6mm cable or 4mm ? (1 Viewer)

Ambilkate

LIFE MEMBER
Jul 15, 2009
8,649
18,037
Shropshire
Funster No
7,509
MH
HYMER 654
Exp
since 2006
What cable do you use 6mm or 4 mm does it matter when only doing a 6 to 8 meter run ?we are looking at putting 1x240 solar on van now but can't buy 6mm over the counter only 4mm we can purchase 6mm of ebay but trying to source all items locally and can only get 4 mm :( may have to give up and buy of eBay have all the links via funsters Thankyou but Kate doesn't like to buy over the net and trying to sorce everything today
Bill
 

scotjimland

LIFE MEMBER
Jul 25, 2007
2,084
9,014
Suffolk Coastal District, UK
Funster No
15
MH
Timberland
Hi Bill

yes.. it does matter ..in a low voltage application, the cable size is critical, not for the load.. but for the losses.

the cable size is determined by the the length of run, wattage, and acceptable loss ..

using the cable sizing tool, the theoretical correct size for that panel for a 6 - 8mt run, allowing for 3% loss, is 10mm

4mm is too small.. and 6mm will just about do it.. the smaller the cable size the greater the volt drop = the less efficient your panel..
 

Gorse Hill

Free Member
Feb 2, 2013
2,364
1,944
Stretford
Funster No
24,533
MH
Burnster Ixeo IT 734
Exp
2000
Depending on what you calcs are
Screw fix do 10mm t&e and if using flex 6mm has a similar current carrying capacity , pretty sure B&Q do as well
I would personally put in place the largest conductor allowing for further expansion
Whats required and the cost involved on that length is minimal

Subscribers  do not see these advertisements

 
Feb 27, 2011
14,670
74,875
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
I always recommend 6mm cable no matter how long the run or how little wattage you are putting on. It also reduces losses. In addition if you want to add additional panels in the future you won't need to upgrade the wiring.

The cost difference between 4 and 6mm cable is negligible compared to the overall cost.

I buy my 6, 16 and 25mm cable on ebay and it is very cost effective.

Auto electricians will have the cables in stock but will be expensive.
 
Last edited:

Freespirit1

Free Member
Sep 3, 2013
731
456
West Wales
Funster No
27,912
MH
A Class
Exp
Short while after a gap of many years.
Hi Bill - just google "Industrial control Panel Manufacturers" in your area - one of those will have the right cable and colour you need - they will even crimp the correct lugs on for you too I expect while you wait.
 
Feb 27, 2011
14,670
74,875
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
PS: Remember when using calculators that the voltage at the solar panel side is higher so the current is lower. My panels from memory are about 17V I think. So 240W / 17V = 14Amps.

Subscribers  do not see these advertisements

 

Theonlysue

LIFE MEMBER
Sep 14, 2009
6,104
7,383
Essex
Funster No
8,456
MH
As Executive 50th an
Exp
Not long enough!
I don't think that their regulator will allow over 300w re panels.
 

scotjimland

LIFE MEMBER
Jul 25, 2007
2,084
9,014
Suffolk Coastal District, UK
Funster No
15
MH
Timberland
PS: Remember when using calculators that the voltage at the solar panel side is higher so the current is lower. My panels from memory are about 17V I think. So 240W / 17V = 14Amps.

that was the numbers I used

Capture.PNG
 
OP
OP
Ambilkate

Ambilkate

LIFE MEMBER
Jul 15, 2009
8,649
18,037
Shropshire
Funster No
7,509
MH
HYMER 654
Exp
since 2006
Bills measuring up on the roof at the minute this is what is on the back of the panel we saw yesterday
solar.jpg

Subscribers  do not see these advertisements

 
Feb 27, 2011
14,670
74,875
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
that was the numbers I used

Sorry my comment wasn't aimed at you but anyone who doesn't understand electrics. I have seen people putting 12V into the calculator and wondering why they have to use 10mm cable where others have only used 6mm.. I knew you would know what you were doing on this ;)
 
Feb 27, 2011
14,670
74,875
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
Bills measuring up on the roof at the minute this is what is on the back of the panel we saw yesterday View attachment 79364
That looks like a 48V panel. Make sure your regulator handles 48V in and 12V out. (I am sure you have already)
AT 52V you would only need 1.5mm cable for 3% losses according to Jim's calculator and 4mm would give you 1% losses. I would still go for the 6mm cable however. Also please check the cable you use is rated at 50V+.
 
Feb 27, 2011
14,670
74,875
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
The cable I use is this Broken Link Removed
It is rated at 600V AC so can handle 50V DC no problems.
10 Meters is £12 inc carriage.

