metal consumer units and DC combiner boxes etc

[Gavin A]

Does anyone know what the crack is with this nonsense about needing to move to metal consumer units under the yellow wiring regs update, and how this will apply to the DC side of solar installations, where we actually need the units to be fully insulated as earthing the box makes bugger all different in safety terms as the DC isn't referenced to earth?

It just occurred to me as we're using string fuse combiner boxes on most of our commercial installs now.

 

[TedM]

Consumer units - IET Electrical

 

[Gavin A]

so it's domestic only then?

well I suppose that answers the string fuse combiner box question.

 

[TedM]

I am left with only one question:

- is bakelite fireproof?

The London Fire Brigade seem to think so. Or at least sufficiently fire-retardant to be acceptable.

Good job that most of the CUs I have here (both installed in my property and piled in the barn) are made from it.

 

[Worcester]

So I guess your CU's are still rewirable

 

[The Solar King]

Reading this I do not think a fused string combiner box would be covered by the definition given, even in a domestic situation. We have in the past fitted them with Thin Film before clarification was available that they were not required.

Gavin, do you fuse just the positive as per new IET draft PV Guide or the neutral as well?

 

[TedM]

So I guess your CU's are still rewirable

Nope, mini trips that are plug-in replacements for the fuse-wire carrier.

All mod-cons here.

Mini-Trip 6A MCB: Amazon.co.uk: Kitchen & Home

 

[Gavin A]

Reading this I do not think a fused string combiner box would be covered by the definition given, even in a domestic situation. We have in the past fitted them with Thin Film before clarification was available that they were not required.

Gavin, do you fuse just the positive as per new IET draft PV Guide or the neutral as well?

erm, we've done it with just the positives fused as per IET, but have now pretty much reverted back to fusing both sides as it's a pain in the arse working out how to combine the neutrals when we're up to 4 strings so above or close to the rating for MC4s and the MC4 y splits, and the cost differential is minimal in the grand scheme of things.

 

[The Solar King]

Here is one I made earlier. Uses IMO components to combine the neutrals. Used for thin film where VOC is 672V and ISC 2.2A. (NOCT 612V, 1.76A). Configuration is six panels per string.

 

[Gavin A]

yeah that'd work.

though is that for solar frontier panels?

Do you not combine 4 strings before using a fuse combiner box?

or am I misunderstanding?

We run them in 8 panels in series, then 4 strings in parallel using MC4 Y splits, then into the fuse combiner boxes with 10A fuses, then down to the inverter.

 

[The Solar King]

Was for SF. Is now confirmed as unnecessary as can take a reverse current if 7A. Strings are now combined on roof using splits down to single input.

Box is is now redundant. Nice bit of work though.

 

[Gavin A]

ah fair enough. Yes it took a bit of investigation to work out that was how to do it.

 

[The Solar King]

yeah that'd work.

though is that for solar frontier panels?

Do you not combine 4 strings before using a fuse combiner box?

or am I misunderstanding?

We run them in 8 panels in series, then 4 strings in parallel using MC4 Y splits, then into the fuse combiner boxes with 10A fuses, then down to the inverter.

Are you talking about using SF panels here? If you are what inverter are you using to match the input voltage of 8 panels in a string? (880v-896V depending on panel output).

 

[Gavin A]

Are you talking about using SF panels here? If you are what inverter are you using to match the input voltage of 8 panels in a string? (880v-896V depending on panel output).

SMA tripower or ABB trio, both 1000V rated