New consumer unit required - does it mean none fire rated down lighters need replacing?

[Ronski]

Well it was more to satisfy my curiosity once I found out the down lighters were already fire rated. I was concerned that the electrician was just making up jobs, but as with a lot of things there are different opinions, and different interpretations, whoever he spoke to could have got it wrong.

I'm ok with CU being done, it's a mess and apart from the cost it will be good to get it tidied up and to today's standard.

 

[Fleeting]

@Fleeting The entire consumer unit is being replaced, and I've opted for RCBO's.

You were questioning whether it should be replaced?

 

[Ronski]

Yes, but only since he'd said yesterday that the down lighters would need replacing if not fire rated, I knew months ago that they had said they would need to replace the CU. Having said the down lighters may well need to be replaced I started wondering more about the CU.

 

[binky]

I think it is just a case of misinformation, rather than anything else, and as my downlighters are fire rated he's happy with that.

there's a huge amount of misunderstanding in regard to fire rated downlighters. In short, you only need fire rated gear if penetrating a fire compartment or firebarrier. Most houses are regaded as a single fire compartment, ergo no need for fire rated downlighters, the most common exception to that being those with built in garages, whereby the garage is fire rated to protect the rest of the house.

 

[rjp44]

@Fleeting The entire consumer unit is being replaced, and I've opted for RCBO's.

Do ensure that you have taken account of the extra sustained current that the inverter can supply over and above your supply cutout rating. Maybe they are replacing the CU in part because they know this, but a bog standard RCBO board will have a 100A main switch with no overcurrent protection other than the individual circuit RCBOs. Connect that direct to the Quattro with 25mm tails and you have a fire risk if the sum total of RCBOs installed in the CU exceeds 100/115A now or in the future.

 

[kerching]

if the sum total of RCBOs installed in the CU exceeds 100/115A now or in the future.

I know nothing about this stuff, can you explain please?

 

[rjp44]

I know nothing about this stuff, can you explain please?

The Quattro is rather an unusual device in that it is an inverter with an input and an output which sits inline with the main feed between the meter head and the consumer unit.
It's output can sum both the mains input and its own synced DC solar/battery output and is not fused within the device.
It will pass through the full (100A?) feed from the utility, and add in 45A sustained from its own batteries and solar to boost the supply to the CU if called upon to do so.
Normally a consumer unit total sustained current is limited by the DNO cutout to, say 100A so you are fine with 25mm tails and a 100A main switch and no other protection. You can and typically would load the CU up with lots of RCBOs which when summed up come to >100A. This isn't a problem because they don't normally simultaneously draw anything like the max current and, if they did, the DNO cutout would (eventually) blow before the tails or main switch melt.
Put the Quattro in without a separate output fuse and you now have a possible sustained current of at least 145A which is going to warm up both the 25mm tails and the 100A main switch a fair old bit. It's pretty unlikely to happen, but the cable between the inverter and the CU and its main switch definitely aren't protected from overcurrent unless there is an additional fuse or MCB in the mix.

 

[binky]

The Quattro is rather an unusual device in that it is an inverter with an input and an output which sits inline with the main feed between the meter head and the consumer unit.
It's output can sum both the mains input and its own synced DC solar/battery output and is not fused within the device.
It will pass through the full (100A?) feed from the utility, and add in 45A sustained from its own batteries and solar to boost the supply to the CU if called upon to do so.
Normally a consumer unit total sustained current is limited by the DNO cutout to, say 100A so you are fine with 25mm tails and a 100A main switch and no other protection. You can and typically would load the CU up with lots of RCBOs which when summed up come to >100A. This isn't a problem because they don't normally simultaneously draw anything like the max current and, if they did, the DNO cutout would (eventually) blow before the tails or main switch melt.
Put the Quattro in without a separate output fuse and you now have a possible sustained current of at least 145A which is going to warm up both the 25mm tails and the 100A main switch a fair old bit. It's pretty unlikely to happen, but the cable between the inverter and the CU and its main switch definitely aren't protected from overcurrent unless there is an additional fuse or MCB in the mix.

Interesting, you sound like you have worked with Victron or done some extensive research into them?

So given the doomsday scenario of a possible 145Amps, would it not be wise to fit 100Amp MCB between the victron connection into the meter tails and the CU?

 

[rjp44]

Interesting, you sound like you have worked with Victron or done some extensive research into them?

So given the doomsday scenario of a possible 145Amps, would it not be wise to fit 100Amp MCB between the victron connection into the meter tails and the CU?

Yes, I've installed one, and yes, I would fit a fuse or MCB somewhere in the output circuit to protect the tails. The alternative is to ensure the tails and CU were big enough to pass the max available boosted output current. I don't know that off the shelf consumer units with 150A+ main switches and bus bars are commonly available though. Maybe they are.
You can configure the total max current draw on each of the AC inputs on the Quattro, so I guess you could wind that down to 55A which would reduce the total output to 100A, but would also reduce your charge rate when other loads are present, so not ideal. I'm also not sure about the idea of using software settings, which can be messed with, to stop things catching fire.

