Dillsue

It's not sugar coating, it's just a balanced view. Constant slagging of the company/engineer could well cost them work and be the start of a bad reputation if the OP doesn't consider the possible flip side.

Agreed. If I can do what I'm hoping to do I won't be using a single kwh of PV but letting the neighbours have it all whilst racking up export credit:)

Perfect, thanks. Like you say it's very much what fits the individual

Work out average daily consumption for each month. Put 20 units of each day or whatever the average is if its less than 20, into a battery at 8.5p=£1.70/day cost for 20 units to use during peak rate. At peak rate of 32p/unit the 20 units used during peak time would have cost £6.40 so there's £4.70/day saving. December's saving would be £4.70x31=£145.70. With my usage I'd get that Nov-Feb, a bit less Mar and Oct and quite a bit less for the summer when the HP isn't running and the PV is going full chat. Total for me is just under £1100/yr. 30kwh of Fogstar batteries and 6kw solis inverter is just under £4k. I'm also hoping to be increasing PV export by exporting most of what we currently use by using the battery and off peak eleccy rather than the PV. Not as lucrative as the peak to off peak saving but it's a bit more in the savings pot. That's a rough estimate based on current Octopus Go rates and doesn't include charge/discharge losses. With 30kwh of batteries I think I'll be able to use more than 20kwh of off peak eleccy which will hopefully offset the system losses?? Figures pan out for me so just fine tuning things before taking the plunge

Didn't the company send in a quote for remedial work together with a service report??

If you use Excel it's straight forward to do room by room heat loss calcs. Work out the area of each surface x U value x temp diff and that's your heat loss. If a surface has an element with a differing U value ie a window or door, deduct that elements area from the main surface and work out that elements loss separately, if it has a differing U value. Add all the losses for each surface of the room, 4x walls+floor+ceiling, and youve got the room loss. Repeat for each room and you've got the whole house loss. Simples:) After that you need to account for ventilation losses and I can't remember how I calculated that without opening up my laptop which I haven't got access to!! Someone else will likely guide you on that??

I believe IOG needs an Octopus approved EV charger which we don't have so we're stuck with the basic Go. Assuming you do all those calculations automatically with a bespoke system then that level of automation is beyond where I want to go with this, but....... If the battery inverter supports it, I suppose I could configure the inverter to dump what's in the battery to export after we've gone to bed?? Any suggestions for inverters that might do this??

The battery inverter will be a separate inverter to the 2 x PV inverters so that's OK. The physical layout is problematic as both PV systems connect to consumer units at the back of the house whereas the ASHP that will be the biggest battery load is fed from a CU at the front by the DNO incomer. I'd need to get a chunky cable from the back to the front to take the PV to the Henley block. That's doable if this is a solution. So PV needs to be connected nearest DNO incomer then CT connected between PV connection and house load?? Battery connected anywhere on house side of CT?? Have you done this....be awesome if thats a solution??

If I charge the battery from PV then I'm charging at 15p/unit(export rate) rather than 8.5p/unit(off peak rate). If I power the house from PV rather than drawing off peak battery charge then it's the same....15p to self use PV and 8.5p to use the battery. I appreciate your description is the normal PV/battery set up but I'm just trying to see if it's possible to force export of all PV generation and use the battery until it's empty then use any available PV followed by the grid if there's no PV.

What's the rationale for switching between the tariffs?

A flip side to the companies approach maybe that the guy that attended for the service is an employee with a set schedule of services to complete in the day with householders taking time off work to wait in for him to arrive. If he gets drawn into doing unscheduled work there's a fair chance he'd mis subsequent appointments and the company would have an unhappy customer or two??

I'm looking to install batteries to charge on discounted off peak to then supply the house during peak time. We have significant PV that we get paid to export at 15p/unit. On our current Octopus Go tariff we could charge the battery at 8.5p/unit so it will help our £ROI if we can let all our PV go to export and run the house on off peak rates via the battery. I can't see a way to stop us using the PV when it's available so is there a way to force house loads to use the battery and not draw on the PV??

If the Go rate disappeared I assume I'd be able to jump onto the Cosy rate if that wasn't withdrawn as well??

