Circular reasoning (Rolfe's solar energy system)

[SimonS]

Our heating is gas rather than oil but I have the immersion (fed by Eddi) set about 5c below the boiler HW thermostat. Eddi heats the water 0230 until 05:30 then the Boiler is used 0830 - 0930 to heat the tank after the morning showers etc and the 5c margin stops the Eddi kicking in for the rest of the day. This assumes you have a well insulated hot water tank.

 

[Rolfe]

I suspect new rates will be higher on all fronts ?

Apart from:-
Charging up to 7.2kW
Variable charging rate to match solar excess
Compatible with IOG
I agree, no advantage at all.

I have several, some are removed when a new car includes a new charger, I have bought some with stuck relays and some people sell when they move house.

It was the fast charging I was after. I had a spell where I was running around I think three days in succession, and there just wasn't time to get enough charge into the car in the time I was home, even plugging it in every available moment. I was only saved by a destination charger in the car park where I was parked while I was at the theatre one evening, which gave me enough in about three hours to avert disaster the following day. (I suppose I could have used the 50 kw DC charger five minutes from my house, but the weather was poor and I really didn't want to give them 60p/unit. The destination charger was 40p.) Knowing I can charge from practically zero to 100% overnight if I have to is a great feeling.

The 7p/unit part of it is an even greater feeling. The car took 52.25 kwh last night to charge from 5%. That's £3.66 for in effect a full charge (or actually £1.83 last night with the special offer). Even allowing for the fact that my Golf had more than twice the range of the MG4 that's still something like £7.50 for the equivalent of the Golf's full tank. I was paying around £75 to fill that.

And for the icing on the cake, the addition of a house battery to the system means that my entire household electricity consumption is at 7p/kwh. I know there are some tariffs that give cheap granny charging for a few hours in the middle of the night, but they ain't going to compete with that.

 

[Rolfe]

Our heating is gas rather than oil but I have the immersion (fed by Eddi) set about 5c below the boiler HW thermostat. Eddi heats the water 0230 until 05:30 then the Boiler is used 0830 - 0930 to heat the tank after the morning showers etc and the 5c margin stops the Eddi kicking in for the rest of the day. This assumes you have a well insulated hot water tank.

That might be the way for me to go. I need to talk to my central heating engineer about it, because the water isn't really as hot as it should be, the way the boiler is set up.

In other news, I just had a call from my oil supplier, who had scheduled a regular delivery to me for today. They deliver at 10-week intervals and top the tank up regardless of the time of year. This can be a bit pointless in the summer, I feel, and the call was in fact to ask if the delivery was actually required, to save an unnecessary visit. I was pleased to be able to tell the caller that my oil sensor was still showing ten bars out of ten, and they were welcome to cancel the visit!

 

[johnb80]

Our heating is gas rather than oil but I have the immersion (fed by Eddi) set about 5c below the boiler HW thermostat. Eddi heats the water 0230 until 05:30 then the Boiler is used 0830 - 0930 to heat the tank after the morning showers etc and the 5c margin stops the Eddi kicking in for the rest of the day. This assumes you have a well insulated hot water tank.

You should have a good look at your gas tariff, I pay an average of 4.2p kWh for gas, boiler efficiency around 90% so water heating on gas costs me 4.7p kWh. Export of solar PV pays me 15p kWh. EDDI remains off for me!

 

[Rolfe]

"13.1.6 Supply Grid – Exp Threshold This is the amount of export that must be exceeded before eddi starts diverting power to the heater loads. Once diverting starts all the surplus power, less the Export Margin (see below) will be diverted to the heater load."
Set this figure above what your maximum export value is and EDDI will do what youre wanting.

"Export Margin This sets a minimum level of export power which is maintained when zappi is charging in ECO or ECO+ modes. Export Margin would normally be set to 0W (zero Watts) so that all available surplus will be used to charge the vehicle. In some cases, it may be desirable to always set a minimum export level set. An instance of this would be when using zappi with a hybrid PV/battery system."
As above, this time for Zappi.

John, would you mind telling me how and where to find these settings? I don't even know where my Eddi is, never mind how to adjust it. I have dug down to everything that seems to be possible on the MyEnergi app but can't find anything like that.

 

[johnb80]

John, would you mind telling me how and where to find these settings? I don't even know where my Eddi is, never mind how to adjust it. I have dug down to everything that seems to be possible on the MyEnergi app but can't find anything like that.

