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Fireman switch

  • 04-01-2021 12:57am
    #1
    Registered Users Posts: 2,787 ✭✭✭ irishchris


    Midway through self install PV and just wondering if fireman switch is a requirement or optional. This will not be a grant install so just wondering if it is a regulation to have one of these. If not should I install a dc switch also at panels?

    Lastly if anyone here has done a self install ground mounted system could they pm or post pictures of how they did the final run of cables from ground level into house


Comments

  • Registered Users Posts: 2,787 ✭✭✭ irishchris


    Unkel,championc or anyone here who have done a self install, just wondering if any of you have installed a safety fireman switch, DC switch beside array of do you simply only install DC switch at the inverter?


  • Registered Users Posts: 2,683 ✭✭✭ graememk


    My parents house, there isnt one.

    Panels are on the roof of the shed, and come straight into the DC isolator beside the inverter. and the inverter is under a roof but still outside.

    My install will have a switch as the inverter will be 50m away from the panels.


  • Registered Users Posts: 1,381 ✭✭✭ Evd-Burner


    graememk wrote: »
    My parents house, there isnt one.

    Panels are on the roof of the shed, and come straight into the DC isolator beside the inverter. and the inverter is under a roof but still outside.

    My install will have a switch as the inverter will be 50m away from the panels.

    Where are the panels going to be installed vs the inverter?
    Also how big are the cables you are going to run?

    I am hoping to do a DIY install on my shed in the next year or 2, I can fit about 3kW, I have cables between the house and was thinking that in future I may want to install more on the actual house but I am limited to 6sq cable on a 30m run.


  • Registered Users Posts: 2,683 ✭✭✭ graememk


    Evd-Burner wrote: »
    Where are the panels going to be installed vs the inverter?
    Also how big are the cables you are going to run?

    I am hoping to do a DIY install on my shed in the next year or 2, I can fit about 3kW, I have cables between the house and was thinking that in future I may want to install more on the actual house but I am limited to 6sq cable on a 30m run.

    im putting up 7.2kwp of panels, on a 5 core 6mm2 SWA armoured, (2 strings of panels) also with a 1.5mm2 3 core nymj cable ( for the fire switch). The path is all under a roof but the SWA was recommended for the DC cables.

    Panels are going on a shed at one end of the yard and inverter is going in the barn at the other end.. which will be more accessible and away from animals & machinery in the summer.


    From the yard to the house is about 70m, Recently put in a 16mm2 cable but that was to power other things in the yard, having it being able to send electricity back was just a bonus.


  • Registered Users Posts: 2,787 ✭✭✭ irishchris


    Evd-Burner wrote: »
    Where are the panels going to be installed vs the inverter?
    Also how big are the cables you are going to run?
    .

    I'm using 4mm double insulated solar cable. The inverter is situated in house about 20m from ground mount with 3.2kwp. the cable is protected with 50mm esb ducting along the whole run.


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  • Registered Users Posts: 333 ✭✭ handpref


    irishchris wrote: »
    Midway through self install PV and just wondering if fireman switch is a requirement or optional. This will not be a grant install so just wondering if it is a regulation to have one of these. If not should I install a dc switch also at panels?

    Lastly if anyone here has done a self install ground mounted system could they pm or post pictures of how they did the final run of cables from ground level into house


    My install was the in the early days of the first grant period back in 2018, it was a while after the grant was announced that seai started to include this fire man switch. No installs before required it.
    My initial install did not have it.

    The installer then said they would fit it and process my grant but only if I came them €1000, swines.


  • Registered Users Posts: 1,381 ✭✭✭ Evd-Burner


    handpref wrote: »
    My install was the in the early days of the first grant period back in 2018, it was a while after the grant was announced that seai started to include this fire man switch. No installs before required it.
    My initial install did not have it.

    The installer then said they would fit it and process my grant but only if I came them €1000, swines.

    Did you pay them, if you didn't did you still get the grant?


  • Registered Users Posts: 333 ✭✭ handpref


    Evd-Burner wrote: »
    Did you pay them, if you didn't did you still get the grant?

    Ye, I had to hand over the grand after they fitted the switch, then they did the paperwork. They dragged their heels for nearly two years, it was extremely stressful. The sales guy stopped answering the phone and fobbed me off to another lad, then onto someone else.
    It was a northern based company with a proxy address in Donabate so there wasn’t even an office I could call into.

    Big life lesson there...think the grant worked out at €3800, which was €2800 after paying them off. I felt like not paying them out of principal and sacrificing the €2800 but it would have been only hitting our own finances.
    I also have to depend on them for technical support because of all the online portal stuff and I’m afraid that if I left an honest review on google for example that they would not be too helpful if I needed assistance. Another user here has done that already I believe.
    The new grant portal has taken the power away from the companies now and if anyone is considering solar only pay the price with the grant deducted.


