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ADVISE PLEASE

Jon

By Jon
in Boat Building & Maintenance

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Tommo Contributor

Tommo

Posted
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FOR ORIGINAL THREAD, SEE HERE

 

Richard

 

You are allowed a 4% voltage drop. On 230 Volt that works out at 9.2V, but this is overall including shore line etc.. I would advise that you allow about an 4 volt drop on the internal wiring. By the way, single phase is always calculated at being 230 volt these days.

 

Regards

 

Tommo

 

(Electrican for more years than I care to remember !)

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timboharticus Collaborator

timboharticus

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:rolleyes:

 

Re. Volt drop.

 

4% is used in buildings for 230V systems = 9.2V see Tommo above.

 

Where does the 0.5V for 12V systems come from? Is it a regulation or good practise?

 

1.5 mmsq has volt drop of 29mV/A/m

2.5 mmsq 18

4 11

6 7.3

 

These are for copper pvc cables and are for single conductor so need to double up there and back. Actual volt drop is likely to be less as these figures are at max current carrying capacity of cable.

 

So, for a typical lighting load say 40W, volt drop of 50m of cable (total)

 

Power (W) = I(Amps) x V

 

Amps = W/V = 40/12 = 3.3 Amps

 

Current carrying capacity of 1.5mm cable is about 12Amps so no problem here.

 

Volt drop will be 29mV x 3.3 Amps x 50m = 4785mV = 4.8V too high if 12V system ok if 230V system.

 

If we half the load to 20W and use 2.5mm cable get

 

Amps = 20/12= 1.67 Amps

 

Volt drop = 18mV x 1.67Amps x 50m = 1.5Volts still a bit high for 12V system.

 

Suggest wiring in 2.5mm in a ring circuit. This would give a volt drop of about 1V.

 

Perhaps my assumed cable length is a bit long.

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Bernie Proficient

Bernie

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You are doing nothing wrong John, I found this out by accident. Instead of clicking the "REPLY button bottom R scroll down to the very bottom and click the ADD REPLY button, you will then find you don't get the quotes in your message.

Bernie.

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Richard Bustens Experienced

Richard Bustens

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Hi John

So i use the same formular as for 12v ?and that means that a volt drop of 2/3 volts is to high for safty?

This is only a prob on the gen set to dist box and the dist box to cooker so far and this gives me a volt drop of 3v and 1.5 v respectiveley. or should i add th cable length together ie:- from genset to cooker adding the two lengths together as one then it gives me 4.5 v drop,

Regards Richad. :rolleyes:

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John Orentas Veteran II

John Orentas

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Richard.

 

As Tommo says your are allowed up to 4% (9 volts) on 230 volt sytems. I don't know where you have got these 'maximun allowed' figures from for you 24 volt circuits, it all depends what equipment you are powering.

 

3 and 1.5 volt drops in 230 are nothing.

 

John Squeers

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Richard Bustens Experienced

Richard Bustens

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Thanks John

i will continue with the knowledge that you said it was ok :rolleyes:

Chris

I was joking about the bath, i was going to put one in but the bathroom was going to have to be so big to make it look right it was not pratical as it is i have only 12' left for the lounge. so i got a corner bath from B&Q our branch is closing down and they open a new superstore in 2 weeks so everything was going cheep like a budgie, got for £150. <_<

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