Nickfromwales

Vaulted ceiling maybe?

Same in mine, they're shredded polystyrene ceiling tiles. Forget the mess.....fire hazard and all the cables we're entombed in the stuff . Not good removing that when I did the attic out for my boy.

The hydro set up makes me think you should go bigger. Do you have any info regarding expected yield, eg pattern of delivery for the hydro ? Can we assume the hydro will give 3kw idle and 5kw peak, with 3kw a fairly constant ( over 24hrs ) figure? If the 3kw is a constant, then I'd say much bigger. I'd want to harvest as much of the hydro generated energy, convert it into heat energy in the TS, and have it stored ready to be used to off-set the shunt heating load, eg when the house is asked to attain the target / comfort temp, plus DHW. To do that in a TS of say 300L capacity would be IMO a stretch. I'd go for ~800L, more if the space is there, but that is wholly dependant on the hydro figure being accurate. You stated 2kw in the OP but now your saying 3-5kw, so have you had some feedback from the unit installers ? Also, can they provide an excess generation controller ( hydro equivalent of the Immersun ) that will pump excess into the second immersion ? If not, make sure one of the immersions is a 6kw, and the second at least a 3kw so you have 9-12kw of electrical boost ( also a backup if the oil ever runs out and you need to temporarily switch to electricity to keep things running ). Id deffo want to design this so the hydro is providing the maximum yield, and that is best achieved by using it to trickle charge a large heat battery, aka TS.

Nah, just fill the void with acoustic wool like you get in speakers. .

4 off cuts of FR PB expensive ?

Dewalt DWS 780 XPS shadow line. She's the beast. Hire one, it's too much to buy and own ( unless your doing all the internal carpentry and joinery ? ). ?

You clearly stayed on to take your GCSE's

Should these be going into fire rated 'pockets' to maintain fire barrier integrity, if above space is hallway / habitable ?

Try saying that in 80 characters or less . Agreed. If they apologised and refunded you should leave pos feedback. I just bought a tile cutter 'used once' and it arrived with no blade guard. When I asked where it was he replied "did you see one in the pics?" Did he EVER! After a couple of exchanges where i enlightened him as to how listings are made by genuine sellers ( his pics were taken when the machine was first taken out of the box not after the once that it was used so the blade guard i assumed was still in the box ) he stumped up. He admitted in his first reply that he knew it was missing so I had him banged to rights. He stumped up and we both left pos feedback. "Live today, fight tomorrow"

I'll do the abuse section. When the F**** do I start ?!? .

Yup. When you get to the standing-and-staring-at-it stage, it's time for a kick up the arse. Chomping a pie whilst deciding MAY help . Better than granola. ?

We'll just hijack @ProDave's one. Imagine his families face as they wake in Lancashire . "Everybody out !"

Just about get the 5 pairs ( days written on the labels ) of @PeterW's favourite cream and brown Y-fronts ? ? in there.

Ian, it takes a big set of brass balls to undertake what you have so far, even if that's been quietly reinforced by the presence of a 'builder'......That has obviously boosted your basic knowledge and confidence in what you can, and more importantly cannot do, so as you already know in the back of your head, this is down to how you feel you will cope. Simple. To break it down into the obvious, it's apparent you now feel that you can overtake the builder by replacing him with yourself + necessary others ( sub-contractors as and when ) and are, from what I'm reading, being held back by said lack of competency / and commitment from Bob ( the builder ). If this thread is what you need to fortify your 99% already made up mind, then do just do it. Today. Sleeping on it is another 24 hrs where your pandering to someone else whilst they decide how and when your build will progress, whilst your sat around twiddling your thumbs ( ), keen to crack the fack on. The "Dear Bob" chat needs to be calm, quiet and stone cold sobering, so it soaks in quickly and stealthily. Best to prepare some of the major hiccups and issues as bullet-points before hand, as the mind gets disorganised when ( if ) placed under duress, and you need to keep the upper hand to carry it through. If you were clueless I'd probably advise otherwise, but with advice from here there's not much which cannot be solved, methodically, it's just down to how you will achieve it physically. All you need is one decent all-rounder as your +1 and you'll be fine. Contact Bob ( revisited ) on gumtree and sound him out ASAP. It's only a phone call. If you were planning on PM everything after weathertight anyway, there's not much left in between, so my 2-cents.... GO FOR IT. ?

