Nickfromwales

The Eddi is very versatile and a great bit of kit. It'll do most of what anyone would want / need. You would need to look at the minimum thresholds for diverting power, but, IIRC, the Eddi will do this proportionately. The equation can only be answered by knowing how much PV you have, it's expected yield, and what consumption ( and when ) you intend to offset or manage with a diverter. There is no quick answer I'm afraid. Excess can very easily be be diverted to hot water, for eg, but the ASHP needs access to power 24/7 normally so would just rely on taking that direct from the CU. As it's a multiplier, it's running costs are negligible and therefore rarely the focus of diversion per se.

If it's injected straight into the CU and not delivered through a diverter the PV will power anything and everything, when generation is sufficient of course.

That's better than 3kW so good news. Didn't think they'd have allowed a 6kW as that's a lot of heat in one place.

£3k for a 12? Where did you get that number? You’re not looking on the Fisher website are you?

Depends on how its read I suppose. Was only said in jest. I'll edit it to save the feint-hearted.

I can't answer that as it may constitute commercial content, which we never discuss on public forum. There.

That is an option, but check that won't stuff your warranty up first

Pretty pointless if it’s a gas burning dwelling tbh. Don’t forget the inverter will snuff it at 6-10 years and need replacing. It’ll take all of your export payments to cover that and put you back to zero. ?. Maybe consider a SA plus gas system boiler ( doing heating only ) for that flat if you do.

Yes, but not a cheap cylinder compared to other generic offerings. Still 2kW is not insignificant. You get what you pay for etc, so get better offerings from bigger name manufacturers. It’s a lot to do with all the additional connective pipe work in the worst cases. Can you recall the price of the cylinder at all? Or was it a package offering with the ASHP?

Head vs heart Right now, it’s “head time”....Save money and buy PV for your home instead, if you're in need a hug from the planet. It’s a shame this kind of choice is down to the general population though, rather than a government driven directive. IMHO every single house should have 2-4 PV panels on for low input, widespread mass injection into the grid. That wouldn’t please the fat cat big 6 so will still be a way off. Instead of the massive FIT payments making rich people richer, the money from that scheme should have gone towards that with the big 6 forced to take some of their grotesque profit margins and actually reinvest into the infrastructure, where necessary.

But a traditional cylinder will waste upwards of 3kWh / 24hrs of heat energy vs 800-900W with a SA. So, at least 2 kWh of PV will go each day to offset losses from the previous day. If you’ve not used much / any DHW, a cylinder will still go cool very quickly, whereas a SA will retain heat ( useful heat ) for much, much longer, eg extending times between full recharges. Horses for courses though, and all have pros and cons. Ball ache with an UVC will always be G3 and D2 discharge, ball ache with SA will always be cost / weight / lack of control feedback ( unless you remortgage and buy a massively inflated Uniq9 via Fisher ) as SA prioritised giving those ‘customer friendly’ internal controls and LED indicators so Fisher could market them more easily. The 12’s got neglected ( don’t know if they still aren’t going out with this upgrade? Anybody? ) as Fisher were primarily fitting 9’s and that’s where the volume sales / money was........

Same for an UVC though isn’t it? That uses a cylinder stat at the 1/4 - 1/3 height, so if that hadn’t seen depletion occur to the point that it changes state, that also will not call for heat Not as problematic as with a SA for sure, but still a consideration. Good thing with an UVC is you can easily boost via immersion if the primary heat source is a boiler, whereas it’s a pita to do with a SA.as it’s a single call for heat for both boiler and immersion ( so you can’t force feed it like you can a cylinder / UVC ).

Why the PV? Do you provide the gas / electricity in with the rent or does each flat have a meter and the tenants pay as they go? Norm is pre pay meters so you’re never in the red. It has to be gas for fit and forget value alone. If they’re flats then you don’t want to waste m2 with tanks / SA’s etc, so whack some reliable combis in. Ideal are great for the money, at change of £650, and sleep at night. Renters can be creatures of hugely differing habits, so storage heaters are quite a naff choice for rentals imo. Kerb appeal is important so avoid an all electric rental afaic as that just screams “expensive to run”. Maybe ditch the PV and use the money to buy the boilers and run the gas supplies

Agreed, but the OP mentions high'er' DHW so am addressing the answers as per the OP's needs. UVC's and SA's both have 22mm inlets / outlets, so putting a 15mm 'restriction' inline is converse to my thinking.

