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PV Inverter Essential Load and How to best use Excess PV?

  • 13-10-2019 2:33pm
    #1
    Registered Users Posts: 435 ✭✭ mike_2009


    I've just had a Solar PV system commissioned. I have some excess currently. It's a 4.2kw array with a 6kwh battery pack. I have an Eddi diverting to the immersion, and it's working away even in October!

    Anyway, I wanted to know if it's worth hooking up a double socket to the inverter's essential load output? It would be nice to run the fridge/freezer and prevent food spoiling if we ever had a power outage. Any thoughts?

    The other question is how best to use any additional excess - until the FiT comes in and we see what that looks like. I was thinking of installing an LHZ electric radiator in the living room,it's the coldest room in the house with 3 outside walls. At least on any sunny days in winter it might take the edge off before the gas boiler kicks in each evening.

    During the summer though, space heating isn't really needed, so after the hot water tank is sitting at 60oC, what could I do with the excess then?

    An Electric Car is still a year or two off at least....!


Comments

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


    mike_2009 wrote: »
    Anyway, I wanted to know if it's worth hooking up a double socket to the inverter's essential load output? It would be nice to run the fridge/freezer and prevent food spoiling if we ever had a power outage. Any thoughts?

    Sure, why not. I'm connecting an outside waterproof socket to the essential load output of my inverter. In case of a power outage, I'll connect an extension lead to it, to power the essentials in my house like fridge, wifi, phone chargers, microwave, etc.
    mike_2009 wrote: »
    During the summer though, space heating isn't really needed, so after the hot water tank is sitting at 60oC, what could I do with the excess then?

    The most responsible thing to do with your excess production in summer is to just give it back to the grid for free. This is likely also the cheapest thing to do ;)

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



  • Posts: 0 [Deleted User]


    I'd divert to heat storage before a battery.
    I'm a big fan of electric gardening tools on sunny days.
    I've a boycot on small petrol engines.

    I second giving it away being cost-effective and responsible. I'm happy to let what I can't use go down the road.


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


    I always try cut the grass when the sun is out. And I do the twice yearly cutting back bushes / hedges job with my hedge trimmer typically on a sunny day. Powered by the sun :D
    I'd divert to heat storage before a battery.

    I've had my cryptocurrency miner running in the last few days, heating up our north facing (cold) living room, while the rest of the house was pretty much heated up directly by the sun rays. Love sunny weather in winter more than I love it in summer! Hardly any heating being used at the moment, except for water. The solar thermal isn't so good anymore now.

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



  • Posts: 0 [Deleted User]


    One has to be careful not to spend more on diversion control systems than the power is worth. Sigh I miss the immersun...that was a great product.

    I design systems to work in Spring and Autumn if they can do that they can do Summer with ease.
    The cold weather contributes a lot to the panel efficiency.


  • Closed Accounts Posts: 3,364 ✭✭✭ rolion


    mike_2009 wrote: »
    I've just had a Solar PV system commissioned. I have some excess currently. It's a 4.2kw array with a 6kwh battery pack. I have an Eddi diverting to the immersion, and it's working away even in October!

    Anyway, I wanted to know if it's worth hooking up a double socket to the inverter's essential load output? It would be nice to run the fridge/freezer and prevent food spoiling if we ever had a power outage. Any thoughts?

    The other question is how best to use any additional excess - until the FiT comes in and we see what that looks like. I was thinking of installing an LHZ electric radiator in the living room,it's the coldest room in the house with 3 outside walls. At least on any sunny days in winter it might take the edge off before the gas boiler kicks in each evening.

    During the summer though, space heating isn't really needed, so after the hot water tank is sitting at 60oC, what could I do with the excess then?

    An Electric Car is still a year or two off at least....!


    I'm on the same boat like you except never got the battery side of the things.

    What i am planning to do with the second output from diverter is to create a pre-heat cylinder.Once main cyinder reaches 70 degrees is switching off the output.

    Connect second output to pre-heat cylinder immersion,a small cylinder,maybe a 120litres. Immersion will take the excess,warm-up the water and feed it to main cylinder input to a higher temperature than the main piping have.
    Get a second hand cylinder,few meters of cable,chose a location for a horisontal cylinder and happy warm water days.

