# Incorporating solar panels into UFH system



## highdef (3 Mar 2010)

I am about to install the heating system in my new build. I will have UFH heating downstairs and rads upstairs, powered by an external Grant or Firebird condensing boiler. I will be installing solar panels onto the roof. I know they're good for the hot water but would it be easy to incorporate them into the UFH? I plan to have a 300l twin coil stainless steel hot tank. There will only be 2 people living in the house so that should be more than enough.
The running temperatures of the UFH are very low so I would imagine the solar panels could provide enough heating for the UFH during the transitional spring and autumn seasons when the sun is quite strong but the nights are generally cool. I will also have a wood burning stove in the main living area, which is very large. This will provide additional space heating to much of the ground floor, if needed. The house is very well insulated so in theory, I would often get away with the stove and UFH only for the downstairs and just a little bit of rad heating upstairs......well that's plan anyway.

I've a feeling I'm missing something here and am hoping someone can point me in the right direction. From what I've been reading, I may need a buffer tank. And from what I can tell, a buffer tank is a big oversized hot water tank??? The problem there is that I may not have room for a massive 800l buffer tank in my hot press, located off the hallway.

If anyone can help, I would be most obliged. I did a search first but could not find the answer there......maybe there's a reason for that!!!

Thank You


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## villa 1 (3 Mar 2010)

Keep your panels for heating hot water only. Unless you want to completely cover your roof with panels(which you can't) then you would be wasting your time and money. You would have to put in a large buffer to satisfy your downstairs UFH heating load and this would be a waste of money.
Remember that it rains a little bit in this country and cloudy skies can't heat much water for washing let alone heating.
Install a condensing oil fired boiler, 200 litre cylinder, a hot water circuit, 2 panels, an downstairs underfloor circuit(if you choose, not my choice) and an upstairs radiator circuit and finally insulate. People are wasting glutinous amounts of money on systems they don't need!!


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## highdef (4 Mar 2010)

Thanks villa 1. You sound like you know your stuff and I will be doing exactly what you have just said....well that was the plan anyway if I could not incorporate the solar into the UFH.

Thanks again


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## quentingargan (4 Mar 2010)

Villa is bang on the money here and I get irritated by people trying to sell solar panels to heat a house. The concept originated in Austria where there is much higher sunshine in winter than we have. Our summer sunshine is similar to theirs, but our winter sunshine is about half. I've pasted a table of the comparisons below.

Even then, there is a very narrow band of time in which you need heat which can be provided by solar panels. Ironically, the more insulated your house is, the less this time is. 

Also, you have surplus heat in the summer which needs to be dumped, and they mount solar panels at a steep angle to make them less efficient in summer to cope. 

So spend your hard-earned dosh on insulation. Put in a system that maximises your solar hot water production in spring and autumn because you won't be having your central heating on and it is during that time that your hot water is most expensive.


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## yclarke (31 Mar 2010)

villa 1 said:


> Keep your panels for heating hot water only. Unless you want to completely cover your roof with panels(which you can't) then you would be wasting your time and money. You would have to put in a large buffer to satisfy your downstairs UFH heating load and this would be a waste of money.
> Remember that it rains a little bit in this country and cloudy skies can't heat much water for washing let alone heating.
> Install a condensing oil fired boiler, 200 litre cylinder, a hot water circuit, 2 panels, an downstairs underfloor circuit(if you choose, not my choice) and an upstairs radiator circuit and finally insulate. People are wasting glutinous amounts of money on systems they don't need!!


 
Hi Villa,
Would what you have outlined above be sifficient for a house approx. 3k sq ft?


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## quentingargan (31 Mar 2010)

yclarke said:


> Hi Villa,
> Would what you have outlined above be sifficient for a house approx. 3k sq ft?


The hot water requirements of a solar water heating system really depend on the number of people living in the house, and the way hot water is used. Showers use less than baths, and if there is a dishwasher, you'll use less than if there isn't. Also, the design of the system will depend on a number of factors such as the direction of the roof, and whether the house is occupied during the day (more water used, but usually smaller cylinder required), whether there is hard or soft water (hard water causes limescale so you tend to store a larger amount of water at a lower temparature) etc. 

If you are building a new house and want your system to comply with Part L, there are more limitations, particularly for a large house because the software used by BER assessors makes all sorts of assumptions about the number of people in the house and how much water they will use..... With some large houses, it is almost impossible to design a sensible system that will comply.


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## villa 1 (31 Mar 2010)

3k square foot is some size of a house!!. If you go solar allow approx. 50/60 litre storage of hot water per building occupant.  Solar Panel /tubes are best positioned facing due south or south west/east. Install an oil fired condensing boiler and hook it up to a solid fuel stove that has an integrated boiler(use a gravity circuit for your primaries between sf boiler and cylinder) Anyone who tries to sell you a heating system fed from solar sources is not operating on full power
Get your water tested as this can have a bearing on future plumbing problems, eg: Temporary hard water - lime scaling, furring, poor cicrculation. Soft acidic water - copper pipe/brass fitting corrosion and green staining on sanitary appliances.
As quitengargen says every house has it's own particular needs. Many BER  specialists have no experience whatsoever in heating design and control, so be carefull when making your choices. Be sure to max out on insulation though as this will most definetly slash your heating bills


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