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Firemans switch

  • 24-03-2022 6:52pm
    Registered Users Posts: 9,761 ✭✭✭

    Spent ages typing up a post but it didn't work and got swallowed when I tried to post.

    So basically, I ordered a kit, and it came with a Projoy firemans switch. Is this a new reg requirement? Last install I had done in 2017 didn't come with one of those, just an isolator switch on the panel side. It also has a din rail meter. I don't need this, given that the inverter will tell me the output is, right?

    Post edited by Effects on


  • Registered Users Posts: 11,031 ✭✭✭✭the_amazing_raisin

    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

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Moderators, Home & Garden Moderators Posts: 5,906 Mod ✭✭✭✭graememk

    Its SEAI grant requirements for both.

  • Registered Users Posts: 9,761 ✭✭✭Effects

    So if it’s not for a grant then I don’t need them?

    My first install was a new build, so no grant.

    This one is a semi self install, so again no grant.

    Is there a needed benefit to the fireman’s switch? Obviously don’t want to scrimp on safety.

  • Registered Users Posts: 11,031 ✭✭✭✭the_amazing_raisin

    Basically if there's a fire the firefighters will want to turn off the power to the house

    If they cut the power at the meter normally the DC side of the solar will still be active

    I believe the purpose of the fireman switch is that it will cut power to this as well, so the house is completely electrically isolated

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 9,761 ✭✭✭Effects

    On my homes install, my panels are on the roof, and inverter on the ground floor. So DC would still be live to it.

    The inverter on this new setup is in the attic space, 300mm from the panels, and the fireman’s switch would be right beside it anyway.

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  • Registered Users Posts: 6,581 ✭✭✭SouthWesterly

    Mine is the same with the switch in the attic. How do you turn it off in the event of a fire 😱

  • Registered Users Posts: 2,476 ✭✭✭bullit_dodger

    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/'s probably not a bad thing to do.

  • Registered Users Posts: 6,581 ✭✭✭SouthWesterly

    Thanks for the explanation. I'm planning on doing a ground array during the summer. Something to consider.

  • Registered Users Posts: 11,031 ✭✭✭✭the_amazing_raisin

    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


    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

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 11,031 ✭✭✭✭the_amazing_raisin

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

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  • Registered Users Posts: 2,476 ✭✭✭bullit_dodger

    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

  • Registered Users Posts: 11,031 ✭✭✭✭the_amazing_raisin

    Oh I agree that it's safety first, and firefighters don't need to be worrying about whether there's live cables in a building they're going into

    Reading a little deeper, it says the PV system must be isolated by "removal" of the AC supply. Removal to me implies deliberately disconnecting the supply rather than a loss of mains

    So I wonder is it sufficient to have something like toggling the mains disconnect outside triggering a bunch of relays to isolate the PV supply. This is kind of similar to the product in the OP but probably just wired in a specific manner

    What I really don't get is what's so wrong with a dedicated fireman's switch that's clearly labelled and disconnects both the AC and DC sides of your PV system? The wording above seems to cause more confusion than solutions

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 5,113 ✭✭✭John mac

    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 . ?

  • Moderators, Home & Garden Moderators Posts: 5,906 Mod ✭✭✭✭graememk

    Simply put if the fire man switch has power it will allow power from the panels.

  • Registered Users Posts: 11,031 ✭✭✭✭the_amazing_raisin

    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...

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 771 ✭✭✭SchrodingersCat

    From what I am aware, you do not need to install the firefighter switch if your inverter is in close proximity to the entry point of the DC cables into the home.

    The installation manual that I used for my PV install had the following note:

    I ended up not using my firefighter switch as a result. They are a pretty pricey component (~150e) too.

  • Registered Users Posts: 9,761 ✭✭✭Effects

    I put the DC isolator about a metre from entry point, which was above the inverter. AC isolator went below the inverter, close to where the cables entered the attic.

  • Registered Users Posts: 5,113 ✭✭✭John mac

    I'm getting my inverter put into the garage , so will be about 12M from the pannels .

  • Registered Users Posts: 771 ✭✭✭SchrodingersCat

    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.

  • Registered Users Posts: 2,258 ✭✭✭SD_DRACULA

    Yes the SEAI will be very peculiar about this, I had two of these fireman switches in my attic one from the string on the roof of the house another for the string coming from the shed about 10m away.

    The inspector failed it because of that 1.5m BS rule and had to put the second switch on the shed, it needs to be 1.5m max from the panels.

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  • Registered Users Posts: 771 ✭✭✭SchrodingersCat

    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.

  • Registered Users Posts: 2,258 ✭✭✭SD_DRACULA

    Yes I just moved the second one to the shed so it is within 1.5m of the panels as per their guidelines (of course it can be moved where ever after the inspection)

    No idea who the guy was, he wasn't from SEAI, they contract some crowd to do it.

    He did tell me that if I had the shed string disconnected from the inverter at the time of the inspection he would have to ignore it completely.

    Just goes to show how stupid the whole thing is since you can plug it in once the inspector goes away but it's an option if you want to not bother with a second switch at all.

  • Registered Users Posts: 2 mickoo7

    Hi Effects, do you do semi self installs.?