Powering up a new conservatory

[Richard C]

I am in the middle of renovating a 60’s property & the electrics look like they may be about to turn into an expensive nightmare!

Question 1
A ‘part P’ electrical contractor brought in by my main contractor has stated that since my house has an old fuse board system with a Voltage ELCB, my new conservatory socket outlets, lighting & underfloor heating system cannot be connected to the existing system without upgrading the whole house with a new consumer unit & upgraded safety provision. Both myself & the conservatory company were under the impression that only the new spur would need to comply with Part P; we have asked a couple of other electricians with conflicting results & have also tried to clarify by studying the new regs but find them very less than clear! Is our electrical friend correct or is he indulging in a little exploitation to get some work?

Question 2
I have discovered that one of the kitchen ceiling plasterboard nails has punctured the neutral feed to the cooker outlet & looks like it has been like this since built! I have been told that I cannot repair the cable using a junction box & must replace the whole cable, right back to the fuse board, is this correct?

Help would be greatly appreciated.

 

[Spark123]

1) I believe your electrician friend to be correct, the voltage operated ELCB was removed from the regs in the early 80s as they are now deemed not safe. To do a streight swop with an RCD will is now not as streight forward as this would leave the property prone to tripping out all the circuits should an earth fault occur (inconveniance, no lights etc.) You may also not have RCD 30mA protection on sockets which may provide power to appliances outside.
I personally would go for some type of split load cu depending on the installation.

2) It is possible to joint the cable using the correct size crimps, proper ratchet crimping tool and heat shrink sleeving, the probable reason why a jb can't be used is it needs to be accessable which it isn't deemed to be under the floor or above the ceiling.

 

[ban-all-sheds]

1) I believe your electrician friend to be correct, the voltage operated ELCB was removed from the regs in the early 80s as they are now deemed not safe.

Yes, but there is no requirement to replace them.

Is yours a TT supply ( //www.diynot.com/forums/viewtopic.php?p=141310#141310 ) ?

How is the conservatory to be wired? One new circuit from the existing CU, with spurs for heating and lighting?

Several new circuits from the existing CU?

One new circuit from the CU supplying a second CU in the conservatory?

A new CU alongside the old to supply the conservatory?

Extending existing house circuit(s) into the conservatory?


There will always be ways round replacing the old CU - however , replacing it is probably the best approach. It might not cost much more than the alternatives and it is good thing to do anyway.

If you do go that route, get the existing wiring properly inspected and tested, and get a firm understanding with the electrician about what he'll do if hitherto undiscovered faults start to cause nuisance trips.

 

[Richard C]

The electrical contractor did say he would need to test all the circuits before proceeding with the new CU installation but I am concerned about how many more problems he will find, so escalating the price. The main contractor has agreed to stump up part of the additional cost of the new CU but not the cost of rectifying any other problems found, which is fair enough I suppose! I am also a little concerned about nuisance tripping as my father had the same problem when his 50’s ex-council was upgraded. Our contractor friend is intimating I have no option but to upgrade the whole lot before any of the conservatory services can be connected & signed off but this didn’t really sound right to me, hence the post!

In answer to earth provision, I have a metal rod in the ground connected to an earth lead back to the fuse board, is this a TT?

Before our part P contractor appeared with his message of doom, the conservatory company’s proposal was to break into the existing kitchen ring main for the 3 x 13A double sockets & fan/light unit & run a separate supply (4mm cable) directly from the fuse board for the under floor heating system. The problem is that there are no spare fuses so they were originally going to install an additional single CU alongside the existing fuse board to feed the heating system. This raises another question with me in that is it possible/acceptable to install a separate RCCB with the old Voltage ELCB still in situ?

Re joining the damaged 6mm cooker cable; there are several junction boxes already in the ceiling cavity that are used on various parts of the ring main & lighting circuits, what about the accessibility of these? I would have thought using a junction box would have been safer/preferably to crimp connections & heat shrink tube or am I stuck with replacing the whole cable run back to the board because some clod stuck a nail through it 40 years ago?

