Nickfromwales

'Cold mains priority' to the house if you do it that way Never have the O/S taps off after the PRedV as it hugely affects the available dynamic flow to the dwelling.

And a resale value too, vs a bespoke DIY timber shed.

Installed, with gubbings and consumables, that's about right, if not cheap!! Companies do actually need to make some money to stay in existence https://www.google.com/search?q=eddi+pv+diverter&rlz=1C1CHBF_en-GBGB910GB910&source=lnms&tbm=shop&sa=X&ved=2ahUKEwjUz-i0vZjrAhXLTsAKHfCBB2AQ_AUoAXoECA0QAw&biw=1280&bih=610#spd=988388954505620188

No need to write any cheques tonight

I'm going to the NSBRC on Saturday and I will then have ACTUAL facts, derived from a meeting I'm having there. I can update here once I'm all 'myths dispelled', and in possession of the details regarding the new Heat Pump Tariff also. Best you keep them at arms length for the moment...........

So question remains.....16mm2 or 25mm2 3-core SWA then. @ProDave ? 16mm2 won't leave much headroom over 12m IMO.

Best to compare apples with apples as the OP is in their situation, not the situation of others? Solar gain through glazing is, a little behind, linear with it's presence, but heating by other means, eg auxiliary systems, is by design and deemed ( known ) from feedback of the occupants being in habitation. Those events colliding to cause overheating ( from them being so far out of phase that they overlap or meet more significantly ) would be an error that you would have to strive to create as we're only talking about a model suitable for a 24hr period at the end of the 'day'. Seasonal adjustments may be required, but the fabric first rule resides over the auxiliary systems so the collide can be anticipated and mitigated by a wee dram of human intervention.

@Alexphd1 Can't you condense into that PV CU and steal that 12 way for the house?

Henley blocks into those tails, into a metal clad switch fuse with an 80A fuse, and then SWA between the switch-fuse and the house CU. Not sure on 18th ed specifics, but my spark refused to run 16mm2 tails over 18m distance, even off an 80A fuse, mainly due to it being an all-electric dwelling ( so assume he worked out the loads and insisted on 25mm2 ). Future plans for an EV(?) and can the EV charger be fed from the garage CU? If so, that would future proof the install against any adverse loads being added to the house CU retrospectively.

Is the second CU being fed off a 50A breaker in the first CU?

I'd always promote using a constructional slab with UFH though, as that's the most sympathetic method IMO and also lends itself to ASHP 'background' cooling. It does bode well for thermal inertia too, but the biggest benefit is deffo smoothing out the heating delivery. Have had feedback from folk who have built an insulated cube ( to PH standards, eg no slab / screed / UFH ) and the results are less than comfortable when in the heating season as most have had to use the MVHR for circulating warm air ( much higher airflow rates required / increased system audibility etc etc ) and have also had to employ auxiliary heating to fortify this via 'feature' radiators downstairs and towel radiators in every bathroom which are left on 24/7. Conversely cool feet vs very warm head was one comment.

In a nutshell, stopping the worst of the external temp swings from affecting the dwelling interior. Once you are close to equilibrium the space heating ( and cooling ) requirements will be quite negligible, just a question of how big a hill you have to climb ( and how much it costs ) to get there vs what you will save on energy.

Turn the PRedV up to 3.5 or 4 bar and enjoy the benefits. Yes, shite can block the fine gauze filter in the cartridge of the PRedV but that should all be worked out by now so a clean up should see you enjoy trouble-free motoring for a good number of years. 3 bar strangles the flow to death BTW, especially if fighting that ridiculous primary pressure.

It'll withstand a bit more exposure than regular OSB, nothing else, and will degrade quite happily if left exposed to very high humidity / water ingress etc so take that statement with a pinch of salt You need a DPC, go buy some ?

Exactly my point above, to create a space largely unaffected by external influences. Wind and cloud are outside, and only thing affected by wind really is the MVHR. Yes the wind adds to the heat / cool 'wrap' around the exterior of the dwelling, but investing in staving off any big influences from external conditions is a plus afaic.

"The longer the better" is the bottom line Will add sustain to the thermal inertia of the internal fabric and core structure, ( that which is within the heated envelope ), which is a good thing for heating via load shifting eg ASHP > UFH in slab via 3x E10 'chunks' which should afford you zero input in between those off-peak times. Quite a 'big' question / subject, so specifics would be appreciated if we're to expand

Can't afford meat now though, due to the electric bill of running the damn things constantly!!

Got exactly this in the boys attic room, and you could keep meat in there.

Recently picked up a Daikin one with 2x internal units BNIB's off someone who was fed up of tripping over the boxes....for £200.00. My house is like a furnace and the home office is unbearable so this is getting done ASAP as it's just not survivable ATM ( plus these will provide heat in the winter and PV will offset AC function ). Just wish we still lived deep in caves, then no issues would exist!! 25.2oC inside today, office was hotter.

Can't help wondering how structures have been erected without such technology, in days gone by.....

I'd be very interested in how you modelled the 2 hour divide?

Deffo. I would get in touch with Vaillant directly if the noise persists. I'd say that is installer error for the most, in placement of the internal unit and execution of the install as a whole. It'll pick a few ears up if you kick off suitably, but politely. I doubt that you are very far away from a good install, just the company makes money by being "in and out" so I supect a little attention to detail has gone to the wayside. Approach the installers again and say the noise came back. Make it their problem not yours.

Lip service for most I'm afraid ( bloody expensive lip service too ).

I think you could just fill it in in crayon and they wouldn't give a shit in most instances.

Put his back out quite badly from what I gather, so is laid up.