Christiano

I’m not an electrician but I would have thought your diverter would take care of that.

Yes I thought so too, as I had to give details of meter serial nos and readings on application.

We always panic when we see we’re exporting but it’s partly because we’re the only supply off a transformer so we know it’s going to waste.

I’ve just had a look at our energy consumption for heating hot water via heat pump. Tank is 250l, 2 in the household. It runs each morning at 2am to heat to 50c with a weekly legionella run. 2am is not the best time for efficiency as it’s pretty cold outside but we’re on Octopus Go so only 5p/kWh. Typically it is heating from around 44c and stops between 50.5c and 51.0c. On Sunday morning, legionella runs after this and takes just the top half of the tank from 50c to 68c. The day after legionella it doesn’t heat because the tank is still hot enough. For the last week of January it used 11.9kWh, so is about £31/year! In warmer times we will get greater efficiency from the heat pump and may return to PV diversion in really sunny times. Thinking about it though, perhaps it would be even better to heat water in the afternoon using the heat pump with either PV or stored energy. Just harder to control and more expensive if I get it wrong because of using full-price kWh!

We have exactly this problem, even with the configurability of the iBoost+. With an ASHP and battery storage my advice would be not to bother with the PV diversion, let the battery have it all. Maybe set up some automation so if the battery has capacity in daytime then pop the heat pump on for the water. A few thoughts: Diverting PV to heat water is 100% efficient while I expect using your heat pump will be 200%+ efficient. You would get lovely hot water from diversion whereas using the heat pump it will probably be less warm. You’re probably not getting RHI but you get nothing for heating the water via diversion whereas you would get something back for using the heat pump. The actual kWh required to heat your water isn’t that much, according to our EPC it’s about 10% of the heating requirement. We had to replace our iBoost after 4 years so that cost us about £60/year where our annual water heating was probably only about £100 before the heat pump, I need to check what it’s costing now. Someone said keep it simple above, it’s a good idea!

I believe the Samsung warranty covers paying your installer to replace faulty parts, if that was your question?

Thanks; I too use emonPi/Tx and had considered trying to use these to switch the power to the iBoost sender on/off but this is a different approach. I think it will be too complex given my already very congested consumer unit cabinet etc. but more food for thought; thanks! I had a little google around, it looked like there were devices from AliBaba for £100-200. I don’t need the increased inverter input/output enough to justify this plus paying an electrician to put it in. Best talk to your new installer and see if they think you need to ask your DNO for permission in the first place.

Thanks!

Calor want £295 + vat to take our tank away. We don’t get anything back for the 11-1200l of LPG inside it either; we didn’t decide on the heat pump until after they topped us up in the spring. We had an unvented cylinder installed in 2017 so we could use PV diversion to heat it via Solar iBoost and immersions. Our installer got a custom build cylinder with 3 coils in case we got a heat pump; good call!

Our DNO is UK Power Networks, they have useful info on their website (even giving outline costs for certain upgrades like moving power supply, going to 3-phases etc) as I’m sure others do. My PowerVault battery has 2 inverter settings; 3.68 & 5.5kW. I wanted to have the higher (which is set by the PowerVault mothership) so I had to make a G99 application to the DNO. They gave me permission so long as I fitted an export limiting device (£££s) so the battery can’t export. That’s a bit useless as I got £1k off the battery if I allowed EDF to occasionally force discharge it to help balance the grid. As far as I understand you can only have a single battery per phase. I think it was Robert Llewellyn from Fully Charged who had a Tesla and got a second, free Tesla due to the number of referrals he had but couldn’t put it on until he had 3-phase. I think it’s because it would be a complete nightmare for 2 independent batteries to read your main power line to decide whether to charge or discharge. You could find that one is discharging to charge the other up! I have a kind of experience of this where we have a Solar iBoost as well as the battery; they really don’t work well together. When the batter is discharging, it tends to discharge about 200w more than is needed, presumably so lights don’t dim if we switch something on. This 200w is usually exported but if it’s on, the iBoost sees the 200w, so uses it to heat the hot water tank. The battery thinks “oh, I need to provide another 200w” so increases it’s output and the iBoost soaks it up, so the battery increases by another 200w yada yada ending up with the battery just heating hot water! We’ve had to switch the iBoost off at least until sunnier times. Edit: I suppose I should qualify this by saying you could have multiple batteries behind a single control unit per phase, but as you have a PowerWall I think you can only have one per phase.

It’s also a bit late ‘cos the boilers have gone and we have a heat pump ? I was wondering 2 things related to your comment though: 1) I wondered what the flow rate was on the boiler system compared to the ASHP. It seems the pump on the Alpha CB24 we had was a Grundfos UPS 15/60 which apparently has a flow rate of 3.4m3/hr which is about 55l/min. That’s over double the 24l/min we’re getting now. Does that sound right or would the boilers have operated the pump at a lower speed? 2) I’ve watched a few YouTube videos about balancing radiators which recommended a 10-11 degree temperature drop but I haven’t seen anything suggesting it’s the same or different for an ASHP. Is there a recommended differential for heat pumps? Does it change depending on the outside temperature? Or should I accept that it’s running okay so leave well alone?

Agreed.

I've seen people saying that you may need to change your radiators/piping; it's potentially true but needs to be tested. We did a test on our LPG (two boiler) system; turn the heating output right down so the radiators are getting less than 50c. Leave it like that for a few days; are you all warm enough? If not, then you probably need to change radiators and/or piping.

We had LPG until the heat pump this year. (We still have about 1200l which we can’t use and it looks like we will have to pay for it to be taken away!) Anyway Google says there are 6.9kWh in a litre of LPG. We used about 3000 litres a year which is just under 21000kWh. EPC says our heat demand is about 24000 but there’s only the 2 of us in a family house so I reckon it’s about right. Our gauge was quite difficult to read because the plastic cover was perished, but we also took readings when we did elec/FIT readings and I made a reasonable demand curve. (Tank is 2000l so 1% is 20l or 138kWh) With LPG we tried TRVs calling for heat and it was hopeless, took them all off. With the heat pump we only have 1 in the bedroom to stop it getting too warm. Finally, WRT oversize or not. Ours is oversized “in case we build the extension (that would be nice but we don’t really need)”. A 16kW Samsung comes on at about 5kW and rarely is on long enough to drop down much lower. I’m trying to fine tune it but mostly to make it run for longer to get the lower kWh figures. I wish we had known this as we would probably have gone for a smaller HP and dealt with it if we did the extension.

We installed it in 2017 to use Solar PV Diversion for free hot water, but the cylinder was designed for a heat pump. It’s a custom build with 3 coils, 2 of which are fed by the HP. I have separate monitoring (emoncms) so I can be sure water was flowing to the cylinder. I’ve had another call with Samsung support and am going to try changing 1 more setting, hopefully that works. It’s for performance, I sent the Ofgem RHI team an email explaining that the HP showed monthly/yearly performance but not all time to date. They sent me a reply explaining how to read meters. My main reasons for avoiding putting a separate heat meter in are 1) it’ll be about £600 and 2) if it has to go on the return it’s very congested.

Hiya, I had one of these installed in September, it’s nice to find someone else who’s got one! It’s also from Freedom Heat Pumps, connected to existing unvented cylinder and radiators. Can I ask: 1) do you have separate heat meters for RHI (my installer said to use the info from the remote but I don’t see how I can report it as readings) 2) it’s hopeless at heating water except via the immersion. I’ve had a call with Samsung and changed some settings but it burns a couple of kWh not heating any water before deciding to use the immersion so I don’t bother with it. How are yours? If any good, can you share you field settings values? Thanks!