Could use some help with wiring

[Sean9461]

hi,

I'm looking for some help in regards to working out the load calculation of a wire.

I'm pretty sure it should be ok but I just want to double check.

I have an outhouse workshop and have a mcb in my main house.

I had an electrician in to install a sub panel in the outhouse.

He installed a 10mm2 cable which only extends 3m max to the sub panel.

He installed a 50a breaker in my mcb leading to the sub panel.

The mcb has a rcd in it.

Now I'm aware about having to get an electrician in however my question is very simple.

The 50a breaker I would like to upgrade to 80a.

To run more load as I run a business from home several servers etc.

From all calculations I have done the 10mm2 cable over 3m should be able to handle 80a.

So I should be able to simply switch out the breaker for a 80a.

I would just like to confirm this with you guys. Can anyone confirm that this should be ok?

I really don't plan on paying or even getting someone to drive here to simply install a new breaker for me when it's literally as simple as switching a 3 pin plug.


Cheers

 

[Octopus]

So you have a house, with an office and you are planning to add an annex..... Best you get this all laid down as you may need a supply upgrade....

 

[Sean9461]

Yeah it's more complicated than I thought then. I'll get an electrician in with the builders at the same time.

Thanks for help

Appreciate it

 

[davesparks]

Seen 80A mccb but not mcb?

MCBs are available up to 125A, above 63A they are normally three units wide (27mm) instead of the standard 2 units (18mm)
The only standard DB I know of which can take them is the 200A (might be 250A) memshield 3 boards which can have a number of 27mm ways as required.

Also see the Schneider (Merlin Gerin) C120H range of mcbs.

Ive got a 125A C type Terasaki sitting on the bench in the workshop at the moment,

 

[Sean9461]

I'm getting someone out for a quote tomorrow and builders coming out today.

I have what may be a stupid question though guys,

If a breaker is rated for 50a and it's a type b. I've read type bs overload at 2-3x its rated value?

So can you run more than 50a through a breaker?

As off my 50a breaker I have a 16a breaker on my sub panel. Which if I worked it out properly would be max 3680w. Now I have several servers on this circuit well, 8 servers each with a 600w psu.

Now psus hardly ever draw their full rated power but my question is,

If they draw 4000w in total for a couple of hours will the breaker be ok or will it instantly trip as soon as I go 1 watt over 3680w?

Cheers

 

[Octopus]

If you try and run a breaker over its limit for a period it will

A. Trip

and

b. Fail after a while

 

[Sean9461]

So it can't run even 1 watt over the rated amount for any amount of time?

 

[Pete999]

So it can't run even 1 watt over the rated amount for any amount of time?

 

[Darkwood]

Mcbs and all fuses follow a time/current curve chart when they are over there rated value, a very small overload may be present without the overload device ever operating but through regulation and design, this should not happen, you are also mixing up what the b,c,d ratings mean they allow for an initial inrush which is associated with inductive loads and choosing the correct type will limit nuisance tripping.
It may be quite difficult explaining in depth what is what and why due to your limited knowledge hence it is always best to get a competent person in even if you perceive it may be a simple mcb change, a simple mistake can put property and lives at risk.

 

[telectrix]

I'm getting someone out for a quote tomorrow and builders coming out today.

I have what may be a stupid question though guys,

If a breaker is rated for 50a and it's a type b. I've read type bs overload at 2-3x its rated value?

So can you run more than 50a through a breaker?

As off my 50a breaker I have a 16a breaker on my sub panel. Which if I worked it out properly would be max 3680w. Now I have several servers on this circuit well, 8 servers each with a 600w psu.

Now psus hardly ever draw their full rated power but my question is,

If they draw 4000w in total for a couple of hours will the breaker be ok or will it instantly trip as soon as I go 1 watt over 3680w?

Cheers

50A equates to 12kWatts ( single phase) so i doubt you'll be able to overload a 50A MCB unless you're adding a 9kWatt boiler.

 

[Sean9461]

12kwatts? Do our houses in U.K. Still run at 240v I thought it was 230 now?

When I was working out my 16a circuits I was working it as 230 x a

 

[DPG]

The new 'standard' is 230V but in reality you will find it is pretty close to 240V in reality due to the major work needed to actually change the distribution system to 230V. You could always measure it and see what you actually have. Daz

Might be worth reading this thread
Domestic - is it 230v or 240v? - http://www.electriciansforums.co.uk/threads/is-it-230v-or-240v.47949/

 

[davesparks]

12kwatts? Do our houses in U.K. Still run at 240v I thought it was 230 now?

When I was working out my 16a circuits I was working it as 230 x a

No in the UK substation output is still 250V, this has not changed since the whole country was standardised and the national grid was established.

the power rating of an appliance will be at a stated voltage, this is the voltage you need to use in calculations for that appliance as it will only be applicable at that voltage.

Also you cannot establish the actual load by adding up the ratings of the mcb's, if you want it accurate then a load study carried out over a few weeks is the best way.