Cable Size

[newman]

Can anybody tell me with a Voltage of 250 at the house CU and a grid impedence of .4 ohms what size of cable would I need if the inverter is 70m away generating 16 amps

 

[newman]

Can anybody tell me with a Voltage of 250 at the house CU and a grid impedence of .4 what size of cable would I need if the inverter is 70m away generating 17.39 amps

---------- Post Auto-Merged at 22:41 ---------- Previous post was made at 22:37 ----------

You'd be better of calculating it at 4000Watts (17.39 amps @ 230 V) as the installer has probably not set the mx output to 3680 watts and you have (if we take into account the +5% tolerance of your panels) 4200Watts of panelsMy mistake above re the 262 volts, long day

---------- Post Auto-Merged at 22:33 ---------- Previous post was made at 22:26 ----------

With a grid impedance of 0.4 according to SMA's chart at 250 Volts the max you can push out before tripping is less than 2kW

But we know that you only trip when the suns out and the inverters running flat out - yes ?

The PV generates about 3KW then inverter cuts out

 

[newman]

Volt Drop of BS 5457 PVC SWA (Taken from Eland data)70 Meters

17.4 Amps (4000 watts)

10mm2 would give a VD of 5.73

16mm2 would give a VD of 3.53

25mm2 would give a VD of 2.3

35mm2 would give a VD of 1.64

1% (the Guide) fro those interested would give 2.3Volts

---------- Post Auto-Merged at 22:45 ---------- Previous post was made at 22:44 ----------

Remind me how long the existing run is and what the cable is ?

It is 130m of twined 6mm then 20m of 4mm twined

 

[newman]

And the grid impedance measured at the inverter is .97ohms

 

[ivor dispatch]

I think the DNO are being a bit avoidal,if they refuse to give you a datalog tell them you require it to be done again and a datalog provided as you are having an independent log done and if they are misleading you you will bill them accordingly.

if they are pushing their voltage limits then the inverter is really going to struggle with the small cable trying to push the power back down it.

---------- Post Auto-Merged at 22:12 ---------- Previous post was made at 22:10 ----------

ivor, even though the DTI guide may say to use a longer DC cable, the cable must have the approval of the manuf to be used for the potential DC that may flow through it, it must also be MCS approved, I dont think many manuf of SWA have had their cable type approved by MCS.

you got me kid, I have installed lots of swa on PV some times on the AC side and have not checked the MCS approved list . Could you show a list of approved manufactures

god dang, you never know when things can bite ya

thanks mate I look forward to your extensive list of MCS reg cables

 

[newman]

you got me kid, I have installed lots of swa on PV some times on the AC side and have not checked the MCS approved list . Could you show a list of approved manufacturesgod dang, you never know when things can bite ya

thanks mate I look forward to your extensive list of MCS reg cables

LOOK this solution is not going to happen ,so why discuss it

---------- Post Auto-Merged at 23:12 ---------- Previous post was made at 23:11 ----------

For 250 V at the DNO then 25 sq mm should work, 35sq mm would be on the safe side

Thanks for that

 

[kme]

I have installed lots of swa on PV some times on the AC side and have not checked the MCS approved list .

C`mon! This is a wind-up, now - it has to be.

If an NICEIC approved contractor, "trustmark" approved, with his PV as well, is going to post stuff like this - you must be thinking you`re fishing :slap (Yes - I DO know )

Could you show a list of approved manufactures

thanks mate I look forward to your extensive list of MCS reg cables

You`ll be waiting a while - if you want to know, look `em up. (but you already know, don`t you.?)

 

[steptoe]

you got me kid, I have installed lots of swa on PV some times on the AC side and have not checked the MCS approved list . Could you show a list of approved manufacturesgod dang, you never know when things can bite ya

thanks mate I look forward to your extensive list of MCS reg cables

I dont have a list, if Im using a different cable from normal I simply check with the manuf that it has MCS approval,

its just that I dont know of any DI SWA, so I dont know of any that would be MCS approved for DC cables, as they are required to be DI, in my understanding,

I could be wrong in that though.

if you find any let me know, would be good info to have.

oh, hey, he called me kid, did you see that, he called me kid, so less of this old guy **** from the rest of you, OK. I got called KID.!

now, to find me milky bars.................

 

[kme]

now, to find me milky bars.................

your son ate them all :slap

 

[ivor dispatch]

LOOK this solution is not going to happen ,so why discuss it---------- Post Auto-Merged at 23:12 ---------- Previous post was made at 23:11 ----------

Thanks for that

at 250v a 0.5572ohms impedance,,,, could be very tight, that is your 0.4 grid and 0.1752 ohms 35mm mcs approved swa of course.

its going to be a big shout

 

[steptoe]

oh dear, you obviously dont understand the differences between AC and DC cables, and where the MCS starts and stops. :slap

you were the one after all wanting to use an 600v AC rated SWA on the [possibly] 800v DC side when you moved the inverter,

or have you now decided you were hopelessly out of your depth and knew nothing about it and couldnt find anything to cut&paste to try and BS your 'idea' up.?

:slap

 

[kme]

He`s just (trying) to wind us up, for some unknown reason - he MUST know these posts are nonsensical............

Hey! Why not use a MCS approved, water cooled, "superconductor" cable - we could have <1% v.d. on a 1.5mm cable. After the MCB, we could step up the AC voltage, and run a cable back to the substation - it doesn`t matter which "tap" the DNO are using - we can go straight onto the HV (MV?) side...........

 

[ivor dispatch]

oh dear, you obviously dont understand the differences between AC and DC cables, and where the MCS starts and stops. :slap you were the one after all wanting to use an 600v AC rated SWA on the [possibly] 800v DC side when you moved the inverter,

or have you now decided you were hopelessly out of your depth and knew nothing about it and couldnt find anything to cut&paste to try and BS your 'idea' up.?

:slap

so you are saying a mcs installation is only the DC side:innocent,,,,, so how can you all moan n f n groan about newmans installer not meeting MCS/real and all,,,,,, when it is a AC problem:|

you guys

 

[Manator]

I would suggest if you are going to take part in this discussion then state facts and not assumptions based on bad/incorrect background knowledge.

 

[steptoe]

so you are saying a mcs installation is only the DC side:innocent,,,,, so how can you all moan n f n groan about newmans installer not meeting MCS/real and all,,,,,, when it is a AC problem:|you guys

when did I say that?

I said the cable had to comply with MCS, and as yet I have never used a SWA that was MCS approved for use on the DC side.

BTW, any numpty like yourself can install an AC radial, but the MCS competent person installing the inverter MUST ensure the AC radial meets his/MCS requirements,

is this where you went wrong ivor,?

you thought you were only responsible for the DC side?

oh dear, you may have a lot of work to do and some cable to pay for........

:slap

 

[ivor dispatch]

when did I say that?I said the cable had to comply with MCS, and as yet I have never used a SWA that was MCS approved for use on the DC side.

BTW, any numpty like yourself can install an AC radial, but the MCS competent person installing the inverter MUST ensure the AC radial meets his/MCS requirements,

is this where you went wrong ivor,?

you thought you were only responsible for the DC side?

oh dear, you may have a lot of work to do and some cable to pay for........

:slap

I think manator knows you well kid

 

[Manator]

Again this thread is going the same way as the last. Closed for moderation.