so in previous videos on testing the protective bonding conductor here 10 millimeters squared in
a domestic dwelling i've talked about the need to make sure that the consumer unit is isolated could
be a distribution board consumer unit is isolated and you disconnect from the actual consumer unit
your 10 millimeter squared conductor under test it might be an MET a main earth in terminal when
doing it however for AM2 AM2S or AM2E they require you to disconnect this conduct to this end as well
in order to carry out the test in my previous video I talked about testing it at the screw and
the pipe work with the other end of this cable within the consumer unit disconnected or MET
however to do the AM2 AM2S and AM2E they expect this disconnected why is that they will talk about
parallel earth paths this installation here is a great example of how we've created a parallel
earth path so it could be that i'm testing here at the water but i've actually disconnected the
green and yellow protective bonding conductor for the gas you would think when testing here and the
end in the DB where your other probe is connected you've probably got a long wandering lead between
the two you'd expect to get no reading but in this case this will clearly show you that you
would get a reading so i'd be testing here at the water and potentially the other end at the gas
because of parallel earth paths so let's just pull back so that's the the pipe work in the bathroom
and this is where the other side of the wall we have um obviously metallic gas boiler and all
our metal pipe work here we've got both water and gas connections okay and i'm talking about
piped connections here as well as our protective bonding conductor just here which is going on to
our gas okay we can talk about the fact it's not in the right place obviously the safety
labels are missing etc but this video is really to show you parallel earth paths so of course
all of that metal work eventually connects down here to the water so if I was testing from here
and that the DB or consumer unit the end of the gas I would get a reading because the water
pipes end up here and it would return on this conductor which is the gas one so in order to
remove parallel earth paths for AM2 AM2S and AM2E you need to disconnect at both ends disconnect the
clamp for the gas disconnect at the clamp for the water and test your conductor I would then like
us to reconnect and test at the screw and the pipe so effectively doing the test three times for the
gas and three times for the water you would record the highest reading i'd expect them all to be the
same but you would record the highest reading that you get but this illustrates quite clearly doesn't
it that all the metal work from the gas boiler which is also connected obviously to the water
creates a parallel earth path to the water and to the gas meaning that if I test only with it
connected in this case i'm going to be picking up the return power from the gas if at the other end
i'm connected to the gas but test into the water I would get a reading but I wouldn't have proved my
protective bonding conductor is continuous because I would have picked up the return path for the gas
so back here look at that all of those parallel earth paths so during your AM2 AM2S and AM2E
examinations please make sure we turn off the consumer unit or dis-board we remove
the protective conductor under test so which bonding conductor are you using disconnect it
come down to the location where the gas and water is disconnect the conductor test it long wandering
lead between the two as shown on the channel previously in our protective bonding videos
reconnect it test again at the actual connection and that the pipe in order to carry out our
protective bonding conductor test we can clearly see all the parallel earth paths from the gas
and water being here in the same location at the boiler and obviously the water is just down here
hopefully that's explained to you why you need to disconnect your protective bonding conductor
at both ends during the test obviously with the board isolated in order to carry out your
protective bonding conductor test as always I hope this short video has been some help