Solar Heating with Combi Boiler

[hughie999]

I have a combi boiler installed in my new house. Is it possible to install solar heating panels with this system - if it is what do I need to do?

 

[cr0ft]

You could if you installed a hot water cylinder with a twin coil but this would largely defeat the point of having a combi-boiler in the first place in my honest opinion. Solar heating is still not a good purchase in terms of payback at present and personally if you have the money to spend on one of these I would put it towards solar PV instead which offers a fairly quick payback (around 10 years).

 

[EPH]

You can use it to pre heat your boilers hot water but manufacturers aren't keen.

 

[hughie999]

Hi Kieran,

Thanks - reckon that's good advice re PV alternative.

You could if you installed a hot water cylinder with a twin coil but this would largely defeat the point of having a combi-boiler in the first place in my honest opinion. Solar heating is still not a good purchase in terms of payback at present and personally if you have the money to spend on one of these I would put it towards solar PV instead which offers a fairly quick payback (around 10 years).

 

[fuzzy]

thought payback on solar was better than pv?

 

[ecowarm]

I have fitted a few Grant CombiSOL valves, you install a solar unvented cylinder and the valve mixes or diverts the hot water to the combi or straight to the taps if hot enough, more info here [DLMURL="http://www.grantuk.com/products/solar-thermal/solar-thermal-solutions/"]Solar Thermal Solutions | Grant UK[/DLMURL]

 

[cr0ft]

It can certainly be done as ecowarm says. Put it this way, my business will be paying for a solar PV installation when we move to our next house and will be keeping the income from it as an investment. When you do the maths it's still the best earner by far with the shortest payback on the market just now. Sorry to go off topic but if you have the roof for it fill it with solar PV cells, not solar thermal cells.

Payback on most PV systems is around 10 years. I thought the payback on solar thermal was around 18, correct me if I'm wrong. All of that may change next April though if the government starts offering feed-in tariffs for thermal though.

 

[tackleburger]

You could if you installed a hot water cylinder with a twin coil but this would largely defeat the point of having a combi-boiler in the first place in my honest opinion. Solar heating is still not a good purchase in terms of payback at present and personally if you have the money to spend on one of these I would put it towards solar PV instead which offers a fairly quick payback (around 10 years).

Lot's of combis are solar compatible but you will need a mixer valve to maintain a set temperature going into the boiler a store if often the way to go which store preheated hot water prior to it entering the combi via the mixing valve so you present your combi with premixed water say at 30 degrees the combi does the rest. If you happen to have an Alpha boiler they have a sepecific kit for their boilers. You should speak to the boiler manufacturer and go with their recommendation.

 

[tackleburger]

It can certainly be done as ecowarm says. Put it this way, my business will be paying for a solar PV installation when we move to our next house and will be keeping the income from it as an investment. When you do the maths it's still the best earner by far with the shortest payback on the market just now. Sorry to go off topic but if you have the roof for it fill it with solar PV cells, not solar thermal cells.

Payback on most PV systems is around 10 years. I thought the payback on solar thermal was around 18, correct me if I'm wrong. All of that may change next April though if the government starts offering feed-in tariffs for thermal though.

You can't say categorically what the payback on solar is. It depends on a number of factors. I am in scotland an will only fit evacuated tubes and wouldn't fit for a house unless there are 4 users of hot water. I also crank up the boiler stat on the solar to 80 deg and fit a tmv on the outlet and generally only do it on unvented, and set the time controls on the boiler accordingly. The sizing of the cylinder is vital and all these thing maximise solar gain thus reducing the payback period. A family of 4 with two bathrooms on a 250l unvented solar with evacuated tubes in the right position could get the payback within 5-8 years easily. When you go to house and find flat plates with an old couple living there then you are looking at 13 years.

 

[AWheating]

You can't say categorically what the payback on solar is. It depends on a number of factors. I am in scotland an will only fit evacuated tubes and wouldn't fit for a house unless there are 4 users of hot water. I also crank up the boiler stat on the solar to 80 deg and fit a tmv on the outlet and generally only do it on unvented, and set the time controls on the boiler accordingly. The sizing of the cylinder is vital and all these thing maximise solar gain thus reducing the payback period. A family of 4 with two bathrooms on a 250l unvented solar with evacuated tubes in the right position could get the payback within 5-8 years easily. When you go to house and find flat plates with an old couple living there then you are looking at 13 years.

if you crank up the stat on the solar to 80, what temp does the cut out stat work at? and does your cut out stat close a solar rated motorised valve?

the reason i ask is last year i refused to commission some unvented cylinders that had a solar heat source because i believed the solar controls did not meet G3 regulations because it did not have 3 levels of thermo control, with one being a manual resetting cut out.

 

[AWheating]

Lot's of combis are solar compatible but you will need a mixer valve to maintain a set temperature going into the boiler a store if often the way to go which store preheated hot water prior to it entering the combi via the mixing valve so you present your combi with premixed water say at 30 degrees the combi does the rest. If you happen to have an Alpha boiler they have a sepecific kit for their boilers. You should speak to the boiler manufacturer and go with their recommendation.

Alpha solar smart is a combi system, you can use it on any combi as long as that combi has the ability to measure the cold inlet temp and adjust to suit. Atleast i think thats right, i did the course about 5 years ago.