Double-Pole, Single-Pole, North Pole.. What on earth is everyone talking about?
Here we are going to cover the main considerations you should be making when choosing between different types of consumer unit, so let's jump straight in.
What is a consumer unit?
A consumer unit in 230V electrics refers to the enclosure that houses the protective devices for the circuit.. You What? .. Don't panic!
We can guarantee you are already familiar with the consumer unit, as every house in the UK has one. It's commonly referred to as the 'Fuse Board' and is usually found in the entrance to your house. Okay.. You're back in the room!
What does it do?
The consumer unit itself does very little, except act as a housing for the circuit protective devices; the Residual Current Device (RCD) and the Miniature Circuit Breaker(s) (MCB). In short, the MCB's job is to protect the circuit and the RCD's job is to protect the user.
So a consumer unit with an appropriate RCD and MCB('s) that are correctly rated will provide protection to both the circuit and the user.
Single Pole / Double Pole
In simple terms, the difference between single pole and double pole consumer units is the difference between the type of RCD and MCB('s) contained within the unit.
Single Pole units (as in the kit on the right) will only contain single pole MCB's.
Double Pole units (as in the kit on the left)will only contain double pole MCB's.
A single pole MCB only 'breaks' the live connection between the incoming circuit and the final circuit.
A double pole MCB 'breaks' the live and the neutral connection between the incoming circuit and the final circuit.
What Do The Engineers Say?
Simply put, in the "Requirements for Electrical Installations, IET Wiring Regulations, Eighteenth Edition (BS 7671:2018)" under Section 721 "Electrical Installations In Caravans and Motor Caravans" it states that the RCD's should break all live conductors and that the overcurrent protective device (in this case an MCB) should also break all live conductors..
Note: live conductors are considered to be both live and neutral cables!
.. are you still with us?
What does this mean for us?
Well this is where the wonderful grey area comes in for those of us who convert vans in to campervans, as these are not considered "Caravans" or "Motor Caravans" in BS7671:2018. Which also complicates things further as there are cases of electricians who will happily sign off installations in campervans with single pole consumer units and cases where other electricians will not.
So there is no wonder that there are a large number of Home Built Campers (see what we did there?) with single pole consumer units installed in their vans.
Why is this important?
This topic becomes important when we consider something called "reverse polarity". Which is where there is a supply (in this case, from a campsite) with the live and neutral wired the wrong way around. This will still power your devices and you would not know any different, however your device would no longer be protected by a single pole MCB. With a double pole MCB the devices connected to this circuit would still be protected from potential over-current.
Note: Reverse Polarity is known to be common in some European countries.
What are our recommendations?
Note: To be clear, the author of this column is not an electrician, nor are they offering electrical advice.
If you consider your campervan build to be similar to that of a "Caravan" or "Motor Caravan" then the regulations suggest you should be looking to install a double-pole consumer unit with the appropriate protective devices.
All electrical installations should be undertaken by a competent person and inspected and tested by a fully qualified electrician.
What does Home Built Campers Have To Offer
Our team here at Home Built Campers have put together a range of 230V kits which are based around three different consumer units. One of which is a single pole unit and the other two are double pole consumer units with additional polarity indicator light.
All kits have been designed with the correct rated cables for the consumer unit and all are fully customisable to your needs. Should you have any additional requirements from our kits, please do not hesitate to contact us and one of the Home Built Campers team will get back to you as soon as possible.
We hope this article helps !
We are passionate about the community we are part of, and always work hard to provide information that is of real value to those of you building your campervans!
We look forward to seeing you out on the road!
The Home Built Campers Team.