Tommytipee

Just get a bigger immersion. Baxi do a 9kw one. https://www.heatingspareparts.com/boiler-spares/partno/94110302

Not keen on them. Dry my eyes out and is hard to explain but it’s never a nice heat as soon as it turns off the room feels instantly cold. it’s not so much that it’s draughty it’s just houses here are poorly insulated. There’s not a whiff of celotex anywhere it’s bog standard polystyrene at best unless you import it. Here’s the building regs as they stand today for insulation I’m in climate zone 3 which is about as cold as it was in south west uk I reckon. Zone 1/2 includes the far north which is similar weather all year to Sydney!. Not much difference in the regs considering.

Not keen on them. Dry my eyes out and is hard to explain but it’s never a nice heat as soon as it turns off the room feels instantly cold.

https://www.daikin.co.uk/content/dam/dauk/document-library/Brochures/Heating/Heating Installer brochures/Daikin Altherma 3 H HT_767.pdf

Thanks that explains a lot. I’ll try and get some figures together for the build spec. You can all laugh at how bad kiwi houses are compared to Europe. Im glad you’ve worked out that the 1000L will only last for 30 mins as I can see that it’s pointless now. Before I didn’t have a clue how long it would last so that’s narrowed it down for me. Just been looking at the daiken altherma 3 HT are they any good?, I can’t find the COP figures at high flow temperatures anyone know what they are?.

Will running the rads at 50 degrees with a small buffer tank and underfloor manifold with take offs direct to the rads work ok on 16mm pipe over a 25m distance or no chance. I reckon biggest rad size will be 1400x600 t22 that will fit in the wall space.

What HT split unit is worth looking at?, I’ve only looked into vaillant mainly because it’s the only gas boilers I liked working on lol

This is what I’m trying to put across the daytime temps here are good so it makes sense to time shift the ashp to produce when it’s most productive. Without a slab of concrete I thought a massive lump of water is next best. I was only going to use the immersion if it makes sense to if the ashp can get to 70 degrees at a cop of higher than 1.0 then I’d obviously just use that. The hot water I would eventually plumb into the ashp but the standard cylinders here are immersion heated unvented ones and with the house probably being a new build it’s not worth the savings to rip it out and replace with a new cylinder when I don’t use much dhw anyway. In 10 years when the cylinders gone I’d replace and integrate it then.

Haha it’s not too bad. The pics above show it on a new build done at first fix phase but for retrofit it’s clambering in the loft drilling down through the top plate of the wall and any dwangs you encounter. Normally 2 but sometimes 3!. This further limits where to put rads as can’t normally get onto outside walls as the slope of the roof where it meets the external walls mean that you can’t get a drill into the space let alone a 1m long drill extension. Just remove the plasterboard I hear you all cry, there’s a 6-9 month wait on sheets of plasterboard at the moment it’s causing carnage in the building industry. 🤣

I’m not using any of this for dhw this is solely for heating. I was thinking it’s more cost effective to use the ashp to heat in the day when it’s 7 degrees plus temp rather than when I need it and the temps are -4 to 3 degrees. I was going to heat the thermal store to say 55 via heatpump and top up the rest via immersion. The other issue is installing the rads it’s all done by getting in the loft drilling down through the timber frame with 2m long drill bits and feeding the pipes down cutting a small hole behind the rad and feeding the pipes out. Other issue with larger rads for lower temps is amount of wall space there’s a lot more windows in kiwi houses and can only fit smaller rads not always 1800+ ones. I don’t like the MLCP pipe here either with crimp fittings so I wanted to use underfloor manifolds so I could run straight from manifold to each rad in one length with no fittings in the wall, this is also not going to fit well with running lower flow temps direct to rads I’m guessing or will it be if I ran the pipe in 20mm rather than 16mm to each rad?. (The furthest run from manifold to rad will be 25m in length shortest would be a 10m run.

Anyone know how well a ashp will work with a large thermal store setup?. I’m a uk gasfitter currently living in New Zealand and about to buy a house and have to fit some central heating. Underfloor is not an option for retrofit so I’m left with rads as the only option. costs per kWh are: LPG 14p Diesel 15p elec 11.75p elec is renewable here mainly hydro and has not risen in cost during the 2 years I’ve been here so hopefully won’t be as inflationary as the others. Diesel has doubled since January and kerosene is dearer than diesel. Nightime temps go as low as -4 daytime is normally sunny 5-15 degrees. Because of the daytime temps I’m looking into fitting a heat pump to charge the thermal store can get 1-2000L tanks. Demand will be roughly 15kw over 10 rads. Insulation is not as good as in the uk and timber frame so no thermal mass apart from the concrete slab but generally these are not insulated. Walls are 100mm timber stuffed with rock wall and ceilings rock wall about 250mm thick. House is 200m2. How will a heatpump work with thermal store effiency wise if I was to run it in the day charging the store then pump around the rads at night and morning. I will need 15kw output for probably 6hrs a day will 2000l heated to 60/70 degrees do this?. I know heat pumps don’t work best at higher temps but looking at the kWh pricing even if it runs at a COP of 1 it’s still cheaper than gas or diesel. We get about 5 days a week of 6/7hr days sun as well in winter so solar is an option although the upfront costs for solar, 2 massive buffer tanks and a vaillant arotherm plus 16kw is going to be £20k plus. Winter is about 4 months long I need about 700kwh a week so about 11,200kwh a year. Looking online 2000L of water heated from 20-70 degrees takes 116kw how do I work out how long the thermal store will supply the rads for I’m guessing I will get roughly 116kw back out obviously at the end it will be pumping 20 degrees water back out so pretty useless at that point.