Rewire advice (and automated wiring too...)

[vichouse]

A newb on this forum but reading previous posts I know this is going to get a lot of criticism but here goes.

I am planning to do a complete rewire of my house but have a couple of questions on certification and automated wiring.

I'm not part p qualified so I plan to notify the council and get the inspection before work commences for the plans and at first fix and after completion. Installation wise I intend to install a completely parallel and, initially, dummy system with all wires connected to a new unconnected consumer unit. Then for the switch to disconnect the old system and connect the unit to the mains I hope to hire a qualified electrician either after first fix or completion (if the completion check can be done to a redundant system as this will mean I can show the electrician the BS7671).

So first question do you think this is a viable approach.

Second question, I am looking to install automated wiring using cat5 to carry the signals but can not find any information in the regs for this (if there are any). Does anyone have any experience of this or any idea how building inspectors may react to a system they've never seen before. If its not in the regs would I be better doing a normal rewire and adding the automation after the certificate (as it wouldnt be a notifiable alteration)

This is the main reason I want to do the install myself as I havent found any electricians with experience here which means the quotes I have got are overpriced for work that isnt quite what I want.

Plus before anyone asks I do have some experience here, rewired a few lighting and ring circuits at my parents pre-regs change and studied some electronics at uni.

Any advice welcome

Cheers

 

[electronicsuk]

I'm not part p qualified so I plan to notify the council and get the inspection before work commences for the plans and at first fix and after completion. Installation wise I intend to install a completely parallel and, initially, dummy system with all wires connected to a new unconnected consumer unit.

Possible, but means you wont be able to re-use existing accessory positions and the like. Seems like a lot of unnecessary effort unless you're trying to live in the property at the same time.

Then for the switch to disconnect the old system and connect the unit to the mains I hope to hire a qualified electrician either after first fix or completion (if the completion check can be done to a redundant system as this will mean I can show the electrician the BS7671).

Why? If you're going through building control, you can do all the work yourself. There will be no need for you to hire an electrician at all, and if you don't feel confident in completing the supply side connections to the consumer unit, I'd be considering whether or not you're really confident enough to complete a full rewire!

Second question, I am looking to install automated wiring using cat5 to carry the signals but can not find any information in the regs for this (if there are any). Does anyone have any experience of this or any idea how building inspectors may react to a system they've never seen before. If its not in the regs would I be better doing a normal rewire and adding the automation after the certificate (as it wouldnt be a notifiable alteration)

That's an interesting question. I expect they wont have seen much in the way of home automation, but that shouldn't put you off. After all, a building inspector may not have come across a 3-phase industrial deep fat fryer in a domestic installation before, but that wouldn't stop you installing one if you so desired!

Although BS7671 does still apply to extra low voltage, control and data wiring, you will find that quite a large amount of information will not be applicable to these parts of the installation.

 

[vichouse]

Thanks good comments.

Yes I'm living in here which is why I was going for a parallel system and with 3 exceptions all the light fittings are going and all the sockets and switches are going so there wont be too much waste this way (its my first house and I've moved into somewhere thats had no work in 26 years).

I was planning to get a qualified electrician to connect to the consumer unit as I understood that was essential, or is that only for moving the meter and not the consumer unit?

 

[ban-all-sheds]

I am planning to do a complete rewire of my house

• For a circuit to supply a given load (doesn't matter what), how would you go about deciding what cable and protective device to use?
  
  
• How do you calculate maximum demand and how can diversity be used?
  
  
• What are the 3 different types of domestic single-phase supplies provided in this country, how would you recognise them, and what differences do each make to the requirements for the rest of the installation, particularly any outdoor supplies?
  
  
• Can you correctly identify all components and connections of a circuit by method of testing or otherwise? In doing so can you identify or recognise anything wrong or dangerous with the circuit?
  
  
• Do you understand how the way in which you install cables affects how much current they can carry?
  
  
• What are the rules concerning cables concealed in walls, partitions and under floors?
  
  
• What are the rules for cables run outdoors, buried in the ground or overhead?
  
  
• Where cables need to be joined, how should this be done / not be done and in what circumstances are different methods acceptable?
  
  
• Can you identify extraneous conductive parts, and do you know the requirements for main and supplementary bonding of them?
  
  
• Which circuits should be RCD protected?
  
