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New install for social alarm system PSU

Stewart Mason

Hi

I'm going to let the photo speak for it's self. The RCBO is powering a PSU with battery back up, which is powering a social housing alarm system. All the equipment is mounted in a steel cabinet on the outside wall of a bungalow. The supply is a TNCS.

All comments will be gratefully received.

Thanks

  • 0

    £8 could have been saved by using an MCB instead of the RCBO.

    Or £20 could have been saved by retaining the ordinary main switch.

    The RCD main switch may trip on a surge or even be damaged by it.

  • 0

    I can't make out the residual rating of the incomer RCD - if it were an S-type (100mA or 300mA) it might not be unreasonable (if still probably more expensive a setup than it need be for TN). A 30mA upstream of an SPD would be a bit silly though.

       - Andy.

  • 0 in reply to AJJewsbury

    it is one of these  RTA630302

    looking that up it appears to be a 30mA type A for £20 + VAT ;-)

    https://www.ukelectricalsupplies.com/fusebox-63a-30ma-type-a-double-pole-rcd.htm

    The main switch would be  less than a third of that

    https://www.ukelectricalsupplies.com/fusebox-100a-2-pole-isolator-main-switch.htm

    Mike

  • 0

    Thanks for the replies.

    My main issue is the power supply being protected by RCDs. If one of the RCDs was to trip, it would leave "X" number of properties without a social alarm system and no way of calling for help. The power supply does have battery back up, but there is no monitoring of the system. Unfortunately I am not familiar with BS8604-1 and the requirements for not using RCDs. 

  • 0 in reply to Stewart Mason

    It will depend if it has been wired in a way that can avoid an  RCD - perhaps SWA or steel conduit but if it is in twin and earth or something there may not be much choice.

    Mike.

  • 0 in reply to mapj1

    Its all surface. Out of the consumer unit and straight into the PSU, less than 50cm of flex. All contained in a metal cabinet.

  • 0 in reply to Chris Pearson

    That's my concern, the main RCD tripping due to a surge. I have raised this with the consumer unit manufacture - they have not replied.

  • 0 in reply to Stewart Mason

    I wouldn't be overly worried about a RCBO feeding the alarm supply, it clearly isnt needed, but what really is going to cause it to trip?

    Very little, and if it does trip, it shows the RCD could have been needed.

    Overall, it's a poor installation, no discrimination between the RCDs, and no real need for the RCDs.

    I suspect it would have been a domestic installer, or someone who mainly does domestic work that installed it, as anyone with a clue wouldnt have done it that way. I've had 2 'discussions' with different people in the last week about codes for EICRs. 1 was a single socket outlet , 2.5mm T+E, fed by a 32A CB. It was coded as a C2. His reasoning was that the cable rating was 27A, so should have a breaker less than that, and, another with a 6mm T+E feeding a 8.5kW shower on a 45A CB. Another C2 was given due to the cable only having a CCC of 41 Amps, when the shower could only pull 35 amps at 240V. That he was going to fit a  32Amp CB to replace the 45 did not register that it would not comply as the demand was greater than the overcurrent device.

  • 0 in reply to alanblaby
    alanblaby said:
    I suspect it would have been a domestic installer, or someone who mainly does domestic work that installed it

    That may or may not be the case!

    I can just imagine those "pre-populated" little CUs being on "manager's special" at around £25, so what's not to like? I am not sure that I'd want one in my own house though.

  • 0 in reply to alanblaby
    alanblaby said:
    I've had 2 'discussions' with different people in the last week about codes for EICRs. 1 was a single socket outlet , 2.5mm T+E, fed by a 32A CB. It was coded as a C2. His

    Agreed Alan. It doesn’t help when it is on the City andGuilds 2391 assessment with the required answer being a code 2! 

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