Replacing double space MK RCBO's with single space ones

[phatboy]

Hi,

My CU currently has a mixture of MCB's and RCBO's. The RCBO's are MK LN6348 32amp. They each take up 2 spaces in the unit.

Is there a model that has superseded this, that could be installed in a single space, so I can have a couple of extra circuits installed?

This would save a lot of money compared to replacing the whole 12 circuit CU!

Thanks

 

[JohnW2]

My CU currently has a mixture of MCB's and RCBO's. The RCBO's are MK LN6348 32amp. They each take up 2 spaces in the unit. Is there a model that has superseded this, that could be installed in a single space, so I can have a couple of extra circuits installed? This would save a lot of money compared to replacing the whole 12 circuit CU!

The short answer is yes. In fact, nearly all single-pole RCBOs (which is what you've got) being sold these days are 'single module width'. Your electrician should be able to find ones that would fit your CU.

Kind Regards, John

 

[phatboy]

My CU currently has a mixture of MCB's and RCBO's. The RCBO's are MK LN6348 32amp. They each take up 2 spaces in the unit. Is there a model that has superseded this, that could be installed in a single space, so I can have a couple of extra circuits installed? This would save a lot of money compared to replacing the whole 12 circuit CU!

The short answer is yes. In fact, nearly all single-pole RCBOs (which is what you've got) being sold these days are 'single module width'. Your electrician should be able to find ones that would fit your CU.

Kind Regards, John

Thanks John, so it would be OK to fit a newer model in my existing CU? Read a lot about type testing etc. so wasn't sure....

I would like to source them myself as I have a friend (who IS an electrician) who will do it for me, and I don't want to push my luck asking him to source things for me as well as fit them on his weekend.

Is it a simple case of any current MK RCBO of the correct current rating, curve and trip current would fit? Or are there differences with the busbar types?

This is just for my interest really.... I am comfortable doing electrical jobs around the house but always leave it to trusted professionals to work in the CU

Thanks

 

[JohnW2]

Thanks John, so it would be OK to fit a newer model in my existing CU? Read a lot about type testing etc. so wasn't sure....

That an interesting question for Mr Jobsworth. Technically, I suppose it ceases to be 'type tested' if any of the contents are changed for anything else. However, replacing a component with the 'currently available equivalent' (which is what you would have to do if it broke) is so close to the original that I would hope that few people would get excited about that. The world is full of CUs with a mish-mash of contents

I would like to source them myself as I have a friend (who IS an electrician) who will do it for me, and I don't want to push my luck asking him to source things for me as well as fit them on his weekend. Is it a simple case of any current MK RCBO of the correct trip current, type and trip current would fit? Or are there differences with the busbar types?

Unfortunately not. Electrically speaking, if it has the same current rating and trip current that's fine. The issues are physical/mechanical. There are two issues. Firstly, modern single-module RCBOs are much taller than what you have. You would have to make sure that there was room in the CU to accommodate them, and the associated wiring. Secondly, there is an infuriating lack of standardisation of the exact position (and type) of the terminal for the L busbar. One might hope that a modern RCBO of the same make (MK) would stand a better chance of fitting than would a different make, but there's no guarantee. Without 'sucking and seeing' (and the price of RCBOs being what it is, that could be an expensive business), I would think that the best solution would be to ask MK about physical compatibility of their current products with their obsolete one.

Kind Regards, John

 

[phatboy]

Thanks again John. I think I will speak to my friend and see if he happens to have any of the new MK RCBO's in his van, then we can have a look and see if its workable. Last time the cover was off I do recall it being a bit tight at the top due to the number of circuits.

Failing that, might just bite the bullet and get a new, fully RCBO Hager board fitted, the same as the heating board I had installed when I bought the place 18 months ago.

The house is only 16 years old so seems a shame to rip the box out, although I guess there will be some value in the MCB's and RCBO's currently in it......

 

[JohnW2]

Thanks again John. I think I will speak to my friend and see if he happens to have any of the new MK RCBO's in his van, then we can have a look and see if its workable. Last time the cover was off I do recall it being a bit tight at the top due to the number of circuits.

You're welcome. If it's already 'tight at the top', you could well have a problem. When they halved the width, the 'works' had to go somewhere, so they expanded them upwards, quite appreciably

Failing that, might just bite the bullet and get a new, fully RCBO Hager board fitted, the same as the heating board I had installed when I bought the place 18 months ago.

If modern RCBOs won't fit, then that might, indeed, be your only option. As you say, that would be a bit of a pity in a house so young, but there may be no practical alternative. If there is a problem, and your issue is just that of needing more circuits than will currently fitin your CU. you could discuss with your friend the option of installing an additional 'supplementary' CU for them, rather than replacing the existing CU. However, sooner or later those RCBOs you have might well need replacing, in which case you may be 'forced' into a new CU, if currently-available RCBOs won't fit.

Kind Regards, John

 

[phatboy]

I will pop the front off and see what the space is like, its been a while so may be more space than I thought.

Unfortunately there isn't a particularly neat place to add a supplementary board.

If I go ahead with a full replacement I will get it done by the same company who did the heating board - for something of that scale its nice to have a warranty and be able to call them back if there are any issues

 

[JohnW2]

I will pop the front off and see what the space is like, its been a while so may be more space than I thought.

It's your electrician friend who will have to make the judgement about whether there is enough space. However, don't hold your breath. Even many CUs sold today don't really have enough height to use RCBOs comfortably.

If I go ahead with a full replacement I will get it done by the same company who did the heating board - for something of that scale its nice to have a warranty and be able to call them back if there are any issues

Indeed - but probably even more important than that, if you are happy with work they've done for you before, that's about the best recommendation you can get!

Kind Regards, John

 

[phatboy]

It's your electrician friend who will have to make the judgement about whether there is enough space. However, don't hold your breath. Even many CUs sold today don't really have enough height to use RCBOs comfortably.

Of course, I mean I will open it up, take a photo or measure from the top of the current MCB's or RCBO's to the top of the unit

Today I have arranged for the company who did my heating CU to come and scope out the work next week - hopefully not too expensive for a pretty straightforward swap out, although I am in Jersey! They always give a fixed price, which I suppose is a good thing

 

[JohnW2]

Of course, I mean I will open it up, take a photo or measure from the top of the current MCB's or RCBO's to the top of the unit

Sure, I realised that. Howver, I was pointing out that, whatever your view of the amount of space, it's really your electrician who would have to decide whether he would be happy putting modern ('tall') RCBOs into it.

I think that old RCBO you have is probably the same height (or roughly the same height) as the MCBs. To give you some idea, a single-module RCBO is about 40mm taller than those.

Of Today I have arranged for the company who did my heating CU to come and scope out the work next week - hopefully not too expensive for a pretty straightforward swap out, although I am in Jersey! They always give a fixed price, which I suppose is a good thing

Sounds good.

Kind Regards, John

 

[333rocky333]

I think Ln was the older range and same mould as the merlin gerin.
although the m/g double ones changed to single width and stayed same,
You may find the mk ones changed the bus bar alignment, to fit the newer boards, when they went from double to single and may have changed yet again since, so may be best check that as well

These are the latest range

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