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Discuss Adding to an old mem board? in the Electrical Forum area at ElectriciansForums.net

happyhippydad

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Morning..

I need to get a shower supply from the 45a mem fuse in the picture below, this will first go to an RCD enclosure next to the board.

mem.jpg

I haven't added to a REALLY old mem board before (fuses). I realise it may be a silly question but is it ok to add a circuit to this board? With the more common wylex fuse box it's fine but this board does seem really old. The customer has said he doesn't want to change the board.

Also, does this board contain asbestos rope behind the fuses?

Thanks.
 
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telectrix

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fine to feed a separate RCD in enclosure from the 45A fuse. don't worry about asbestos. as long as it ain't disturbed, you'll be able to father children for years to come.
 

littlespark

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Don’t you just hate it when someone puts a fuse in upside down?

I’d try to convince customer into a board change. False economy adding an rcd enclosure now, then a new board in the future.
Tell them it’s a serious fire risk or something.... can no longer get spares etc.

Think of the grief you’ll get when, after you’re finished the shiny new shower circuit with rcd protection, their sockets or lights develops a fault.... first thing they will tell anyone is: “there was an electrician in last week, and it was all fine before that”
 

Leesparkykent

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Don’t forget your 0.725 factor. And if your adding an RCD in an enclosure why not just add a two way board just for the shower instead?
 

Gavin John Hyde

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Agree with @Leesparkykent i would go down the new small board just for shower route. On the positive side get one with an extra spare way for future works.
Saves messing with the current board. Wont be looking at too much cost wise either.
 
T

Toneyz

Tell them it’s a serious fire risk or something.... can no longer get spares etc.
Sorry, I think this is morally wrong, I am sure that Happyhippydad has done an assessment on the existing supply, existing consumer unit and bonding (inc supplementary) One question would be that if by adding an electric shower all the other circuits need to be RCD protected then a professional argument can be made on compliance and fact.
 

happyhippydad

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  • #8
Is there not a cooker circuit then?
No, it's actually feeding a 9.5kW shower at present, although it still states 'cooker' on the fuse. The present cable is 6mm and runs through conduit and insulation throughout most of the run so it's not acceptable. I'm going to be upgrading to 10mm and moving the isolation switch. At present the isolation switch for the upstairs shower is the old cooker switch in the downstairs kitchen and the elderly couple have lots of walking to do just for a shower!
 

happyhippydad

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  • #9
Don’t forget your 0.725 factor. And if your adding an RCD in an enclosure why not just add a two way board just for the shower instead?
Are you suggesting splitting the tails in a Henly block to feed the separate shower unit? That would probably end up being more work and a higher quote as I would also have to fit a separate isolation switch to isolate both the fuse box and the shower unit so that it meets reg 462.1.201 (BBB) [reg 537.1.4 - BGB-just for Tel ;)]

It would definitely be a better job I agree, but coming straight from the 45A mem fuse would still be acceptable? CCC of 10mm 64A x 0.725 = 46.4A (just above the 45A fuse!)
 

happyhippydad

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  • #10
Sorry, I think this is morally wrong, I am sure that Happyhippydad has done an assessment on the existing supply, existing consumer unit and bonding (inc supplementary) One question would be that if by adding an electric shower all the other circuits need to be RCD protected then a professional argument can be made on compliance and fact.
Quite agree Anthony although I'm sure Littlespark was saying it a little tongue in cheek. I will however be pushing for a new CU, but I shall be honest in my facts! :)
Main bonding has all recently been done. 10mm to gas and water.
 

freddo

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As much as I like these fuseboards the IP rating isn't very good for household use, fingers can easily touch exposed parts. The wax missing from the 30A fuse isn't great either. Now would be a great time for an upgrade, tell the customer to stop being a stingy old c***. After all safety would be improved quite a bit with a properly installed modern consumer unit.
Ps.. do they have asbestos?
Yes as it appears these are rewirable fuses. However removinng a fuse carrier isn't going to cause a Chernobyl.

As mentioned above, for a client I would install the new circuit in a separate small consumer unit if they won't replace the existing one (which really is a false economy). Can't get blamed for any problems further down the line then.
 