    However,not suitable for any "dreamer" ...


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  • Registered Users Posts: 569 ✭✭✭ thos


    What battery have you got?
    My Givenergy setup essential load circuit couldn’t handle the startup of fridge or freezer. Couldn’t handle water pump either. Reckon it’s good for lighting circuits only.


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


    That's pathetic. If a fridge isn't an essential load, then I don't know what is. What does the spec sheet say? My Sofar ME3000SP can handle the full 3kW it is rated for through its essential loads circuit.

    Maybe it's something else why your fridge / water pump don't start. Maybe your inverter doesn't provide a pure sine wave AC on the essentials load? :confused:

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



  • Registered Users Posts: 569 ✭✭✭ thos


    Yep, can handle 2.5kw typically, but on the essential circuit nothing but a lamp.


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


    Did you check the spec sheet? Does it have a value for max current on the essential loads? I did double check the spec sheet of my inverter after posting the above and indeed it can provide 13A (3kW) on the essentials load output.

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



  • Registered Users Posts: 569 ✭✭✭ thos


    Specs call it as 2.5kw, but most devices will have a higher initial spike so I suspect it just can't handle that spike.
    The key to switchover's is usually slow and gradual load, so I'm guessing these might be a little more sensitivity or possibly slower to react.

    "The back-up MAX output power is 2500w. If the load is greater than 2500w, the inverter will stop outputting and draw from the grid. The output power of back-up depends on the battery capacity."

    Tested during recent power cut, so was certainly no grid power to support it.

    Interestingly, the circuit is live in normal operation, and switches to battery only when mains dies. I'm not sure how quick this switchover is, and whether it would stand a greater chance of sustaining the continuous load, versus trying to take on the initial load.

    I have a generator also, and intend putting in a cutover switch to use the generator. Would have been great to use this circuit on a temp measure, so still looking into that as a possible option, without over complicating things.


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


    thos wrote: »
    Interestingly, the circuit is live in normal operation, and switches to battery only when mains dies.

    That's what it's supposed to do. A fridge surely doesn't have an initial spike of >2.5kW???

    I'd contact the tech support of your inverter. Something is not right here.

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



  • Registered Users Posts: 407 ✭✭ phester28


    spike in I for a fridge should be around 6 times the rated power. Newer fridges may have an inverter compressor and would be less. So to use typical figures a fridge freezer would normally be 150w. Six times this is still less than 1Kw. (and only for an instant)

    I looked into this after the hurricane but could not get a stand alone inverter or battery bank cheap enough that I would rely on for the inrush. Bought a Chinese pure sine wave 24V inverter but only taken it up to 200w constant at PF1.0.


  • Registered Users Posts: 2,820 ✭✭✭ air


    Very surprising that a 2.5kW rated inverter output can't start a domestic fridge. I see spikes of around 1.1kW when my fridge starts (which could be higher in reality admittedly).
    They must have really undersized the output stage capacitors or something.


  • Registered Users Posts: 435 ✭✭ mike_2009


    I've a Givenergy Battery and inverter also. Surprised to hear about that problem with the fridge. The Electrician did say it's only for small loads, stressing 13 amps max but I expected a fridge/freezer to be possible. Will have to rethink that and check the spec sheet.
    I'm not getting as much excess as I'd hoped except when it's a really sunny day. The Battery absorbs any excess on those other days. Holding myself back until more data comes in. I did enjoy seeing the meter go backwards for a few days until the ESB replaced the old meter with a digital one!!


  • Registered Users Posts: 2,441 ✭✭✭ wexfordman2


    mike_2009 wrote: »
    I've a Givenergy Battery and inverter also. Surprised to hear about that problem with the fridge. The Electrician did say it's only for small loads, stressing 13 amps max but I expected a fridge/freezer to be possible. Will have to rethink that and check the spec sheet.
    I'm not getting as much excess as I'd hoped except when it's a really sunny day. The Battery absorbs any excess on those other days. Holding myself back until more data comes in. I did enjoy seeing the meter go backwards for a few days until the ESB replaced the old meter with a digital one!!

