Maximum diversity and Garage DB

[Mo Fard]

Hi

We are doing some refurbish work at my house and I am planning to run a new feed to the garage and install a DB. Mainly because I don’t trust the exciting wiring in there and I have no idea where its supplies from. Plus I would like a separate DB as I use a lot of tools in the garage and I would like to allow for future lights or power I may install in the garden.
I am having two problems.

1. I have calculated the maximum demand for the house and after considering diversity we are using around 130A. I know we don’t come nowhere near that, as there is only 4 of us in the house. I am not sure how much power we can use before it becomes a problem.
2. I don’t know if I should install a MCB in the main DB an take the feed from there or take the feed after the main isolator.

Thank you
Mo

 

[Risteard]

at home have the induction hob (40amp), two showers 40amp each and a lot of other things running and dont have a problem on 100amp service head.

I wasn't suggesting that you would. For a start the induction hob won't be using anything like 40A.

My large Electrolux induction hob shares a 30A circuit with my oven. And I have no doubt that the load never even approaches 30A.

I was merely pointing out that unless things are going to be used simultaneously then there is no need to just add the loads together. Furthermore, with an electric shower you are likely to be in it for 5 or 10 minutes, and so there will be no significant heating of the cable. Overloads which are likely to last for an hour or more are of far greater concern.

Small overloads of short duration can essentially be discounted.

 

[Mo Fard]

I think the idea of a separate DB in the garage is a good idea if large compressors/welders etc. are going to be used. Saves any worry about overloading existing circuits. Daz

How would you go about installing a DB in the garage?

 

[DPG]

Depends on many things! Is garage attached/detached? Length of run? Etc. Daz

 

[Darkwood]

How would you go about installing a DB in the garage?

What exactly are you asking here... if your fitting a distribution board 'DB' (consumer unit) in the garage -'same thing' then just weigh up the requirements of your circuits and calculate the size of your cable needed to supply the new DB from the origin of the installation in your house.

 

[Mo Fard]

at home have the induction hob (40amp), two showers 40amp each and a lot of other things running and dont have a problem on 100amp service head.

to open your eyes have a search to see what max demand is allowed per property.

compressors will use hardly any power cause they will cycle to keep the tank upto pressure.

unless this is an industrial welder it will be plugged into a wall with the max of a 13amp fuse and the same with the compressor.

go to screwfix and buy a clamp meter they cost say £40-50, clamp the main tails and start turning things on and you will be suprised at how low the draw is

Both the equipments are plugged so I know they are limited to 13A each. But the garage is supplied with a 16A fuse and the lighting is ran off that. Plus I don't trust the supply cable, it looks like a 2.5mm2 twin buried under the house. So a new supply will have to be ran and I rather run a large SWA.

Measuring the demand is a good idea and I will do that. But I do want to learn how to calculate maximum demand in case I want to design anything in the future.

 

[Mo Fard]

What exactly are you asking here... if your fitting a distribution board 'DB' (consumer unit) in the garage -'same thing' then just weigh up the requirements of your circuits and calculate the size of your cable needed to supply the new DB from the origin of the installation in your house.

I have seen elctricians taking a supply for a second DB from the incoming tails before it enters the main DB. Is this common practice and is it safe to do? Or should I take the supply from a MCB inside the main DB?

 

[Mo Fard]

Depends on many things! Is garage attached/detached? Length of run? Etc. Daz

It is a detached garage with total run around 7-8m. And I do want a 32A power and a 6A lighting plus room for extra breaker if possible