  
• How do you propose to isolate your supply so that you can connect up your new CU?

I'm not part p qualified so I plan to notify the council and get the inspection before work commences for the plans and at first fix and after completion.

That may be your plan, but is it theirs?

"before work commences for the plans" sounds like you might be expecting them to check your designs - I've never heard of any council doing that.

You really do need to see what your council's position is, and charging structure is, for DIY electrical work. They are now supposed to charge per visit, so your plan might end up an expensive one.

Installation wise I intend to install a completely parallel and, initially, dummy system with all wires connected to a new unconnected consumer unit. Then for the switch to disconnect the old system and connect the unit to the mains I hope to hire a qualified electrician either after first fix or completion

You "hope to"?

If you want an electrician involved, then you need to find one before you start, and agree with him what he's happy for you to do.

But ATEOTD, if you are not confident enough that you could carry out this rewire without any involvement from an electrician then you shouldn't be doing it.

(if the completion check can be done to a redundant system as this will mean I can show the electrician the BS7671).

1) Not all of the necessary tests can be carried out on a system which is not energised.

2) The council will not issue you with a BS 7671 certificate, so you'll have nothing to show the electrician.

3) I can't work out what you think you want the electrician to do, if you think you might already have an EIC before he comes.

So first question do you think this is a viable approach.

Not really.

Second question, I am looking to install automated wiring using cat5 to carry the signals but can not find any information in the regs for this (if there are any).

Table 52.3
537.5.3
537.4.2.2 Note 1
Table 51
132.3
537.3.2.1
515.2
528.2
.
.
.

What did you look under in the index?

Does anyone have any experience of this or any idea how building inspectors may react to a system they've never seen before.

The chances of it being a BCO checking your work are vanishingly small. They will either expect you to have a qualified electrician do the work, or provide an certificate from one, or they will subcontract the work to one.

So if you've done it, without the involvement of the electrician, and you've not done it right, then he'll react badly.

If its not in the regs

It is.

would I be better doing a normal rewire and adding the automation after the certificate (as it wouldnt be a notifiable alteration)

It might be notifiable.

 

[electronicsuk]

I was planning to get a qualified electrician to connect to the consumer unit as I understood that was essential, or is that only for moving the meter and not the consumer unit?

Nope. An electrician cannot move the meter or cutout, as these are owned and operated by the Distribution Network Operator. An electrician can, however, move the consumer unit, but you can legally do this yourself if you've notified the work to your LABC.

The only issue may be isolation of the supply to carry out the work. If you find out the DNO for your area and contact them, they should be able to install a DP isolator switch between the meter and existing CU. This gives you a suitable point of isolation to safely connect up the new consumer unit.

Many electricians will just pull the service fuse, and in some cases there are even unwritten agreements with the DNO, who will then come and re-seal the cutout at a later date. This isn't normally a problem if the cutout is quite modern, but there is a risk of damage to older units which are no longer mechanically sound, so it'd be wrong to advise that you do this yourself.

FWIW, you could also arrange for the DNO to power down your supply and then come back later to re-energise it, but it'd make more sense to have an isolator installed while you have the chance.

 

[ban-all-sheds]

I was planning to get a qualified electrician to connect to the consumer unit as I understood that was essential, or is that only for moving the meter and not the consumer unit?

Neither.

There's no requirement to use a qualified person to connect the supply to a CU, and an electrician may not move the meter.

 

[OwainDIYer]

Installation wise I intend to install a completely parallel and, initially, dummy system with all wires connected to a new unconnected consumer unit. Then for the switch to disconnect the old system and connect the unit to the mains I hope to hire a qualified electrician either after first fix or completion (if the completion check can be done to a redundant system as this will mean I can show the electrician the BS7671).

Certain tests have to be done on the installation live, it's not possible to certify a 'dummy' installation.

If there is space one typical way of doing it would be to put in a new consumer unit, and get it connected to the meter and certified. Then connect the old consumer unit (if the wiring's not too shonky to be used temporarily) to a way on the new CU, probably through a 40A RCD protected circuit*, then take new circuits to the new CU and disconnect the old circuits from the old CU as you go. (*adjusting the load on the old CU to be below 40A if necessary, eg provide new cooker/shower circuits straight to the new CU)

Second question, I am looking to install automated wiring using cat5 to carry the signals but can not find any information in the regs for this (if there are any).

