andy

Thanks Nick, would I take the insulated pipe up through slab and to loft to avoid joins? Assume that's probably safest long term. Locating it on the other side of the loft area would give a run of about 13m - this does seem to be on the long side for monobloc ASHP from what I'm reading. I think a circa 6kW ASHP should be right for our requirements (2,700W peak heating load plus DHW). I think I need a plumber who knows Sunamps...

As ever, thanks @JSHarris. Clearly I'm getting confused as to when a split system is needed... Here's a pic to explain the planned location of the external unit and where the plumbing needs to be (that could easily be move left to decrease the distance a little). I was wondering about either running a heavily insulated pipe through/under the slab to minimise distance or around the perimeter (that would seem a more future proof approach).

Ah ha - this is exactly what I'm thinking of! Would seem to be a good solution to me for my place - the only unknown I've got is the ASHP would need to be a split unit with quite a run between the units (circa 15m, TBC). Is that likely to be an issue? I will upload a picture as that'll explain better...

Thanks for the input all, appreciate it. Like the idea of ASHP direct to UFH but what about the DHW bit? KISS suggest Sunamp(s) with mains electric/PV immersion would be good?

I will need to do the calculations to see if the off-peak is worthwhile as like you say it may not be. This area could change with demand based pricing which the Powerwall will hopefully be aware of, so it would fill up at the cheapest time possible and then everything else draws off that. Another benefit of the Powerwall is you aren't tied to using the PV energy when the sun is actually shining, so you're able to shift that utilisation to fit your realistic usage patterns but it still makes sense to use such appliances when there's an excess of energy available. Going back to my whole design though and having received revised figures for heat/DHW requirements as circa 3,000kWh/a and DHW probably about 2,000kWh/a what I'm thinking is: ASHP running underfloor heating - would a buffer tank be needed or is that only needed if we went for a gas boiler? Sunamp for DHW - topped up via PV & mains electricity immersion, leave ASHP out of the mix? Our DHW usage during the week is pretty much nil so keen to minimise standing loses here Could I get 2 Sunamps, one to act as lower temp buffer for UFH which the ASHP feeds into and also pre-heats DHW then DHW goes into a second Sunamp to raise up to required temp? I'd like to be able to get enough simultaneous hot water to run both showers but not sure which models fit the above. Gas boiler will no doubt be cheaper but by not bothering with it I save re-connection fee for gas (£1,000 or so) plus standing charge. If we did go gas boiler route, would there be any point with Sunamps? Yours confused... Andy

I will need to do the calculations to see if the off-peak is worthwhile as like you say it may not be. This area could change with demand based pricing which the Powerwall will hopefully be aware of, so it would fill up at the cheapest time possible and then everything else draws off that. Another benefit of the Powerwall is you aren't tied to using the PV energy when the sun is actually shining, so you're able to shift that utilisation to fit your realistic usage patterns but it still makes sense to use such appliances when there's an excess of energy available.

On that front, the batteries are fully recyclable: https://www.tesla.com/en_GB/blog/teslas-closed-loop-battery-recycling-program

Thanks for the welcome and detailed reply @JSHarris. The 4,000kWh/a has come from our PHPP consultant but it seems high to me too! I have just asked him to check this as I think we should be coming in at circa 17.5kWh/m2a on a 142m2 house, which brings us down to about 2,500kWh/a heating demand. Our DHW demand is low as there's only 2 of us and we only shower on the weekends (gym before work during week before anyone says anything!) but we need to ensure it's sized correctly to be able to deliver DHW for a 3/4 bed/2 bathroom house when occupied fully. I hope that our excess PV will be doing 2 jobs: 1. Run the day to day requirements of the house 3. Top up Sunamp until it's full 3. Once the Sunamp is full, top up the Powerwall Planning to have an E7/E10 tariff and during off-peak the Powerwall and/or Sunamp will top up if required (e.g. in the winter) but I haven't done the calculations on this. When we're not covered by PV, the house uses Powerwall first and only if that is empty do we resort to mains feed. For me, saying not gas and yes to Powerwall isn't so much about the money but about trying to not consume from the grid as much as possible, which Powerwall will help us achieve. I don't mind being a (relatively) early adopter of this and paying a premium. The Sunamp UniQ 9 model - how does the "half buffer" concept fit into this? I am guessing it's something like UFH and DHW go into an initial Sunamp which outputs at a temperature suited to UFH and the the DHW goes into a second Sunamp for heating to e.g. 55C?

Hi all New poster on the forum and need to decide what on earth I can do for DHW/UFH. It seems like the above would be a good fit for my solution too but I'm not too clear what the half buffer idea is? My plans at present are to install: 6kW PV (about - up to max for a single phase is the aim here) Wet UFH ASHP (I am on mains gas but morally I don't want to use it plus don't want to pay the re-connection cost as it's now capped at the road) Tesla Powerwall 2 - although appreciate the conflict of this for storage vs. Sunamp Sunamp(s) for DHW/buffer for UFH? My annual heat load is anticipated to be circa 4,000kWh/a and DHW probably about 2,000kWh/a. House will be near passive but not quite there due to shape. I really like the concept of Sunamp but I'm getting a bit lost on the new UniQ model range and what the best design is for my requirements. Hopefully the above all makes sense and happy to provide more info if that helps. Cheers Andy