Are Hager MTN MCBs backwards compatible with Hager MT MCBs? EVSE consumer unit upgrades.

An apparently straightforward question

  • I watched an Efixx video earlier and it was said a Hager consumer unit with MT MCBs is obsolete and adding additional MCBs is the consumer unit is not viable but it  already has a MTN in it, which maybe doesn't help to prove a point?

    The EV consumer unit installation is certainly a good job, but it does seem rather over the top.

  • I think it is a bit of a red herring. EFIX are a training company which is heavily supported by many mainstream manufacturers who donate their switchgear and accessories. Of course efix will say that the mcbs in question are unavailable, and then go on to showcase a new cu and surge protection device. It's all part of the deal. Plus, as a professional training organisation they need to project the right image.

    I agree about it being over the top, but it also struck me they seemed happy about the omission of RCD protection for the supply cable running through the garage, which has no mechanical protection which makes it subject to potential damage by rodents for example. I was once called out to a similar set up a few years ago whereby the householder was turning a set of double ladders around inside the garage and whilst doing so, caught the T&E run which fed 2 fluorescent lights. The corner of one of the ladder feet dug straight in and caused a short circuit trip.

  • Only Hager could answer the question as to whether they say the MTN is compatible with the MT unit.

    OK, I take the point regarding "no less safe", but if someone made it "less safe" in the first place, that's no excuse for another installer to follow suit.

    Finally, no-one (including BS 7671) has said you can't fit other devices into a consumer unit, but that the original manufacturer won't be responsible for the assembly. This is clearly logical and reasonable, and was also the case before BS 7671 reminded us about it - a manufacturer can only test what they know, not every eventuality! This also might help:

  • Did the newer consumer unit have a device not from the original manufacturer installed? I didn't pay 100 % attention to the manufacturers involved and have not researched compatibility, so I'm not making a statement about that (it may be OK), just highlighting for further discussion.

  •  Graham,

    The thing with that old chestnut is that in reality it is just pure protectionism. All such kit has to be made to BS60898 for example, and that should be good enough. Just look at who comprises the BEAMA membership roll for the answer. Also, many manufacturers use a common supplier of mcbs and just re-label them with their own branding. So does this mean that a different label on 2 identical mcbs makes them incompatible?

  • We are now going to mix two conversations and discussions.

    I read some of the comments on YouTube and it seems that installing a new tails from Henly blocks and a new consumer unit alongside the existing is seen as the way to install a supply for EVSE, to avoid taking any responsibility for any issues in the existing installation, rather than fitting a two pound fifty MCB in the existing consumer unit and working from that.

    In the video there is a SPD in the new consumer unit, but it’s not OEM from the consumer unit manufacturer, which doesn’t help the argument in favour of fitting an additional consumer unit because the existing has “obsolete” devices.

  • The thing with that old chestnut is that in reality it is just pure protectionism. All such kit has to be made to BS60898 for example, and that should be good enough.

    That depends upon how specific the BS is. It would be a queer business if one could only use MK plugs in MK sockets. However, the two types of Wylex MCB are certainly not interchangeable - the busbar won't fit.

  • I was stood looking at a consumer unit a few days ago and thought this looks good and actually said to the customer it is one of  the best consumer units I have seen in a house, which it is.

    However there is not any spare ways and it actually needs upgrading for installation of EVSE and I came away wondering if it would actually be easier to fit an additional consumer unit. 

  • I can't understand the objection to the fact that the manufacturer can only test what they have available?

    Or are we saying that BS EN 60947 series ought to provide more standardization in terms of physical properties?

    Having said that, things are a little more tricky these days, as products to other standards are incorporated into these Assemblies.

    The best advice I can give, is to provide proposals for the relevant standards (in this case, that's not BS 7671), and perhaps to concede the fact that a manufacturer of a product cannot be liable for every eventuality of the in-service use or modification of their products.

  • Agreed - but isn't this a design decision of the original installer ... and the manufacturer ... that leads it to where it is now?