Does solar hot water work with a combi-boiler?
Posted by Paul Hutchens on 8 June 2012 at 9:05 am
Q: We are about to install a new combi boiler. We also want to install a solar water and CH system. Would like to use an unvented solar store with heat exchanger coil to CH flow on combi (with temperature controlled diverter valve) and the mains pressure cold feed through a heat exchanger in solar store then into the combi hot water circuit. We want to get this installed soon. Any information would be appreciated.
A: First of all - don't install a combi-boiler!
Combis are designed to heat water instantaneously from the mains and do not require hot water storage. They are designed for relatively low hot water usage households and are convenient as they provide hot water on demand and save space on a hot water storage cylinder.
Solar thermal heating systems require a storage cylinder as the energy generated from the sun in the form of heat is sporadic and is produced in proportion with daylight and sunshine which means that, as it cannot be guaranteed to be available when you need it, it must be stored in a hot water cylinder.
Existing combis can be modified to fit a hot water storage cylinder and a solar heating system by fitting a cylinder and splitting the heating circuit of the combi to heat it - this is what you appear to describe.
However, if you are fitting a new boiler, fit the correct one for solar heating in the first place. I suggest a good quality system boiler with an unvented stainless steel hot water cylinder along with your solar heating system.
I strongly suggest that you contact a reputable MCS certified solar installer who is a member of the Solar Trade Association. They should be able to provide good advice and quality service.
If you have a question about anything in the above blog, please ask it in the comments section below.
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