That's true, if the available surplus remained static which don't beleive is the case. AFAIK there's still considerable wind power still to be installed to reduce the peak time reliance on gas. If that's the case then that wind power will need somewhere to go during off peak periods which could include any batteries I get:). Assuming I've not dropped a clanger in my calcs then what I have in mind will easily pay for itself in 3-4 years and it's a fair bet cheap TOU tariffs will last that long, if not much longer

Demand is 24/7 from the HP which is the biggest user. EV gets charged in the 8.5p off peak period every few days. The rest is consumption that can't really be shifted in any meaningful way.....asking the missus to cook overnight isn't an option. The majority of heating emitters are radiators so I don't have the thermal capacity to boost heat into a big slab using a Cosy like tariff. Ramping the HP up and down to track a Cosy like tariff would likely give us swings in temperature which I'd like to avoid.....we've just had 3 months of a steady 21 degrees with the HP running WC 24/7

The 20kwh/day is battery capacity charged at 8.5p off peak and discharged to offset 32p peak use.....daily usage can be way more than that. ASHP has gobbled an average of 40kwh/day on its own over the last week in freezing temps. We've already got PV but it doesn't do much in the winter

Maybe I'm missing something but has the system been seen to be over pressured and lifting the relief valve that likely feeds the tundish?? OPs video shows the tundish dripping with the pressure guages showing around 1 bar?? At that pressure the relief valve shouldn't be passing which suggests a leaking relief valve?? Giving the releif valves manual actuator a full turn or 2 to lift the relief valve may well get it to reseat??

So a year on from this chat and I wonder if things have changed significantly from an environmental and £ROI perspective?? Having just had our Octopus Go day rates go up to 32p/unit I've been looking at getting batteries to charge with off peak rates and use during peak rate times. Having put in an ASHP in the autumn our usage has jumped up significantly and Nov and Dec total usage averaged around 30kwh/day. If we could shift 20kwh/day of that and most of our usage for the rest of the year to off peak rates that would be quite a saving. Other than the Octopus rates changing and charge/discharge losses what else needs factoring in??

For reference on expansion vessel longevity, our solar thermal EV is 20 years old this summer and had its pressure topped up with a bike pump around 10 years ago

Anything outside the heated envelope ie everything in the shed and pipes between the shed and the house, use at least 25mm wall thickness. You can buy guides to make accurate cuts but with a bit of practice you can do a pretty good job with a pair of large scissors. Search eBay for pipe insulation cutting guide. For insulating valves and compression fittings use soft insulation a size up from the pipe work, so use 28mm insulation on 22mm fittings. Armflex black nitrile insulation moulds itself very well around fittings. Hold it in place with insulation tape but only tight enough to close up any gaps without overly squashing the insulation

Questionable UFH and known undersize radiators are never going to give you a working system. Running at 50 degrees flow temp is always going to mean bigger bills than running at lower temps. One thing to be conscious of is that ASHPs guzzle electricity when it's cold so best not to get too hung up on what it's using in a cold snap. Look at the average for a few weeks or month at a time. If your landlord cut corners to save ££ at what seems to be at your expense then her being an acquaintance is where your biggest problem lies. If a tactful conversation doesn't get her to sort out the heating then you're a bit stuck. If you want to sort out the heating then starting point is a heat loss assessment so you can resize the radiators and get someone knowledgeable to see if they can make an educated guess at the output of the UFH. If it's not adequate for a low temp heat pump flow then it can either be replaced or add radiators to the rooms with UFH. If the landlord isn't going to sort it out then there's alot of effort and expense for you to do it!!

Agreed, they can be cheaper but there's too many poor/mediocre installs that mean gas is still cheaper. Even if boilers and HPs reach cost parity there's still a bigger capital outlay to get an efficient system with large rads and UFH.

Not sure gas will ever be phased out but likely/hopefully it will start to attract an ever increasing carbon tax in the near future.

That will be a whopping battery to run an ASHP for 24 hours in freezing weather. Not sure it's cost effective to have a battery that size rather than use peak time grid eleccy for the few freezing days a year most people have???

From a quick peak at Google gives the following- 14300 kwh of gas@0.18kg co2/kwh gives 2574kg carbon per year currently 14300 kwh from HP at COP 4 uses 3575 kwh grid eleccy@0.177kg co2/kwh which gives 632kg carbon per year with HP. Google suggests 200-400kg of embodied carbon in boiler manufacturer and install. Assuming HP embodied carbon is the same as a boiler then first year of scrapping boiler and installing HP gives 632+300(boiler)+300(HP)=1232kg co2 for new HP versus 2574kg co2 continuing with gas boiler. Half the emissions in year 1 by switching to HP now. Second and subsequent years is 632kg co2 for HP versus 2574kg co2 continuing with gas boiler. Quarter the emissions in future years after switching to HP. More than happy to have these calcs challenged but seems that moving to a HP beats sticking with a gas boiler from an emissions perspective. OP has significant PV and storage which would likely lower the HP emissions further??