Jump to content

Cable length question


shumbaman
 Share

Recommended Posts

I am planning an installation with 12 panels (3KWatt) in a 4*3 arrangement with a Vmp of 92.1 volts and an Imp of 32.6 amps. Using 16mm2 cable I determine that on a 50M length my voltage drop will be  3.3429 OR 3.6297% and the power dissipation will be 108.9 Watts. Based on my research I feel confident that the voltage drop to the MPPT controller is acceptable but I have no idea on whether the 108 watts is OK or not.

Can anyone give me some feedback on how serious or not 108 watts of dissipated power is.

Link to comment
Share on other sites

Welcome shumbaman,

It all depends on the charge controller you have for the charge controller dictates the max volts and amps you can connect to it.

50m length of wire, only if you REALLY ABSOLUTELY have to, but then I would consider other options, like rather 220v AC over 50m.

Link to comment
Share on other sites

15 hours ago, shumbaman said:

I am planning an installation with 12 panels (3KWatt) in a 4*3 arrangement with a Vmp of 92.1 volts and an Imp of 32.6 amps. Using 16mm2 cable I determine that on a 50M length my voltage drop will be  3.3429 OR 3.6297% and the power dissipation will be 108.9 Watts. Based on my research I feel confident that the voltage drop to the MPPT controller is acceptable but I have no idea on whether the 108 watts is OK or not.

Can anyone give me some feedback on how serious or not 108 watts of dissipated power is.

50m is quite far, but if you don't have any other option, go for it. You are going to loose 108 watts in the cabling, if you can live with that, it is OK.

Link to comment
Share on other sites

I agree with superdiy. 

The power will be dissipated along the length of the cable so only 2.16 Watts/m.

You also have the option of throwing more copper at the problem. This will reduce your volt drop and I2R power losses. 

Link to comment
Share on other sites

2 hours ago, viper_za said:

Hi Shumbaman
Are you running those cables per string or do you run them to a combiner box first?
 

The strings will be combined close to the panels so I am looking at what cable to use from the combiner to the controller.

Link to comment
Share on other sites

13 hours ago, The Terrible Triplett said:

Welcome shumbaman,

It all depends on the charge controller you have for the charge controller dictates the max volts and amps you can connect to it.

50m length of wire, only if you REALLY ABSOLUTELY have to, but then I would consider other options, like rather 220v AC over 50m.

I did consider this option but there are all sorts of other issues that render it a no go. I can live with the loss of 100 watts and just need to know that the cable will be safeand stable.

The inverter is a 5KVA Axpert with inbuilt MPPT controller.

Link to comment
Share on other sites

Excellent.

You can mitigate the losses by getting thicker wire. Yes it does some at a premium but consider that you could be using the wire for many many years.

Link to comment
Share on other sites

29 minutes ago, Chris Hobson said:

have a look at http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

At maximum power your PV voltage should be about 75V maybe as low as 68V. at that sort of voltage we talking 35mm2

 

Hi Chris...thanks for the reference...confirms that thicker cable is necessary. Wher do you get the 75 volt figure from? My Vmp is 92.1 volts

Link to comment
Share on other sites

Experience - Yesterday max PV output @ 73.5V (2499 W)

                     Day before  74.5V (2455W)

                    Monday  69.8V (2381W)

                    21 Feb  73.7V (3000W)

The lower the voltage the thick the cable for the same current. I only see voltages as high as 90 V when the system is idling and there is not a big current draw. If you  are drawing power the PV Voltage drops.

                

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...