You can change it daily if you want. All you need is a suitable sized manometer for LPG, whack it up to 37mb working pressure and Roberts ya mothers brother. All you'll need to do is purge each time to get the correct gas to the valve. "Simples"

Do you only have screw fixing vertically at each end? If so, don't forget to cover these with a matching wood product to define the start / stop points and provide a good break between the plaster / wood finishes. They'll need to be on before starting any final finishing work, plus you'll ideally want to bond those strips on so there's no surface fixings to fill. Laquers etc behave differently on wood fillers so, as said, practice on a sacrificial piece first.

Only real negative is the extra heat loss from having this open to atmosphere. @JSHarris' blog highlights this in detail.

Telford vs Newark eh? There's only one way to settle this............

Just to get a more uniform delivery from the heaters. Two in parallel would require the pipework to each heater to be near identical to guarantee even flow through both heaters, just my OCD from that point probably. More on point though, with the series arrangement the secondary heater can then also be set to a much lower temp to 'kick out' when the system is up nearer to operating temp = or < the 3kw of one heater. Should add longevity to the system as the secondary heater should spend a lot of its time off as it'll only really be needed for starting the system from cold / adverse conditions. IMO it's better to have one running near constant than two switching in and out like yo-yo's.

Any cylinder holding stored, heated water that is sealed and pressurised, needs G3. A combination aka open pipe TS does not. Im a Telford man, and I prefer the fact that they make theirs out of all stainless steel. As far as bespoke goes, Telford manufacture to each order using their basic dumb cylinders as the base for each order. The cylinders are off the shelf but you can specify where the tappings go, within practicable reason, at no extra cost. Turnaround time is still less than a week from placing the order iirc. I see zero benefit from the tank in tank ( TIT for short ? ) option, with its reduced capacity for the same size cylinder. Id only go for the two tank UVC + buffer option if there was an ashp involved. With a 37kw oil boiler I'd be really worried about such a small second vessel as the oil boiler performs best when allowed to do a long burn at full wallop, rather than cycling in short bursts, and would reheat a 100L buffer very quickly indeed. I'd go for a single cylinder stat to stretch out the hysteresis of the on / off cycle to further promote this.

Ok, another option for you. The vailant gas valves will switch to LPG in the time it's taken to write this. It's just a screw adjuster on the side of the gas valve, and the circa £7-8 for the 'LPG conversion kit' just buys you a yellow sticker saying "Converted to LPG" !!!! If your gas meter is going outside then just hook up a 47kg bottle/s, connect it accordingly to the 22/28mm gas feed to the house, and run the 638 on LPG for the meantime ? Oh, and tell your plumber the Willis heater will do the job for space heating, as long as your reasonably insulated and have windows etc, it'll just take a full day to get up to temp. If it's struggling do as I say above and fit two. Edited to add : check with LPG gas regs, iirc you may need an internal emergency gas shut off valve ( EGC ) and an internal test nipple. Your plumber will know this if he's LPG qualified.

@Crofter is doing just that in his modest holiday rental . Just size the cylinder bigger for a bigger let ? If in any doubt, just fit 2 Willis heaters in series, not parallel, and then you've got 6kw. . Cheap as chips and you'll sell them on when your done.

3kw Willis heater ? 5 minute retro fit into your intended system and near zero doing / undoing and no pointless boiler installing. .

Fibaro

Size the TS as small as you can, as a suitable gas boiler can easily match your max demand eg space heating at nominal draw plus DHW being run simultaneously at typical max flow. The only reason to oversize it would be to dump excess pv into it, so best to commit to pv so you can design now accordingly. The last 500ltr TS i fitted was in a 4 bathroom house and I complimented that with a Vaillant 637 ( 37kw ) system boiler. Even though it will very rarely see full demand it is capable of regularly delivering as little as 9kw whilst fully modulating, however you need to avoid full modulation to get the operating / return temp into the realms of the optimum for condensing to occur. By using a TS you can set the boiler to come on at the premium flow vs return temp to maximise efficiency. That basically means the boiler pulses heat into the TS, controlled by the cylinder thermostat, rather than 'trickle' heating linear to the current demand. That said I'd say you can get away with a 300L TS, and a 30kw boiler.