SimonD

It really depends on the unit you choose. For example, selecting 2 completely random units - Midea multi-split with a Panasonic multi-split, both on R32: Midea heating output nominal 6.59/ cooling 6.15 kW Panasonic heating output 6.80/ cooling 5.20 kW The Midea lists an SEER of 6.5 A** on cooling and SCOP of 4 A* on heating The Panasonic lists an EER of 4.48 A on cooling and COP of 4.79 A on heating (yes, I know SEER/SCOP is different from EER/COP but that's the published data and the Panasonic is as a kit with 3 room units with multi-room control whereas the Midea is the outdoor unit). These clearly demonstrate a difference between heating and cooling modes - e.g if not on output, then on efficiency. But also something I think is relevant in this kind of decision is the proposed phase out of refrigerants with a GWP of over 150 from 2027 in the EU (the UK will probably follow course). This means that a whole house system using R32 is on a time limited trajectory - and what happens a few years down the line with maintenance?

Of course, heat pumps for heating versus heat pumps for cooling actually require fundamentally different designs, which is partly why one designed primarily for heating won't be as good at cooling as one designed primarily for cooling and vice versa. This is because they have very different operating conditions, different demands on the compressors and also different condenser and evaporator design requirements, not to mention variations in the vapour compression cycle conditions.

Yes, get your heat loss calcs done - but also remember that the heat loss doesn't translate directly to cooling capacity, so you'd need to model that separately. You will be reading MIs but I like Panasonic as all the data is readily available in easily accessible format - https://www.aircon.panasonic.eu/GB_en/ranges/aquarea/fan-coils/

That's awesome!

Oh yes. Finally got it sorted by about 9pm!!!!! It's interesting this and token burn rate. This morning I needed to do some financial modelling and analysis so selected Opus 4.8 for the conversation. 30 min later I looked at my session stats and I'd gone through nearly 80% of my session allocation. Then I select Sonnet 4.6 for another conversation - involves maths but nowhere near as complex and the conversation only burns 3% of session allocation but provides the answers I need. It certainly pays to switch models for different needs.

Bastard! 😉 I'm having a shit day today. Realised it had left a glaring security hole in the Auth model. Decided to fix it, but instead has broken the (expletive deleted)ing app. It fixed part of the problem and then tried to tell me the rest wasn't important until I told it that I could grab an id and post it into the browser in a string and it would expose the entire records for a user, even when not logged it! What was supposed to be a couple of hours at most has ended up taking all bloody day and I'm still trying to explain to it what's going wrong and it still misunderstands me! Thank (expletive deleted) I'm on a dev server.

Wouldn't put it past them.

Seriously? I think OpenAI are pretty out of order. Do you not have access to a screen like this? I've not done much except for a couple of basic chats today, but I'm actually very surprised I've only used 9% this week - not done much coding though tbh.

There are debates going round and round in circles in the heat pump installers forums that I'm on about this. Some still seem to think you need it, but basically you haven't got a heat source that's ever going to get close to problematic temperatures, so it's simply not required. I have a shelf full of unused 2-ports as they come with every cylinder I buy and never get used. If you're worried, you can take your switched live from the controller to 3-port through the cylinder thermal cut-out, but really not necessary - just check the three port model specific wiring diagram as some will have permanent and switched live, some will just have a switched live, for example.

You've missed a trick there! 😉 This one will do that - cross-cut guide rail fixes to the saw itself - just bring the saw up to the material and compound cuts galore - and then buy a normal guide rail for boards and longer cuts. This saw will work as a plunge saw too! I have the HK85 mains powered version and have used it like this for the last 8 years doing that. The other great thing about this saw is ripping capability with the right blade. Since I've had my HK85 the chop saw hasn't left the shelf in the garage. The other option with a workshop is the MFT workstation: https://www.festool.co.uk/accessory/accessories-for-equipment/work-benches/work-benches/495315---mft3

This is a timely reminder to always run the numbers!

Nowhere near doubling the install cost, partly because it's a self install. It takes me up an inverter size (just), but this is helpful if I can add more panels somewhere else in time. The marginal cost of this is less than £100 for the inverter up-size, plus about £500 in panels and the rails, a few hundred quid maybe. Using planned 510W panels, and only assuming a 30-35% generation ratio, I'd still get about £120-£250 generation gain per year - it's essentially a free way to widen the generation window during the summer due to gains morning and evening. Personally I think the numbers actually stack up as the TOU tariff we're on is 30p peak/kWh A few years ago someone in the solar industry talked me out of accepting a load of panels removed from a commercial installation where they were going through a standard 10 year swap out. I always regret that decision. If I have the opportunity now to build in long-term almost free value, I'm going to take it.

This is pretty much irrelevant tbh. The 'losses' aren't really losses as they go into the heated envelope of the house, so do their bit on contribution. Honestly, I'd wait and see what your heat loss calc says and then review from there as they may be so small if you're going near ph that even a 4kW heat pump would be too big. The other ball to chuck into the mix for a highly efficient house for heating is an exhaust air heat pump, which simultaneously deals with your heating, MVHR and DHW. The you can go multi-split for your air-con. Just make sure that the person doing your heat loss actually understands whole house MVHR and models the heat loss accordingly - lots don't and then calculate normal ventilation losses.

I think I was the one napping. When I was asking about the inverter I was told it had two MPPT strings so I could run the north face on the second, not using MIs - that bit was me being dopey.

Lots of ifs and buts on this one. There are only really three practical ways of moving the heat into and out of the building: water, air, refrigerant. Air specific heat capacity is poor so you need lots of volume and flow, refrigerant needs its own specific pipework, qualifications etc. with lots of limitations to things like pipework length. Water is definitely the most effective way to move the heat. The aircon units will probably also need condensate drainage so added complexity there. I don't think the solution is that simple, or not as simple as the Samsung marketing department makes it look. Maybe okay for a new build, but for a retrofit? I'm not so sure. Like with all these things, the complexity lies more in the cooling than in the heating, especially if you want aircon type cold.