QR code 2 -- Protective supplementary bonding test

[@Ayrtech2009]

I like this guy I could sit in a classroom and listen to him all day he has a good clear approach explains things well, keep the videos coming Chris

[@cfgman9176]

@Linda, what Chris is trying to explain when the resistance is less than 1667 ohms the 30mA RCD will trip because 30mA fault current will flow. When the resistance is higher than 1667 say 2000 ohms the fault current will be 25mA and therefore the RCD will not trip as its rated at 30mA. The result will be a touch voltage approaching 50V on the metal work which could be lethal. We need to some how reduce the resistance so that its below the critical 1667 ohms (remember anything below this will trip the RCD).... hence supplementary bonding within that zone helps to bring the resistance down. Practically that means connecting the metal work via a single core cable to a CPC on an adjacent fitting say pull switch of a shower circuit; there is no requirement to take it back to the MET. I hope that helps.

[@Moley8W]

Another great set of straightforward well-explained vids...thanks Chris! :)

[@Andrew-ke6ik]

thank you so much this really helps alot

[@PJB71]

excellent this guy

[@train4905]

Superb

[@zapszapper9105]

We are a bag of salt and water, we have stuff all resistance when our skin is wet.

[@lindagomez7179]

Surely, at 1:56, if the resistance is less, it does need bonding.

[@londontrada]

no, as the reading is low enough we can be confident that enough fault current will flow. If it is higher then the current may not flow so it needs to be bonded.

[@colinhumphryes5664]

Can someone explain why the need for supplementary bonding in the bathroom in the example shown as its showing an installation containing a 30 mA RCD and calc from the that to find 1667mA to see if bonding is required or not. In IEE regulation 701.415.2 (v) states all sup bonding may be omitted providing "All final circuits of the location have additional protection by means of an RCD in accordance with regulation 701.411.3.3" so unless lighting circuits are not protected by the RCD It would seem supplementary bonding is not required or am I missing something?

[@ja_adam_]

Should we be doing this test every new installation and on every EICR???

[@dominicryan2783]

Do you test at 230v or 500v as the formula on the video is at 230, but often if you're testing d.c. you need to test at a higher level. So do we jump up to 500v test? Or do it at 230?

[@Prawnchowmein]

This is confusing I've watched this over and over. Please can someone explain, how come the voltage used is 230v for the calculation in a bathroom instead of 50v and why do you bond the extraneous pipe work if you get A resistance reading under 22000 ohms in a bathroom but you don't bond the pipe if you get 1667 ohms outside of a bathroom, I just don't get the logic.

[@crigeorge9549]

I measured resistance from one finger to another and is not 1000 ohms. is somwhere aroun 1300 koms. how come? I used a cheap multimeter. Trying with a megger 1730 at 500 v I got 0.07 Mohm, so 70 kohm. Still no close to 1000 ohms. The test was from one hand to another and from one finger to another finger of same hand, on a 500 v insulation test. Got little electrocuted by my megger :)

[@peterstiles1]

1,000 ohms is when you're wet - like you could well be in a bathroom. Dry it's often quoted around 100,000 ohms - pretty much what you found.

[@madcatmolly]

Where i get confused is, when is supplementary bonding required?

[@keithdunn9497]

what about a shower test,why carnt a polumber fit shower,

[@Kk-hs4qf]

Metal part is extraneous if the resistance. Is between 1.6K and 20K. Am I right ?

[@crigeorge9549]

yep

[@mattthompson8657]

It's also extraneous if it's below 1.6k, it just doesn't require any supplementary bonding

[@TeamSimpsonRacing]

Great video. Could you please answer me this please? If the resistance is below 1667 ohms or above 22000 ohms it doesn't need bonding. It only needs bonding if its inbetween those readings?

[@geoffball5803]

@@peterstiles1 Great info but could you clear a couple of things up that are confusing me. A. Why hasn't the live exposed conductive part tripped the MCB or RCD if fitted? (is it a case of not low enough resitive contact between the live of the final circuit and the exposed conductive part which is connected to the circuit cpc?, thereby not creating enough fault current to trip the device) B. You're suggesting that more current would flow through the person in point 1) vs point 3) but youre saying point 3) is more dangerous situation?

[@geoffball5803]

@@peterstiles1 Thanks for taking the time and effort to reply, I'm still a little confused though. obviously your point 2) is very clear and I get that but at points 1&3 i'm imagining the path to earth is from the line conductor touching the exposed conductive part through the person who is touching the exposed part and whilst simultaneously touching the earthed extraneous part, so the current path in 1&3 is identical? If that being the case I can't see that the bonding will help limit the current through the person at all, if anything I'd imagine more current to flow through the person as the low resistence path of the bonding is incouraging more current to flow through the person as the person is the only link from the live exposed part and the extraneous metalwork.... I'm obviosly not getting something with this, I totally get how metalwork with a resistance over 22k is safer as this would be high enough to discorage current flow through the human path

[@zapszapper9105]

How much current do you need for continuity test"?

[@johnj5467]

lol

[@crigeorge9549]

you mean how much voltage.

[@peterstiles1]

According to GN3, 18th Edition, page 109: 200mA