Garage fed by 4mm SWA

[SarahB]

Hi all, I hope you're all well and looking forward to the weekend ! Can I ask a quick one please? I've been asked to put a 16 Amp MCB on to a garage Distribution Board, but its full so will obviously need changing. However, it is being fed by 4mm SWA. I thought it had to be 25mm tails, or have I misunderstood? I don't want to do it if it's wrong from the start. It's already running some sockets and lighting. Thanks for any advice on this

 

[Spoon]

Usually the garage consumer unit is fed from the consumer unit in the house. If you look at it you should see the 4mm cable going into it. Also if you are changing the garage CU or adding extra circuits to it, then this falls under Part P.

 

[SarahB]

Hi Spoon, and thanks for the reply. It certainly is fed from the main consumer unit, so does this mean it would be OK to go ahead? The Part P issue is fine, I'm registered to do the work. I really appreciate the help.

 

[Hawk81]

I don't mean to seem unhelpful but if you really need to ask these questions are you really sure you can be doing any of this work? It's very simple and basic questions. My first year apprentice can answer your questions.

 

[Spoon]

I have to agree with Hawk on his comment, but as you have stated that you are Part P registered then I will take your word for it, seeing that its nearly xmas and im in a happy mood.
Now you have to start doing all the calcs to see if you can add the 16A MCB. What is it for? What rating of MCB is the 4mm cable wired to in the house CU? How is the cable installed?

 

[Amp David]

Yes, you will need to install new 25mm SWA, i'd choose 3 core, the 4mm is no good imo:santa_smiley:

Take the 4mm an weigh it in:willy_nilly:

 

[ab1978]

first of all how far is the garage from the c/u in house what other mcbs are in the c/u in garage what size mcb is the 4 swa on? what circuits are in garage

 

[micknew]

Another DIYer, obviously!!

 

[seb77]

you dont need 25mm2 SWA to supply a garage with only 6amp lighting and 2 x 16amp circuits!!!!

 

[SarahB]

Right, thanks for the replies. I just want to clarify something, I was of the opinion that the 4mm was fine and was happy to do the cable calcs. This isn't a job I have been to, but was asked about by one of the lads who works for the same company. Have you ever given an answer to someone, and they are so sure that you were wrong that you have even started to doubt yourself? That is why I asked. I'm a bit upset by the response, if I'm being totally honest. Is it a sexism thing? "It's just a stupid woman." Fair enough, I'm fairly newly qualified but I always thought this was a great place to ask a question. Sorry, but I really am genuinely upset now.

 

[topquark]

The 4mm is probably ok, if it's xlpe sheathing (that would take up to around 42Amps total). You should also look at the earthing arrangements in the garage (and whether any bonding is needed).

 

[DurhamSparky]

Sarah, ignore some of the idiots on this forum! they like to lurk about and jump out every so often. ironically they are the same people who when a technical question is asked they shy away and don't say boo to a goose! they may have the qualifications but they are a breed from the 2.5 for sockets and 1.5 for lights school... or monkey see monkey do...

any way moving on 4mm is good up to 32A MCB installed in certain situation but anything below that is fine.

Check the Bonding and Earthing as usual and just swap the bloody box to a larger one.

Is the SWA using the 3[SUP]rd[/SUP] core as earth or the sheath!??

We all have to start from somewhere but people forget where they come from.

 

[Octopus]

Have I missed something but what is at the "house" end? If the client wants another 16A mcb have they said what they want to do with the circuit?

Sorry if this has been covered but that's where I'd be starting from.

 

[telectrix]

agree with both the last 2 posts. as long as your 4mm is protected by the correct fuse/MCB for the method of installation, then it will be fine, as long as you know the limitation of what you can load it with.

 

[Andyfm]

I don`t think it was a "sexism" thing, its just sounds like a very basic question from someone who is allowed to "sign off" their own work.

 

[Hawk81]

I did not look at your name when I replied to you so I did not know your sex. I would have replied the same to anyone asking the same questions. Read through some of my replies to others and you will see I have answered the same way to others. If you think all critisism you receive is sexist then you will find it tough to make it in the trade. I appologize if I upset you, but I stand by my first reply. Your questions do not make you sound ready to do these jobs on your own.

 

[SarahB]

Sarah, ignore some of the idiots on this forum! they like to lurk about and jump out every so often. ironically they are the same people who when a technical question is asked they shy away and don't say boo to a goose! they may have the qualifications but they are a breed from the 2.5 for sockets and 1.5 for lights school... or monkey see monkey do...

any way moving on 4mm is good up to 32A MCB installed in certain situation but anything below that is fine.

