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tony gh

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First post here so bear with me, this is by far the most helpful forum I have found and great that it is UK based.
I had the expensive outline prices from installers and then when I told them I did not want grid tied they said they could not install anyway.
From this outcome I have decided to do the install of the solar kit myself.
I am fortunate my daily usage is never more than 5 Kw and this is due to reductions in sizes or appliances and lighting changes to l.e.d. This means I do not need such a large array or storage, never the less I am hoping to get a 5000 watt ready build system and add 2 of the 5.5 Kw h lithium Ion batteries.

The only question I have is this. If I supply my power hungry appliances from the solar/battery system (My hot water is from solar thermal I have recently installed) and still keep the mains supply as a backup how can I connect the backup power input to the inverter for charging the batteries on cheap rate electricity overnight from my mains supply to the house.

Do I need to have a separate consumer unit fitted or can a supply be run from the now redundant economy seven consumer unit that was used to power the 5 storage heaters in the house? All of the storage heaters were 2.8 kw so they all have the same circuit 15 amp protection in the consumer unit. My proposed inverter has a Max 60 amp backup input rating which I will not be able to get anywhere near to, but I want to ensure that if it takes power from the main supply it will not overload the cables from the consumer unit
any advice would be very welcome please. PS I realise getting an electrician in is a long wait but that is something I can live with if I get a decent one.

regards tony

Split and slightly edited as it was hi-jacking another thread
 
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You need to bear in mind that a 5kW array wont generate 5KW, thats a theoretical maximum that you will never achieve in reality.

The inverter you need is a grid tied hybrid inverter, this will have the ability to charge the batteries during off peak times and to take solar energy to both feed your house and charge the batteries with any surplus. Using a grid tied inverter it monitors current flow in / out of your property and adjusts it's voltage accordingly to keep your import to zero.
 

tony gh

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Hi johnb2713

thanks for replying. My proposed array is only quite small it is 6 panel string in series of 420 watt panels. The inverter is 5 KW Conversol off grid inverter and mppt charger, this is part of a silent cabinet system that you then connect the p.v. and battery to when it is installed. It has an input for the ac/generator backup as well as AC out. The ac out will go to my appliances etc on a separate supply to the mains supplied from the grid.
I am trying to find a way to connect the ac, that is the backup, to my home supply so that I can set the timer on the inverter to use ac overnight to make up any deficit in the battery store. The inverter has a max ac charge current of 100 A but I wont be able to supply anything like that. I am trying to find out if or how to limit the draw by the inverter to match the amount you can supply from the consumer unit i.e to something closer to 15 amps.
Do you know if the inverter will simply charge the battery store using the available supply from the consumer unit albeit 15 amp?
I am not sure if I have confused myself and am overthinking the issue, I just want to ensure that by charging overnight on economy seven power I am not going to overload my system by drawing too much to the inverter /charger.
regards

tony
 

tony gh

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Hi Murdoch
I am looking at getting a small wind turbine to supplement the p.v a bit later down the road. At present i am just looking to reduce the mains electricity usage by storing what I can and using as little from the main as possible.
 

Richard-the-ninth

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Wind turbine? Do you have any neighbours? or are you out in the open?
(It may sound a daft question, but there is a lot more than folk think to be considered before you get a wind turbine.)
 

tony gh

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Hi richard-the-ninth, i am in the quiet end of a village with open fields on three sides, only 1 neighbour and they are at the far end f the garden. I have looked at a lot on turbines and realise the issues. I am thinking of a small boat type as a supplement to the P.V but that will be some way off if ever.
 

Richard-the-ninth

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Oh, ok. It's just that most folk assume (It used to include me) that you just buy a wind turbine, put it up and it will work, it does sound like you have done some research. :)
 

tony gh

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Hi
I have spent so much time researching and not buying that everything has gone up and up.
I am in the finals stage of getting a full kit but am struggling to work out the load the charger/inverter will draw when using 240 volt ac as a standby charging supply on overnight electric. I am getting a 48 v lithium ion battery store and will have 2 together to give 11 Kw h storage if possible. Any quick way to work this out as I think I have fried my brain trying.
regards

tony
 

binky

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Hi
I have spent so much time researching and not buying that everything has gone up and up.
I am in the finals stage of getting a full kit but am struggling to work out the load the charger/inverter will draw when using 240 volt ac as a standby charging supply on overnight electric. I am getting a 48 v lithium ion battery store and will have 2 together to give 11 Kw h storage if possible. Any quick way to work this out as I think I have fried my brain trying.
regards

tony
Charge rates are governed by the inverter not battery capacity. Max AC demand will be on the data sheet
 
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Hi johnb2713

thanks for replying. My proposed array is only quite small it is 6 panel string in series of 420 watt panels. The inverter is 5 KW Conversol off grid inverter and mppt charger, this is part of a silent cabinet system that you then connect the p.v. and battery to when it is installed. It has an input for the ac/generator backup as well as AC out. The ac out will go to my appliances etc on a separate supply to the mains supplied from the grid.

regards

tony
Why are you going the off grid route rather than grid tied?
 

tony gh

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Hi Binky, so the 23A mppt input is the max amperage it will pull when charging then?

