Garage Electrics Help

[Rhohno]

Hi Guys,

I am new to this forum so please be nice.

My girlfriend and I have just bought a 1960's flat in Surbiton, Surrey and the fuse box looks like it is 50 years old! Not that it isnt working but during the survey the morgage company said they wanted it updating for them to be happy. We have had a sparky quote £500 to rip out the old, put in the new unit and test all connections, plus change the sockets from the old ones to the new I will supply. Firstly is this a good price for London?

Secondly I want to run power to my garage downstairs and the landlord has given consent. I will be using powered items such as lights, air compressor, washing machine, general power tools and also my small arc welder (30a-130a). Now in order to run the power I have been recomended to run twin and earth from the consumer box to the junction box nearest the garage inside the flat (12-15m) then tack run SWA down the edge of the building wall into the garage (about 25m). But he suggested I need to use 10mm cable for that load rating. Does this sound right as thats like £200 of flex to the garage alone?

Thanks
Carl

 

[riveralt]

My girlfriend and I have just bought a 1960's flat in Surbiton, Surrey and the fuse box looks like it is 50 years old! Not that it isnt working but during the survey the morgage company said they wanted it updating for them to be happy. We have had a sparky quote £500 to rip out the old, put in the new unit and test all connections, plus change the sockets from the old ones to the new I will supply. Firstly is this a good price for London?

That sounds about right for the area, but if you are unsure get two other quotes.

Secondly I want to run power to my garage downstairs and the landlord has given consent. I will be using powered items such as lights, air compressor, washing machine, general power tools and also my small arc welder (30a-130a). Now in order to run the power I have been recomended to run twin and earth from the consumer box to the junction box nearest the garage inside the flat (12-15m) then tack run SWA down the edge of the building wall into the garage (about 25m). But he suggested I need to use 10mm cable for that load rating. Does this sound right as thats like £200 of flex to the garage alone?

You cannot do this yourself without notifying your Local Authority Building Control. If the electrician is going to do it - sounds a good price.
10mm SWA is around £4 per metre - plus the cable clips and bits and bobs in the garage. Given the voltage drop, cable route and potential load this sounds about right.
Just make sure that the electrician is going to notify the LABC on your behalf for both pieces of work and that you receive the appropriate Electrical Installation Certificate et al. He may/should be a member of a competent persons scheme.

 

[westie101]

You or your electrician should also complete an additional load request to your DNO (UK power networks) for the compressor and the welder. There is a risk that they could cause other customer's supplies to flicker so they need prior approval before being connected.

I appreciate that you may be using them at another location and you should have got permission to connect them there as well!

 

[chapeau]

When he says the arc welder is 30a-130a that is the output current.

He will almost certainly be plugging it in using a 13Amp plug like you use when you plug your christmas tree fairy lights in.

So absolutely no requirement to tell the DNO anything.

If something really really peculiar happens and his arc welder starts to draw 130 amps at 230 volts then the fuse in the plug will melt. If that fails, a local breaker in his property will trip and nobody else in the street will even know about it.

 

[bernardgreen]

So absolutely no requirement to tell the DNO anything.

Any motor above 1 kw or transformer isolated load above 1 kw had to be declared when I applied to the DNO for a new supply. The small print in the contract suggests that any alterations I might make later that would involve loads of that type had to be notified. I aksed specificallyabout a cool room compressor that might be fitted in one of my out buildings and if more than 1 kw then it would need to be notified.

The problem is the starting current of the motor and the in rush current to the transformer is very high so creates voltage drops that will affect other properties supplied by that phase. The high current will seriously un-balance the loads on the phases creating high current in the neutral. The voltage drop for that current will "bounce" the neutral to other properties on that DNO cable which will then bounce the "earths" that are derived from that neutral.

 

[westie101]

So absolutely no requirement to tell the DNO anything.

And if his neighbour starts getting flickering lights he is risking disconnection of suppy, it is part of the National Terms & Conditions of supply that a significant change of load (significant as defined by the DNO) is notified!

3. Network constraints. Our obligations under this agreement are subject to the maximum capacity and any other design feature of the connection. You must contact us in advance if you propose to make any significant change to the connection or to the electric lines or electrical equipment at the premises, or if you propose to do anything else that could affect our network or if you require alterations to the connection.

As has been stated motor start & transformer inrush can affect the network!!

 

[chapeau]

Turning your light on affects the network.

If it's plugged into a socket then you don't need to tell anybody.

Otherwise where do you stop? Electric shower? Induction hob? Hoover? All have high current draws and will 'unbalance' the network. You aren't going to get a balanced network on a street, but the network is designed to cope for things that plug into sockets.

Should I tell them I have an audio visual system than draws 2.5kw at peak output. And that all goes through a transformer so what if I turn it on at full volume?

These devices have bits of kit inside them to limit inrush currents. Not that it will cause a problem anyway.

You have to get things in perspective. Scaring posters that they need to tell the electricity board when they put a power cable into the garage is somewhat excessive.

 

[bernardgreen]

These devices have bits of kit inside them to limit inrush currents. Not that it will cause a problem anyway.