Leesparkykent

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Are you suggesting splitting the tails in a Henly block to feed the separate shower unit? That would probably end up being more work and a higher quote as I would also have to fit a separate isolation switch to isolate both the fuse box and the shower unit so that it meets reg 462.1.201 (BBB) [reg 537.1.4 - BGB-just for Tel ;)]

It would definitely be a better job I agree, but coming straight from the 45A mem fuse would still be acceptable? CCC of 10mm 64A x 0.725 = 46.4A (just above the 45A fuse!)
I wouldn’t fit an isolator on the tails if both boards are next to each other.

Technical Guide: Henley blocks and isolation - https://www.voltimum.co.uk/articles/technical-guide-henley-blocks-and


And if you didn’t fit the isolator then realistically how much is it going to add to the quote by adding the 2nd board rather than an RCD in an enclosure....£20?
 
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Risteard

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I wouldn’t fit an isolator on the tails if both boards are next to each other.

Technical Guide: Henley blocks and isolation - https://www.voltimum.co.uk/articles/technical-guide-henley-blocks-and


And if you didn’t fit the isolator then realistically how much is it going to add to the quote by adding the 2nd board rather than an RCD in an enclosure....£20?
Neither would I generally speaking. They can be said to be two installations from a Regs point-of-view (even stated in IET publications), strange as it may seem.
 

happyhippydad

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I wouldn’t fit an isolator on the tails if both boards are next to each other.

Technical Guide: Henley blocks and isolation - https://www.voltimum.co.uk/articles/technical-guide-henley-blocks-and


And if you didn’t fit the isolator then realistically how much is it going to add to the quote by adding the 2nd board rather than an RCD in an enclosure....£20?
Thanks for that article Lee, very interesting.
I will definitely give this some thought as it's a much better idea. The only reason I'm now still hesitant is that (as you can see from the pic) the tails are not accessible from the fuse box side. It would mean fitting a henly block in the meter box and feeding through new tails for the shower unit. I'm just not sure how easy that route is!
 

Risteard

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Thanks for that article Lee, very interesting.
I will definitely give this some thought as it's a much better idea. The only reason I'm now still hesitant is that (as you can see from the pic) the tails are not accessible from the fuse box side. It would mean fitting a henly block in the meter box and feeding through new tails for the shower unit. I'm just not sure how easy that route is!
I think the Shower DB option is the only realistic route without putting in a new DB for the lot. I would have priced for a 2-way DB personally. I wouldn't entertain using that 3036 DB - depending on shower rating you may even exceed its rating given that 45A I'd already in use. And as mentioned remember the correction factor for rewireable fuses. After you add an RCCB and enclosure you won't save much money on a 2-way DB and it will be much less hassle.
 

littlespark

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Could you put an upfront rcd on the tails and protect the whole board?
 
T

The Ghost

You could always leave it and walk away. I know I would not touch a job like that personally.
 
T

Toneyz

You could always leave it and walk away. I know I would not touch a job like that personally.
WHY?
 

littlespark

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Upfront rcd isn’t ideal, I know.... but it might convince the customer to replace the whole board if he’s given options and explained the pros and cons of each
 
T

Toneyz

Am I correct in that if a new shower circuit is installed this would need to be RCD protected as well as the other existing circuits in the bathroom. Supplementary bonding would also need to be installed if not already done so but can be omitted if conditions are met.
 

happyhippydad

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  • #24
I think the Shower DB option is the only realistic route without putting in a new DB for the lot. I would have priced for a 2-way DB personally. I wouldn't entertain using that 3036 DB - depending on shower rating you may even exceed its rating given that 45A I'd already in use. And as mentioned remember the correction factor for rewireable fuses. After you add an RCCB and enclosure you won't save much money on a 2-way DB and it will be much less hassle.
I cant see how it would be far less hassle? I would have to find a route for the tails from the meter box to the new DB next to the existing fuse box, this will not be easy. Granted, it's the better option but I think it will be more 'hassle'.

You could always leave it and walk away. I know I would not touch a job like that personally.
Could I ask why Vortigern?
Am I correct in that if a new shower circuit is installed this would need to be RCD protected as well as the other existing circuits in the bathroom. Supplementary bonding would also need to be installed if not already done so but can be omitted if conditions are met.
All circuits in the bathroom are existing. I can't see that I have to offer RCD protection to existing circuits if I am not carrying out any work on them. I'd be happy to hear any opposing thoughts?
 
