Armoured cable 16mm or 25mm

[Cliff C]

I am not an electrician. Can anyone help please?

I have an outbuilding which I am converting into two offices.

The building is currently served by a 16mm armoured cable running underground from my house, the distance is about 100 metres.

Potentially the building could have a maximum of the following appliances:-

2x2kw electric oil filled radiators
1x1.5kw electric oil filled radiator
Hand wash 2.5kw
Electric Kettle 2.5kw
Saniflo 400 watts
Vacuum Cleaner 1kw
4 Fluorescent Lights
2 Computers
Total aprox 13kw

Will the existing 16mm cable be adequate or will I have to have it replaced with a 25mm armoured cable.

Thank you

 

[telectrix]

bear in mind that not all loads will be in use simultaneously. applying diversity, I'd allow for an aveage load of 8kW. that equates to c. 40A, so as far as current capacity, 16mm will,be fine. volt drop however may be a factor.

 

[Strima]

For a 40 amp load over that distance you will have a volt drop of 11.2 volts.

As you have lighting the maximum permitted is 3%, 6.9 volts, even using 25mm you are just over for volt drop.

Also depending on your current earthing arrangements and protective device type you would be looking at 35mm as a minimum.

My advice is to employ the services of a local electrician to design and install this for you, a few figures and a bit of SWAG on the internet is no substitute for a full site visit and survey.

 

[telectrix]

i could not be arsed to work out the VD as books are in van. however, for wtat it would cost to replace the 16mm cable versus exceeding the 3% for lighting, I'd fit LED lights which are happy with a slightly reduced voltage and sod it. at the end if the day, it's only a shed, not a hospital operating theatre. tin hat ready.

 

[Spoon]

With your current 16mm cable, you can have a 25A breaker.

 

[telectrix]

With your current 16mm cable, you can have a 25A breaker.

and what purpose would that serve apart from OP wearing ot his shoes going backwards and forwards to reset???????

 

[Spoon]

it's only a shed, not a hospital operating theatre.

Following on from this mate. If he is to reduce the items going into the shed then the max breaker he can have is 25A..

 

[Pete999]

I am not an electrician. Can anyone help please?

I have an outbuilding which I am converting into two offices.

The building is currently served by a 16mm armoured cable running underground from my house, the distance is about 100 metres.

Potentially the building could have a maximum of the following appliances:-

2x2kw electric oil filled radiators
1x1.5kw electric oil filled radiator
Hand wash 2.5kw
Electric Kettle 2.5kw
Saniflo 400 watts
Vacuum Cleaner 1kw
4 Fluorescent Lights
2 Computers
Total aprox 13kw

Will the existing 16mm cable be adequate or will I have to have it replaced with a 25mm armoured cable.

Thank you

Will that be a 3 phase or Single phase supply?

 

[Cliff C]

Will that be a 3 phase or Single phase supply?

Single phase.

 

[telectrix]

Following on from this mate. If he is to reduce the items going into the shed then the max breaker he can have is 25A..

i'm at a loss to see why he should fit a 25A breaker protecting a 16mm cable.

 

[Spoon]

i'm at a loss to see why he should fit a 25A breaker protecting a 16mm cable.

Voltage drop.
Any higher than 25A and the voltage drop would exceed 3%

 

[Silly Sausage]

Cowboy hat ready.

Sorry, couldn't resist

 

[bill01803]

I make just over 20A max

 

[Spoon]

I make just over 20A max

I'll show you mine if you show me yours...

 

[Silly Sausage]

I make just over 20A max

You're obviously in possession of warm clothing.
I get 23.91 Amperes with just the heaters on full balls.

 

[Wilko]

Hi - 100m is a long run and as usual the heating becomes a load problem as it might be on all day.

 

[telectrix]

the breaker is there to protect the cable from overload/short circuit, not to minimise volt drop. it' s Ib that should not exceed 25A, not In.

 

[telectrix]

Hi - 100m is a long run and as usual the heating becomes a load problem as it might be on all day.

yeah. but OP would have a warm lawn.

 

[Spoon]

Get yourself a wood burner and save yourself 3.5kW..

 

[telectrix]

wood shed, burn nice.