    If the electrician says it will run at 13a, then your fridge would be no more than that would it?

    In any case, to make backing up a fridge or freezer in any way viable, you would need a huge battery back up . For example, an idle house with a load of say 400w, will only run for max 12hrs with a 5kwh battery, and that's just idle background power. How long do you need to keep your fridge running ?

    A day without power wont tumour fridge or freezer would be ok, but 3 days, then you've probably split food. How mich battery power would you need to keep your fridge going for 3 days?

    Essential.load to me, is lights, a few sockets for phone charging and keeping the internet going, that's about it, anything more than that, and you would prob be looking at a generator


  • Registered Users Posts: 19 ✭✭✭ JBinWaterford


    Essential.load to me, is lights, a few sockets for phone charging and keeping the internet going, that's about it, anything more than that, and you would prob be looking at a generator

    I've a 6kw battery and 3.6kw inverter, and from what the installer advised me, regarding expectations for essential load circuit limitations - the above is what I'm expecting to be able to run in event of power outage. Depending on the charge state of the battery - a router, laptop, some LED lighting, phone charger and maybe boiler/pump (ie total of approx 300-400w) for 12hrs.


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


    Your installer was right. With a full 6kWh batttery, you should be able to run those appliances for 24h easily (taking into account you have to sleep too) if the grid goes down. You'd probably want to hook up your fridge / freezer too, which possibly uses more than those other appliances you mention put together though, so do take that into consideration.

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



  • Administrators, Computer Games Moderators, Sports Moderators Posts: 31,017 Admin ✭✭✭✭✭ Mickeroo


    Can the panels still charge the battery if the grid goes or is it a case of just being able to use what's in the battery?


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


    Mickeroo wrote: »
    Can the panels still charge the battery if the grid goes

    No.

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



  • Registered Users Posts: 737 ✭✭✭ Zenith74


    Mickeroo wrote: »
    Can the panels still charge the battery if the grid goes or is it a case of just being able to use what's in the battery?

    Discussion on this had here a few weeks back as I wondered the same thing with my new system - https://www.boards.ie/vbulletin/showthread.php?t=2058049928

    I've a 6kw battery and 3.6kw inverter, and from what the installer advised me, regarding expectations for essential load circuit limitations - the above is what I'm expecting to be able to run in event of power outage. Depending on the charge state of the battery - a router, laptop, some LED lighting, phone charger and maybe boiler/pump (ie total of approx 300-400w) for 12hrs.

    FWIW I used mine during an outage recently, used about 20-25% of a 5kWh battery over the 12 hour outage. Ran desktop PC+32" screen+speakers, Internet (modem, switch, two wireless APs) and gas boiler. Was pretty delighted with that to be honest, I didn't know this was going to be a feature when I put the solar in.


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  • Registered Users Posts: 19 ✭✭✭ JBinWaterford


    Just out of interest Zenith74, how did you run the power from the Inverter's essential load terminals to your boiler ?

    We got our consumer unit replaced when we put the PV in, so created an 'essential load' circuit (extension LED lights, and sockets) but didn't think to include the boiler fuse position on that circuit at the time 8-/


  • Closed Accounts Posts: 3,364 ✭✭✭ rolion


    Mickeroo wrote: »
    Can the panels still charge the battery if the grid goes or is it a case of just being able to use what's in the battery?

    "NO" my arse...those with off grid installations will have to wait for the fcuking grid to come back online to charge the batteries ! New smart AI technology "inverted" by unkel !

    Read here:
    https://en.wikipedia.org/wiki/Intelligent_hybrid_inverter

    Use in off-grid mode (without network) with the possibility of linking to a generator. The inverter must be connected to a battery bank and must have true off-grid capabilities - not all Hybrid inverters are created equal or can be used in off-grid applications.
    Use in on-grid or grid-tie (connected to the network) with the possibility of selling energy or excess energy. There is a need to have the norm compliance of protection and decoupling (DIN VDE 0126.1).
    Use in hybrid mode the inverter functions with a battery bank, but also connected to the grid. This dual functionality is the highlight of hybrid inverters that hence enable energy management (smart grid).
    Use in Backup mode, or storage mode prevents blackouts by switching from on-grid mode to off-grid mode at the moment of a grid outage, thereby eliminates network cuts.


