Help with solar panel set up...

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DonGould

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#128978 30-Aug-2013 12:07

Got a bunch of bits and need a bit of help figuring where best to get the bits to tie it up...

8 * BP Solar 585 Panels.
1 * MPPT controler
1 * 1800w inverter

Currently have no batteries as destroyed by earthquake.

We have the unistrut mounting system.

Can we put them up without covering them before they've got load on them?

What's the best cable to use to tie them together (4awg?). They have built in cable packs on the back of each modual.

Where do we get the cable from locally? (at a sensible price! :) )

Do most people solder terminals on to their wires or just crimp them?

The cable run is likely to be less than 8 meters in total.

The plan it to get out of 12v ASAP up to 240v.

Is there advantage of running 12v feed around the house?

Should we run 12v around house or 24v or 48v?

This is all going into a new house build and none of the wiring is in place. We have a blank canvis to play with, so comments would be very welcomed.

D

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#887168 30-Aug-2013 17:51

You should load the panels, not open circuit, but they will survive. I do not have info on what exactly happens, but the energy has to go somewhere or else it will likely turn into heat or something no ideal.

If I was in your position and had the time, I'd distribute 48V (lower cable losses than 12V for the same power transfer) for running LED lights with my own LED driver (instead of mains-to-300mA drivers). This means I can change the lights as technology changes.

Then I will also get some 12V regulators to power my modem/router/NAS.

Wikipedia has a good page on wire gauge vs. resistance so you can calculate the losses vs. cable cost. Typically you try and go for the largest size that fits your connectors, if you are willing to pay for the wire.

Crimping works great if you have the correct, expensive tool. Myself, I solder my crimps. One of the reasons not to solder is because if the solder alone is holding the wire in place then when there is a fault the solder can melt and the loose wire cause further short-circuits. It is a good idea to cable tie wires to the structure in case they do come loose.

You can never have enough Volvos!

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gregmcc

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#887177 30-Aug-2013 18:47

I think that you need to get updated with the changes in the electrical regs.

Installation of solar cells has now become classed as high risk perscribed electrical work, this means that it must be done by a registered electrician with a current practising license

it must be installed according to manafactures instruction, it must be certified desgin, it must have a certificate of compliance, it must be inspected......an so on

more info here

DonGould

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#887181 30-Aug-2013 19:10

gregmcc: I think that you need to get updated with the changes in the electrical regs.

Installation of solar cells has now become classed as high risk perscribed electrical work, this means that it must be done by a registered electrician with a current practising license

it must be installed according to manafactures instruction, it must be certified desgin, it must have a certificate of compliance, it must be inspected......an so on

more info here

Personally... when we start actually paying teachers I might start to care about stuff like this.

I could go on with a list of issues in the past 12 months.... but you get the idea.

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DonGould

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#887184 30-Aug-2013 19:13

Niel: You should load the panels, not open circuit, but they will survive. I do not have info on what exactly happens, but the energy has to go somewhere or else it will likely turn into heat or something no ideal.

If I was in your position and had the time, I'd distribute 48V (lower cable losses than 12V for the same power transfer) for running LED lights with my own LED driver (instead of mains-to-300mA drivers). This means I can change the lights as technology changes.

Then I will also get some 12V regulators to power my modem/router/NAS.

Wikipedia has a good page on wire gauge vs. resistance so you can calculate the losses vs. cable cost. Typically you try and go for the largest size that fits your connectors, if you are willing to pay for the wire.

Crimping works great if you have the correct, expensive tool. Myself, I solder my crimps. One of the reasons not to solder is because if the solder alone is holding the wire in place then when there is a fault the solder can melt and the loose wire cause further short-circuits. It is a good idea to cable tie wires to the structure in case they do come loose.

Thanks for the info Niel. You raise some good points to be considered.

D

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gregmcc

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#887185 30-Aug-2013 19:20

Your call, but it's a new build, to get a code of compliance from the building inspector you will need to get an electrical certificate of compliance which may prove difficult if you haven't followed the rules.

Technofreak

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#887211 30-Aug-2013 21:09

That inclusion of photovoltaic installation as high risk is over the top in my opinion. Does it include any experimental type kits with photo voltaic panels?

I did a photovoltaic installation some years ago, it wasn't that hard nor damgerous.

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gregmcc

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#887215 30-Aug-2013 21:29

Technofreak: That inclusion of photovoltaic installation as high risk is over the top in my opinion. Does it include any experimental type kits with photo voltaic panels?

I did a photovoltaic installation some years ago, it wasn't that hard nor damgerous.

experimental kits are not fixed wiring, so most likely not covered.