What’s the correct way to do it? I don’t want any future problems with insurance/house sale; I am only an inquisitive amateur trying to make sure it’s all done properly but a little knowledge is sometimes more dangerous than none at all. I seem to be doing all the running & answering all the questions at the moment rather than the guys who are supposed top know so advice would be very welcome.

 

[Adam_151]

Could have a main isolator installed (before the ELCB), split the tails with a henley after this, and install a new CU with 100ma S type and 30ma split load config, upgrade the bonding, and put new circuits on this cu, and maybe move any circuits that test out ok onto it as well, for the circuits that don't test out ok, thde contractor can leave them on the existing cu, and inform you of the problems with them, there is no requirement that says he has to bring circuits that he doesn't do work on in line with the regulations, though if he does a PIR style thing on them, then it'd be very wise to eliminate all code ones.

The best thing would be to have all circuits moved onto new board and old board removed, but if there is a neutral, earth fault somewhere thats gonna be too expensive to track down, if the spark does not touch that circuit, then there is no reason for him to have to correct it

Yes, metal earth rod in the ground is TT, might be worth enquireing to your DNO if its possible for them to install PME for you (earth terminal on the neutral supply line at the meter point)

Crimps are regarded as mechnaically sound, and can be buried, where as screw terminals are not, though as long as the connections are made nice and tight, there are far worse things than a JB buried under floorboards, recommend you have your cooker cable crimped though

 

[Spark123]

1) I believe your electrician friend to be correct, the voltage operated ELCB was removed from the regs in the early 80s as they are now deemed not safe.

Yes, but there is no requirement to replace them.

True as it stands, but I too would refuse to carry out work on a system with one of these devices installed unless I were replacing it.

 

[Lectrician]

I too always say the ELCB has to go.

The cost of a 100mA type S RCD, and putting a 4mm earth to rod (as usually only 2.5mm were used with ELCB's) is easilly approaching the cost of installing a 10way split loader ready for a PME connection.

You dont mention bonding anywhere......I expect your main equipotential bonding to the water (and gas/oil if you have it) will be the wrong size or non existant. This requires sorting before ANY works go ahead.

 

[Richard C]

There is no earth terminal from the service provider at present as we are on overhead cabling, do they charge to supply one? Can they in my circumstances?

The TT earth cable is 4mm & there is some local bonding to the steel sink units & the bath etc. but there is no equipotential bonding of service pipes at the moment, is it a requirement this be retro-fitted before the other work can be carried out?

I am having difficulty resolving this issue with my main contractor as we both seem to be getting conflicting advice on the requirements of Part P from various sources; Does anyone have the definitive answer as to weather or not our electrical contractor is correct in insisting that changing my existing CU is mandatory before the conservatory & under floor heating system can be connected? Or, as others have suggested, it is only necessary for the new spur to comply with Part P!

 

[Lectrician]

there is no equipotential bonding of service pipes at the moment, is it a requirement this be retro-fitted before the other work can be carried out?

Yes, definantly.

Your Supplymentary bonding probably is not up to scratch either, but as you are not working in a bath or shower room....or swimming pool, this doesn't need to be upgraded.

An earthing terminal can be provided by the lecky board in most, if not all, installs these days. Rare to be refused one. My DNO, Wester Power Distribution, used to fit for free, they now charge around £18 I recall, as of last month. Some DNO's charge around £80-£100.

I would strongly urge you to go for a new CU and upgrade the bonding, as this seems the most appropriate time to do so.

_________________________
moderator

edited to correct quote

 

[Richard C]

Thanks all for the replies so far; the row goes on & my main contractor has now produced a second part P registered contractor who is saying I don't have to upgrade anything on my existing system, not even the equipotential earth bonding! He says that all that is required is a new RCD piggy backed of my existing consumer unit. I don't trust this at all & my my suspicians have now gone from being 'ripped off' to being totally 'snowed'; any additional comments/amunition I can use anyone? I fear I may never get my new conservatory powered up!

 

[Lectrician]

I think everything you need is in this post.

