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.

 

[DPG]

wood shed, burn nice.

Typical scouser attitude

 

[Andy78]

wood shed, burn nice.

No no, you get extra wood to put in the burner. You don't have to snap bits off the shed.

 

[DPG]

No no, you get extra wood to put in the burner. You don't have to snap bits off the shed.

He misunderstood bless him. It's an age thing.

 

[buzzlightyear]

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

you at a lose ,me thinks some one lost the plot .

 

[Cliff C]

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.

Thank you everyone for your advice.

The reason I put my post was that I had two conflicting quotes from local electricians.

One said that my existing 16mm armoured cable would be OK and quoted me £480 to upgrade my outdated fuse box with a new consumer unit including safety certificate.

The other said that 16mm would be unsafe and a fire risk and quoted me £6900 to replace with 25mm armoured cable.

Will my 16mm cable by unsafe and a fire risk, or just a voltage drop that will mean I might have to replace my existing fluorescent fittings?

 

[Spoon]

Thank you everyone for your advice.

The reason I put my post was that I had two conflicting quotes from local electricians.

One said that my existing 16mm armoured cable would be OK and quoted me £480 to upgrade my outdated fuse box with a new consumer unit including safety certificate.

The other said that 16mm would be unsafe and a fire risk and quoted me £6900 to replace with 25mm armoured cable.

Will my 16mm cable by unsafe and a fire risk, or just a voltage drop that will mean I might have to replace my existing fluorescent fittings?

What size circuit breaker/fuse did the electricians quote, for this circuit?

 

[Wilko]

Hi - 16mm SWA buried is good for 78A single phase, which is about 18kW load. Your loads add up to less than this so in my humble opinion it's not the 16mm that might be a fire hazard. (It might be something else he's spotted?). Certainly there would be a significant voltage drop over 100m.

 

[Cliff C]

What size circuit breaker/fuse did the electricians quote, for this circuit?

The quote wasn't detailed and did not say.

 

[Spoon]

The quote wasn't detailed and did not say.

Ok.
As mentioned above, if you want to use the existing 16mm cable then the max size breaker/fuse you can have is 25A. Anything bigger and you will exceed the 3% voltage drop for your lighting.

 

[Nebu1a]

Could you have a small LPG combi-boiler fitted for your heating and hot water. Sockets on a 20amp radial and lights on a 6amp.

 

[ChrisElectrical88]

If you are using the office for yourself and are concious on what you are using together then the 16mm on a 25A MCB should be ok. Must be a big shed for that many heaters?

I would go with the upgrade however and get a fully detailed quote before placing the order.

 

[ChrisElectrical88]

Deleted duplicate

 

[Strima]

I would be using a fuse at source otherwise it could be a long walk when something trips out.

 

[UKPN]

I am not an electrician. Can any

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

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.

one 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

 

[UKPN]

25sqmm, then you can sleep at night.

 

[Yr ys]

Just change to led and use the 16mm cable. No worries.

 

[DPG]

Just change to led and use the 16mm cable. No worries.

LED heaters?

 

[Pete999]

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

That's a testing course aint it, 2391 I mean?