Check the Bonding and Earthing as usual and just swap the bloody box to a larger one.

Is the SWA using the 3[SUP]rd[/SUP] core as earth or the sheath!??

We all have to start from somewhere but people forget where they come from.

Haha, thanks DurhamSparky. As I said, I've not seen the job and it may not even need doing. I was asking a generic question really as I've always found people on here to be helpful to each other. As I mentioned, you know how things are when you start doubting yourself? I admit I'm certainly not experienced enough to know all aspects of the job, far from it. I hope people don't mind me asking questions though. You have been very, very helpful DurhamSparky

 

[Darkwood]

I doubt any of the replies were sexist in any way, we have many female members on this forum and obvious sexism wouldnt go down well with admin'.
I myself work in technical, control systems; building and upgrading etc but shove me back in a house rewire i would also start questioning my own knowledge as although i did it for 10yrs of my 20yrs history it needs to be regular to stick in the head and become second nature, we often get well educated and qualified ppl on here asking simple basic questions just to give them more of a re-cap than a lesson. From reading your opening post it did come across wrong as did your reply to the challange, this made it sound like you were a DIYer thus the responses that followed as they are a burden and health hazard to our industry in their own right.
I can only say; try to approach the question a little bit different if not with a bit of humour i.e. im having a blonde moment (no sexism intended), you may find a lot better responses and help.

 

[malcolmsanford]

Hi Spoon, and thanks for the reply. It certainly is fed from the main consumer unit, so does this mean it would be OK to go ahead? The Part P issue is fine, I'm registered to do the work. I really appreciate the help.

I'm sorry whether your male/female, black/white or tinge of pink, whether your straight/gay or not sure and whether your believe that aliens live among us, that god is by our side or in my last life I was a penguin, how can you be classed by a scheme as competent and not know that we are talking about a distribution circuit to that garage, that it is not a set of mains tails, which also don't need to be 25mm.

I'm sorry but hawk was right, I think we have to ask whether the OP is competent or not as the OP scheme seem to think they are!!

We have reams of threads on here concerning the pitiful state of our industry and it's training in general, and this as got to be systematic of both. I'm probably going to get slated for this,but I'm afraid I don't think the OP should be able to sign off work as safe.

 

[1shortcircuit]

I'm a bit upset by the response, if I'm being totally honest. Is it a sexism thing? "It's just a stupid woman." Fair enough, I'm fairly newly qualified but I always thought this was a great place to ask a question. Sorry, but I really am genuinely upset now.

Sarah, you should by now realise the way of the forum. When certain members see a place to feed, they feed... until the next one comes along.

You must remeber that regardless of your question the helpful people will arrive soon enough. Unfortunately they will occasionally make it only after the feeding frenzy because they spend much of their time contributing to posting informative posts throughout numerous threads on the forums.

Thicken your skin and keep reading to familiarise yourself with the helpful ones

I too have the "Doubt myself" feelings on occasions

:thumbsup

1SC

 

[SPARTYKUS]

Best advice you can get Sarah, as above, grow the skin of a rhino, let the negatives slide off your back like water off a ducks, grit your teeth, KEEP asking at the end of the day you want to know something, this is a forum! Ask ask ask.



Its the people that don't ask, Then guess, that are my worry.

Head down, tighten belt, ask next question!

 

[Deleted member 9648]

I'm sorry whether your male/female, black/white or tinge of pink, whether your straight/gay or not sure and whether your believe that aliens live among us, that god is by our side or in my last life I was a penguin, how can you be classed by a scheme as competent and not know that we are talking about a distribution circuit to that garage, that it is not a set of mains tails, which also don't need to be 25mm.

I'm sorry but hawk was right, I think we have to ask whether the OP is competent or not as the OP scheme seem to think they are!!

We have reams of threads on here concerning the pitiful state of our industry and it's training in general, and this as got to be systematic of both. I'm probably going to get slated for this,but I'm afraid I don't think the OP should be able to sign off work as safe.

SarahB,it would be interesting if you could tell us a little about your experience,route into the trade and qualifications that has enabled you to be registered with a part p scheme......I'm afraid many of us old lags can be a bit short when people who are in the trade ask questions, which we feel someone who is doing this for a living,and charging the public for,shouldnt have to ask.
There has been a lot of debate on here about falling standards of training...and people who are on paper competant,being....well,not competant.
It's as well to ask,and you have got some helpful replies here,but I also feel the doubters have a point....if you are registerd to carry out this work,perhaps this is not a question you should be asking?
Discuss if you will.