T

The Ghost

Could I ask why Vortigern?
With a board like that I imagine the tails and everything in it is somewhat suspect although it is true you did not pan out enough to see the DNO gear. Asbestos in the fuse carriers. The fact that from the sound of what you say the person does not really want to spend a penny more than they have to, to achieve a safer installation. I do not like patch and mend approach or piecemeal additions. And I get the feeling that anything that goes wrong with the rest of the installation will be your fault. My spider sense would make me walk away from it. But what about the 0.725 factor?
 

Lucien Nunes

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It seems HHD has taken the 0.725 factor into account when working out the CCC of the new cable, and it complies.

Those Memera MkI boards were reliable and there must be many still about. But it's unusual to see a 45A Memcert carrier, so if you do end up taking it out, please could we have it for the museum?
I'm also a bit leery of that 30A second from left with the live screw accessible, although this was a remarkably common occurrence with this form of carrier in general, especially the cheap ones. The filler would crack and fall out, or melt and run out if a fuse was subjected to a prolonged low overload for hours on end. Yes, there should be a flash pad made of a popular heat resisting fibrous substance inside.

One final thought, who carries 45A fuse wire these days (20 SWG TC)?
 

happyhippydad

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  • #27
With a board like that I imagine the tails and everything in it is somewhat suspect although it is true you did not pan out enough to see the DNO gear. Asbestos in the fuse carriers. The fact that from the sound of what you say the person does not really want to spend a penny more than they have to, to achieve a safer installation. I do not like patch and mend approach or piecemeal additions. And I get the feeling that anything that goes wrong with the rest of the installation will be your fault. My spider sense would make me walk away from it. But what about the 0.725 factor?
Thanks for the reply.

The 0.725 factor would have been ok, i.e 64A x 0.725 > 45A.

Hoewever, I am moving further and further towards brining new tails in for a separate shower unit therefore avoiding all contact with the mem board.
 
T

Toneyz

With a board like that I imagine the tails and everything in it is somewhat suspect although it is true you did not pan out enough to see the DNO gear. Asbestos in the fuse carriers. The fact that from the sound of what you say the person does not really want to spend a penny more than they have to, to achieve a safer installation. I do not like patch and mend approach or piecemeal additions. And I get the feeling that anything that goes wrong with the rest of the installation will be your fault. My spider sense would make me walk away from it. But what about the 0.725 factor?
This is so negative, what should go wrong with the existing installation?
I know that the regs call for all circuits in the bathroom to be RCD protected, however, I do not do this type of work day to day so am interested from those who do in this situation protect the bathroom light with an RCD and yes I can see how there could be a chance of an existing fault or borrowed neutral. Over the years the regs have got us to upgrade things by default. If it was me I would come off the 45A fuse and feed a 2-way C.U. and if the lights had to be on an RCD/RCBO explain this to the customer then the ball is in their court.
 

happyhippydad

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  • #29
It seems HHD has taken the 0.725 factor into account when working out the CCC of the new cable, and it complies.

Those Memera MkI boards were reliable and there must be many still about. But it's unusual to see a 45A Memcert carrier, so if you do end up taking it out, please could we have it for the museum?
I'm also a bit leery of that 30A second from left with the live screw accessible, although this was a remarkably common occurrence with this form of carrier in general, especially the cheap ones. The filler would crack and fall out, or melt and run out if a fuse was subjected to a prolonged low overload for hours on end. Yes, there should be a flash pad made of a popular heat resisting fibrous substance inside.

One final thought, who carries 45A fuse wire these days (20 SWG TC)?
I would have loved to have been able to send the 45A fuse carrier to you Lucien after all the good advice you have given me over the years. However, even if it doesn't get used for the new shower I think I had better leave it in place rather than leave a big gap :).
 
T

The Ghost

If you come off the 45a fuse how will you deal with asbestos. That is a pita already. Will the customer pay for testing/removal. Will you remove the fuse. What are the chances the fuses are wired in anything but the correct fuse wire? I will be interested to see how you progress with the job and customer.
This is so negative
What can you mean? Do you mean what you are saying or me?
 
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