  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 58,818 CMod ✭✭✭✭ unkel


    Or avoid all the hassle, save the tax payer some money and go the non-subsidy way. Either with an installer or DIY or a bit of both...

    "Wind is Ireland's oil" - An Taoiseach, 25/05/2022



  • Registered Users Posts: 2,683 ✭✭✭ graememk


    unkel wrote: »
    Or avoid all the hassle, save the tax payer some money and go the non-subsidy way. Either with an installer or DIY or a bit of both...

    Yep,Bit of both here. just waiting on the weather here. Steel roofs and ice/snow/rain aren't nice to work on!

    Will be putting a switch in as the panels are literally at the other end of the yard and will be quite in-accessible.

    Off the roof and into an inverter, it wouldnt be needed.

    If its a ground install, for a belt and braces approach, stick a normal DC isolator at your ground mounted panels. would do the same as a fireswitch. but not automated.


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  • Registered Users Posts: 1,381 ✭✭✭ Evd-Burner


    handpref wrote: »
    Ye, I had to hand over the grand after they fitted the switch, then they did the paperwork. They dragged their heels for nearly two years, it was extremely stressful. The sales guy stopped answering the phone and fobbed me off to another lad, then onto someone else.
    It was a northern based company with a proxy address in Donabate so there wasn’t even an office I could call into.

    I really dislike the way the grant system over here is done. I would much prefer if you applied for a grant and then got the system installed per regulations and then received the grant as the individual and not as a company.

    For my own installation once finances are sorted I am of 2 minds. I have a garden office/shed with a 25m2 roof. I reckon I could get 4kW worth of panels up. There is a distribution board in there that has a 4 core 6sq cable running to the main consumer unit in the house, as this has only been built I put the extra in for the future solar potential.

    I am also looking to remortgage in another year or 2 and do an attic extension, one where the roof will need to be rebuilt and as such will have scaffolding up etc, I could even get the roofer to put in the hooks and flashing while putting the tiles back on. I reckon I could haggle a the price on 6kW install on that roof with the grant. I'm not sure which way to go.

    I'm not sure which way to go, DIY or professional install with the grant. One other possibility is going with the attic install (south/south east) and running the solar cables about 30m away to the office/shed and running those off 1 MPPT, meaning I could install another few kW on the office/shed (westerly) on the another MPPT, with the infrastructure already in place this wouldn't cost a massive amount to do and would boost production in the winter and evenings.


  • Registered Users Posts: 1,627 ✭✭✭ quentingargan


    It is worth being clear here about what a firefighter safety switch does. All it does is disconnect automatically in a mains failure, so if firefighters switch off the grid, they aren't exposed to high voltage from panels on the roof. It provides no other protection, so you still need to use SWA or steel conduits. High voltage DC is potentially lethal, and the firefighter switch doesn't change that.

    They are mandatory on new houses unless the inverter is within 1.5m from cable entry point. Some inspectors still look for them, even when that is the case, but I can't see any benefit, as there is no risk of DC coming back through the inverter.

    They are mandatory for all grants, even when using micro inverters with isolation relays, where again, I can't see the benefit.

    If you have a battery and want to run loads during power outages, you won't be able to charge your batteries on solar, unless you take the firefighter safety switch out of the loop. Originally, SEAI said they would accept a push-button latching relay which ran the switch off the backup supply, and went back to normal when mains returned. However, they changed their minds on that later.


  • Registered Users Posts: 114 ✭✭ blue chuzzle


    I still can't figure out the firefighter switch - I suspect there is something obvious I'm missing:

    The firefighter switch turns off the panels if there is a power outage with the mains electricity. It detects this by being plugged into the house grid, which is powered by the panels and the mains. If the mains drops during the day, won't the house still have power to provide to the firefighter switch from the panels? How does it know what source it's AC is from?


    Separately, if the purpose of the firefighter switch is to de-power the house in a general power outage situation, this would be redundant if there is a battery backup that's providing power. How is that battery not a danger to the grid workers in the same way the panels would be?

    If you have a battery and want to run loads during power outages, you won't be able to charge your batteries on solar

    Thanks!



