Firemans switch

Actually that's something I was wondering about too, I saw some articles on how the house has to be isolated from the grid in the event of a power cut, but it didn't mention that the DC side had to be disconnected as well

I'm guessing that fire regulations aren't really part of ESBN's responsibilities so that's the reason for that

Personally I'd prefer if a manual disconnect was an option, so you could anti islanding to isolate you from the grid but keep your solar power running

I thought the same thing myself SouthWesterly, but the answer is actually "quiet easy". The way that it works is that it's a spring loaded solenoid, with the grid voltage keeping the circuit live. Effectively the live current pushes the spring.

When someone (a fireman) comes along and kills the power to house, that firemans switch is no longer powered, and the spring stops the current from flowing beyond that switch....meaning in the case of "Effects" above, that wire coming from the attic down to the ground floor in his house is no longer "live". You never actually have to go into the attic to turn it off, which was how I originally thought it worked.

It's not a requirement in the UK I believe, only in Ireland. I was originally "meh" about it, but if it doesn't cost much time/effort.....it's probably not a bad thing to do.

Problem with that is that you lose your PV in the event of a power cut which kind of negates half the purpose

The guidelines from SEAI seem a bit weird

Here's the isolator switch section

Through these requirements of Part B of the building regulations and I.S.10101, all domestic PV installations installed under this Scheme must:

• Provide an automatic (i.e., automatically operated by disconnection of the main AC supply

to the building) shunt (or interlocked) isolation of the circuit (whether AC or DC, and two pole) from the solar PV modules into the building, as close to the solar PV modules as possible, and a maximum of 1.5m internally from the point of cable entry to the building.

• Where the circuit from the solar PV modules does not enter the building, this point of automatic isolation must be within 1.5m of the solar PV modules.

• For ground mounted system the shunt (automatic isolator) must be within 1.5m of the solar

PV modules.

• This system of isolation shall automatically isolate the circuit from the solar PV modules when the AC supply is disconnected to the building, i.e., a shunt or interlocked isolation function.

• ‘Shunt’ or ‘interlocked’ isolation of the DC circuit is the only acceptable manner of meeting the Building Regulation TGD B – Fire Safety (2017) for the purposes of this Scheme.

• For the avoidance of doubt the disconnection of the circuit from the solar PV modules must

be automatic and operated by removal of AC supply to the building and must not be operated by means of a dedicated switch, pushbutton, ‘fireman’s switch’ or other manner.

• For the avoidance of doubt an isolation of the supply from the PV modules is required in ALL cases, whether micro-inverters, DC optimised inverters, where the inverter is within 1.5m of cable entry or any other configuration is used.

• This system of isolation must automatically reconnect upon restoration of AC supply to the

building.

A warning label must be applied to the main external AC connection point to the building

stating “In Emergency Solar PV DC Circuit Automatically Disconnected with Disconnection of AC

Supply to Building” or an equivalent statement.

And here the section on backup power supplies:

Off-grid operation is defined here as a solar PV (and battery storage) system which is not connected to the electrical distribution system (typically a remote dwelling). Backup operation is defined here as a solar PV (and battery storage) system which is required to provide electricity to the dwelling during periods of grid outage.

• Off-grid systems must comply with the requirements of this code of practice but do not 

need to meet the requirements of Section 4.8, and can achieve the requirements of Section 

4.7 as per the backup operation requirements below

• Backup operation is permitted so long as the below conditions are met;

- The backup supply from the PV and battery energy storage system must be on the load side of the ESB meter and cannot feed any other premises.

- The requirements of I.S. 10101 must be met, particularly relating to the requirements of ‘standby supply’ and break-before-make changeover switch, and the requirements for neutral treatment in island mode and impacts on protection operation.

- There can be no circumstances where the PV and battery system will feed energy into the grid during backup operation.

- Ensure that, by design, loss of mains (LOM) protection is not compromised. This could be either by relocating LOM to ESBN-Customer interface or by interlocking LOM changeover switch.

My reading of this is that you can have a backup power supply, but it needs to disconnect automatically in the event of a grid failure, which kind of seems pointless

Thanks for that 'raisin'. They do go out of their way to make the thing unreadable with the English they use don't they, but there's some sense there I think. The main safety thing that they are trying to cater for is that there will be people who have their inverter located "some distance" away from the entry point of the wires into the abode, hence the "located not more than 1.5m from entry".

If there was a fire, and a fireman swinging an axe, I guess he doesn't want some 450-550v wire "live" knocking about the house. I think that makes sense. They don't really care about the whole backup thing, that's secondary to the safety point I reckon. It's interesting that the UK doesn't have it as a reg. I guess electricity must behave differently over there - LOL.

Personally, I've not had the occasion to test the behavior of my own one as I don't have a socket wired up to the EPS on my inverter. To be fair, it's not really an issue for me, although I know some readers on here out "da whest" face more frequent and longer black outs that I would in Dublin

so. if i have this right , the firemans switch wil close when the power is cut . cutting off power from the panels .

if i have a backup transfer (off grid) switch , when i enable this to pull power from the battery the firemans switch will open.

is that right ?

or is it a case of maually operating the firemans switch after switching to backup / power is restored . ?

I believe that is correct, you need a manual transfer switch to connect the fireman switch to the backup power output of your inverter so as to reconnect your solar panels

The basic idea seems to be that in the event of a power cut your panels are disconnected and require you to manually restore them, which presumably you wouldn't do if the house was on fire (unless you have some very odd priorities)

Of course the issue with a manual transfer switch is that you could accidentally leave it in the backup power setting, rendering the fireman switch useless

I wonder is there such thing as a transfer switch that'll auto reset when the grid is restored...

It doesnt depend on the distance of the inverter to the panels, it depends on the distance of the inverter to the entry point of the DC cables.

If this distance is more than 1.5m you will need to install a Firemans Switch.

I getcha.

Does that mean that you moved one of the two fireman switches from your attic out to the shed, or did you have to install a third one in the shed?

Also, who was the inspector? I am interested as I did a self install. An electrician friend inspected and signed off on it at the end. I am interested as I never applied for the SEAI grant as I thought it were not possible with self-installs. However, if there are SEAI inspectors, im wondering if it is actually possible.

Hi Effects, do you do semi self installs.?