DenkiJidousha

That does help JohnMo - thanks. The house is about 125m2 all UFH, pipe spacing unknown but my guess from a few inconclusive thermal camera images something like you suggest - giving about 60 litres for the house as the effective volume if simplified to a single zone, or only about 30 litres each if upstairs and downstairs are kept as separate zones. So, I think from the examples above we might get away with no buffer if the entire UFH was combined into one zone. But on balance the buffer is probably the sensible choice.

Is there a good way to estimate or even measure the water volume in an existing UFH system? I can measure total floor area and the external pipe diameter (at the manifolds), but would be a bit of a guess for internal pipe diameter and actual length of each loop. i.e. How tightly they were laid as they snake round each room. (I am trying to determine if we really would need a buffer for an ASHP retrofit, or if by simplifying the UHF from room based thermostats to single/dual zone we'd be able to avoid it. Avoiding a buffer tank would help with space constraints.)

Or another thought - do any monoblock ASHP manufacturers have the buffer in the outside unit? Seems to me that would be useful for the space constrained retro-fit market (even if they have to use more space outside to have a well insulated buffer tank).

Thanks all, that's helpful - seems no obvious differences then, unless a manufacturer is willing to do a warranty without any buffer? It was the AroTHERM monoblock we were looking at, with a SunAmp rather than HWC due to the very limited space. Then control box, values, buffer, expansion vessel - plus critically working space for doing all the pipework - quite a challenge. There is loft space so in theory room for a horizontal HWC, but the timber re-working seems challenging, and additional pipework would be needed from the ground floor boiler cupboard up through the upper floor - would be cosmetic challenge too.

Hello all. As per the title, are there any ASHP systems on the market with a clear advantage on minimal equipment needed inside the house? Should it matter, the background to my question is a retrofit. We have a reasonably modern and comparatively well insulated home, built with underfloor heating upstairs and down, with a mains gas combi-boiler. I've posted before about our planned 7kW Vaillant aroTHERM ASHP with SunAmp UniQ install which sadly we had to cancel this summer - the installer realised there wasn't going to be enough space in the cramped boiler cupboard after all, fortunately before any work was done.

I think I had posted details on another thread, but very tight on space replacing an existing combi boiler - the planned install would have used a Sunamp heat battery. I did have a couple of other quotes using a traditional slimline hot water cylinder, but with caveats - one firm thought they could use the existing cupboard but would have to cut a large side access panel via the master bedroom. Fingers crossed things continue to improve in heat pump technology (CO2 maybe?), and I can try again in a year or two - assuming we haven't moved house in the interim.

Sadly our installation has been cancelled. The installers quoted a while ago (what with the pandemic etc), and in the interval did a couple of similar installations elsewhere. They concluded in hindsight our old boiler cupboard was simply too small to get all the gear in plus adequate access space to do all the pipe work. An alternative was taking over space from the adjacent built in wardrobe in the master bedroom, but not a popular idea. It was always going to be tight, but still rather a shame.

Looks like he's switching cars, so more likely to be on the Speak EV forums now than on the Tesla UK forum - but is/was an asset to both. Regulars here on build hub won't be surprised to see in depth technical commentary on the finer points of electrical circuits. After all, why buy one when you can build one yourself ?

We're going for the 7kW Vaillant aroTHERM plus, rather than the physically much larger and noisier 10kW unit.

Guess I'll be replacing two existing mains powered hall smoke alarms (with battery backup, but probably without an existing interlink) with new ones - plus the additional sensors now mandatory in the kitchen and lounge. Any product recommendations if forced to go down the RF route? Looks like the Aico range would require buying multiple RF modules which would get pricy...

I got a quote from https://greystone-energy.co.uk/ and was impressed with their engineer, and past project photo portfolio (mostly on Facebook, some on Twitter). They are based in Monikie (north of Dundee), so ought to be able to handle the Aberdeen area.

We had a quote with the Panasonic R32 which was cheaper that the R290 Vaillant aroTHERM plus. I've not checked the quoted noise levels, but the Vaillants do not seem to be the quietest out there.

We're in Scotland, near Dundee. Sustained cold spells below zero are rare but have happened, like the winter of 2010/2011: https://en.wikipedia.org/wiki/Winter_of_2010–11_in_Great_Britain_and_Ireland Good point that only in those extremes (when you need most heat) does the Vaillant areoTherm plus' output fall to 7kW, or below if making even hotter water. At power level A7/W55, and 1m away, they quote 47 dB(A) for the 7kW and 52 dB(A) for the 10kW - neither is as good as the 42kW for that Mitsubishi Electric Ultra Quiet Ecodan example (assuming this is a fair comparison). I don't have a feel for how loud these actually would be in situ.

