Solar panel circuit MCB size?

[Gavin A]

A 16 A mcb is a reasonable starting point for a system that has a nominal 16 A output.
But it could mean running the mcb near maximum for many hours in the summer.
When in doubt read the manual!
ABB recommend 20 A for the 3.6TL and 25 A for the 4.2TL
SMA recommend up to 32 A for their range from 3000TL to 5000TL

I don't think we've had a single case of nuisance tripping on any of the 16amp MCB's we've installed on 16A generation limited systems, which would be all of those hundreds of systems.

I've had to swap out a couple of 30mA RCDs for nuisance tripping, but that's it.

 

[davesparks]

Of course you won't have, a 16A mcb will handle 16A, that's the whole point of it being a 16A rated device.

 

[Leesparkykent]

The DC side of the installation will be run in galvanised 20mm steel conduit which has been flushed into the corner (150mm). Inverter will be housed on ground floor. 2 x isolators have been installed in the loft by the installers.

i think burying DC cables in the wall is an awful idea IMO

 

[driverman]

i think burying DC cables in the wall is an awful idea IMO

How would you normally install DC cables in a new build house? Surly, not surface in say trunking? The Solar people wanted it done that way and agreed the route which is basically straight up from main / inverter area to loft space. They wanted it in steel conduit. I went galvanised, even though it was behind dot dab. I even used female /male brass bushes. Would be interesting to know how you and others would do the job though?

 

[Leesparkykent]

i would of tried getting the inverter closer to the array or used micro inverters.

 

[driverman]

i would of tried getting the inverter closer to the array or used micro inverters.

I know nothing about solar installations, just doing to their spec. The distance between the two is not that great really. I would say the depth of a bedroom 3.4m ish plus another 3m. Would you consider that a long DC run? For whatever reason customer or installers wanted the inverter on the ground floor. Possibly for maintenance? Save going up into the loft? I don't know really,I'm just trying to get it done! lol

 

[Gavin A]

i think burying DC cables in the wall is an awful idea IMO

If it's mechanically protected what's the issue?

 

[shanky887614]

nothing wrong with it but i prefer the inverter up in the loft.

that way only the ac cable goes to meter then board

 

[TJ Anderson]

Of course you won't have, a 16A mcb will handle 16A, that's the whole point of it being a 16A rated device.

All well and good as long as G/83 settings applied which limit output. These inverters are made to work in different markets. We had an SMA TL 4.0 that went quite a bit over before it was realised.

 

[Leesparkykent]

Because in my view burying them in the wall even in galv conduit, customer turns main switch off in house for whatever reason they still have live cables running down the wall buried! the customer doesn't know they are there, only the person who done the install will.

 

[Gavin A]

nothing wrong with it but i prefer the inverter up in the loft. Reply With Quote

that way only the ac cable goes to meter then board

reasons not to would include the inverter operating at a higher ambient air temperature when at peak output, and therefore reducing the lifespan of the inverter (which ultimately is dictated by the lifespan of the capacitors), dustier environment, and the inverter being less accessible to check for repairs.

We'll install in lofts when there's no other option, but our preference is for the inverter in a garage or other accessible cooler space within the house if there is the option for those reasons.

 

[davesparks]

Because in my view burying them in the wall even in galv conduit, customer turns main switch off in house for whatever reason they still have live cables running down the wall buried! the customer doesn't know they are there, only the person who done the install will.

Then perhaps the customer should read the label at the CU which warns of the dual supply and the location of isolators required to achieve complete isolation

 

[Leesparkykent]

reasons not to would include the inverter operating at a higher ambient air temperature when at peak output, and therefore reducing the lifespan of the inverter (which ultimately is dictated by the lifespan of the capacitors), dustier environment, and the inverter being less accessible to check for repairs.

We'll install in lofts when there's no other option, but our preference is for the inverter in a garage or other accessible cooler space within the house if there is the option for those reasons.

agreed but could possibly go in a cuopboard upstairs etc, or just use enphase.

 

[Leesparkykent]

Then perhaps the customer should read the label at the CU which warns of the dual supply and the location of isolators required to achieve complete isolation

hows that going to stop the dc cables from being live? is there an isolator to turn the sun off? lol

 

[davesparks]

All well and good as long as G/83 settings applied which limit output. These inverters are made to work in different markets. We had an SMA TL 4.0 that went quite a bit over before it was realised.

I don't understand, how will the settings cause a 16A mcb to not be able to handle 16A? That is what my post stated, a 16A mcb will be fine with 16A flowing through it.

If what you are saying is that if the inverter could deliver more than 16A if not correctly set up then obviously that is a different scenario.