[Bennie_R97]

Great conversation going on here, from boilers to sustainable choices and the prices behind each choice.

Personally, I hope that in the future, the Government decided to implement measures that can support everyone to choose what benefits the environment without being forced to choose between moral and finances.

What makes me wonder is, if the current technology becomes obsolete and we will be forced to implement new measures, I really hope there will be found a way to recycle the current gear, which I believe can be challenging when thinking about a gas combi for example.

[meldrewreborn]

Originally Posted by wizzo227

It would be a waste of money to replace an old fossil-fuel boiler with another fossil-fuel boiler. Better to put the money towards something else which will be compatible with nil net zero and won't get banned and be unusable in future, possibly before your payback interval.
https://www.itv.com/news/2023-01-13/...ut-in-a-decade

You can always do what I did, adding solar panels and renewable heating when you can, and using the old fossil boiler so much less that it won't matter when it does get banned or stop working completely.

so that report has gone into the dustbin. I’d like to get solar but my existing thermal panel takes up much of the roof and the orientation is almost exactly east west rather than south. I’d rather fit a new gas boiler than a heat pump, because the efficiency of a heat pump is far from guaranteed, which makes it too risky for my liking.

[wizzo227]

Can you tell a little more about your East/West solar thermal? I did some estimates expecting that a properly sized sufficient solar thermal collector ought to require an "overflow" "heat dump" capable of getting rid of 6 kW of heat on sunny days, from 2x4 meters of collector south facing. What have you got, and how does it turn out to work for you ? I'd expect E/W on 40 degrees pitched roof to work best with both collectors oversized and the same "overflow" "heat dump". What does yours have ?

[meldrewreborn]

@wizzo227

i have 2 panels side by side facing due west.
these were provided as part of a council scheme and the whole lot(panels, fitting, pipe work, controller, sensors and twin heating coil cylinder cost me £500. Bargain.

I had no say in the design. It works well but no sun = little hot water in the summer months. The tank is quite tall, and is heated to 75 degrees when fully charged. So it can cope with the odd cloudy day.

Outside of the summer months, the lower sun and shorter days limit the benefit of the system, and of course it saves me gas costs, not electricity, but it’s been very worthwhile.

[wizzo227]

Originally Posted by meldrewreborn

@wizzo227
£500. Bargain.

Indeed. Just an unvented twin coil tank on its own has a list price above that, so we cannot rely on anything in this post for proper costings of an applicable system. What size and technology are the panels ?
Ones which I recognise start at any old black thing, then any old black thing under a greenhouse roof, then under multilayer coating (that would have a 'nice' sheen to it, like camera lenses and fancy office windows). What is the capacity of the tank ?

[retrotecchie]

@wizzo227

DIY Solartwin can easily be accomplished for that sort of money if you know what you are doing.

Flat panel collectors can be as simple as an old radiator painted black and fitted into an insulated box with a sheet of glass over the front.

Not the best in these northern lattitudes though. although pretty reasonable in summer. ET collectors are much more efficient an need a lot less surface area for the same energy harvest and are still pretty good even in winter.

And you do not need a heat dump to get rid of excess heat. Correctly sized and with a very simple three sensor differential temperature controller, systems can be a lot smaller and simpler these days.

Even a square metre of flat panel and a passive thermosyphon system can work wonders to reduce DHW costs significantly.

And semi-passive warm air space solar heating systems might not be a first choice here in the UK, but I have one and it keeps my shed well above freezing even in the depths of winter.

[meldrewreborn]

@retrotecchie

my system has an expansion tank. I’ve seen the upper sensor report 150 Celsius, which is more than the melting point of lead solder, so my system has all mechanical joints on the pipe work, most of which is corrugated stainless steel.

[retrotecchie]

@meldrewreborn

No, standard 60:40 common plumbing solder is no good for solar thermal. Compression joints are the preferred way of doing it although 2% silver solder is fine for about 300 degrees. You only need a dab on the joints, but it's not cheap and you can't use a regular blow lamp!

All my system used compression for the primary solar circuits and had an overflow/expansion tank too. But a 10mm heat exchanger coil to fit a standard boss where the immersion heater normally fits doesn't cost an awful lot more than a regular immersion heater.

Being a bit of an electronics whizz, I built my own controller and wrote my own software for datalogging. A fun project and even in winter meant I usually had enough hot water for a couple of washing up sessions plus a good dhobi for myself.

[meldrewreborn]

@wizzo227

The tank is about 4t high and about 20" in diameter inclusive of foam insulation. the panels are quite large - the bay window front 3 panels are 6ft across.

[wizzo227]

Originally Posted by meldrewreborn

quite large - the bay window front 3 panels are 6ft across.

I'd rate that as too small for November and here is why:

Suppose that you have 2 square metres. Best UK sunlight is 0.8 kW/m^2, so maximum 1.6kW. If overheated the sort pictured will re-radiate to sky, so no heat dump is needed. The house pictured is likely to want about 60kWh / day of heating in November (you replace with actual figures from the sum of your gas use plus electricity use.) On a bright-overcast day in November, 1/4 sunlight of about 0.2 kW/m^2 is more common. The party-killer: your due west orientation never gets good sun in November. If it were to get good sun, to get 60kWh in a six hour winter "day" should want 10kW average, so 50 square metres to do that when bright overcast. Nobody has that much roof space, so it is only going to deliver supplimentary free heating at sunny times.

Wanting "the bigger the better", I suggest keeping your existing and tank but rigging something south facing at 70 degrees incline in the back garden to drop more free solar heat into that same tank. For winter, the bigger the better, especially if you might throw a sheet over it next summer.

How far North are you and what was the coldest winter night temperature noticed in the past five years ? I ask because now that the climate has warmed up a bit, 1980's fears of freezing and cracked pipes in all the plumbing regulations might be less applicable than they used to be, unless you live north of a big dark hill near Aviemore.