Mains wiring is mains wiring, doesn't matter whether it's to 13A socket or to a DIN rail dimmer pack etc. As long as you segregate mains and non-mains as necessary.

 

[vichouse]

haha ban-all-sheds 6 years and you havent changed a bit. I discovered DIYornot by googling "home rewire" which has the first result as the 2005 post where you slated davedasave for attempting a home rewire
//www.diynot.com/forums/viewtopic.php?t=31811

Anyway you'll be happy (perhaps thats asking too much so maybe just mildly reassured) to know I took note of your post then and have been researching this a bit including reading the regs, to the point I was going to ask if you could provide a more up to date book list.... (and i would still be grateful if you could do this)

Anyway seems its quiz time and I do like quizes so lets have a go....

But first a quick point: as I understand it part of the point of the 3 part inspections is that my wiring plans would be inspected at the first inspection prior to first fix which would address many of your concerns.

Anyways back to quiz time and my answers for what they're worth.

For a circuit to supply a given load (doesn't matter what), how would you go about deciding what cable and protective device to use?

Cable: 1mm lighting. 2.5mm ring main and up to 20 amp appliances. Cat5e for information
Protective device as in RCD/trunking/or other. RCD's see answer to your qu below. Trunking see answer on safe zones below. Other, please tell me or tell me what to read...

How do you calculate maximum demand and how can diversity be used?

- Max demand on an individual circuit I'm guessing. Well my house floorplan is less than 100 sq m and the most high demand appliance I have is probably my kettle and other kitchen appliances (gas heating). So demand wise ring mains 1 upstairs, 1 downstairs, 1 for kitchen, seperate supply for certain kitchen applicances is the plan and is anything ott on providing for demand.

What are the 3 different types of domestic single-phase supplies provided in this country, how would you recognise them, and what differences do each make to the requirements for the rest of the installation, particularly any outdoor supplies?

Supply to houses is generally 240v +/- 10 single phase, is this what you're refering to? (no outdoor supplies intended)

Can you correctly identify all components and connections of a circuit by method of testing or otherwise? In doing so can you identify or recognise anything wrong or dangerous with the circuit?

- I might be misunderstand this one but surely that would be more relevant for alterations or additions to a circuit or testing a circuit where you need to understand whats already there, whereas I'm planning on a rewire from new.

Do you understand how the way in which you install cables affects how much current they can carry?

- lets see I=V/R and R=pl/a (cant type greek) so length and cross-section of cable would be key but I'm guessing loops and/or other cabling in parallel will have an effect through the magnetic field from the other ac wires but I assume that would be negligible with the number of wires and accuracy of current required in a residential set up - (as with others please correct if wrong)

What are the rules concerning cables concealed in walls, partitions and under floors?

- I'm guessing you mean safe zones, and use of armored cabling/metal trunking outside. That do or you want the details?

What are the rules for cables run outdoors, buried in the ground or overhead?

- Vague ideas here but not doing any of the above so not really read into it yet.

Where cables need to be joined, how should this be done / not be done and in what circumstances are different methods acceptable?

- Hmm I assume you are refering to uses of junction boxes but the question is ambiguous to me please rephrase.

Can you identify extraneous conductive parts, and do you know the requirements for main and supplementary bonding of them?

- Yup and if you ask me the regs are way OTT here, basically any bit of metal sticking up anyway that could be deemed to be earthed (pipework being a prime example) and is near an electrical supply needs to be bonded to the mains earth terminal. (I say its OTT as from what I understand if a metal pipe goes into a metal tank and another metal pipe comes out the end both need earthing and if all your pipework is metal (to outside the house) its earthed anyway as it comes from the ground - rant over).

Which circuits should be RCD protected?

- Trick question perhaps - as its a complete rewire all sockets, and anything to bathroom or kitchen (gas heating so need boiler circuit). Additionally any unprotected wires running less than a certain depth into the wall (50mm I think).

How do you propose to isolate your supply so that you can connect up your new CU?

Use my supplier as following an earlier reply I've investigated and there is no standard isolator so it appears the suppliers fuse pre the meter. Obviously I'm not even thinking of going there so I will liaise with them to fit an isolator and move the meter and perhaps the consumer unit all in one if they are willing. If not use their newly fitted isolator switch.



