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Solartwin

Does anyone have any thoughts on:

http://www.solartwin.com/easy_to_plumb_in.htm

I don't know much about solar water heating but always thought it involved substantial plumbing changes- their system looks very simple. But is it any good?
dougal

Solar water heating is not really a good match for a combi boiler. Almost (but not quite) all combis. Whatever solar water heating system.
If you have a combi, solar means a big re-think.

With a 'conventional' system (with a hot water tank) its not too bad.

Simplest is to swap the immersion heater element for a 'solar coil' - that will hook up to the solar panel, solar circuit pump, etc BUT you don't have to mess at all with the existing plumbing. This may not be super-effective, but it doesn't require any alteration at all to the existing plumbing.
Or you could insert a solar pre-heating tank 'upstream' of your hot tank.
Or do it the most effective way, swapping your hot water tank for one with two coils (one for the boiler and a lower one for the solar circuit).

"Flat panel" collectors are pretty ineffective. But they are cheap.
"Evacuated tube" collectors can have a really HOT output - so you really really ought not to plumb them with plastic central heating pipe - they can get too hot for it! For similar reasons, they need to have a sealed, pressurised 'solar circuit'. I don't think that's rocket science to construct, most plumbers should find it straightforward.
See what Ivan has to say about flat panel collectors (read down the page) http://www.navitron.org.uk/solar_collector_panel.htm He is selling evacuated tube collectors for less than some people charge for flat panels!

This solartwin system uses a flat plate collector. So it ain't going to do very much outside high summer.
It uses a 'drainback' concept. The pump only runs (filling the collector) when there is heat to be captured. So the panel wouldn't freeze 'cos it'd be empty.
But the panel is using 'new' water - it isn't just going round - it's going to come out of a tap eventually, so the circulated solar heated water is going to be replaced wth new water from the mains.
OK, we have a warmish panel in the sun, that is drained and refilled, with constantly replenished fresh water.
That sounds to me like a recipe for scale formation, reducing the efficiency even further, and likely corrosion as well, with sludge before the thing starts leaking. (Air from fresh water is a prime cause of ch corrosion.)
For a diy installation using old ch radiators, etc, a flat panel with drainback system can be made cheaply out of scrap. It'll be inefficient, but if it has only cost pennies, it hardly matters. And the drainback solar circuit would be filled with inhibitor, if not anti-freeze as well. (The anti-freeze has a second benefit, increasing the amount of heat that each litre of flow can transport - it raises the water's 'specific heat' - which is why lack of anti-freeze can cause cars to overheat in summer...)

Personally, I wouldn't buy a system like this.
Your mileage may vary.
zigs

solartwin wouldn't stop phoning me up after i made an enquiry, i told them i hadnt started the project yet, but they bombarded me with letters & messages.

they almost subsided after a strongly worded e mail, but i still got another one today.

wondered where all the double glazing salesmen had got to Mad
liddy

Same here... they were like a dog with a bone once we first made contact with them. Wasn't until my hubby got really angry and pointed out that he had noticed the increase in their prices once everyone, even us off-gridders, got access to grants! Bloody cheek.
MrWomble

dougal wrote:

"Evacuated tube" collectors can have a really HOT output - so you really really ought not to plumb them with plastic central heating pipe - they can get too hot for


never ever install solar evacuated tubes in plastic - most will run pressurised water 3 bar at over 100'C - all joints must be silver soldered (not standard solder) to withstand the temperatures.

i'm afraid i wont post my views on solar twin because they are rude.

yep - solar is fine to use as a pre-heat for a combi which is compatible - unfortunately most arent Confused

the navitron heat pipes are fine - being cheap though dont expect any fancy mountings that you get with more expensive products

above all dont be frightened of it - its quite simple really - need any help just ask

kindest regards,

alex
dougal

MrWomble wrote:
... never ever install solar evacuated tubes in plastic ...
Which is precisely Very Happy what I meant when I said:
dougal wrote:
.... you really really ought not to plumb them with plastic central heating pipe ...




MrWomble wrote:
most {evacuated tube systems} will run pressurised water 3 bar at over 100'C - all joints must be silver soldered (not standard solder) to withstand the temperatures.
Alex, isn't it simplest to use bought-in pump/expansion chamber/etc modules, that shiny-(stainless?)-clad pre-insulated flex pipe and compression fittings?
But I'm afraid I don't know of a decent source for the fancy flex piping!
MrWomble

hi dougal

- yes definately - and a great deal cheaper too - and unless you're installing a silly big system the flow rate is going to be quite low so drop down to microbore off the collector - comes in a roll so not much soldering Very Happy

regards,

alex
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