Buffs Posted January 2, 2022 Share Posted January 2, 2022 Good morning all. This is my first post so please point me in the right direction if I've posted in the wrong place, asked a question that's already been covered or broken the forum rules. I bought my house around 5 years ago and I have slowly been renovating it ever since. About 3 years ago I had an Air Source Heat Pump installed, as we have no mains gas and at the time, the RHI was generous (it paid for the system). Last winter I picked up an absolute bargain of 4kw solar panels with an inverter for £400. I installed it myself and I am mostly happy with it. Since then I have changed the inverter so I can connect via bluetooth. Recently i have had a smart meter fitted.......... Now that I have the smart meter fitted I can see exactly what the power I'm sending back down into the grid. Actually, I knew this before, but its different when you can see the display 'laughing' at me!!! After the install, I did contact an MSC company and ask them if they would inspect and certificate. They told me, that it was virtually impossible for them to do this as they had to provide proof of where the panels came from. In any case, they said I'd only get about £60 a year back from the one or two electrical suppliers that offer a feed in tarrif (5.5p per KW). So......I was thinking, there must be a smarter way of using my solar and ASHP. I have my heat pump set for 21degrees in the morning and evening and all other times it's set to 18 degrees. There is an 3kw immersion in the tank, but it's only used to prevent legionnaires disease. When the heat pump is on it draws around 1.5 kw. At the moment, the heat pump thermostat/programmer is not wireless and I am not able to connect to it via bluetooth. I was thinking that maybe if the sun was shining during the day and producing over 2kw I could somehow activate the heating to go up to 24 degrees. This would warm the house during the day and therefore require less heating after the sun sets. Obviously, I would need some kind of app or software to run this. My ASHP is a Mitsubishi Ecodan and my inverter is an SMA. Thanks in advance for your replies, Nathan. Link to comment Share on other sites More sharing options...
ProDave Posted January 2, 2022 Share Posted January 2, 2022 No 1, try and use all your big appliances near the middle of the day, one at a time, that's washing machine, tumble dryer and dishwasher. No 2, I have set the timing so my ASHP does not heat the DHW until 11AM, by then there should be reasonable solat PV generation. No 3, fit a solar PV diverter. I am out of date with what is on the market at the moment (I made my own). These send surplus PV to an immersion heater to heat hot water. Even if you don't "need" more hot water it is better use of it than exporting it, and will save the ASHP heating it later. I have my DHW set to be heated to 48 degrees by the ASHP that leaves plenty of headroom for surplus PV generation to heat it further. Just doing these simple measures means I self use almost all I generate, and if I were eligible for the poxy 5p payment for export, that would earn me about £5 per year. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2022 Share Posted January 2, 2022 1 hour ago, Buffs said: I installed it myself and I am mostly happy with it. You did inform your local DNO about it, didn't you? Link to comment Share on other sites More sharing options...
Radian Posted January 2, 2022 Share Posted January 2, 2022 (edited) 2 hours ago, Buffs said: There is an 3kw immersion in the tank, but it's only used to prevent legionnaires disease. I would look upon that as an opportunity to dump your excess power somehwere less piss-taking than the grid. The problem though is that you would only want the excess to go into the HW. That's what @ProDave is suggesting in point 3 above. A solar PV diverter like this one does it all for you. However, with some off-the shelf electronics from Ebay or Amazon and a bit of coding I would say it was probably something within the scope of a DIY'er for under £50 Edited January 2, 2022 by Radian Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2022 Share Posted January 2, 2022 1 minute ago, Radian said: That's what @SteamyTea is suggesting in point 3 above. Was not my point. Was just checking the the install is legal to protect the installer and the DNO workers. Diverting to DWH is the easy way, but may only use 6 kWh a day, and in the summer it may be possible to generate 4 times that. Worth remembering that energy and power, the kWh and the kW, are different things. To run a heat pump purely off PV will require a minimum constant power, plus a bit for initial pump/fan startup. Batteries can help here. Batteries are still expensive, but at 20p/kWh to import energy, the levelised cost must be getting close to parity now. Link to comment Share on other sites More sharing options...
