Nickfromwales

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 ?

The overflow is gravity, so won’t fill a water butt unless it’s lower than the softener. Outside is fine, even if you need to fit a frost stat and a small tubular heater to cover you for the depths of winter. MI’s will dictate that you make sufficient provision there. You shouldn’t keep the salt outside as it’ll absorb moisture. Depends on how well sealed it’s is and if the packaging is kept completely intact. Just store that indoors IMO it’s no bother. The stopcock should only be indoors and easily accessible in accordance with BCO / regs for M - 4 part (2) ( iirc ) compliance. The softener will come with a bypass but not always with isolations. Nothing stopping you fitting more outside though.

Oh, that makes it interesting!

Issues with not being able to fit noggins ? May have to fit thicker beams to compensate.

A basic drawing of the existing layout would help, but here were just procrastinating as the SE and BCO will dictate what you need so as to issue the relevant certification Remember if you want to get some extra cheeky head height you could go to doubles up smaller joists and make them Flitch beams.

Are there any underlying intersecting walls which can assume some of the loads?

Yup. So assuming worst case I rate these as equivalent to a 500L UVC. I edited the comment you quoted earlier btw.

The higher volume is assumed at the blended temp.

2x 12’s is over 500L I’ve never seen a 3ph electric shower, do you mean a 3ph instant water heater feeding a mixer shower?

2x 12’s is a LOT of hot water capacity! Reason for that?

You’re good to go Bruce. ??

Also, if a bedroom is mothballed, you’d get no heat from it’s origin so the hallway would then get nowt from that loop.

They won’t sign off on that design as you’d then be dissipating heat into the hallway that’s destined for satellite rooms. That would see reduced flow temps arriving at those rooms. Best to remember that this is not a full ‘passive’ insulated raft, it’s a relatively thin screed over insulated block and beam so will be heavily reliant on the design specifications not being lost. I’ve suggested to @Russell griffiths that he insulates the flow pipes where the runs are congested and just uses the return ( residual ) heat to warm the hallway. The hallway loop should not be removed though, as it’s cost is negligible, and to not have it wouldn’t make any sense ( imho ) even if it doesn’t get used ( for provision of auxiliary heat in the hallway ) for 10 months of the year its better to have it than not to for the sake of £100.

You need to check which family of gas this is permissible to be installed onto. The advice needs to come from the actual installer, not an Internet forum ?.

It’s a “fusion weld” fitting that you want ( need ). If it was me, I’d not fit anything else, especially on higher pressure ( if LPG ? ). The last thing you want is a tank of gas gone to an undetected leak. No short cuts with gas in my world sorry.

I’ve only ever used standard compression tightened up fully and never had a problem tbh. The Euro rubber reducer deffo looks a good solution if you’re not a plumber and want to fit with more confidence.

First question, why is the timber floor necessary? If the floor was tiled and they were glazed ceramic or porcelain then they would never have breached damp upwards, and if using a DPC then it would be bombproof. Hammer in fixings with an all plastic contact surface, installed avoiding grout lines ( which would be the only weak points as far as damp bridging is concerned ) would have caused no issue whatsoever. So, why the timber floor ?

Yes, as due to the very low volume the LLH can remain inline during cooling. They come with factory insulated jackets so make sure you go for that option when buying or you may end up with a condensation bomb.

It’s the flow rate that the ASHP needs to see on the primary side eg the flow to and from the unit itself. To ensure that is always met on low energy builds I design in a low loss header for most instances, basically just a tiny buffer tank, to achieve hydraulic separation between the ASHP and the load. That allows the pump of the ASHP ( primary side ) and the UFH pump(s) on the secondary side to never ‘meet’ hydraulically, therefore the primary side is nigh on free-flowing. You then just set the primary pump to the desired flow rate, eg the rate that satisfies the minimum unit flow rate requirement, and then it doesn’t get affected by changes with downstream loops opening / closing etc. Plumbers usually follow the MI’s, so if they’re at all worried you’ll probably end up with them wanting to fit a buffer tank.