Hi johnb2713 I am trying to go off grid in phases and get a system up and running without having to have an approved company come in and do everything for a huge amount of money and then have to have the meters changed etc. (current wait is 6 months to a year at the moment)
I am happy to get consumer units changed and or have new supplies run for the standby power but I just don't want to be completely off the grid with no alternative backup at present. Perhaps if having it installed was not so expensive I might have considered getting it done but I really don't have £12.000.00 plus scaffolding to spare and that was the last price 3 months ago, which has doubtlessly gone up by 20% or more since.

It is really a method by which I can reduce my reliance on the grid but have it as a standby if needed. I don't really have the space to get a large array fitted so I doubt I would ever produce enough to justify surplus power going to the grid anyway.
 
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Hi Binky, so the 23A mppt input is the max amperage it will pull when charging then?

Hi johnb2713 I am trying to go off grid in phases and get a system up and running without having to have an approved company come in and do everything for a huge amount of money and then have to have the meters changed etc. (current wait is 6 months to a year at the moment)
I am happy to get consumer units changed and or have new supplies run for the standby power but I just don't want to be completely off the grid with no alternative backup at present. Perhaps if having it installed was not so expensive I might have considered getting it done but I really don't have £12.000.00 plus scaffolding to spare and that was the last price 3 months ago, which has doubtlessly gone up by 20% or more since.

It is really a method by which I can reduce my reliance on the grid but have it as a standby if needed. I don't really have the space to get a large array fitted so I doubt I would ever produce enough to justify surplus power going to the grid anyway.
The thing is, going with an off grid inverter as soon as you exceed the inverter capacity it will trip. So washing machine running switch kettle on and off goes the power, ditto oven and hob etc. With a grid tied inverter you will run on solar / battery until such time as the demand exceeds the inverter capacity then additional power is imported from the grid, no interruptions etc, the inverter will still be supplying the maximum it can. The charging overnight is also taken care of by the inverter, timers set to use off peak tariff and the batteries are charged to the % you set.
 

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Hi Tony
Do you still have a connection from a Consumer Unit (fuse box) to the grid via the Company's fuse ?
That still has your house's circuits connected (lights, sockets, cooker etc) ?
Then connect the Hybrid Inverter AC output to a MCB in that CU.
Then whenever PV output falls below house power demand, the house demand can be fed from the grid.
Or the batteries can supply the house if they have charge.
And the batteries can be charged from the grid.
 
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Hi Tony I'm experimenting with similar ideas, and practicing on an isolated system for my pool ( see my previous threads). what ive learnt so far is go for more panels. If you have the space double up. My 2.8 kw array peaks at 2.1 Kw and that only and hour or two, mid summer.
 

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Hi Binky, so the 23A mppt input is the max amperage it will pull when charging then?
sounds like you are confusing yourself, the MPPTs tweak the DC leccy from the panels, nothing to do with anyting else. I'm not quite sure exactly how they work myself, but they alter voltage and ampage from the panels to get maximum useable power from the panels in line with the irradiance they are seeing at any point in time.
 

binky

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The thing is, going with an off grid inverter as soon as you exceed the inverter capacity it will trip.
Off grid needs to feed a battery(s) to smooth out power delivery, power being delivered via a pure sine wave inverter. Not had much to do with off-grid, but from what I have seen it's quite normal to have multiple energy inputs to the battery, ie solar and wind turbine or a generator. Grid tied is far easier to work with and ultimatley more flexible.
 
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Off grid needs to feed a battery(s) to smooth out power delivery, power being delivered via a pure sine wave inverter. Not had much to do with off-grid, but from what I have seen it's quite normal to have multiple energy inputs to the battery, ie solar and wind turbine or a generator. Grid tied is far easier to work with and ultimatley more flexible.
The point I was making is the OP is talking about a 5kW inverter. If he exceeds the 5kW then the output will trip. My suggestion of a hybrid grid tied inverter in the same scenario would give out it's 5kW and then add grid power to cover the additional capacity needed. With the proposed setup, you couldnt make a roast dinner if the cooker was electric.
 

binky

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The point I was making is the OP is talking about a 5kW inverter. If he exceeds the 5kW then the output will trip. My suggestion of a hybrid grid tied inverter in the same scenario would give out it's 5kW and then add grid power to cover the additional capacity needed. With the proposed setup, you couldnt make a roast dinner if the cooker was electric.
I was just trying to add to your post.

I've had a few customers keen to go completely off-grid over the years, the numbers never work out at anything sensible unless they don't have a grid connection already, or are prepared to live like hermits...
 

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