 

[1shortcircuit]

SarahB,it would be interesting if you could tell us a little about your experience,route into the trade and qualifications that has enabled you to be registered with a part p scheme......I'm afraid many of us old lags can be a bit short when people who are in the trade ask questions, which we feel someone who is doing this for a living,and charging the public for,shouldnt have to ask.
There has been a lot of debate on here about falling standards of training...and people who are on paper competant,being....well,not competant.
It's as well to ask,and you have got some helpful replies here,but I also feel the doubters have a point....if you are registerd to carry out this work,perhaps this is not a question you should be asking?
Discuss if you will.

With all due respect I don't believe any of us need know the OP's past or route into the trade???

This is just bait to the sharks surely? and in no way relevant to the question asked in terms of an answer to the original post?

 

[Hawk81]

With all due respect I don't believe any of us need know the OP's past or route into the trade???

This is just bait to the sharks surely? and in no way relevant to the question asked in terms of an answer to the original post?

What sharks??? I am confused by this appolgizing and others calling members idiots. The op claims to be qualified and registered. Then asks questions that would lead me and others to think otherwise. I think we have a duty to ourselves to ensure we do not give out help to people who should not be taking on work they are not capable of

 

[SPARTYKUS]

I refer to my point made regarding guessing.

 

[1shortcircuit]

What sharks??? I am confused by this appolgizing and others calling members idiots. The op claims to be qualified and registered. Then asks questions that would lead me and others to think otherwise. I think we have a duty to ourselves to ensure we do not give out help to people who should not be taking on work they are not capable of

wirepuller is asking for the OP to post up infromation explaining

experience,route into the trade and qualifications that has enabled you to be registered with a part p scheme......

which to me is absolutely of no benefit to helping answer the OP's question?

By the OP providing the above information it may be nothing more than bait to the "Sharks" that turn on those who have not opted for the same route into the industry (they know who they are)

If people don't want to help answer a question because they don't like the look of the level of competence then they have the right not to help but that does not mean that the question should not be asked. We are all at different levels and at different stages in our lives, if we all knew everything then would this forum have been created?

 

[ipf]

SarahB,it would be interesting if you could tell us a little about your experience,route into the trade and qualifications that has enabled you to be registered with a part p scheme......I'm afraid many of us old lags can be a bit short when people who are in the trade ask questions, which we feel someone who is doing this for a living,and charging the public for,shouldnt have to ask.
There has been a lot of debate on here about falling standards of training...and people who are on paper competant,being....well,not competant.
It's as well to ask,and you have got some helpful replies here,but I also feel the doubters have a point....if you are registerd to carry out this work,perhaps this is not a question you should be asking?
Discuss if you will.

Agree totally Wirepuller, very good points. When all said and done, as the vast majority of us know, dangerous situations regularly occur. It is better to ask than go in blind though.

 

[Deleted member 9648]

wirepuller is asking for the OP to post up infromation explaining which to me is absolutely of no benefit to helping answer the OP's question?

By the OP providing the above information it may be nothing more than bait to the "Sharks" that turn on those who have not opted for the same route into the industry (they know who they are)

If people don't want to help answer a question because they don't like the look of the level of competence then they have the right not to help but that does not mean that the question should not be asked. We are all at different levels and at different stages in our lives, if we all knew everything then would this forum have been created?

I thought the OP's question had been answered satisfactorily by the time I posted??
If you read my post it is a response to malcolms post....not a derogatory response to the OP's question.....

 

[1shortcircuit]

If you read my post it is a response to malcolms post....not a derogatory response to the OP's question.....

I did read your post and after reading your reply in the above comment I re-read your original post. I can see now that I may well have read your original by adding the wrong tone to your comments.

I thought it was another dig at the OP.

Please accept my apology if I got it wrong.

:thumbsup

 

[malcolmsanford]

wirepuller is asking for the OP to post up infromation explaining which to me is absolutely of no benefit to helping answer the OP's question?

By the OP providing the above information it may be nothing more than bait to the "Sharks" that turn on those who have not opted for the same route into the industry (they know who they are)

If people don't want to help answer a question because they don't like the look of the level of competence then they have the right not to help but that does not mean that the question should not be asked. We are all at different levels and at different stages in our lives, if we all knew everything then would this forum have been created?

