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Author Topic: DNO Changed?  (Read 1158 times)
Bikerzz
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« on: February 13, 2020, 07:09:31 AM »

I was inquiring with a company how many PV panels I could get on my roof and they told me the DNO is now 5.8kw. Anyone know if this is true?
I can only get a max of 22 panels on my roof which was what I really wanted to know hence I got them round, 20-22 panels they recon.
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knighty
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« Reply #1 on: February 13, 2020, 08:33:18 AM »

did they not mean.... you can have as many panels as you want, but they'll limit it to 3.6kw generation at the inverter?
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oliver90owner
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« Reply #2 on: February 13, 2020, 08:49:00 AM »

The DNO couldn’t care less how many panels your roof could accommodate. Max power might depend on size and panel conversion efficiency.

Some companies don’t care how many panels they quote for - they just want to fit (and charge for) as many as they can sell.

My advice is never to enquire with only one company unless you are sure you can trust them.  Simply enquiring to your DNO would give you the correct answer - “straight from the horse’s mouth”!

On here, we trust Navitron, our forum sponsors.
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dan_b
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« Reply #3 on: February 13, 2020, 09:50:27 AM »

So - let's wind back a bit.  The 4kW (3.68kW!) limit was as much to do with how the FiT payment system worked for new installs as it was to do with the export capacity on the local network. 
It used to be the case that if your domestic system was over 4kW, your FiT payment would be lower per kWh. That's just the way the Govt designed the FIT scheme.
This was partly to do with not having a requirement for measuring actual export with a meter when FiTs were introduced, but also to reduce paperwork and not need prior DNO-approval for every install, the 16A limit was set - therefore the two became synonymous.

The way it works now is without a FiT, there's no financial penalty for having a domestic system under 4kW anymore. In fact, with the Smart Export Guarantee via Smart Meters as the only way you can get paid for what you export, you now want as big a system as you can fit.  You can still get a 4kW system installed without DNO pre-approval, but you can always ask for DNO pre-approval for systems over 4kW.  They'll do what they always do - check the capacity of your local network/ transformer/ other properties in the area with solar and will let you know if you can go above 4kW with our without any network reinforcement.

DNOs are now in a position where they're having to change how they work to support more renewables locally, but they just want to ensure it's planned.

So yes, if your DNO says you can have 5.8kW, then go for it.  As mentioned, all they're actually worried about is the capacity of the inverter and its potential maximum export capability.  The number (and power rating) of panels you install is actually not relevant to them. You could install 30 x 350W panels if you wanted to and have a 10kW array, but you'd need to have it limited via a 5.8kW inverter.

Are you considering a battery as well?

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Countrypaul
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« Reply #4 on: February 13, 2020, 10:38:27 AM »

Bear in mind that even if you have 6kWp of panels the number of times in the year when that amount of power will be produced is relatively small, so having a larger PV array and limiting the export by inverter setting, for example, will usually be of more benefit to you than liiting the PV array to the maximum the inverter will handle.

PV arrays do not produce the peak power for a number of reasons, including: location, orentation, weather (if it is warm and sunny the get hot and downrate, so not just clouds), dirt, wildlife, corrosion (happens in the connectors as several threads on here have highlighted).
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Bikerzz
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« Reply #5 on: February 18, 2020, 07:24:49 AM »

I live off the gas network. Have a 300L Thermal store with 2 x 3kw immersions and a oil boiler.
I plan to maximize my roof full of PV which is 20-22 panels.
House is 130m2 downstairs with UFH, upstairs rads.
Im pretty sure I want maximum PV that fits on the roof as my home usage should be able to "trickle feed" the floor during day and maximize PV usage.
Its 30-150mm insulation and 67mm liquid screed on average.
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Countrypaul
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« Reply #6 on: February 18, 2020, 10:20:55 AM »

Bear in mind, if your export limit you have is 3.68 kW, there would be nothing to stop you having the PV split into two sections, one with a GTI, and one with an standalone Inverter which is linked to puely resistive loads like immersion heaters.  There would be the addional cost of a second inverter and possibly some addional wiring but the actual installation of panels should be the same. You could move to a more sophisticated solution (Sunny Island type ?) in the future if you didn't/couldn't put that in straight away.
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Bikerzz
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« Reply #7 on: February 18, 2020, 12:35:22 PM »

Cheers Paul.
I have a single height front south facing roof that would take 9 panels which I might buy second hand, mount and wire up myself to a immersion and just trickle that 24/7 as a cheap solution for now. Im getting married in a year, Mrs lost her job recently, so not loads of spare money for a full system.
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Countrypaul
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« Reply #8 on: February 18, 2020, 01:35:54 PM »

Cheers Paul.
I have a single height front south facing roof that would take 9 panels which I might buy second hand, mount and wire up myself to a immersion and just trickle that 24/7 as a cheap solution for now. Im getting married in a year, Mrs lost her job recently, so not loads of spare money for a full system.

I have 10 x 330W panels as that is the most we could get on our south facing roof above the dormers.  You might find it worthwhile to get a grid tie inverter as in summer you are highly likely to produce more electricity than the immersion can use and it could offset your other usage. It may also be a safer approach as the panels produce DC rather than AC.

If you wire the panels direct to the imersion be very aware that using DC will wreck the thermostat no time at all - it might not be safe to even do that. I'm not an electrician but hopefully those with more knowledge may be able to comment as switching DC is rather more "exciting" than AC. sh*tfan
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Bikerzz
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« Reply #9 on: February 18, 2020, 03:51:23 PM »

Ha ha, thanks mate Im a development engineer for an automotive company on Power systems, so more experienced in DC  than AC.
I was going to just get a off grid inverter to do DC to AC. If I went wiring it to Fuse Box I think I would get a company in to cover the roof.
I cant do ladders or whole house as physically not very capable with a broken back.
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Countrypaul
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« Reply #10 on: February 18, 2020, 05:39:36 PM »

In that case you probably understand the issues far better than I, but for those that just read your post at face valueand don't know any better I though there is/was a danger of someone doing something dangerous.
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Bikerzz
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« Reply #11 on: February 18, 2020, 08:05:08 PM »

I was still going to do dc to ac to immersion. To get DC right would be too big risk and stress setting up.
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