Subscribers  do not see these advertisements

 

laird of Dunstan

LIFE MEMBER
Feb 15, 2015
1,464
3,953
lincolnshire
Funster No
35,111
MH
Rapido 9000DFH
Exp
ex caravanner
Those cable calculators are very helpful , I'd work out the run and have the cables cut to size ,don't use anything that will chew up the end of the cable when cutting, if you buy the lugs online make sure that they are the crimping type ,pop into your local control panel shop ,ask for the workshop and they guys will most likely crimp the ends for you ,its important that the correct tool is use to crimp as it will stamp a number at the same time as the crimp ,ask the guys in the panel shop to put on some heat shrink at the ends.
I've built the odd control panel in my time ,it's best to use multi strand cable rated to the correct voltage, twin and earth is solid copper and is not suitable for your application :)
 

Freespirit1

Free Member
Sep 3, 2013
731
456
West Wales
Funster No
27,912
MH
A Class
Exp
Short while after a gap of many years.
I've built the odd control panel in my time ,it's best to use multi strand cable rated to the correct voltage, twin and earth is solid copper and is not suitable for your application :)

Snap - all good advice there - and memories of Brand Rex Tri rated eh!

Subscribers  do not see these advertisements

 

Judge Mental

Funster
Deceased RIP
Sep 2, 2009
6,650
5,883
Sarth London
Funster No
8,272
MH
Possl 636 FR panel van
Exp
1994 and beyond...
I started off as an apprentice electrical fitter on flameproof, explosion proof ,HV and LV switchgear , I've built untold numbers of control panels :D
oh yes we know what tri rated cable looks like :D

and I have installed them in another life(y)
 

laird of Dunstan

LIFE MEMBER
Feb 15, 2015
1,464
3,953
lincolnshire
Funster No
35,111
MH
Rapido 9000DFH
Exp
ex caravanner
and I have installed them in another life(y)
"Laughing" I'm looking at one right now with an old satchwell bms system ,been there to judge ,built them,installed them ,tested them ,commissioned the poxy things :)

Subscribers  do not see these advertisements

 

Judge Mental

Funster
Deceased RIP
Sep 2, 2009
6,650
5,883
Sarth London
Funster No
8,272
MH
Possl 636 FR panel van
Exp
1994 and beyond...
"Laughing" I'm looking at one right now with an old satchwell bms system ,been there to judge ,built them,installed them ,tested them ,commissioned the poxy things :)


I remember now!....your ones were Rubbish!lol Still have nightmares regards wrestling with monster armoured cables:)
 

Freespirit1

Free Member
Sep 3, 2013
731
456
West Wales
Funster No
27,912
MH
A Class
Exp
Short while after a gap of many years.
I started off as an apprentice electrical fitter on flameproof, explosion proof ,HV and LV switchgear , I've built untold numbers of control panels :D
oh yes we know what tri rated cable looks like :D

Wow - me too (well a few) - small world eh! and I've built some in nuclear subs, and a few nuclear power stations (tongue in cheek) - one was in Russia (Chernobyl if I remember rightly) - mind you we ran out of the tri rated at one point and had to use a bit of twin and earth I found in the back of the van - it seemed to do the job ok?

Subscribers  do not see these advertisements

 

JeanLuc

Free Member
Nov 17, 2008
3,304
2,199
Warwickshire
Funster No
4,952
MH
Hymer B630 Star-Line
Exp
Since 2007
If that panel is indeed a 48V model it will not work with the LR1218 regulator which is suitable for panels with a maximum off-load voltage of 25V.

The label you showed states an open circuit voltage of 52.4 volts!
 
OP
OP
Ambilkate

Ambilkate

LIFE MEMBER
Jul 15, 2009
8,649
18,037
Shropshire
Funster No
7,509
MH
HYMER 654
Exp
since 2006
If that panel is indeed a 48V model it will not work with the LR1218 regulator which is suitable for panels with a maximum off-load voltage of 25V.

The label you showed states an open circuit voltage of 52.4 volts!


Thanks Philip
regards Kate x
 

DBK

LIFE MEMBER
Jan 9, 2013
17,969
47,804
Plympton, Devon
Funster No
24,219
MH
PVC, Murvi Morocco
Exp
2013
You will need something like the Victron BlueSolar MPPT 100/30 controller. This can take both the voltage and current of your panel. The make is the only one @eddievanbitz recommends.

Subscribers  do not see these advertisements

 

Join us or log in to post a reply.

To join in you must be a member of MotorhomeFun

Join MotorhomeFun

Join us, it quick and easy!

Log in

Already a member? Log in here.

Latest journal entries

Funsters who are viewing this thread

Back
Top