What people don't seem to think about is when there is a extra low voltage wiring used there is ntot the risk of electric shock is as much compared to 230V, but the currents flowing will be quite a lot higher, the extra heat generated becomes a fire risk, sizing the cable to handle the current needs to be done right, thermal de-rating, and many other factors.

From what I understand soldering of joints are assocated with solar panels are no longer allowed, only crimp joints or solar panel plug/sockets.

There is a reason why it is now regulated - to stop people who think they know what they are doing from causing fires.

DonGould

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#887224 30-Aug-2013 21:53

We either want green energy or we don't.

Regulation is nothing but industry protection.

If we want to have a chat about safety let's start by sitting down with folk in the CTV building?

Or we could just stick to the topic and answer the questions directly posed while also offering up useful education.

If people want safety in this space then start building safe products at a sensible price that people can use. Even professionals get it wrong.... in this city they manage to do it regularly!

Thanks for engaging the topic, but let's dispense with the FUD and focus on the prize - a clean energy future.

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Niel

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#887229 30-Aug-2013 22:35

Fully agree with all the posts above that you need to follow regulations, but I also have recent experience that the inspectors do not check thoroughly and the electricians do not follow (or know) the rules. In our ceiling the wires are all over the place, not attached to rafters, and not separated from signal/data cables. Not using outdoor rated fittings. The certificate does not reflect what was installed (number of fittings, number of power points, the outdoor power points) which I only found out when I saw the certificate left on site for the power company. The list goes on. And it is not only electrical, it is also wet area moisture barriers, extraction, etc. The council inspection was a joke.

We actually sell solar panels and wiring for electric fencing, but I'm not involved in that group so don't know the exact requirements. However, it does come with the equipment you have purchased so do read/follow that.

I can't help with supply of wire/connectors as we do the wiring low volume to get people started so we still pay retail pricing. We get panels for very cheap, but being low volume it is frowned upon if I do a staff purchase of all our stock.

Does anyone know why soldering is not allowed? A very old version of the electrical wiring rules say you can't tin wires that are to be crimped or screwed down, but there is a clause 4.6.1.2 and 4.6.2 talking about you can sweat a conductor into a solder lug (if minimum 7 strands) which I assume is the same as soldering after crimping? And 6.4.2.1 explains you can't tin a wire and then clamp it. This is from a 20 year old version. So does anyone know why it changed? Is it because people did not properly read the standard and tinned wires before crimping/clamping? Or some people used acid core solder and you don't find out until a months/years later when the wire corrodes off and start a fire?

Regulation does not stop people from doing stupid things, it moves the accountability. It does also allow for experimental and small qty products as long as it is designed with sound engineering principal (like a fuse at the batteries, sized according to the wiring). Of cause you still need to follow building regulation regarding weight loading on your roof, which requires a consent/permit, but there is allowance for designing/experimenting.

You can never have enough Volvos!

Niel

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#887230 30-Aug-2013 22:38

BTW, in AU they solder mains wires and wrap with insulation tape. Even to extend wiring. No boxes, not even flush boxes (they use C-clips).

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Bung

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#887258 30-Aug-2013 23:55

This forum post covers some ranting on both sides of the argument and some reasoned comment. http://www.electricalforum.co.nz/index.php?action=more_detais&id=1370220520

webwat

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#887976 1-Sep-2013 22:03

I remember seeing the logic of avoiding solder once, because it can come loose after a while and then compromise the crimp. The comment about acid flux in the solder makes sense too. Lugs are cheap, and the tool not that expensive for the nature of the job, but will need big lugs and therefore a big crimping tool to terminate a heavy cable that can handle much current.

A lot of the issues around 48VDC wiring are similar to installing protective earth wiring — there would be no need for a sparky if there wasn't much at stake but it has to be done right. I do have to admit I fixed our sparky's earth screw on a data cabinet last week after the inspectors failed it, hadn't been bolted directly to the structure. And when you start putting banks of batteries on a ELV system there is potential for lots of current so circuit breakers in the right places would be quite important.

Maybe Power over Ethernet would be the way to go...

Time to find a new industry!

raytaylor

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#888005 1-Sep-2013 23:44

DonGould: Got a bunch of bits and need a bit of help figuring where best to get the bits to tie it up...

8 * BP Solar 585 Panels.
1 * MPPT controler
1 * 1800w inverter

Currently have no batteries as destroyed by earthquake.

My opinion is that with the drop in solar panel pricing over the last 2 years, its better to use the national grid as a battery. Batteries have stayed close to the same price, where as solar panels have dropped by 70%
What i was paying 3 years ago for a 120 watt panel ($1300) is now down to $300

So the idea is that during the day, you use whatever power you generate straight away, and sell the rest to the grid at 15c/kw
Overnight you buy from the grid at the normal 24c or whatever a kw, but when buying, you buy as little as you need to.