It's not in the APP, you have go onto the units. IIRC EDDI is near your consumer unit.

I think it will depend which unit is set as Master between Zappi and EDDI.
I tried to send you a video of Zappi setting which in my case is Master but forum wont let me.

Whichever unit is Master in your system, go down the menus into the advanced menu. In the case of Zappi it's:-
Menu
Other settings
Advanced
Supply Grid
Network
Export Margin.

J

 

[Rolfe]

I have no idea which is Master! I tried the Zappi and couldn't find "export margin" anywhere. So I found the Eddi, squirrelled away beside the fuse box, and I did find a setting for "export margin". Does that mean the Eddi is Master? I found settings allowing me to change which was Master but I left them (and everything else) alone.

So I changed the export margin in the Eddi to 5,000 watts, which is my export maximum, and turned it back on. We'll see what happens in the morning, but this could be the answer. I don't know if this does the trick for the Zappi too, but that's less important. There isn't going to be any solar excess by the time I get home tomorrow evening.

Thank you very much indeed. (It would be nice if this sort of thing could be done on the app, but I suppose it doesn't matter so long as it can be done.)

 

[GaryMG4]

Apart from:-
Charging up to 7.2kW

So far I've coped fine with the granny, Never wished I could charge faster at home in around 11k miles

Variable charging rate to match solar excess

Excess never exceeds 3.3 kW, mostly seems to be about 1.5-2, often less than 1.4. A battery would be a better option assuming it would work with a lower threshold.

Compatible with IOG

True, 7p vs 8.5p per kWh so £140 on 8k miles per annum vs £170 over the same distance, plus any time shifted savings or around £45 per annum if 100% of household use was from off peak battery.

 

[Rolfe]

Different setups suit different people. I gave it a year before I decided whether I could go on living with just the granny lead. (There's nothing quite like driving your new car home and - just plugging it in to a 13A socket like it was a Kindle or something!) I could have, but I was getting tired of it being so slow, and I'd stopped using the DC charger at the end of the road because first the weather turned cold and then they doubled the price.

Also, I hadn't got an EV charging tariff at all, I'd just been using the normal fixed tariff. I probably should have got something, but I had decided I'd just carry on as I had when I got the car until I felt my mind was made up. So I went for the full package.

But the decision could have gone the other way. You can buy a lot of normal-price electricity for the price of the kit you need to get really cheap/free power.

 

[johnb80]

So far I've coped fine with the granny, Never wished I could charge faster at home in around 11k miles

Excess never exceeds 3.3 kW, mostly seems to be about 1.5-2, often less than 1.4. A battery would be a better option assuming it would work with a lower threshold.

True, 7p vs 8.5p per kWh so £140 on 8k miles per annum vs £170 over the same distance, plus any time shifted savings or around £45 per annum if 100% of household use was from off peak battery.

You said "I'm still not convinced that a Zappi offers any significant benefit over a granny especially if I have a battery" so I just listed benefits over a granny charger that sprung to mind, it may or may not be a benefit to you and your normal usage. To me, convenience alone is worth the money.

 

[GaryMG4]

You said "I'm still not convinced that a Zappi offers any significant benefit over a granny especially if I have a battery" so I just listed benefits over a granny charger that sprung to mind, it may or may not be a benefit to you and your normal usage. To me, convenience alone is worth the money.

As you say in your circumstances the convenience is worth the money, if I was doing my pre retirement commute a 7kW charger would be essential. All the points you made were considered last year after I bought the car but I decided to see how it worked out over the winter before committing. As it turned out winter was fine, I did one DC charge for a journey that didn't materialise and I used a destination charger a couple of times to use up the credit I'd added to it.
Last (billing) month I put 230kWh into the car, of that I did 11x5 hour overnight Go sessions the rest was solar (FiT), so a Zappi would have reduced the 11 sessions to 3 or 4 but made marginal difference to the solar as my the excess from the 4kW array was rarely above what the granny would consume.
Horses for courses.

 

[johnb80]

As you say in your circumstances the convenience is worth the money, if I was doing my pre retirement commute a 7kW charger would be essential. All the points you made were considered last year after I bought the car but I decided to see how it worked out over the winter before committing. As it turned out winter was fine, I did one DC charge for a journey that didn't materialise and I used a destination charger a couple of times to use up the credit I'd added to it.
Last (billing) month I put 230kWh into the car, of that I did 11x5 hour overnight Go sessions the rest was solar (FiT), so a Zappi would have reduced the 11 sessions to 3 or 4 but made marginal difference to the solar as my the excess from the 4kW array was rarely above what the granny would consume.
Horses for courses.

