is limited space for a 'proper ' power supply, transformer and so on, so it ends up being a capacitor and resistive dropper, with attendant inefficiency, and it has to be able to fire the actuator, so the active devices have to be quite bosky, not 1.8volt microamp CMOS logic. A custom chip on a mixed voltage process,  could be a solution to that, but I suspect there is not the market volume to justify that yet.


  • Realistically, for an establishment big enough to require 20 circuits, the cost of installing and running those circuits is going to absolutely swamp the £13 pa overhead.
  • perspicacious:
    Has anyone measured the standing losses on these and other 'electronic' devices? 


    I've posted several times about parasitic USB outlets built into double sockets which in a typical domestic, probably exceed your figures..................


    Regards


    BOD


    My observation ... our kids leave their plug-in USB chargers plugged in and switch on the socket-outlet left on, all of the time anyway ?


  • Given that the values quoted are per pole, I suspect these are I2R losses, predominantly - with a small contribution to the operating op amps


    At the other end of the scale, a 3200A ACB could easily be putting about 800W into a switchboard cubicle


    Fuses also have quite significant I2r losses as a comparison - often more than ACB's


    Regards


    OMS
  • gkenyon:
    perspicacious:
    Has anyone measured the standing losses on these and other 'electronic' devices? 


    I've posted several times about parasitic USB outlets built into double sockets which in a typical domestic, probably exceed your figures..................


    Regards


    BOD


    My observation ... our kids leave their plug-in USB chargers plugged in and switch on the socket-outlet left on, all of the time anyway ?




    Time to educate them then.


  • Hello Statter. Thank you for posting this, and thank you to the forum members that have replied! I had cause to tidy up my 19-way full-RCBO Wylex plastic consumer unit 18 months ago, and replaced it with a corresponding Wylex metal-cased unit.  As always, I took great care to make sure that all terminations were correctly made and secure. I subsequently noticed the metal case was always about 2 deg C above ambient and this has puzzled me until I read your post and the replies.  I never noticed the thermal gain on the old plastic consumer unit as it would not manifest itself to the same level on the plastic case. Now I know why - interesting!

    Regards,

               Colin Jenkins.
  • Thanks Colin, interesting that you saw a 2 degree rise.  Were these SP RCBOs or double?
  • This level of static dissipation with no load is ridiculous, I would expect a few mW maximum as there really is nothing which needs any power in an MCB or RCBO. A few cmos op amps need a few microamps, and the supply should be via capacitive dropper and simple zener stabilizer. This sounds like another design problem which needs to be sorted.  A few measurements of an electric nature rather than temperature are indicated.