In this q a video we'll be answering the question do I need to install
a double pole rcd to protect an ev charge point
this question relates to the recent video that i made on the new consumer unit from luden so please
do go and check that video out after this one but what's prompted this question about
double pole rcds well we get asked quite a lot about this on our channel when the
subject of ev charges comes up and we've also heard reports that even some wholesalers
aren't familiar with what a double pole rcbo is so let's try and clear it up a bit
first of all we're going to turn to the regulation in question that's causing the fuss we'll find it
in section 722 which is concerned with electric vehicle charging installations and specifically
regulation 722.531.3.1 now i'm reading this from the second amendment to the 18th edition of
bs7671 and it says rcd shall disconnect all live conductors gloriously simple so surely in a single
phase system a single pole device will suffice as it disconnects the live conductor but hang on a
moment why does it say live conductors plural obviously it must be referring to three-phase
systems where we need to disconnect all three phases is that right no this is where we need
to be really careful about how we read and apply the regulations let's look at it again
it says all live conductors and if we turn to the definitions section of bs7671 the definition for
live conductor sends us to live part where we read a conductor or conductive part intended to
be energized in normal use including a neutral conductor but by convention not a pen conductor
so in a single phase supply for an ev charge point we would need to install rcd protection that
disconnects the line and the neutral generally speaking we're moving away from split load boards
that have an rccb protecting several circuits but in principle as long as this wasn't a type ac rcd
and the other requirements of section 722 were met then this would be an acceptable device to
use for more information on the different types of rcd and ev installations please check out
the free accredited training modules that we've made on these subjects they count towards your
annual cpd requirement and can be accessed via the links in the description below what about
if we're using an rcbo to protect our ev charge point how can we tell if the device is acceptable
well first of all there's the manufacturer's data to consider but often you can tell just by looking
at the symbols and diagrams on the devices first of all if we look at the diagram on this other
device you can see that it shows the incoming line conductor going through a little bump and then a
square and then a switch contact with an x on the other side so let's break that down a little bit
the bump means the device has magnetic over current protection good for protecting against
fault current the square indicates thermal over current protection good for protecting against
overload the switch contact indicates that the line connection will be disconnected if there's
a fault or the switch on the front is operated and the x indicates that the disconnection mechanism
inside can withstand braking and making fault current it then carries on up through a loop and
out to the circuit and the load now let's consider the neutral conductor for this device can you see
it just comes in through that loop and then off to the load that loop represents a current
transformer which is how the device looks for high impedance earth faults again check out our
free training module for more information however what's really clearly missing from here is any
form of switching device in the neutral connection therefore when this device trips it leaves the
neutral connected in many situations this is not a problem think of all the thousands of single pole
mcb's you've installed over the years that leave the neutral connected when a fault occurs however
if this device is used to protect an ev charge point then it doesn't comply with regulation
722.531.3.1 now what about this device it's the same width as the single pole rcbo we just
looked at so will this be acceptable well again looking at the diagram on the front here you can
see that the line conductor is very similar to the previous one we've got the same symbols along its
length but turning our attention to the neutral conductor you can see that now it passes through
a switch as well before it goes off through the current transformer and off into the circuit and
load you'll also notice that there's this tiny dashed line connecting the two switches together
so that when one contact is operated the other is two meaning that in the event of a fault
all the live conductors that's line and neutral in this case are disconnected it is just worth noting
that there's no over current monitoring on the neutral conductor in this device you see there's
no bump or square in the incoming connection there it isn't needed because that's all taken
care of and monitored on the line connection so it would be a bit redundant so it's not like
a double pole mcb that would monitor both the line and neutral for overcurrent so sometimes
you may hear this referred to as single pole with neutral switching or double pole but either way
this rcbo would be suitable to disconnect all live conductors if used to protect an ev charge point
so there we go that's why it's really important to make sure that our rcd protection
is disconnecting all live conductors and also how to tell if a device is suitable or not
of course there's lots more to consider for both rcds and ev charger installation so please keep
your knowledge refreshed and up to date by looking at our free training modules that we mentioned
earlier but as always we want to hear from you are you installing ev charge points we were aware
that the rcd protection needed to disconnect the neutral too whatever your thoughts and questions
please leave them in the comments section below and as always thank you very much for watching