 

[JACKC]

Trust what your sparkie is telling you, if not find another one willing to do what you want and not what years of experience is telling you. Inform your family to save a few days holiday for the funeral as I can see a small fire and shocking news coming there way.

 

[ban-all-sheds]

The problem is that he's got 2 sparkies, and they are telling him different things.

But if we cut to the chase, and ignore the arguments about what is/is not/may be "required to be done" before the conservatory circuits can be connected up, then the differences become irrelevant.

1) Voltage ELCB: No question, this should be replaced, whether "required" or not.

2) Lack of equipotential bonding: No question, this should be installed, whether "required" or not.

3) New CU: To comply with the wiring regulations (not strictly a legal necessity, but damned hard to avoid in these Part P days), you need 30mA RCD protection for all socket outlets, and you don't have that, so your fusebox needs to be replaced with a split-load CU, 100mA Type S incomer, 30mA normal RCD at the split. You are not forced to upgrade, the electrician could comply with the regulations in respect of his work by putting in a small CU to provide the necessary protection to the new circuits, but the regulations are there for good safety reasons, so again I would say that there is no question that the CU should be replaced.

The only rider I would add is that maybe you should contact your DNO to see of your supply can be changed from TT to TN-C-S (PME), which would remove the need for an installation-wide RCD. But not the one for 30mA protection for sockets reasonably expected to supply portable equipment outdoors. If you do want to look into this, then have the main bonding installed to PME specs, not TT, so that it wouldn't need to be re-done.

If your electrician is local, and familiar with the area, then he may well know if you could easily get a PME supply.

Accept though that this may not happen in your conservatory timescales, and that therefore you will have to spend money now on facilities that you later discard, e.g. the 100mA incomer.

What size is your existing fusebox, and what runs off it? - Maybe this would be a good plan:

1) Install main bonding to PME specs.

2) Install a split-load CU, TT-specced, and sized ready to take the entire house.

3) Supply the new conservatory circuits from the new CU.

4) Supply the existing fusebox from a 63A MCB on the pre-split side of the new CU. This would get rid of the voltage ELCB problem, but wouldn't require any other changes to the existing installation, unless tests showed that there was something genuinely badly wrong with it.

5) At a later date, move the rest of the house onto the new CU, possibly replacing the RCD incomer with a normal switch if the supply becomes PME.

 

[Richard C]

The problem is that he's got 2 sparkies, and they are telling him different things.

Thanks for spotting my problem; This problem arose because the main contractor did not survey the current power installation & spot it was not suitable before I accepted his quote & I had no idea at that time!

When it came to light, I was happy to contribute to the additional cost of installing a new C/U & upgrading the earthing & bonding provision but now my main contractor is saying it's not necesarry to go this route, presumably because he no longer wants to foot any of the additional cost as we initially agreed.

I have been doing a lot of reading & digging around in the last couple of days & had come to the very conclusions you have recommended. It's very satisfying to know I was on the right track & many thanks for the difinitive response. As an ameteur trying to argue my case with 'professionals' at least I now have some concrete & authorative information to quote that's not buried deep in sometimes difficult to fathom specifications. God help the average punter in this minefield!

 

[ban-all-sheds]

Thanks for spotting my problem; This problem arose because the main contractor did not survey the current power installation & spot it was not suitable before I accepted his quote & I had no idea at that time!

No - not reasonable that you should - I was going to say in my previous post that the contractor was at fault here.

When it came to light, I was happy to contribute to the additional cost of installing a new C/U & upgrading the earthing & bonding provision but now my main contractor is saying it's not necesarry to go this route, presumably because he no longer wants to foot any of the additional cost as we initially agreed

He's found a tame spark to back him up. I agree he's pulling a fast one, but look at it this way - if he had spotted these things at the start, you'd have been paying for them all anyway....

I have been doing a lot of reading & digging around in the last couple of days & had come to the very conclusions you have recommended. It's very satisfying to know I was on the right track & many thanks for the difinitive response.

Unless it's just a case of two amateurs thinking alike....