Buffs Posted January 2, 2022 Author Share Posted January 2, 2022 So, I already try to only use the washing machine (dont own a dishwasher and tumble dryer) when the sun is out (haven't seen the sun for a while though). I'm not fully aware of these pv diverterters, but my concern is that if I connect to the existing immersion, will the electricity flow back up into the control box and blow the heat pump control unit. Also, would it require at least 3kw or power to produce heat? I like the idea of setting the DHW to timed at 11am although, my tank had to be the slimline one to fit where I requested. Will have to try this and see how many complaints I get from the family!! @SteamyTea I didnt inform the DNO. The most I've seen it produce is around 3.7kw on a cold sunny day. As I'm not eligible for the feed in I didnt think I had to inform anyone. I was wondering if anyone had some sort of software based system that linked the Smart Meter, Inverter and Heat Pump. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2022 Share Posted January 2, 2022 5 minutes ago, Buffs said: didnt think I had to inform anyone You do. It is a safety issue. They need to know where installations are, how large they are, where the safety cutouts are, and that all the equipment is legal. You better get whoever wired it in to get you the certificates pronto. Link to comment Share on other sites More sharing options...
ProDave Posted January 2, 2022 Share Posted January 2, 2022 1 minute ago, SteamyTea said: You do. It is a safety issue. They need to know where installations are, how large they are, where the safety cutouts are, and that all the equipment is legal. You better get whoever wired it in to get you the certificates pronto. You might have an issue registering it now if it has an old inverter. Today it has to be registered under G98, but it is likely your old inverter does not have a G98 certificate but the older spec in force at the time. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2022 Share Posted January 2, 2022 13 minutes ago, ProDave said: old inverter OP said he bought a new inverter. If a good make it should be possible to download the relevant documents. If it is an SMA, let's hope the correct country code was used while setting up, pain if it isn't. Link to comment Share on other sites More sharing options...
Buffs Posted January 2, 2022 Author Share Posted January 2, 2022 49 minutes ago, SteamyTea said: 1 hour ago, ProDave said: old inverter OP said he bought a new inverter. Well it was new to me, but it was a used one. I'll take a look at informing my local DNO. Link to comment Share on other sites More sharing options...
Marvin Posted January 2, 2022 Share Posted January 2, 2022 @Buffs, what is the kW rating of the inverter you are using? Link to comment Share on other sites More sharing options...
Buffs Posted January 2, 2022 Author Share Posted January 2, 2022 4 minutes ago, Marvin said: what is the kW rating of the inverter you are using? 4kw. Link to comment Share on other sites More sharing options...
Marvin Posted January 2, 2022 Share Posted January 2, 2022 (edited) Well, I fear that it has the potential to go over the threshold of the maximum allowable, and therefore you need to apply to the DNO before connecting to the mains. Although my inverter could supply 6kW - my panels only 5.12kW, and the CT clamp system would restrict it to below the limit, the DNO still assessed the system by the inverter maximum output. This being said I can only comment about my experience with Scottish and Southern Electricity DNO. M Edited January 2, 2022 by Marvin Add info Link to comment Share on other sites More sharing options...
ProDave Posted January 2, 2022 Share Posted January 2, 2022 39 minutes ago, Buffs said: 4kw. Check the SMALL PRINT When I tried to register mine, the DNO came straight back and told me it required prior approval and told me to disconnect it and apply for permission. that is because they had seen the model number of the inverter as TL4000 and assumed it was capable of 4kW output. It was only when I pointed them to the manufacturers certificate that stated the output was limited to 3.68kW that they were happy. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 2, 2022 Share Posted January 2, 2022 9 minutes ago, ProDave said: inverter as TL4000 SMA isn't it. There is a small dial that sets the country code, think it is 9 for UK. Setting it wrong allows the voltage to go higher, do can deliver more power. So the DNO where right to tell you to disconnect it until it is proven to be correct. Link to comment Share on other sites More sharing options...
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