You then set your hot water tank, dishwasher, washing machine to run during sunlight hours so you are buying less off the grid, but sell as much as you can to it (with your own use as priority)

We have the unistrut mounting system.
Can we put them up without covering them before they've got load on them?

When i am setting up my high sites, i dont bother to cover them. But i work with only 120 watt panels and havent really noticed any damage. From the time of being put in place, to the time they have their load is only 30 mins though. Not sure if thats enough to damage them. You always cover them before you start working on them again of course so use a tarpaulin when you wire them up.

What's the best cable to use to tie them together (4awg?). They have built in cable packs on the back of each modual.
Where do we get the cable from locally? (at a sensible price! :) )

from my calculations below, you will loose less than 5% of generated / captured energy in transmission between the panels and controller if they are wired up in parallel with a 4awg cable over 20 metres - so that seems pretty good to me.
Ideal Electrical would be the place to go

Do most people solder terminals on to their wires or just crimp them?
The cable run is likely to be less than 8 meters in total.
The plan it to get out of 12v ASAP up to 240v.

I only work on 12 systems that dont convert back to 240v so im not sure what your electrician will say.
Personally i crimp it all with screw down terminal blocks. Soldering is a pain and you will get dry joints over time.

Is there advantage of running 12v feed around the house?

This can be quite fun. In our house i have 12v running around for some LED lighting and some extraction fans. Also we have a dog kennel heater that runs off 12v
Bare in mind that when using 12v, your transmission losses are quite high - even when using TPS or 3 core 10amp wire. So its best suited for low wattage devices like LED lights.

Should we run 12v around house or 24v or 48v?
This is all going into a new house build and none of the wiring is in place. We have a blank canvis to play with, so comments would be very welcomed.
D

I would suggest you have 12v available in your man-shed, and in the house for backup LED lighting. Remember if you sell the house, the new owners wont be too happy if they want to replace a fixture / light bulb and find its got some weird 12v system rather than a 240v bulb they can buy from the supermarket.

240v for everything else.

Oh a note for your inverter - i am assuming you will have mains supply in your new house as that 425 watts really isnt enough to live on.
And 1800 watts will be used up real fast if you switch on two or three appliances at once. Remember a vacuum uses 2000 watts.

======

You might be fine to install the panels on the roof, cover them with a tarpaulin and get an electrician to come and do the wiring.

Personally, I would be looking at what the maximum voltage of solar input your MPPT controller has. If so, you might be able to run the panels in series, which would mean less efficiencies between the rooftop and controller.
8x 17.5v = 140 volts (if they are 12v panels) so you would need a sparky to do it.

Here is the table that I use
http://www.powerstream.com/Wire_Size.htm

4awg has a resistance of 0.000815 ohms per metre. That means over a 20m cable (40m for full circuit) is 0.032 ohms
So they are 85 watt panels, or 425 watts total
Max amperage is 4.72

So in parallel, you will have 4.72 x 5 amps = 23.6 amps running down the cable
Voltage loss of 0.7 amps or 12 watts of power lost in the cable

ahh screw it, when using such a big wire gauge like 4 AWG, the 12 watts isnt really much so you arent going to save much by wiring in series which results in a higher voltage and lower amps traversing the cable between solar panels and controller.

A solid rod is capable of 60 amps. I am not sure what a stranded wire is capable of in comparison but I assume you should be fine for 24 amps

X

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DonGould

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#888150 2-Sep-2013 10:21

Ray, solid answer thanks! :)

We've got a grid tie converter coming shortly. The batteries got wrecked in the quakes and we're currently looking for more.

I'm also looking for more panels.

I want to set up one of these:

http://www.gowifi.co.nz/tycon-power-systems/tycon-poe-voltage-convertors/tycon-12vin-24vout-poe/solar-battery-charge-controller.html

So I'm after some more solar panels next.

I've been looking around TradeMe. Some of the prices look ok but then I get stung with the freight.

Not sure what panels I should use with that controller above. Currently we're thinking 190w seems to be a good balance between price and performance.

Not sure what batteries to use either. I'm wanting to build a low cost proof of concept.

D

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webwat

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#888313 2-Sep-2013 14:20

You could run the panels in banks of 48V each, with parallel wiring from each bank of panels to the controller?
12VDC to the modem/router cabinet would be handy... You can get 48V circuit breakers but you want to keep any 12V or 48V (extra low voltage) switching and cabling fully separated from 230V (low voltage).

I found something about an exemption for home owners doing wiring but you would still need a nice sparky to give a safety certificate, probably before gib goes up so they can see the wiring they are signing off on. If you don't get it certified there could be legal problems and the insurance companies would love that -- they get to take your premiums but never ever pay a claim.

Edit: remember battery cabinet needs to be in a ventilated area...

Time to find a new industry!

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