You cannot say it will not cause a problem. Starting that type of equipment almost always results in irritating dips in neighbour's lights, sometimes the dip is long enough that their computor equipment freezes or re-boots. Depending on the supply cable impedance and wiring it can result in neighbour's RCD's tripping out.

You have to get things in perspective. Scaring posters that they need to tell the electricity board when they put a power cable into the garage is somewhat excessive.

You have to be more accurate. Telling the District Network Operator that you are installing feed to a garage is not notifiable. Well not to the DNO but is to the local building control office. The discussion is about the high start current equipment that will be used and notifying them to the DNO.

 

[chapeau]

Yes bernard, if it makes you happy you are correct. The DNO needs to be told when a new circuit is put in when they are thinking of plugging an arc welder in.

Or a high end audio visual kit.

Or an induction cooker.

Or anything with a motor in it.

If it makes you happy then tell the DNO.

I won't bother. And neither will they.

They put a main fuse on which is sized (amongst other things) to protect their network after asking you what your load will be when you ask for a connection. After that they really don't care.

But tell them if you want to.

 

[ban-all-sheds]

So they don't care about heavy reactive loads?

I think you'll find that they might.

I'm sure that Westie knows.

 

[westie101]

They put a main fuse on which is sized (amongst other things) to protect their network after asking you what your load will be when you ask for a connection. After that they really don't care.

Hmm perhaps then I need to ring our operations director in the morning and ask him to change a lot of our advice to customers and our Codes of Practice.

Believe me if you connect a load that interferes with another customer's supply you are risking disconnection. Of course if you know the full characteristics of the supply including the network impedance to the PCC (point of common coupling) you can then actually decide to ignore advice and do your own thing

 

[chapeau]

Hmm perhaps then I need to ring our operations director in the morning and ask him to change a lot of our advice to customers and our Codes of Practice.

If you could post a link to a complete authoritative document that would be very interesting indeed. Preferably it will have specific examples of which equipment I can plug into a standard domestic '13A socket' and which equipment I cannot. It will explain the reasons for including some equipment and excluding others.

 

[letinman]

Hi Guys,

I am new to this forum so please be nice.

My girlfriend and I have just bought a 1960's flat in Surbiton, Surrey and the fuse box looks like it is 50 years old! Not that it isnt working but during the survey the morgage company said they wanted it updating for them to be happy. We have had a sparky quote £500 to rip out the old, put in the new unit and test all connections, plus change the sockets from the old ones to the new I will supply. Firstly is this a good price for London?

Secondly I want to run power to my garage downstairs and the landlord has given consent. I will be using powered items such as lights, air compressor, washing machine, general power tools and also my small arc welder (30a-130a). Now in order to run the power I have been recomended to run twin and earth from the consumer box to the junction box nearest the garage inside the flat (12-15m) then tack run SWA down the edge of the building wall into the garage (about 25m). But he suggested I need to use 10mm cable for that load rating. Does this sound right as thats like £200 of flex to the garage alone?

Thanks
Carl

£500 IS roughly right for london , not cheap, not expensive

 

[westie101]

If you could post a link to a complete authoritative document

I'll dig one out in the morning for you, it may only be a copy & paste! Note it is one that applis to one DNO but I have no reason to doubt that it doesn't apply in others

The quote I made earlier is available on line.

Better still, have a look at this page: - http://www.enwl.co.uk/help-and-knowledge-centre/useful-guides

Then under the sub-heading Connection Services Guidance

7th PDF down "Guidance for interference with Supply"

Basically if it is not likely to interfere then it isn't an issue!

Or perhaps as you are in Nottinghamshire this page from WPD (your DNO): - http://www.westernpower.co.uk/New-Connections/Network-Alterations.

Network Alterations

Network Alterations We may need to make alterations to the electricity system. For example:

Building Work

Building work is proposed which requires cables, overhead lines, substations or meters to be moved.

Additional Equipment and Loads

Additional electrical equipment is to be connected which increases the load.

Additional Equipment and Disturbances

Additional electrical equipment is to be connected which could create a disturbance on the electricity system, ie connecting a motor or welder.

Good enough for you?

 

[chapeau]

Oh Deary Deary Me. So Binary.

My house, and yours, is full of motors.

Hoover, freezer, fridge, washing machine, central heating pump, anything with a cooling fan in it, coffee grinder, your computer hard disc drive. All plugged into a '13A Socket' and in every single case I am under no obligation to advise the DNO that I am using a new motor.

What that document of yours means is when you might want to install a three phase motor then the DNO might want to know as they can tell you whether you have a three phase supply. If you are setting up a car repair shop then the DNO might want to know so they can upgrade your main fuse/provide three phase supply.

But if you are plugging a motor into a simple domestic socket they simply don't give a monkeys. And this is exactly the same if you want to plug a transformer into a 13A socket. Because that's what an arc welder is that you buy to use in your garage plugged into a 13A socket.

Would you like a list of all the items in my house that have a transformer???? All plugged into a 13A socket and I didn't tell the DNO about any of them.

If it draws too much current, a local protective device will blow. In the interim few cycles then the local network will not even hiccup.

Anyway, that's all for me on this one.