OK now I've answered these all for a 3 reasons:
1) to learn from errors
2) to show I do know a bit about what I'm doing and therefor hopefully get more helpful advice
3) because I cant stand experts that auto condescend learners. although I dont think you are only giving safety advice.

 

[vichouse]

If there is space one typical way of doing it would be to put in a new consumer unit, and get it connected to the meter and certified. Then connect the old consumer unit (if the wiring's not too shonky to be used temporarily) to a way on the new CU, probably through a 40A RCD protected circuit*, then take new circuits to the new CU and disconnect the old circuits from the old CU as you go. (*adjusting the load on the old CU to be below 40A if necessary, eg provide new cooker/shower circuits straight to the new CU)

OwnerDIY I like this idea. Its all gas for heating and cooking so there are few high demand circuits which should make this easier still. Presumably this is notifiable. In which given I'm not qualified I'd probably be best getting this bit done by an qualified electrician (rather than having three inspections two times over). Would be a qualified electrician be happy to do this and then allow the home owner to do the remaining rewire?

 

[vichouse]

Sorry ban-all-shed missed of a bit of your reply to reply to
Yes bizarrely the council do inspect and insist on a 3 part inspection for noq qual's doing part p work and that includes a pre inspection when they want to see the plans.

And CU wise I think I'll follow OwnerDIY's idea of getting a second CU set up and running (by a pro) with the old CU running off the new one temporarily.

 

[OwainDIYer]

If there is space one typical way of doing it would be to put in a new consumer unit, ... Then connect the old consumer unit (if the wiring's not too shonky to be used temporarily) to a way on the new CU... then take new circuits to the new CU and disconnect the old circuits from the old CU as you go.

OwnerDIY I like this idea. Its all gas for heating and cooking so there are few high demand circuits which should make this easier still. Presumably this is notifiable. In which given I'm not qualified I'd probably be best getting this bit done by an qualified electrician (rather than having three inspections two times over). Would be a qualified electrician be happy to do this and then allow the home owner to do the remaining rewire?

All the work would be covered by the one building control application and fee. It;s up to the council how many inspections they want to do, but they shouldn't charge any more. The DNO would probably want to see a cert before they connect the new CU meter tails.

Once you've got the new CU in quite a lot of work can come under the 'like for like replacement' rules anyway, so is not notifiable.

 

[OwainDIYer]

What are the 3 different types of domestic single-phase supplies provided in this country, how would you recognise them, and what differences do each make to the requirements for the rest of the installation, particularly any outdoor supplies?

Supply to houses is generally 240v +/- 10 single phase, is this what you're refering to? (no outdoor supplies intended)

Earthing system - TT, TNS, TNCS

Can you correctly identify all components and connections of a circuit by method of testing or otherwise? In doing so can you identify or recognise anything wrong or dangerous with the circuit?

- I might be misunderstand this one but surely that would be more relevant for alterations or additions to a circuit or testing a circuit where you need to understand whats already there, whereas I'm planning on a rewire from new.

Still need to test for polarity, open/cross connected rings, borrowed neutrals, etc. on new work before energisation.

Do you understand how the way in which you install cables affects how much current they can carry?

- lets see I=V/R and R=pl/a (cant type greek) so length and cross-section of cable would be key but I'm guessing loops and/or other cabling in parallel will have an effect through the magnetic field from the other ac wires but I assume that would be negligible with the number of wires and accuracy of current required in a residential set up - (as with others please correct if wrong)

Primarily installation in thermal insulation, ambient temperature, and cable grouping in trunking and enclosures

Note eddy currents can be an issue where phase and neutral pass through separate holes in metal enclosures.

Where cables need to be joined, how should this be done / not be done and in what circumstances are different methods acceptable?

- Hmm I assume you are refering to uses of junction boxes but the question is ambiguous to me please rephrase.

If the connection is inaccessible then screw terminals can't be used - crimp or solder.

Which circuits should be RCD protected?

- Trick question perhaps - as its a complete rewire all sockets, and anything to bathroom or kitchen (gas heating so need boiler circuit). Additionally any unprotected wires running less than a certain depth into the wall (50mm I think).

Slightly trick question as it can depend on your earth type and impedance.

 

[1john]

Well done on trying to answer those questions, it's the first time anyone has as far as I am aware!