In a video I saw, the rubber seal at the bottom of the flush pipe ( the bit you're pressing down on to stop the water flowing ) got taken off and flipped over and re-fitted. Simple fix hopefully. Check that where the two surfaces meet there is no 'crud' otherwise you're not going to resolve this. Do you have very hard water?

Dave stores at a very low temp, so has limited DHW capacity because of that. Hence the need for a post-heater. Factor the cost of buying and installing one of those, then the cost of using it at indiscriminate times, eg not always at cheap rate, and then the fact it only has a 15mm inlet, and it's not how I'd ever design a system TBH. The elevated heat thresholds @PeterWmentions expand the energy capacity of the sme sized tank significantly, so will give more DHW during times where the PV is in abundance or when you've 'duress boosted' via the immersion(s). UVC's are given a stated capacity by the manufacturers. If you ring them and say you only intend to heat to sub 48 degrees, they will state that the capacity for DHW will be reduced accordingly.

From a boiler, it’s subject to / affected by the flow temp. With the immersion it’s roughly a kW in per hour so via the ~3kW immersion heater a 12 should reheat from zilch in a bit over 4 hours, in practice I think it’s a bit quicker, but then it does hold around 14kWh of heat energy when heated by a premium heat input. Well matched to be sucked dry by the evening bathing and reheated at midnight on Octopus, or other cheap tariff. If you have any PV then that reliance on the full recharge should reduce in the summer.

Not that bad, but still up to 20% less or worse. You’d need a second recirculating loop for the heating, hydraulically separated from the boiler pump loop, as you can’t pump through a TMV so you have to ‘pull’ through it.

The biggest issue is if you have radiators, as the SA will need the boiler flow set to at least 65 degrees ( arriving at the SA ) which means that the surface of the radiators will be at the same temp. Its a PITA. I've had to use contactors on the 20a supply into the SA controller ( outside of their equipment so as to not interfere with the warranty as SA don't like you going in there ) to arrest the flow of electricity, due to the single discipline ( rather shit ) controller. Idea being, the contactor flips from electricity in + zero call for heat to the W-plan / to call for heat to the W-plan + zero call for electricity. The former for standard 24 hour operation, where the SA heats up off Octopus between 12:00 and 04:00, and the latter is for 'duress heating' so the exception not the rule. That's how I would set it up for normal use, with a single 12HW+I. A simple timer / boost button changes the contactor state. Calculation. Also if you re-use the combi, you should connect the nearest DHW tap to the hot outlet so it gets at least some exercise of the internal components. Combi's don't like to sit dormant. Also remember a 24kW combi prob won't give the full 24kW to space heating The highest rating is reserved for solely for DHW production, and very high temp duties will see you operate outside of the ideal condensing range ( 30-50 for Vaillant iirc ) in a lot of cases. Check the MI's of your boiler and that will give you the true output to 'heating' which is what your SA will get. Don't forget the magnetic filter if going for a SA as the HeatEx has very small bore internals vs an UVC.

Depends how good the screeder is I’m the past I’ve done 4-5mm adhesive under the Ditra, then, whilst still relatively wet, butter the top of the Ditra and then lay 12mm notch over the top. 2-3mm butter on the back of the tile and away to go. Main thing is to roll the Ditra out straight and evenly so it doesn’t quilt. If you get a couple of mm quilt then the adhesive cures underneath and you end up having to add way more adhesive up top or cutting the Ditra to remove the ‘ripples’. I mop the dry screed with 75% water / 25% flexible primer, immediately prior to laying, so the adhesive under the mat doesn’t go off so quickly, a real problem when putting a thin coat of wet adhesive over a bone dry ( often dusty and porous as hell ) screed.

I'm a changed man

Consider a heat store Combi, such as; https://www.vaillant.co.uk/homeowners/products/ecotec-plus-combination-store-1152.html

Yup. Faulty gas valve or even possibly the relay on the PCB ( printed circuit board ). Either will usually require the whole part renewing, and is definitely a GSR engineer call-out. Make the call ??

DO NOT PURGE THIS YOURSELF !!! That is interrupting the gas supply and is extremely dangerous. Only a GSR’d fitter can do that, but I doubt if that’s what needs doing at all. Try the reset cycle a good 5 - 6 times and see if it stays lit after that. How old is the boiler and how long since this had any new parts ?

£2995 ?