Solar Panels wiring

[JohnD]

the DC cables from the solar panels do not have an earth. Only at and after the inverter where they are converted to AC is there an earth.

I don't know if the cable trays would benefit from being earthed. It is a bit of a specialist job.

 

[JohnW2]

the DC cables from the solar panels do not have an earth. Only at and after the inverter where they are converted to AC is there an earth. ... I don't know if the cable trays would benefit from being earthed. It is a bit of a specialist job.

What DC voltage are we talking about? If it is not high enough to present an electric shock hazard, then I certainly would probably struggle to think of any real benefit of earthing the trays (particularly given the lightning hazard that eric has mentioned). Indeed, if (as you suggest) the DC cables are floating relative to earth, I'm not sure that earthing the tray would afford much benefit even if the voltage involved were high enough to be hazardous.

Kind Regards, John

 

[JohnD]

it is hundreds of volts DC. Depending on the type and number of panels. For example, during daylight, ten panels might be between 300v and 800v depending on brightness of sunlight, and might deliver about 3kW (which might be about 4A)

I don't know if a larger installation has all the panels connected in series, or if there would be several groups.

I expect there will be a solar enthusiast along in a minute.

 

[JohnW2]

it is hundreds of volts DC. Depending on the type and number of panels. For example, during daylight, ten panels might be between 300v and 800v depending on brightness of sunlight, and might deliver about 3kW (which might be about 4A)

Fair enough - but, as I said, if it really is floating relative to earth, I can't really see what would be gained by earthing the tray.

Kind Regards, John

 

[JohnD]

it seems to me that it would be safer unearthed. Then you would not be exposed to shock unless you contacted two conductor cores at the same time (they seem to be run in singles).

There is no fusing or breaker between the panels and the inverter, which is (usually) inside the building.

 

[bernardgreen]

The cable tray has about 16 cables in it. This could the panels are divided into 8 groups. These may be feeding a low voltage high current invertor ( panels in parallel ) in which case the voltages on the roof will not be more than the voltage of one group of panels. Or they are feeding a high voltage low current invertor ( panels in series in the equipment room ) in which case the voltage on the roof will be much higher.

It may be that the way the panels are inter-connected is altered in the equipment room to depending on the amount of sunshine. This method of matching variable sun light to the invertor was not uncommon at some isolated sites that relied on solar power. In those days the frame work of solar panels was earthed.

Earthed metal rods with sharp points on the highest part of a building and aimed at the sky are said to discharge the static build up and thus prevent /reduce the energy in a lightning strike.

 

[JohnW2]

it seems to me that it would be safer unearthed. Then you would not be exposed to shock unless you contacted two conductor cores at the same time (they seem to be run in singles).

Indeed ... but, if they were floating relative to earth, exactly the same would be true if the tray were earthed. With floating potentials,earthing the tray would not may any difference - one way or the other.

There is no fusing or breaker between the panels and the inverter, which is (usually) inside the building.

Quite so - so earthing the tray would not even protect the cable, let alone people.

Kind Regards, John

 

[masona]

Depending on the type and number of panels.

207 solar panels !

 

[DetlefSchmitz]

That's an interesting number. There are two types of inverter. One has a single circuit and a number of serial strings of panels are paralleled up on the basis that there are no shadows, and the strings all produce an equal voltage which lies within the range the inverter is designed to work with. The other type has multiple circuits and can have different input voltages. (Sorry I forget the jargon). The point is that if the inverter is the firat type then all the strings must be the same number of panels, if in this case there are eight strings, then the number of panels per string is 217/8 = 25.875 .
Doesn't sound right.

We probably need the inverter's product type.

 

[JohnW2]

That's an interesting number. ... Doesn't sound right.

It is,indeed, an interesting, and seemingly odd (wrong?) number. It has few usual factors - in fact only 23 x 3 x 3.

Kind Regards, John

 

[JohnD]

207 solar panels !

Your club must have paid an absolute fortune. Entitled to a proper job.

 

[masona]

207 solar panels !

Your club must have paid an absolute fortune. Entitled to a proper job.

Didn't cost us anything, from what I understand, the investors company paid for the solar panels and they get bulk of the income from the government FIT.

We get get about £3-4000 reduction on the electricity bill.

We got our own structural engineer report and they condemned the roof being over loading, it's going to get messy. I'm trying to get all the information as much as possible.

 

[masona]

Latest - just waiting for the Electrical Engineer report, they were shocked!

 

[bernardgreen]

Latest - just waiting for the Electrical Engineer report, they were shocked!

That will teach him a lesson. You should only work on solar panels in the dark.

 

[masona]

Any comments?

Untitled

• masona
• 13 Dec 2014
• 1

Join 2 trays together with cable tie and all the wires cable tie to the solar panel bar

Untitled

• masona
• 13 Dec 2014
• 2

All the connections apart for one of them, just taped together with insulation tape

Untitled

• masona
• 13 Dec 2014
• 1

2 difference width trays, not bolted together

Untitled

• masona
• 13 Dec 2014
• 1

As you can see, it's sliding off the roof!