How interchangeable are DIN rail MCBs.

[Ed Sirett]

Question as per title.

Is the answer don't even try. Or usually OK. Or always OK.

[Guy King]

The message from Ed Sirett contains these words:

I've not yet found one that won't.

[Matt]

Don't even try. The only thing that is compatible is the rail fitting (sometimes) and the terminal for the wire. Virtually every manufacturer seems to use their own busbar setup. MK even have two incompatible busbar systems - old and new.

[Nick]

Seconded

[Guy King]

The message from Matt contains these words:

I must have been very lucky then. I've fitted perhaps half a dozen over the years and they've always just plugged in. I don't recall any of them being the "correct" ones.

[John Rumm]

Sort answer is it depends. Often you can, but there are plenty of exceptions.

I started a thread about this last year... Alas it never got much interest. However it may help:

[Andy Wade]

Three, actually:

(i) the original type with U-slotted fingers for Siemens MCBs;

(ii) single finger type when they changed to Merlin Gerin components c.

1992 - this type had a wider finger for the incomer connection and finger bent over at 90 deg. from the bar;

(iii) the current K type, flat with all fingers the same and generally a bit thinner and cheaper-feeling.

[legin]

Always worth a try.

interchangeable. In fact put the MCB's side by side and they even have the same markings on the side. I guess produced in the same factory and then badged accordingly. GE and Steeple being another example where by they are almost identical and I have found to be interchangeable with the Marbo/ Volex. Hager slightly different but will usually fit. Crabtree totally on there own with there own unique plug in MCB's. I know from previous threads that this has been favoured by some and with the more ample head room in the CU for terminations. For me it is a concern as if any thing went wrong in years to come what will the availability of breakers be? As for other makes I cannot comment. It has been a while since I have fitted a Wylex or MK board. Shame really because I would have tthought that these would be the better items. However in this day and age it seems that the price appears to be more important to the customer, especially when the products work. Unlike boilers I suspect? Ed, A friend of mine used to fit a lot of WB but has changed to Vaillant cos he reckons that the circuit boards were more suspectable in the WB. But I also know that the rep messed him around a bit and there may be some sour grapes. I would be particularly interested if you have fitted many and if you have noticed any failure patterns. Soon to choose my own system boiler and I cannot choose between the two.

Regards Legin

[tinnews]

My answer would be somewhere between the first too, try it and it may be OK. The usual problem is incompatible bus bars.

[Christian McArdle]

They usually fit (but not always, and sometimes with cosmetic issues). However, they often come with dire warnings not to mix manufacturers' products as it invalidates the type approval. This alone might cause the panel to fail inspection.

Christian.

[HLAH]

Wylex and MK will fit the same DIN rail in a MK box but the bus bars are quite different, I don't think they would mix.

H

[Dave]

They do mix but you need to bend the busbar. It's OK if you can group the same type together then you only need one bend.

[Ed Sirett]

In this case we have a number of issues and the panel failing it's type approval would be the least of my concerns with the unit.

1) The downstairs sockets, alarm and immersion on the non-RCD 2) We have all the lighting and the rest of the sockets on the RCD side. 3) The 20A double oven was wired as an unfused spur direct off the 32A ring. 4) There are blank plates missing in the spare ways on the breaker box.

etc.etc.

[Andrew Gabriel]

Whilst I generally rate MK accessories very highly, I have never had the same high regard for their CU's -- they've been just "OK" by my rating. Their current design of domestic plastic CU's is definately a much cheaper-feeling product than the previous ones with the clear plastic access door. I have bought the occasional one to use as a DIN rail enclosure, but not as a CU. I suspect the issue with their CU range is that they don't make much/any of it, but feel they have to have CU's in their product range or it would be incomplete. Dependance on others is probably why they've run though a number of different styles.

For the last couple of domestic CU's I've fitted, I have chosen commercial grade CU's which are just so much better made and more amply sized, it's a real pleasure to work with them. I've used the MEM (now call Eaton) Memshield2 range. This will cost you more than a domestic plastic CU, but as I do DIY to get a better quality result, I don't mind paying for quality.

[Andrew Gabriel]

This is something the US is very hot on* (UL type approval applies to a combination of breaker and enclosure, and is voided by using an enclosure the manufacturer didn't include for certification), but providing the accessories fit properly, I've never seen this regarded as an issue here.

• If you look in a US panel, you'll be horrified, and relieved it wouldn't come close to getting approval in the EU.

[Matt]

I stand corrected. I must have somehow missed the middle iteration completely.

I just found an RCD on one of the earlier types that works with a pushbutton test but fails when tested at a socket. It's probably a dead cert the really old RCD's are no longer available!

[Guy King]

The message from [e-mail] (Andrew Gabriel) contains these words:

Plenty here...

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Ed Sirett saying something like:

They'll physically fit - the whole point of the DIN rail is standardisation - but the electrical connections might or might not line up. Most modern ones will interchange, but a mix of old and new might not. Not a real problem is all you have is an oddball one that works and will get the system back up and running- you can wire it in one way or other.