solar panels install and regs and tips
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Joined: Sat Sep 27, 2008 11:21 am

solar panels install and regs and tips

by lickitandsee » Sat Sep 27, 2008 11:34 am

jus joined th forum and would like some help pls if possible

i have 3 x 85wt solar panels, 7 x 300amphr battery(12v), 1700 wt modified sign inverter, 12vt regulator ( does look like come off car typo reg).
i want to run house lightin circuit from above independantly of supply.

can i get electrician to connect from battery bank to switch board , or is it possible to spike into lightin circuit closer to the battery bank?. if so could i have fused on off switch from solar to lighting circuit, and still keep the lighting circuit connected on supply at fuse box, obvously only running 1 at 1 time?

i have yet to install the solar panels etc , i want to install then get it checked out by qualified sparks, but want to hit it right 1st time , how far away does the battery bank have to be stored from building?
as i see it the , i will run in parralell solar panels and batteries to keeping system 12 vt , as i run wire from panels i then need a good charge controller, then feed batteries from this back to charge controler then to inverter , hows does that sound to you?

any useful tips you can help me with would be grateful to hear, im installing on a budget so cant really afford a sparks to install as well

thx in anticipation

great site and some reallly good info .

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by sparx » Sat Sep 27, 2008 9:17 pm

Hi, prior to 17th regs solar PV power was not considered, now whole section in 'RED Book' about 'do's & don'ts' so difficult to comply using made up system such as you propose.
Regs mainly seem to be about systems to run in tandem with mains, however for your relatively low power system only intended to power a single lighting circuit I would say that the old method would still comply.

For reasons of safety to user & to supplier if I where to install such a system I would fit a Double Pole change-over switch in the lighting circuit.

I am going to ussume from your post some level of knowledge of terminology but to be sure :
DP C/O switch = 6 term. device similar to 2 linked 2 way switches, ie it has 2 Common, 2 L1 & 2 L2 terms.

the switch is connected so that the load (house lighting circuit) is on the common terms. L on one & N on the other.
the normal power from Consumer unit go to L1 terms ensuring same polarity.
The supply from invertor goes to L2 terms -again correct polarity.
This set up allows the lights to be run from invertor/battery/PV cell when batts. healthy, or by changeing over switch lights supplied from normal mains.
By connecting thus there is no way mains & invertor supply can be connected together,
I offer this advice for infomation for your 'Leckie and so that you can do some pre install prep, work, If in doubt please repost.

As for physical layout, distance from PV cells to battery MUST be as short as possible, likewise from Battery to invertor. Distance from invertor to change over switch much less important, ideally put cells on roof, batts. invertor in loft. change over sw. near consumer unit.

Remember output from invertor just as lethal as mains,
" It's the volts that jolts - It's the mills. that kills!"

Regards Sparx


by ericmark » Sat Sep 27, 2008 11:38 pm

Back to around 1986 I wired the lights of a farm in the Falklands to work without the generator running. I used 24 volt DC inverters removed from a bus to run 2 foot 40 watt florescent units. It could have run 4 foot units but too easy to break 4 foot tubes.
No attempt was made to light with 230 volt lights instead a charger was made to recharge the battery if the wind generators were unable to keep batteries charged. By using Ni-Fe batteries we were not worried about the batteries being run flat and sulphuration of the plates. The hall light was also connected with diodes to the bedroom lights so if anyone switched on the light in the bedroom they way was lit all the way to toilet it also mean if anyone left a light one we would realise quickly.
What we realised was back then inverters were both expensive and took a lot of standby current so using 24 volt units meant no power was used when lights were not in use.
Control was also a nightmare as you can’t disconnect the wind charger or the voltage will go crazy and even with the huge bus batteries it still required automatic voltage regulation which turned all excess power into heat. All diodes were duplicated as no way could it ever be allowed to go open circuit and fuses in the wrong place could be dangerous all the control gear was in a container outside.
It is the problem of not being safe to disconnect which is also going to be a consideration with solar panels and diodes do go short circuit and it will need careful planning to be able to test. We had shorting links for when we worked on the generator it’s self you may need something similar! And the batteries could easy supply 1000 amp and back feed into shorting links was a worry. A 17mm spanner melted very quickly when it was dropped in error across some terminals. Only the floor of the container could burn so not too much of a worry.
You said the regulator was small that seems odd as the only way to regulate is to turn excess into heat and you can’t really rely on fans so units tend to be on the big side. If multi units are used then you must use blocking diodes as the regulators will not load share and one regulator will try to sink all the power as they are never set to exactly the same voltage.
In short you can’t afford any mistakes and the electrical engineer installing the system should be consulted every step of the way.

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