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Joe Markey

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Hi all imhaving a 4kw solar pv system with an immersion controller(i dont have an emmersion yet)
and im looking at my options with a combi, my biggest worry from what i read is legionares,soif i use megaflow type cylinder alongside my combi what is tbe best size cylinder to use so that it reaches 60c through the winter months, or what alternatives or adjustments to the plan at the top
Thanks for any advice
 
You need a heating engineer to advise you on DHW tank size, not an electrician :),
They will also test water pressure and flow rates to see if an unvented DHW cylinder is suitable for your property.
You need a G3 certified installer to install either a megaflow type cylinder or the unvented pre-heat cylinder shown on your image
Your combi can be replumbed and rewired to work as a system boiler and heat the DHW tank.
You will also need a TMV on that system.

There are days in the winter when it won't reach 60° as the system won't generate enough.

Assume that the incoming water is at 10° (that about the UK Annual Average Air Temperature = Incoming Water Temp)
5.8kWh of electricity raises 100 litres of water by 50° (1kWh raises 100 litres of water by 8.6°)

You need a Specialist Renewables Energy installer to design, specify and install your solution - Any one that does Solar Thermal AND Solar PV should be able to quote you, though some shouldn't be let near a pipewrench or a screwdriver :)
 
you want one of Viridian solar's new Pod set ups.

new solar pv set up, hot water options with combi? {filename} | ElectriciansForums.net

Viridian Announces The Pod - Solar Preheat Store - Viridian Solar News

this is specifically one of the situations they are designed for.
 
High GavinA, That looks as though ot could be a neat solution :)

Is it vented or unvented? If unvented you'll still need to be G3, if vented, then you'll need a header tank, CW feed, and overflow, also not all combis like taking pre-heated water :(

At 100L, working on a max temperature of 80° that can store 7.5kWh of heat - that's about 1/2 the daily requirement of a 4 bed home.

As a fan of Viridian :) What do you think a typical installed cost will be assuming:
1) Plumb cold to attic,
2) if unvented, Pumb F&E, cisterm and overflow,
3) supply and install PV power diverter
4) Supply and install Pod,
5) Plumb cold back to Combi, fit TMV to outlet of combi.
6) what else did I forget?
 
funny that, I asked them most of those questions a couple of weeks back.

I think the tank itself if vented with integral header,

it works as a thermal store with a coil to heat the DHW to avoid the legionella issue

the diversion valve either diverts 28 deg water to the combi, or bypasses the combi to deliver fully solar heated water direct.

1) Plumb cold to attic,
no need if it's just for an immersun set up, can be sat next to the combi.

2) if unvented, Pumb F&E, cisterm and overflow,
not unvented, so no need

3) supply and install PV power diverter
same as normal

4) Supply and install Pod,
not sure, awaiting pricing

5) Plumb cold back to Combi, fit TMV to outlet of combi.
half a day or so if just fitted near combi, more if it needs piping from the loft

6) what else did I forget?

One of the key advantages will be that it's horizontally mounted, so can fit into side lofts, which opens up the potential for installation where there's no obvious place to put a cylinder.

It may be a niche product, but does offer a pretty simple solution for houses with combi boilers fitted, and I must have knocked back at least a dozen such houses for solar water heating before now.
 
I know it's "just" a solar-preheat cylinder :) just neatly packaged, - Do alpha do a "PV Only" option? and also @ 575mm you'll struggle to get the Alpha through a lot hatch.
 
We've been struggling to get unventeds and thermal store through loft hatch's since we started installing navitron kit in 2004 and then moving on to my own and kingspans kit. Did I say struggling? well it wasn't really a struggle until pv hit solar thermal sales really hard.

PV only? pretty simple to achieve that with a store and immersun wouldn't you think.
 
This could be an ideal solution. It is effectively a heatstore with a heat exchanger. There is a specific version for use with a proportional controller. Outlet temperature can be set to max of combi. (Normally 29deg C).

It is vented.

In trials the full ST version has given between 45 and 55% contribution to hot water. Trials were in Scotland, so contribution further south could be greater. Contribution will be affected by household behaviour.

Would be reluctant to quote costs on Public side. Depends on a number of factors involved in procurement of all aspects as well as Pod itself.

Everything produced by Viridian is a premium product. Do not expect Lada prices. As the recent VW advert says, you get what you pay for. We exclusively fit Viridian ST equipment. This is after trawling the market of all product offerings.

I am fortunate enough to know Stuart Elmes, CEO of Viridian. The guy is one of those pushing the industry forward on many fronts. This reflects in the solutions the company produces here in the UK.
It is his unstinting work that has shaped the RHI for ST.

Yes, I am a fan of this business, but they deserve it.
 
Thanks for all the feedback, ill read up on the products youve suggested, my combi is a vaillant ecotec 837, ive emailed vaillant to find out what thechighest acceptable cold water inlet temp is so they might reply tomorrow.
Whichever direction i go in will be down to cost.
Ill pick the solar mans brain when he comes.
I wont be getting any proffessionals to visit until ive done my plenty of research, and i only started looking yesterday.
Thanks again
Joe
 
This could be an ideal solution. It is effectively a heatstore with a heat exchanger. There is a specific version for use with a proportional controller. Outlet temperature can be set to max of combi. (Normally 29deg C).
Does it have a TMV built in then?
So it acts as a combi-assist, if limited to 29° then effectively can pre-heat up to 275Litres / day (or normal usage for 6 people) so combi then only has to work to lift from 29° to 48° so saves that 7.5kWh = (7.5*5.2 ) = 39p / day or approx £140 / year. On oil saves £172 / year and LPG £207 / year.


It is vented.
So F&E plus cistern plus o/flow needed.

In trials the full ST version has given between 45 and 55% contribution to hot water.
That ties up with the thermal storage capability of 100L - you won't get more unless you have a store bigger that 100L and open vented you won't want to raise the temperature any higher

Would be reluctant to quote costs on Public side. Depends on a number of factors involved in procurement of all aspects as well as Pod itself.
Pop it in the sunlounge then, or PM me :)
 

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