If it works for you theres nothing to fix, it aint broke!

You might like to take a look at Tomato energy, they have 5p/kWh for 6 hours with no restrictions to car / charger etc. An extra hour off peak and 3.5p saving is significant.

 

[Rolfe]

Dragging this back on to the topic of my home energy system, that trick with the Eddi "export margin" setting has worked a treat. The water heated to temperature by just after 5 am. It's a sunny morning and the system has been exporting merrily with no interference from the Eddi since the battery reached 100% about 7.40 am.

Thank you John, that was perfect.

 

[johnb80]

Dragging this back on to the topic of my home energy system, that trick with the Eddi "export margin" setting has worked a treat. The water heated to temperature by just after 5 am. It's a sunny morning and the system has been exporting merrily with no interference from the Eddi since the battery reached 100% about 7.40 am.

Thank you John, that was perfect.

No problem m'lady.

 

[Rolfe]

I think this is as good as it's going to get. Most opinion seems to be that Octopus won't have a problem with what I'm doing, and if anything does get said I can worry about it when it happens. I do wonder slightly about whether it's wise long term to make the battery work that hard, but LFP batteries are supposed to be able to take it.

Now I have to finish my project to replace all the incandescent bulbs before the darker evenings set in, then forget all about the whole thing and just use electricity as I want to.

 

[Rolfe]

I should have mentioned that I had a shower when I got up (power shower, so it can take quite a lot of water), and now, at nearly lunch time, the water from the taps is still running too hot to touch. Since I'm going out after lunch and won't be back till maybe ten, this is obviously fine. There will be enough to let me wash my hands and face before I go to bed!

If I was going to be doing a lot of cleaning and using a lot of water it would be different I imagine, but it's pretty easy just to set the Eddi to do a boost if I find I need it. I could also use the central heating, but I need to get that looked at as it isn't heating the water very effectively.

Here's the current situation. The battery finished discharging at 01.20, and started charging again at 2 am, done by 04.40. The Eddi started to heat the water at 04.30 and was at temperature by 05.05. At 5.30 the battery took over from the grid to power the house load. The panels started to wake up properly just after 6 am, and were fully covering the house load by 07.10. It only took till 07.35 for the battery to get back to 100% and the export to start, unhindered by the Eddi grabbing anything.

It's sunshine and clouds, but the panels managed their maximum of just under 5.3 kw for a whole ten minutes at one point. Export is currently sitting at 14.4 kwh, although that obviously includes the battery export after midnight.

I think this is the setup I want to continue with. I still don't know how it will look when I'm charging the car overnight, but I don't see why it should make any difference. What's in the battery will go into the car rather than the grid, obviously, but that's neutral. I expect to be on about 40% when I get back this evening and I'll get a scheduled charge from Octopus to add 70%, so I'll see how that looks in the morning.

 

[SimonS]

I have no idea which is Master! I tried the Zappi and couldn't find "export margin" anywhere. So I found the Eddi, squirrelled away beside the fuse box, and I did find a setting for "export margin". Does that mean the Eddi is Master? I found settings allowing me to change which was Master but I left them (and everything else) alone.

Probably. To check, go to either the Eddi or Zappi then in the menu go to Linked Devices Info and that should give you a list that looks something like this:-

This shows that the Master (M) is the EDDI. ZAPPI being written in capitals tells you you are looking at the data on the ZAPPI (just in case you couldn't recognise the box in front of you ) and the ~ shows that the Grid CT clamp is wired to the EDDI. The X next to the Zappi is telling us that the car is not connected.
Any of the Libbi, Eddi or Zappi could be set as the master and the Grid CT can be connected to any of the three. It doesn't have to be connected to the master. There can only be one Grid CT and it can only be set on one Device. My system initially had problems until it was discovered that the single CT was physically connected to the Eddi but there was also a ~ showing next to the Libbi.

 

[Rolfe]

I'll have a look, thanks. This is a new concept for me. What difference does it make which one is set as the Master?

 

[SimonS]

Nothing other than it is usually desirable to have the Master indoors rather than having to stand out in the rain if you need to fiddle with it.

We got the Eddi first so we just left it as the Master.

 

[Rolfe]

My Eddi is in the cupboard with the fuse box, right down at floor level and a bit of a pain to get to. My Zappi is in the garage with no need to lie on the floor to see it. I might change it, then.