Cable Size

[newman]

OMG what happend when I went to bed,look Ivors views my irritate a lot of you (99.99%) but i am sure you will all agree everybody has an opinion and he does have a right to air his opinion(free speach and all that)

so please no more witch hunts or perceived threats thanks

So Watchdog's Avatar

Watchdog please allow my thread to continue so I can ask resonable inteligent questions to the installer with information gained from this valuble source

 

[Sidewinder]

newman,

It is not that his views annoy, it is that he does not seem to understand some pretty basic engineering principles, that gets some of us.

Oh and the fact that he can't explain or reinforce his comments with the basic laws of physics, regulations or sound engineering principles that gets me.

I hope that you do get an answer, however, I doubt that you will.

The install is just plain wrong, and you have not by the sound of it been given the correct information.

None of us here have seen the install, we can only go on your description, hence why Canoe asked for photo's.

A picture is worth a thousand words as they say.

 

[newman]

BREAKING NEWS BREAKING NEWS BREAKING NEWS

The instaler (in the middle of the volt logging} has decided to fit a new cable

There's nowt funnier than FOLK

 

[Manator]

OMG what happend when I went to bed,look Ivors views my irritate a lot of you (99.99%) but i am sure you will all agree everybody has an opinion and he does have a right to air his opinion(free speach and all that)so please no more witch hunts or perceived threats thanks

So Watchdog's Avatar

Watchdog please allow my thread to continue so I can ask resonable inteligent questions to the installer with information gained from this valuble source

Hello Newman,

your thread was closed for moderation due to the lack of factual content, and some posts that were not in keeping with the forums exemplary record.

Many people have indeed varying views but when a thread detracts from the original question, we do have to call time on further discussion until people have had time to reflect on what was said and how they should progress.

 

[NozSpark]

A proper bit of properly sized cable or just a bit of bell wire? ; )

 

[newman]

Before he fits it's and wastes his money and your timeFind out what cable he is going to fit and what his calcs are !!!!

Will DO

 

[kerching]

Could I make a suggestion here please?

See if you can get them to install the cable into a 'suitably sized duct'...after all they are presumably digging it in?

A duct is a handy thing to have for the future

At least you have got a good result [hopefully]......Percy Verance has won the day... :coat

 

[Andy™]

Especially if they have to come back to fit the correct cable later if the one they fit is (*cough* calc'd on a margin) not quite the ticket......

wonder if their calc assumes using the existing doubled up cable?

and maybe there planning another 4c6mm cable?

4x conductors in parallel could be fun to work with... maybe they will use SWA1 for line, and SWA2 for neutral?

 

[newman]

Especially if they have to come back to fit the correct cable later if the one they fit is (*cough* calc'd on a margin) not quite the ticket......---------- Post Auto-Merged at 22:07 ---------- Previous post was made at 22:03 ----------

Newman - How far is the run that the new cable is going ?

From where the DNO meter is to your Inverter including ups and downs (trenches) etc

I will measure tomorrow

 

[ProDave]

That's a good result.

BUT

He only has half the story.

He has found with his voltage recording that the voltage at the inverter is going too high.

But I still believe before he does anything he also needs to run that test with the voltage recorder at the supply intake, so see the range of variation there as well. i.e get the FULL picture from the test the DNO did and rather brushed under the carped.

Only then will he know how much headroom he has got, i.e how much voltage rise can be tollerated over and above the maximum voltage seen at the intake.

Until he does that, he can't do any sensible calculations. so anything he does now is a bit of a stab in the dark. Try a thicker cable and see?

so the ducting seems a good idea.

 

[steptoe]

thats is a good thought Dave,

if it is really tight then he is going to need to go bigger,

 

[ivor dispatch]

That's a good result.BUT

He only has half the story.

He has found with his voltage recording that the voltage at the inverter is going too high.

But I still believe before he does anything he also needs to run that test with the voltage recorder at the supply intake, so see the range of variation there as well. i.e get the FULL picture from the test the DNO did and rather brushed under the carped.

Only then will he know how much headroom he has got, i.e how much voltage rise can be tollerated over and above the maximum voltage seen at the intake.

Until he does that, he can't do any sensible calculations. so anything he does now is a bit of a stab in the dark. Try a thicker cable and see?

so the ducting seems a good idea.

Prodave, the DNO have hit the dizzy hieghts of 253v at the intake,using the sma guide to grid connection will give the installer a visual represention to show the relationship between voltage/grid&circuit impedance. It may be very expensive to try and match a cable for the AC so moving the inverter to the mains intake and sizing a cable for DC could be a cheaper option

 

[kme]

Prodave, the DNO have hit the dizzy hieghts of 253v at the intake,using the sma guide to grid connection will give the installer a visual represention to show the relationship between voltage/grid&circuit impedance. It may be very expensive to try and match a cable for the AC so moving the inverter to the mains intake and sizing a cable for DC could be a cheaper option

You think????

I wasn`t aware they made DC PV cable in that sort of size!!!! And I`m willing to bet it would be F`in expensive.

Not to mention the inherent dangers of running the DC down to the property - Sorry, but that is one of the dafter suggestions, IMHO

 

[davetheglitz]

I don't do PV so tend to be pretty basic in the way I think about this - but why would it be a hazard to put DC down an SWA cable?

My reasoning is as follows:-

If the 0v dc line is connected to earth internally at the inverter and an MCB and isolater is at the source end any cable fault would cause the MCB to trip.

Now all the volt drops are at the input to the inverter - so in effect it's just a bit cloudier than it would have been if the PV and inverter were adjacent. No problem with the ac volt drop any more - so if you can cope with poor efficiency why not 10% volt drop on the dc side?

I'm sure I've missed something - but can't see what as yet!

 

[Sidewinder]

800V d.c. down the cable?

---------- Post Auto-Merged at 18:30 ---------- Previous post was made at 18:29 ----------

Oh & it has to comply with the standards required for you to get the FITS.

Sorry pressed enter by mistake.

Ordinary SWA does not comply.

 

[davetheglitz]

Ah - didn't know it went up to 800v - always assumed it was around the 200v mark. That would explain it!

Thanks.

 

[kme]

Can be approaching 1KV, dependant on panels used, inverter spec. etc.

And volt drop is far more of a problem on the DC side - the system can`t up the current to compensate; so you`ve "lost" the power you generated

 

[Sidewinder]

Can be approaching 1KV, dependant on panels used, inverter spec. etc.

No it can't ] ] ] ; )

 

[ivor dispatch]

800V d.c. down the cable?---------- Post Auto-Merged at 18:30 ---------- Previous post was made at 18:29 ----------

Oh & it has to comply with the standards required for you to get the FITS.

Sorry pressed enter by mistake.

Ordinary SWA does not comply.

DTI guide says swa is ok?

---------- Post Auto-Merged at 19:09 ---------- Previous post was made at 19:04 ----------

Can be approaching 1KV, dependant on panels used, inverter spec. etc.And volt drop is far more of a problem on the DC side - the system can`t up the current to compensate; so you`ve "lost" the power you generated

3 % volt drop on DC side ,check with the manufacturer they might like it lower

lower current on the DC side as a norm so should be better for the voltdrop

 

[Sidewinder]

Don't care what the DTI say, will the cable maker say it is acceptable?

If not, then it is not acceptable.

Are you prepared to put 800V d.c down a cable rated for say 300V?

(Not saying this is the rating, just an example.)

There are other considerations do you know what these are?