As for your reasons, 1 - you will, 2 - you know a bit, there's alot more to learn, 3 - well from your various answers I would say that he has given safety advice as they are mostly incorrect, and i'm assuming that you thaught they were correct. I am not intectionally being condescending, although it may come across like that as there is alot more you need to learn, which is good that you can tell that now and get clear on everything. My prime concern is that you do a safe job and know why you are doing what you are doing if I am to advise.

I am sure BAS will happily disect this and put you straight on most things although I have got some spare time this morning to get you going on the first two questions, i hope it helps, I would love to see a DIY rewire done with full understanding, I mean that, if you cannot afford to enploy a professional and are going to do work yourself, you should atleast explore every avenue you can to ensure that the work is upto scratch, flexible and above all safe and compliant, which is what you are planning

Pictures throughout the installation are also nice to see once you are ready and prepared to get going

haha ban-all-sheds 6 years and you havent changed a bit. I discovered DIYornot by googling "home rewire" which has the first result as the 2005 post where you slated davedasave for attempting a home rewire
//www.diynot.com/forums/viewtopic.php?t=31811

Anyway you'll be happy (perhaps thats asking too much so maybe just mildly reassured) to know I took note of your post then and have been researching this a bit including reading the regs, to the point I was going to ask if you could provide a more up to date book list.... (and i would still be grateful if you could do this)

Anyway seems its quiz time and I do like quizes so lets have a go....

But first a quick point: as I understand it part of the point of the 3 part inspections is that my wiring plans would be inspected at the first inspection prior to first fix which would address many of your concerns.

Anyways back to quiz time and my answers for what they're worth.

For a circuit to supply a given load (doesn't matter what), how would you go about deciding what cable and protective device to use?

Cable: 1mm lighting. 2.5mm ring main and up to 20 amp appliances. Cat5e for information
Protective device as in RCD/trunking/or other. RCD's see answer to your qu below. Trunking see answer on safe zones below. Other, please tell me or tell me what to read...

If you start your design with the cable size, this will limint your OPD and therefore limit the load you can connect to the circuit.

You need to establish the load first, then you need to select an appropriate OPD and then a cable, you then need to do cable calcs applying derating figures to the current carrying capacity of the cable, you then need to see if the cable you initially thaught was acceptable is, if not, go to the next size cable and re calculate, if it is not sufficient, then the next size cable and recalculate, so on and so forth. This is fairly simple maths so no too difficult, and all the figures you need are in BS7671

How do you calculate maximum demand and how can diversity be used?

- Max demand on an individual circuit I'm guessing. Well my house floorplan is less than 100 sq m and the most high demand appliance I have is probably my kettle and other kitchen appliances (gas heating). So demand wise ring mains 1 upstairs, 1 downstairs, 1 for kitchen, seperate supply for certain kitchen applicances is the plan and is anything ott on providing for demand.

What are the 3 different types of domestic single-phase supplies provided in this country, how would you recognise them, and what differences do each make to the requirements for the rest of the installation, particularly any outdoor supplies?

Supply to houses is generally 240v +/- 10 single phase, is this what you're refering to? (no outdoor supplies intended)

This is in regards to earthing systems, we have three different methods if providing a main earth to an installation, two of which are from the supplier, one is provided by the owner.

 

[ban-all-sheds]

haha ban-all-sheds 6 years and you havent changed a bit.

Probably because neither the laws of physics nor the general requirements of the Wiring Regulations have changed in 6 years, and therefore neither have the sorts of things you need to know.

I took note of your post then and have been researching this a bit including reading the regs,

But maybe not carefully enough?

to the point I was going to ask if you could provide a more up to date book list.... (and i would still be grateful if you could do this)

Already provided for you: //www.diynot.com/wiki/electrics:books

But first a quick point: as I understand it part of the point of the 3 part inspections is that my wiring plans would be inspected at the first inspection prior to first fix which would address many of your concerns.

Fair enough - your council is very unusual. How much do they charge for all this?

For a circuit to supply a given load (doesn't matter what), how would you go about deciding what cable and protective device to use?

Cable: 1mm lighting. 2.5mm ring main and up to 20 amp appliances.

If you'd been reading the regulations you'd know that was wrong.

See Appendix 4.