I just hope to clear up that in over 4000+ posts on my part I think I can count on one hand the negative ones I have posted and hope that I'm never derogatory to anyone.

I trained and pretty sure I asked blindingly obvious questions and I have trained apprentices that have done the same. For me though it is not the asking of questions as even now I read something on here and think I never knew that, and I would never tell anyone not to ask if not sure, but my comment was on someones level of competency.

If a 1st year apprentice asked me this then I would have no problems with explaining it and advising them what to do, after all they are training. If a 3rd year apprentice asked me this I would be asking them if they had picked the right career, as I would expect them to know the answer, as I would deem a 3rd yr apprentice competent to design, install, inspect and test a simple job like this

I'm sorry, and perhaps I expect too much, but I honestly feel that if your at the stage in your career when you are deemed capable by a registered body to be competent to design, install, inspect and test your own work to sign of as safe and ready to use, you should not be asking this. It really is not a matter of waiting to pounce on someone on my part as that is not me, it really is genuine concern that the OP is working in someones house, charging them for their services and expertise and could very well be a danger to themselves and to the customer due to lack of very basic knowledge.

 

[1shortcircuit]

I'm not trying to fall out with either of you guys. I often look for your posts and can admit that I have learnt a lot from them.

On this occasion I believed the posts to be harsh but it seems yesterday I must have engaged my brain incorrectly as this is not the only thread where I read posts in a way that they were not meant.

I think I'll go and clean my ears out so I can hear the tone of the posts correctly next time:bigear:

:38:

 

[BigJonesy]

I'm glad this question has been asked as I also want to know how this works. I'm new to the industry and am just training but don't know how to work out what would be safe. If an extension was fed by a 32 amp breaker, and is running a couple of light circuits both at 6 amps I think that would be fine. But if you wanted to add sockets at 20 amps would that be OK as it adds up to 32 amps? Please don't jump on me, I just want to ask that's all. Also, where would I find out how to work this out? Someone said times it all by 0.4 and that will give you the figure. For 32 amps on the circuit that would give me 12.8 amps wouldn't it? It's like a jigsaw to me all of this, bits and pieces of knowledge from all of the place, I just need to slot it all together. Thanks all.

 

[tuckermot]

Hi bigjonesy
all the information you require for your question is in the on site guide .There is a table in there that gives you diversity for all the circuits .Example if you put in two 13 amp sockets it does not mean you have to allow 26 amps on that circuit thats where diversity comes in it is a average usage likely to be used on that circuit

Richard

 

[BigJonesy]

Hi bigjonesy
all the information you require for your question is in the on site guide .There is a table in there that gives you diversity for all the circuits .Example if you put in two 13 amp sockets it does not mean you have to allow 26 amps on that circuit thats where diversity comes in it is a average usage likely to be used on that circuit

Richard

Brilliant, cheers tuckermot. At the risk of being a cheeky ****er do you know which pages in the OSG will tell me this? I've got the red one, not the new green one. Top man if you can help like.

 

[tuckermot]

i have sold my own red one but itis in there under diversity in the index bud

 

[BigJonesy]

i have sold my own red one but itis in there under diversity in the index bud

You're a star mate, I'll have a look through mine now. Just to get down to proper basics, if the amps are less than the MCB it's on - say it's a 32 amp MCB and it's running 26 amps in the extension, would that be OK? I just don't know where the cable size fits in. I know I'm being a thick tw*t but I just don't know hahahaha.

 

[tuckermot]

just remember the breaker ( mcb is to protect the cable from over current damage ) so the mcb should allways be a lower rating than of the cable thats why 1.5mm twin and earth is rated at 16-17 amps and the mcb is rated at 6amps but it is quite accepatable to put in a 10amp mcb with this cable if you are adding more lights or at design stage if you know the current is going to greater than 6 amps by doing your ohms law power divided by volts =amps so if you have 10 lamps rated at 60 watts each so 600w divided by 230v =2.6amps so you are safe to install 1.5mm cable and a breaker ,mcb rated at 6amps hence the cable can carry 16amps you are going to draw 2.6 amps max with out diversity so 6amp mcb is fine hope that helps using simple ohm laws in different ways to get your answer

 

[Spoon]

Just to add to Tuckers notes, if you look in the BGB at pages 317 onwards it shows you the different installation methods of cables. This will also affect your calcs for the cable size.