Why must the solar gateway be sited near the meter ?

Chordeiles

I live in an attractive house in an attractive location.  Yes, I'm lucky, I know.  I'm so determined to keep things looking nice that I'm probably about to pay a premium for an "in-roof" (as opposed to "on-roof") solar installation.

Been talking to 3 installers, but it quickly narrowed down to just one that got my trust.  And that installer tells me that the solar gateway (probably Tesla Gateway 2) MUST go near the meter.  Now my meter boxes are very visible on the side of the house (but thankfully they are painted to "just about" blend in with the brickwork).  The Consumer Unit ("Fuse Box" in old money)  is at the back of the (linked) garage, about 15m away from the meter).  There must be at least 20m of 100A cable between the meter and the fuse box, but I've no idea now it is routed, except it seems to drop down from the garage ceiling.

According to Tesla the Gateways (and Powerwalls) should never be painted.  If the gateway (and then probably the Powerwall) are sited near the meters, then I think it will look awful.  One solution would be to build a bit of a fenced area around the meters, but I'd still prefer not to have such a thing on that very visible side of the house.  I'd love to see all (or most of) this stuff inside the garage.  Thus far I can't see why the gateway can't go near the consumer unit, with all the switchover circuitry operating on the big cable that comes from the meter.  How different is that from doing the switchover at the meter end ?

Of course there's something I don't know, so I'd be happy if someone could enlighten me.  I'm a retired electrical/electronics engineer (with little domestic experience - except I've been a homeowner for 52 years), so feel free to get technical with me.  Thus far my guesses are as follows:

1. Maybe the gateway needs a connection on the "distribution network" side of the meter.  But surely that's a total no-no ?
2. Maybe the gateway needs an extra wired (or short-range wireless communications connection to the smart meter, so they can chat to each other ?
3. Maybe both meter and gateway need to be in short-range wireless contact with the same consumer display/control unit ?
4. Maybe the network engineers need access to it, to ensure things are safe if they are working locally ?  Except it seems common to put them inside (a garage for instance).
5. Or maybe my installers have never put the gateway anywhere else, and they are just reluctant to step out of their comfort zone ?

Many thanks if anyone is able to help.

Ectophile

So far as I can tell, this "solar gateway" is a fancy name for a switch that allows you to isolate the house from the grid and go into islanded mode if there is a power cut.  It will need some way to communicate to the inverter that it's safe to go islanded.

If so, then it needs to go between the meter and your main consumer unit, or it won't be able to do anything useful.

My rather basic system (Solax, not Tesla) has a big rotary switch, and a signal wire run up to the inverter to tell it what position the switch is in.

Heedtheadvice

As far as I can tell 20M ought to be considered 'close' electrically.

It could be that the issue is that if the gateway ( and it's monitiring/measuring system) is clearly visibly next to the meter then it is certain that it will interface between the grid and ALL  potential supply to the property such as when there may be more than one consumer unit.

As you touch on where does the meter to CU cabling go and what might be connected in that 20M. Potentially a circuit might not get switched and powered from the battery storage plus could also make grid measurement (by the 'gateway' ) of import/export be incorrect.

QrizB

The solar gateway needs to be connected into the meter tails between the meter and the consumer unit. It seems to me that "close to the meter" is on the assumption that, as with many houses, the meter and the consumer unit are pretty much adjacent.

In your case, they aren't nd I would expect that the solar gateway could be placed immediately next to to your consumer unit, in your garage.

I would hope that your installer will make a site visit to agree the details of your installation before you agree to contract them. That might be a good time to discuss these things.

Chordeiles

I think you just hit the nail on the head, Heedtheadvice.

It's obvious to me (and just about everyone else) that the cable from the meter to the consumer unit goes nowhere else, but of course I can't prove it. The distribution authority need proof (for the safety of their workers, mostly), and if it's all visible alongside the meter then that's the proof.

Thanks for your clear thinking !

Chordeiles

Having said that, there are innumerable instances where one can be expected to work on something electrical, yet it's impossible to fully verify the route from the point of isolation.  No-one ever went broke selling "isolate elsewhere before opening" stickers.  But there are ways of managing that risk (clamping everything to earth for instance).

In a sense it's a bit like the water byelaw that insists on the flexible pipe to a shower head being tethered in such a way that the shower head can't possibly fall into the bath or shower tray "in case a drop in supply pressure leads to dirty water being drawn back into the supply".  It's almost universally ignored, but no-one died of drinking bathwater, as far as we know.

But I realise this is an argument I won't win, because "rules are rules" (until they change them).  And in any case "she who must be obeyed" is already in favour of the fence solution - it would give her a convenient place to dump her gardening stuff !

Heedtheadvice

Must admit I posted thinking more regarding functionality rather than safety!

EricMears

Heedtheadvice said:

As far as I can tell 20M ought to be considered 'close' electrically.

It could be that the issue is that if the gateway ( and it's monitiring/measuring system) is clearly visibly next to the meter then it is certain that it will interface between the grid and ALL  potential supply to the property such as when there may be more than one consumer unit.

As you touch on where does the meter to CU cabling go and what might be connected in that 20M. Potentially a circuit might not get switched and powered from the battery storage plus could also make grid measurement (by the 'gateway' ) of import/export be incorrect.

20M (or even 200 metres)  would be  'close enough' electrically.  A major problem might be that installer would find it more expensive &/or time consuming to locate it further away.

Qyburn

EricMears said:

20M (or even 200 metres)  would be  'close enough' electrically.  A major problem might be that installer would find it more expensive &/or time consuming to locate it further away.

They just need to intercept the cable(s) carrying power to the house, it shouldn't be any more difficult doing so near the CU in the garage. That's where they'll be installing other stuff anyway.

69bertie

I suspect the reasoning is what happens if additional wiring is added near the meter. Located near the meter does away with any ambiguity as to what is and what is not connected in the house. Actually 20metres for consumer unit tails is excessive unless they are fused down - irrespective if it is 100amp cabling or not. One shouldn't be relying on the electricity company's fuse to be protecting such a long run. Presumably you have fused switchgear at the meter position.

Is there a reason as to why the equipment can't be located immediately on the inside wall by the meters? Space? You would probably fall foul of the requirements of the DNO if it is sited anywhere else but in the immediate locality of the metering equipment. After all they do have the final say so. They either accept the equipment installation or they don't. Unfortunately, your pretty house doesn't come in to their thinking.

Chordeiles

I just got an update from the solar installer, and it tallies closely with what 69bertie has written above.
They are saying that if they fit a fused isolator at the meter end (at present it's just a 2-pole isolator in the meter box) then they could fit everything else in the garage.  Yes, there should be an extra fuse between the meter and the cable run to the consumer unit, the fact I don't have one is wrong - but not at all uncommon, it seems.  The fuse on the network side of the meter is of course doing some sort of job in protecting that 20 metre length of cable, but it belongs to the network and they can't accept the responsibility for protecting my wiring, so they expect to see a further fuse my side of the meter if the run to the consumer unit is more than 3 metres.
As it happens the meters are on the side of the house which corresponds to the kitchen, it would be an immense upheaval to fit the kit inside there !  It makes a lot of sense to have arranged things the way they did, it's just that they forgot the fuse !
Overall this is a great result, I can have the solar kit hidden in my garage, and also get my house wiring to align with the regulations !
Thanks for all the contributions.