  • Moderators, Education Moderators, Home & Garden Moderators Posts: 7,383 Mod ✭✭✭✭ Jonathan




  • Registered Users Posts: 5,789 ✭✭✭ the_amazing_raisin


    Okay, here's how it was explained to me and what I've pieced together


    Basically, you're correct that the fireman switch has no idea where it's getting power from. So when the house power is cut the fireman switch will isolate the PV panels


    You can still get power from the batteries for power outages

    The reason this is okay is because the batteries and inverter are generally in the same room, no long cable runs that a firefighter might accidentally cut through and electrocute themselves

    So the power cuts and you're on battery and want to get power from your panels, but the fireman switch has disconnected them. What you need is manual transfer switch to power the fireman switch from the backup power supply of your inverter

    Of course you'll need to switch it back to mains power when the grid is restored

    If the house is on fire then you won't be hanging around to mess with any transfer switch, so the firefighters are safe (from electrocution, the fire is still a problem)

    If you're away from the house and the power goes, then too bad. The house will have to survive on batteries until the power is restored or you get home



  • Registered Users Posts: 3,911 ✭✭✭ mp3guy


    @the_amazing_raisin got it pretty much. There's a manual changeover involved. The inverter has a second output that needs to be wired up to provide power to the whole house (which includes the DC shunts). Then everything works as usual, isolated from the grid.



  • Registered Users Posts: 114 ✭✭ blue chuzzle


    Ok, thanks both!


    I confused matters by mentioning batteries, I'm really wondering where and how to connect the house power to the firefighter switch box for it to do anything useful.


    To be clear, the DC from the panels goes in and out of the firefighter switch and that's fine but:


    where should the house ac power that it needs come from (any existing circut in the house for example?) and


    how can it automatically tell if the grid is down on a sunny day when the solar is providing more power than the house needs and finally,

    do i need to have a manual switch somewhere convenient on the cable providing ac power to the firefighter switch for someone to switch to trigger the firefighter switch manually?


    Thanks!



  • Registered Users Posts: 3,911 ✭✭✭ mp3guy


    The shunt is powered just like everything else in your house.

    Your inverter knows the grid is down based on its own meter which will be taking a reading before the changeover switch directly on the ESB supply line from your ESB meter.

    The manual switch is for your whole house, the shunt is part of your whole house setup.



  • Registered Users Posts: 2,683 ✭✭✭ graememk


    Re the inverter detecting the grid (possibly could be different in the solax, my experience is sofar and solis, and just a cursory glance at the others)

    The inverter just monitors the grid at it's normal grid/house connection, yes the hybrids need the meter to know how much to charge and discharge the battery.

    If you flip the rcbo/mcb for the solar it will simulate a grid out situation and the normal work mode of the inverter will stop, this is the anti islanding function.

    Generally the fireman switch(found out recently it's a motorised switch, not a relay!) Is wired into the same line as the inverter (and ofc fused down to protect the cable)



  • Registered Users Posts: 5,789 ✭✭✭ the_amazing_raisin


    I guess I'm probably confusing everything by saying battery power when I should be saying backup power, since it could come from a generator



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  • Registered Users Posts: 114 ✭✭ blue chuzzle


    Thanks for the replies, it's getting clearer alright.

    I'm still a bit confused, and perhaps I'm actually missing something physical in my setup!

    My inverter is a Solis Single Phase 3.6kW 4G Dual Input Inverter. I don't have anything separate that detects the energy flow from the mains to the house and there is to be only one cable from the inverter to the consumer unit as far as I'm aware.

    If you flip the rcbo/mcb for the solar it will simulate a grid out situation and the normal work mode of the inverter will stop, this is the anti islanding function.

    Does this actually simulate a grid out? Its basically unplugging the inverter from the house but in a grid out situation, the inverter will still be supplying power to whatever requires it until the firefighter switch decides to cut the DC power, right?

    Source of my confusion:

    The bit I can't get my head around (and apologies again for the repetition!) is that on a sunny day, there will be power on the house grid, supplied by the inverter that will also provide power to the firefighter switch even if the external grid power goes down. How does the firefighter switch know the mains power is down(and that it should shut off the DC supply) if it's powered (like everything else in the house) by the AC coming from the inverter?


    Thanks all!



  • Registered Users Posts: 114 ✭✭ blue chuzzle


    Separately, my plan is to connect the firefighter switch as a fused spur off the ac cable connecting the inverter to the consumer unit. Is this what you described above graememk?



  • Registered Users Posts: 5,789 ✭✭✭ the_amazing_raisin


    So the Solis has 2 AC outputs, one for normal power and one for backup power

    The normal output will stop if there is a grid failure, but the backup power output will keep supplying power


    (Sorry if I'm naming the outputs wrong, I'm more familiar with victron inverters)

    So the AC supply to the fireman switch should normally be connected to the normal output of the Solis, meaning in a grid failure your PV will also be disconnected

    To get your PV back in a grid failure, you'll need to add a transfer switch to the AC input to select between the normal and backup outputs of the Solis

    So you then switch the fireman switch over to the backup power output and it restores your PV

    As a step further, you might divide your CU into two groups, critical loads and normal loads. The critical loads (fridge/freezer, lights, maybe some sockets for charging phones) would be connected to the backup power output of the Solis so they always have power

    You can use a transfer switch to switch over the non critical CU from the normal to backup power in a grid failure. Since the fireman switch will be in this group then that will restore your PV as well



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