 

[binky]

Yes, I've installed one, and yes, I would fit a fuse or MCB somewhere in the output circuit to protect the tails. The alternative is to ensure the tails and CU were big enough to pass the max available boosted output current. I don't know that off the shelf consumer units with 150A+ main switches and bus bars are commonly available though. Maybe they are.
You can configure the total max current draw on each of the AC inputs on the Quattro, so I guess you could wind that down to 55A which would reduce the total output to 100A, but would also reduce your charge rate when other loads are present, so not ideal. I'm also not sure about the idea of using software settings, which can be messed with, to stop things catching fire.

I've always found victron an interesting if slightly confusing range of products. Clearly good quality gear with quite a fan base, which can make life a lot easier.

150Amp domestic CUs do not exist, although you could fit a 3 phase board with a single phase conversion kit - gets a bit expensive though

Preventing fires by software is not my preferred option, there's nothing like simple, dumb electrical components for ultimate safety.

 

[Ronski]

@rjp44 Thank you very much for pointing that out, its not something I'd considered, and I don't think the electrician has either. I've sent him an email.

 

[Bruspark]

Also confused - no such rule on ‘sum of breakers’ and rarely possible to achieve that

 

[rjp44]

I've always found victron an interesting if slightly confusing range of products. Clearly good quality gear with quite a fan base, which can make life a lot easier.

150Amp domestic CUs do not exist, although you could fit a 3 phase board with a single phase conversion kit - gets a bit expensive though

Preventing fires by software is not my preferred option, there's nothing like simple, dumb electrical components for ultimate safety.

My own perspective is that it is not the cheapest kit, but definitely compares very well to all the marginally specced rubbish out there.
Their background is in ship based systems which fits really well with architectures where you want to view the grid as just one possible source of energy, rather than slapping an inverter on a spare way of a CU to supplement grid. They do have quite a lot of products, but they fit together very logically.

Be interesting to see how they do in the exploding domestic and SMB renewables market. The packaging and product portfolio isn't quite as cheap, simple or targeted as most of the competition. For example the multiplus/quattro inverter/chargers are a perfect spec for a solar storage system, have a decent CPU & software, but you need an external GX device to talk CAN bus with an external BMS (edit: just looked at their product list again, and it seems there is now a "GX" version of the multiplus-II that does include a GX controller).

On the other hand, once you have implemented one of them with a GX device, you seem to be able to do literally anything you can think of with no other hardware: no export meters/clamps needed as long as grid is directly connected to AC-in, mix AC and DC coupled panels, islanding, time of day based charge/discharge policies, API integration are all really easy. They have it all.

 

[Murdoch]

Also confused - no such rule on ‘sum of breakers’

This was "misinformation" from manufacturers stating that the sum of the MCB's shouldn't exceed the rating of the RCD ..............

I suspect this was so that they could just make 100A RCD's ............

 

[binky]

My own perspective is that it is not the cheapest kit, but definitely compares very well to all the marginally specced rubbish out there.
Their background is in ship based systems which fits really well with architectures where you want to view the grid as just one possible source of energy, rather than slapping an inverter on a spare way of a CU to supplement grid. They do have quite a lot of products, but they fit together very logically.

I've always regarded them as 'off grid' products, or kit for motorhomes, camping, boats etc, and I have used one of their simple MPPT battery charger controllers for a 2 panel offgrid sytem, but that was only to provide lights for a stable block. Ive looked at Victron a few times for domestic solar installations, but find their range of products a little confusing, and as you say, it's not really targetted at that market. If I was looking at a fully offgrid system for a larger project, then I think Victron would be the way to go. When you have no mains supply to fall back on, reliablity and build quality becomes far more important.

I mostly fit Solis gear these days, which is proving to be reliable and works well enough, and far simpler to spec. I used to use SMA, but their prices have pushed them out of the market, an equivalent Solis product is around half the price, and from what I've seen, 2 Solis inverters will outlast one SMA.

 

[Ronski]

Here's the Inverter and battery, various things to finish off, and I will add another 14.5kWh battery.

 

[binky]

Here's the Inverter and battery, various things to finish off, and I will add another 14.5kWh battery.

Nice and tidy.

 

[Sidewinder]

There IS a requirement that outgoing circuits are not able to exceed the rating of any grouped upstream protective device, such as a main switch or RCD.
Additionally, one exists in such that it is not acceptable for a device to be fused above its rated value.
So a 60A isolator on a 100A supply would not be acceptable.
This information is in 7671, with greater clarification in the IET supporting documents such as the GNs & the design guide.

 

[rjp44]

Here's the Inverter and battery, various things to finish off, and I will add another 14.5kWh battery.

Nice. How many people did it take to lift the Quattro up onto it's mounting?

 

[Ronski]

Nice. How many people did it take to lift the Quattro up onto it's mounting?

Two, myself aged circa 55 and my 20 year old daughter
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Well, the two of us carried it out from the house, then put it on a workmate/bench in front of the battery rack, I put a pair of steps either side of the workmate, which I then stood on and lifted it onto the top of the battery rack. That was the hard bit done, then I put a ladder against my BBQ, a short scaffold board from the rack to the ladder, and I moved it on to the board under the bracket, then we walked it up on blocks, tipping it one way then the other.

Got it on to the bracket and removed the blocks, but I wasn't quite happy with the position, so then I did this to adjust it.

For anybody not in the know, it weighs 51kg.