Protective device as in RCD/trunking/or other.

Other. As in MCB or fuse.

RCD's see answer to your qu below. Trunking see answer on safe zones below. Other, please tell me or tell me what to read...

//www.diynot.com/wiki/electrics:books

How do you calculate maximum demand and how can diversity be used?

- Max demand on an individual circuit I'm guessing. Well my house floorplan is less than 100 sq m and the most high demand appliance I have is probably my kettle and other kitchen appliances (gas heating). So demand wise ring mains 1 upstairs, 1 downstairs, 1 for kitchen, seperate supply for certain kitchen applicances is the plan and is anything ott on providing for demand.

You're about to embark on a from-scratch design and install of an entirely new installation for a house and you're doing some of it by guessing?

Do you really think that's a good idea?

Both of these have information on maximum demand and diversity:

Supply to houses is generally 240v +/- 10 single phase, is this what you're refering to?

No it's not.

Read Part 2. (Again?)

Do you see what I mean about you maybe not have been reading the regulations carefully enough?

I might be misunderstand this one but surely that would be more relevant for alterations or additions to a circuit or testing a circuit where you need to understand whats already there, whereas I'm planning on a rewire from new.

True.

- lets see I=V/R and R=pl/a (cant type greek) so length and cross-section of cable would be key but I'm guessing loops and/or other cabling in parallel will have an effect through the magnetic field from the other ac wires but I assume that would be negligible with the number of wires and accuracy of current required in a residential set up - (as with others please correct if wrong)

Wrong.

So wrong, in fact, as to make you woefully unable to safely do the design work. Do you see what I mean about you maybe not have been reading the regulations carefully enough?

See Chapter 7 in Appendix 4.

- I'm guessing you mean safe zones, and use of armored cabling/metal trunking outside. That do or you want the details?

There's more to the requirements for concealed cables than just safe zones - see 522.6.6 - 522.6.8.

- Hmm I assume you are refering to uses of junction boxes but the question is ambiguous to me please rephrase.

Sort of - the use of different types of join (screwed, compression etc) and which are to be preferred where.

- Yup and if you ask me the regs are way OTT here, basically any bit of metal sticking up anyway that could be deemed to be earthed (pipework being a prime example) and is near an electrical supply needs to be bonded to the mains earth terminal.

No.

Look in the index for Supplementary bonding conductors, Supplementary equipotential bonding and Extraneous-conductive-parts. And also read about the subject in a decent guide to the regs. (Not, FHS, in the book discussed here: //www.diynot.com/forums/viewtopic.php?t=228045).

(I say its OTT as from what I understand if a metal pipe goes into a metal tank and another metal pipe comes out the end both need earthing and if all your pipework is metal (to outside the house) its earthed anyway as it comes from the ground - rant over).

You should not rant. It's the fact that the pipes are at earth potential which makes them candidates for supplementary bonding, and your rant shows that you don't understand the difference between earthing and bonding.

Which circuits should be RCD protected?

- Trick question perhaps - as its a complete rewire all sockets, and anything to bathroom or kitchen (gas heating so need boiler circuit). Additionally any unprotected wires running less than a certain depth into the wall (50mm I think).

It's not a trick question.

And your answer isn't quite right. Look in the index for Residual current devices.

I will liaise with them to fit an isolator

They might not - maybe someone from your area can advise on what your DNO's practice is.

and move the meter

Have you asked them to quote for that yet?

and perhaps the consumer unit all in one if they are willing.

They won't touch your CU. If you're having the meter moved make sure you provide the right means of connection between it and your CU - the DNO may have special requirements depending on the distance, so check when you get them to quote for the move.

1) to learn from errors

Better to learn from those now than after you've started.

You really do need to get some decent books on domestic electrical design, guides to the regulations etc - trying to learn everything just from reading the regulations is a bit like trying to learn a foreign language just be reading a dictionary.

2) to show I do know a bit about what I'm doing and therefor hopefully get more helpful advice

I fear you don't know as much as you think you do, but you'll get there.

3) because I cant stand experts that auto condescend learners. although I dont think you are only giving safety advice.

Safety advice is what I'm giving.

And also I'm not attempting to disparage your intelligence, manhood or sexual proclivities, but you do seem to be a bit vague on some vital and fundamental things.

When do you want to be starting your rewire?