Thanks - and good analogy. If the installer agrees (they are going to recheck their numbers), I'm leaning to the physically smaller quieter unit. It is going to on the front of the house so the aesthetics are a real factor, sadly nowhere else to tuck it away out of sight.

Resurrecting an old thread, but if heat loss calculations or historic usage puts you on the cusp of two size models of ASHP (in this case 7kW or 10kW), is the rule of thumb always go large? Sadly the larger capacity unit in this case would be significantly larger in terms of the outdoor unit (two fans vs one, I think), noisier, and adds about 10% to the capital costs (combi replacement), but is in theory more efficient. Aesthetics and wallet say go small, but is this a bad idea?

I'm optimistic about getting an R290 Vaillant aroTHERM plus installed soon - I short listed it specifically for the lower green house gas potential than R32, coupled with good performance and low noise. No sign of CO2 based ASHP on the UK market though?

Is CO2 as an ASHP refrigerant still incredibly niche in UK? Seems best choice from greenhouse gas perspective...

(Several people have already pointed out it was R290 propane, not C02 - but that's almost as good from a green house warming point of view)

I think the Daikin Altherma 3 should be OK with SunAmp UniQ PCM58 based on this: https://twitter.com/eLEJOG/status/1192735318543339522 Can you wait 6 months? SunAmp seem confident about having lower phase-change heat batteries on sale then, but also I gather there will be newer monoblocks on the market soon with the next refrigerant gas. I'm tempted to wait and live with our gas boiler for one more winter...

Our first quote was 12kW, second 8.5kW and the third looks likely to also be ~8kW (waiting for paperwork). Having been watching the half-hourly gas usage via the smart meter, and disregarding the combi-boiler's spikes in usage for hot water, I think the lower figure makes sense.

Quoting from another thread, So too small is bad, too big is bad, want it to be just right... Our first quote at 12kW may be fine. Still waiting for the rival firms' quotes, will be interesting to see if they size it the same.

Had to google that, PHE = plate heat exchanger, which can be used to transfer heat into the hot water tank (especially with a low temperature heat pump), versus using a traditional coiled pipe running though the bottom of the tank (with a high temperature heat pump)? Getting this back to the original topic, ASHP sizing, I'm looking at replacing our mains gas combi boiler which provides domestic hot water (DHW) and under floor heating (UFH) to our three bedroom two story approx 125m2 mid terrance house, built about 2005 with reasonable insulation (EPC rating C). We have 5kW of solar PV and a time of use electricity tariff. I'm still chasing local installers to get multiple quotes, but the first one back suggests (before doing an on site visit) a 12kW monoblock HT heat pump (space will be tight so the monoblock makes sense), no thermal store for the UFH, and a 250 litre slimline cylinder or SunAmp for the hot water. I'm wondering if a 12kW ASHP is too about right or too big, and what the trade offs are. Too small a heat pump: Have to leave it running more hours a day (problematic with time of use electricity tariffs), or in extreme cases would need supplementary heating. Too large a heat pump: Wasted capital cost. Would only be on in bursts, making it less efficient (short cycling issues)? Would this strengthen the case for a thermal store for the heating side (again higher capital costs)? In terms of data, I have about a year's worth of hourly gas usage via a Loop Energy Saver (since replaced with a smart meter). Looking at peak daily usage, and peak hourly usage, and counting on the morning and evening hot water demand spikes to be spread out with the storage, I think a 12kW heatpump should be more than up to the demands - perhaps even overkill.

We had our Internorm UPVC/aluminium KS430 big sliding door installed summer 2018, and it has as hoped improved the room comfort - warmer in winter and cooler in summer (although the weather has been relatively mild so not stress tested yet), in addition to improving the view! Being able to leave the dock open half an inch (or more) in the locked position is very handy for ventilation while out of the house. I've yet to convince my spouse that we should replace the rest of the old double glazing, but did go as far as getting quotes from Internorm/Scotia and EcoWin.

The update to allow off peak charging has apparently been released, no news on UK support for power during a grid outage.

My guess is direct solar as DC into the 3rd generation SunAmp would work nicely with a few dedicated PV panels (e.g. a minimal simple system without an inverter for a relatively small capital outlay). We're almost at the end of 2018 Q1, so I'm hopeful for more official news before too long.