Options for Solar Hot Water?

[blueJay44]

I have a very old boiler that i'm hoping to replace soon and would be keen for various reasons to make use of solar for hot water.

I have one main question, should I opt for a thermal store, with which I then use a compatible combi boiler to feed the water through, or alternatively should I use a boiler to heat the aforementioned thermal store?

From my very limited knowledge i'd guess that it'd be better to do the former, however I'm sure somewhere along the line i've heard that the second option may be better and more efficient.

Can anyone help?

[dormouseheating]

OK.. I'll go first.. I will tell you however that I have very limited solar knowledge and I only have experience of one system.
The system that I worked on (and I was told that it was popular) was a basic 'heat only' or 'conventional' boiler which heated the water for the radiators and the water inside the cylinder(thermal store). The only difference between this system and a solar system was that the cylinder had a second coil inside for the solar circuit. The solar had it's own pump which circulated the glycol around it's circuit.

I'm not sure how you would use a combi with solar as I'm under the impression that solar heats up a store of water and a combi draws the water from the mains.
Like I said I have very limited solar knowledge and I apologise if I've confused you but at least you have a repsonse...!

[ben]

I have recently converted a combi boiler for use with a solar system and i would advise that you stick with a Conventional or system boiler, solar cylinder and solar panels, the main reaosn for this is cost of installation will be lower and the system is slightly easier to install than a combi with solar, im not sure on the efficiency side but from installing both systems i would go for the non combi if your going to spend the money

[dormouseheating]

I have recently converted a combi boiler for use with a solar system

As I have little experience of solar I'd love to know how you did it.. did you use the solar store as some kind of mains pre-heat?

[alecmorrow]

its always better to use a system boiler rather than a combi... this is the optimum design...the reasons why you wouldn't use a combi are very technical concerning flow rates and valve settings and minum modulation rates on the boiler...

but the other down side is that you will be limited to one hot tap at that boilers max flow rate....so you have all the frustrations of a combi (low flow rate) with none of the advantages (no space saved!)

make sure that you use a controller that talks to the boiler and a cylinder sensor on the boiler side to ensure that you gain a high degree of control over the temperature...

[blueJay44]

Thanks for all of the helpful replies, some really useful advice. The general consensus seems to be to stick with an upgraded system boiler, I think this is the avenue i'll take, i'd certainly like to retain a good level of control over the water temperature.

[affleckplumber]

We are advising all our clients (where appropriate)to fit solar ready hot water cylinders (twin coils) even if they are not thinking of solar panels right away.

[ben]

Hi dormouseheating, it is relatively easy to do, and there are 2 ways of doing it with a Combi, the manufacturers recommended way which will be far more complicated and cost more as 'alecmorrow' explains, the alternative way is to how ive converted the boiler which uses the stardard central heating but controlled with two zone valves , the wiring is a little more complicated that a standard s plan system but it works very well with out any of the problems with low flow rate (which with a combi isnt an issue is the system is designed properly) and we can manually switch between combi or solar tank hot water, the only reason i did the job this way was the exsisting combi boiler was new so wouldnt have been an option to replace it with a system or conventional boiler, i hope this has answered your questions!!

Ben Grant
Gs Heating & Electrical Ltd
www.heating-and-plumbing.co.uk
birmingham & surrounding area
plumbing - heating - solar

[breezehome]

Combis aren't really designed to couple up to Solar systems. To take full advantage of the heat produced by solar thermal panels it is best to have a large store of water and a system boiler. This can either be a thermal store or an unvented cylinder. Most water is used at night (baths,washing up,dishwashers) and first thing in the morning (showers). These are the times when the sun isn't heating what you need. Therefore its important that there is enough stored water to get you through a 24hr period. The sun does its job through the day and you should design the system to have enough left for the next morning. The boiler is used as backup during the winter months and for heating. Unless you have a huge system and underfloor heating there isn't enough capacity to heat your home.

[jeffstockdale121]

Leave your boilers as they are. Install P.V. panels and use the emmersion heaters for free hot water. Preferably a cylinder with coils at the side not on the top. You also get F.I.T. payments back from the govenment for supplying electricity. Boiler is just for heating then inttit ?