  • Closed Accounts Posts: 3,364 ✭✭✭ rolion


    Just out of interest Zenith74, how did you run the power from the Inverter's essential load terminals to your boiler ?

    We got our consumer unit replaced when we put the PV in, so created an 'essential load' circuit (extension LED lights, and sockets) but didn't think to include the boiler fuse position on that circuit at the time 8-/

    What i love to do is to create two different and separate circuits for plugs/sockets/switches.
    Probably one using normal UK plug and the dedicated one using other type.

    The normal grid connected circuit just plug in the wall as normal, for wife "accidental" usage of iron,wash machine,cooker,hover and so on.That will prevent anyone overloading the backup emergency circuit.

    The "other" circuit fed from the AUX output will have the plugs or connections designed so that only certain appliances or lights to be switched.That will be under your strict control and/or usage,could be nice if they can switch on automatically, as a failover.

    My house has few off the shelves Smart UPS as backup,they are online mode 24/7 and powers the life circuits/equipment such as all LED lights,gas boiler and few others devices. I calculate it will stay on about 1 hour top. Is not to keep me going as a generator but more to avoid that panic mode when main grid goes offline in the middle of my family doing something.But,due to bad design,if you plug in the hover or iron,just gets beeping crazy as it overloads.

    So basically, design it in dual format,fail over manual or auto,special labelled and strict instructions for family on "how-to" use it.

    Have fun.


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


    rolion wrote: »
    "NO" my arse...those with off grid installations will have to wait for the fcuking grid to come back online to charge the batteries ! New smart AI technology "inverted" by unkel !

    :rolleyes:

    He asked about an install of a solar hybrid grid tied inverter (as installed by any SEAI installer as part of the subsidy scheme). It will NOT charge the batteries from solar PV when it senses the grid is down

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



  • Registered Users Posts: 737 ✭✭✭ Zenith74


    Just out of interest Zenith74, how did you run the power from the Inverter's essential load terminals to your boiler ?

    We got our consumer unit replaced when we put the PV in, so created an 'essential load' circuit (extension LED lights, and sockets) but didn't think to include the boiler fuse position on that circuit at the time 8-/

    For this outage I did it in a bit of a hurry because the solar had only gone live a few days beforehand and I wasn't aware the EL output even existed until maybe one day beforehand. So I had an extension lead running from the EL output in the attic to the first floor where I plugged in the PC etc., I then took the boiler supply cable out of the isolator in the hot press, stuck a 3-pin plug on it and plugged it into the extension lead.

    For the longer-term solution I plan to put sockets in the hot-press and have the boiler plugged into that, rather than hardwired into an isolation switch. Then run a socket down from the EL output on the inverter, so in the case of a power cut you'd just unplug the boiler from the 'grid' supply socket and plug it into the 'EL' supply socket. As rolion suggested, using something like t-bar plugs/sockets will prevent the sockets being abused (https://www.edwardes.co.uk/products/mk-647whi-13-amp-3-pin-non-standard-fused-plug-top)


  • Registered Users Posts: 19 ✭✭✭ JBinWaterford


    Zenith74 wrote: »
    ...For the longer-term solution I plan to put sockets in the hot-press and have the boiler plugged into that, rather than hardwired into an isolation switch. Then run a socket down from the EL output on the inverter, so in the case of a power cut you'd just unplug the boiler from the 'grid' supply socket and plug it into the 'EL' supply socket. As rolion suggested, using something like t-bar plugs/sockets will prevent the sockets being abused (https://www.edwardes.co.uk/products/mk-647whi-13-amp-3-pin-non-standard-fused-plug-top)


    Neat...and sounds do-able here, tho a little further to run cabling as our boiler pump is in a boiler-house. Tho, I suppose there may be a solution on the fuse board to bring the circuit into the new dedicated essential load fuse there.


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