help needed with a customer?

[ian.settle1]

Thanks all, I've told him that I was correct when we first met and I seen the 16mm SY.
He was spitting and moaning about already buying the cable! He is going to try and take it back ( hehe good luck with that one )
I've given him a list of bits required including the 25mm 5 core swa, I've got a feeling he isn't going to like the price of that! I've rang my normal wholesales and they quoted me £650 on the swa.

As a few have said its going to be my name on the cert so I can't be doing a dog **** job!
It's up to him now if he takes me on for the job.

Funny thing was when I was leaving a car full of chaps from a un named Easter European place pulled up!
I bet they won't work out the cable and advise, Bish bash bosh thank you will be the answer.

Well if he doesn't get you to the job and lets them do the job, when his place burns down it will be up to him to do the explaining to his insurance company you can say well I told you so.

 

[Chr!s]

Good evening all,

OK so here goes-
I was asked to quote for a new dis board on a factory today with The Main feed being100amps going to a small 3 phase board in another building so-

-Main incomer 100a 3 phase
-50 meters of wire to a second board
-Second board with a 100a rccd acting as the main switch.

I automaticly thought 25mm 4 core swa clipped direct nice easy job as it would be under the volt drop and max rateing of the cable.
Then the customer tells me he has already bought the new board, main disconnector, and 50 meters of 16mm sy 4 core and im to use that?

Could someone give me a bit of a hand with the cable cals as i think the 16mm is to small due to my working out?
Design current 100amps

How have you arrived at a Design current of 100 amps?

Supply voltage 415volts

Supply voltage is 400 v

Fuse rateing 101amps

What type of fuse is this lol?

Cable length 50 meters
ca 1.02 page 267 table 4b1
cg 1.00 page 262 table 4a2 refrence method c
cc 1.00
volt drop 7.37v (1.77%) pf 1.0

Are you sure about the installation factors and the p.f?

so the actual cable rateing is 124amps
where as on a 16mm
volt drop 23.40v (5.64%) so over the max 5%
and the actual cable rateing is 73amps!

What about the final Circuits?

hope i can sort it out as i have to give him an answer tomorrow.

cheers in advance Ashley

I dont intent to be rude, your design is omitting a lot of information, id start at the beginning and design considering all the aspects of BS 7671.

 

[loop3]

What are you permitting as a vd on the submain? %

 

[Knobhead]

His friends may not know mutch. But they won't fill him full of BS and waffle like you.

 

[smiffey]

Better to get it right then mess it up a tony! Awesome comment there.

 

[Chr!s]

Better to get it right then mess it up a tony! Awesome comment there.

Smiffey, id suggest you start with an Assessment of the General Characteristics of the Installation, with what you have put forward you will mess it up.

A 100 mA RCD incomer, they will be happy with you when everything comes to an abrupt stop.

Whats the supply type, earthing arrsangements, bonding requirements etc?

Lightning protection, surge protection?

Whats level of fault current at origin?

EFLI at origin?

Protective device at origin?

What external inlfuances exist?

What installation method will be used?

What sort of factory is it a P.f of 1, a purly ressitive installation?

Type of Lighting, Heating, Machines etc?

Level of Harmonics?

Maximum Lenght of circuits includuing Final Circuits?

An assesment of Maximum Demand?

Future Expansion ?

Risk assements?

This list isnt exhaustive, but give an indication of where you need to start.

You can then move on to Designing the circuits so that they can comply with BS 7671 and you have a happy customer.

 

[Engineer54]

I've given him a list of bits required including the 25mm 5 core swa,

​

Why on earth are you asking him to supply a 5 core SWA cable?? A 4 core SWA cables armouring, will be more than capable of providing this cables CPC requirements....

 

[ian.settle1]

Why on earth are you asking him to supply a 5 core SWA cable?? A 4 core SWA cables armouring, will be more than capable of providing this cables CPC requirements....

When he see's the cost of 5-core he will have a canary fit at the price.

 

[Engineer54]

When he see's the cost of 5-core he will have a canary fit at the price.

Yeah, and by the time Smiffy has gone through Chris's list, to determine the correct installation requirements for this installation, he might even need a 35mm 4 core!! lol!!

 

[Knobhead]

3+2xN It could have high harmonics. The Americans make it now. Shipping may cost a bit.

 

[i=p/u]

well if you ask me £650 for cable at that length and to have 100A per phase is nothing yes you could use smaller cable but protection device will change... you are the spark and he seems a pratt.

 

[Knobhead]

well if you ask me £650 for cable at that length and to have 100A per phase is nothing yes you could use smaller cable but protection device will change... you are the spark and he seems a pratt.

The jury is still out on that one.

From what's been said so far I'm not convinced. To set out with a design current of 100A when it's known the service head is only 100A this whole saga is a farce.
Now if the head was to be uprated then things make sense. Mind you 5 core still doesn't make one iota of sense.