Solar panels and type AC RCBO's what's the situation?

[flameport]

If the RCD is comparing the current passing through two poles, how does it "know" which way the electrons in an AC circuit are "flowing"

It won't.

The difference is those with active electronics will have those components powered from one side or the other, and if it's designed so that they are disconnected when the device trips, connecting it incorrectly would result in those being powered even when the device has tripped. Depending on what it actually detects and how it responds, that could result in the circuitry or trip coil being destroyed.

There is also the issue of the test button on RCBOs with a solid neutral, which would be arranged so that the line is disconnected from the button when it trips. Connected wrongly and it would remain connected after tripping, and someone holding in the button for an extended time or the button sticking would cause the test resistor to overheat and fail, probably destroying other components or resulting in a flashover inside with a very big bang.

 

[ericmark]

Thank you @flameport you have made some good points to look for, the inverter should connect to the system before any RCBO then, I would expect between the isolators? I have two isolators, one in the consumer unit, which turns off whole house, and one before the consumer unit so the consumer unit can be worked on, rules say must be made dead elsewhere so either one needs a second isolator or pull the DNO fuse.

I have often wondered why do we fit isolators in the consumer unit? Other than one needs the terminals to connect to. If supply needs to be isolated elsewhere, they seem pointless.

 

[flameport]

the inverter should connect to the system before any RCBO then, I would expect between the isolators?

It connects to a protective device in the consumer unit, typically an MCB which is not supplied from an RCD.
It's a new circuit much like any other.

The presence and location of isolators, other consumer units and whatever else changes nothing.

 

[ericmark]

Interesting, wonder what circuit they will remove?

 

[ericmark]

The more I am reading the more doubt I am having.
1) How do they ensure I am not charged for power exported, I don't have a smart meter, they say Scottish power will take the reading off the meter the solar panel people install, which are not calibrated, that does not seem right.
2) They have said batteries go in North roof apex, then South roof apex, and then in the flat under the house, I don't like idea of batteries going on fire in the loft, would like to see them outside.
3) They say the switch in event of power cut is automatic, but can't see how that can be safe for any line men.
4) 14 panels to generate 3.5 kW does not seem right.

As yet only scaffold has gone up, which has stopped my using the good steps to lower house, had not realised until after they had left, so to reach flat need to walk around the estate to get to it, as steps other side are being redone so not safe at the moment.

 

[Murdochcat]

Interesting, wonder what circuit they will remove?

could you post a photo of your CU?

 

[JohnD]

4) 14 panels to generate 3.5 kW does not seem right.

It sounds a bit low, but in the right ballpark. Mine are nominally 280W each.

Actual output varies according to sunlight, orientation, latitude and temperature.

A lot of the time you will get less. It can be more, especially in clear, cold conditions.

 

[JohnD]

1) How do they ensure I am not charged for power exported

I don't understand the question. A digital meter records power you have drawn from the grid. A few old spinning meters can run backwards when exporting. Neither treats exported power as if it was imported.

 

[JohnD]

Reading off the meter the solar panel people install, which are not calibrated,

Not calibrated? Says who?

 

[JohnD]

3) They say the switch in event of power cut is automatic, but can't see how that can be safe for any line men.

It's a requirement that inverters do that. I expect it is part of the certification and approval process. I don't know how yours works.

 

[JohnD]

2) They have said batteries go in North roof apex, then South roof apex, and then in the flat under the house, I don't like idea of batteries going on fire in the loft, would like to see them outside.

It's a bit late to raise that. I didn't want equipment in the loft so I said so during the survey, and my quote, and installation, included fitting in the garage, next to the meter and CU.

 

[JohnD]

I don't have a smart meter, they say Scottish power will take the reading off the meter the solar panel people install

Neither do I. This is quite normal.

 

[JohnD]

the inverter should connect to the system before any RCBO then, I would expect between the isolators?

There are (at least) two ways of connecting the solar supply. It can go into the CU, or a block on the tails.

 

[ericmark]

Thank you @JohnD I have compared the battery they are fitting to my e-bike battery, and it is 5.5 times e-bike battery size, so not really that big.

It does seem the survey is a little lacking, it shows a schematic diagram and it seems the battery and inverter will need to be close and shows it connecting to consumer unit, however there were alterations made after the diagram was made, and I don't have new print out with the alterations.

Seems I will have to weight, as as it stands I have no idea how the UPS bit will work.

 

[Murdochcat]

There are (at least) two ways of connecting the solar supply. It can go into the CU, or a block on the tails.

You can't just connect the inverter to the installation at a block it has to have an OCPD and good practice says it mustn't connect to a shared RCD.