Combi Boiler with Solar Heating

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roker

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I have solar panels which heats my hot water tank, also heated from an oil boiler. Is it possible the replace the oil boiler with a combi boiler Possibly it would need some sort of control system because the solar panels need a hot water storage tank and the combi boiler doesn't.
 
That would be a tricky one to plumb. A combi boiler generally feeds all hot taps in the house directly. But then you can't have solar water heating if you're not going to use the water. To combine the two, you'd need a combi boiler that can accept pre-heated water from the hot water tank.

What's the driver for considering a combi boiler? Is the solar system not performing well?
 
These two links from Google are interesting on this topic -

Does Solar Energy Work with Combi Boilers? | GreenMatch

Approximately 50% of British households have a combi boiler and many of them are using also solar energy. Do they work together? Find out here!
www.greenmatch.co.uk

Pre heating water before it enters combi

After a discussion with a mate and some research of my own I now believe that it is not recommended that one feeds pre-heated water into a standard combi boiler (rather than mains cold). Forgetting any pitfalls associated with pressure or safety for the moment (assume hot can be at approx. mains...
www.diynot.com

Seems like plenty of combi boilers do support pre-heated water, but you'd need to check and ensure the input plumbing is designed for hot water. The DIY thread raises the issue of legionella in the tank that is heated by the solar, how would you ensure that tank is getting up passed 55 degrees on a regular basis? I guess you could use the immersion heater in the tank once a week, but the cost of that would probably offset the benefit of having the solar panel per-heating water.
 
Would a condenser boiler rather than combi boiler suffice
 
How many solar panels do you have any how much did they cost you?

You'd probably be better off selling them, replacing them with Solar PV and moving to the combi boiler.

Is your house suited to a combi boiler? E.g. you likely will only be able to have one shower
 
It takes a long time running the tap before hot water comes through, and we will not be heating a large tank which is the main point of having a cimbi boiler
 
roker said:
It takes a long time running the tap before hot water comes through, and we will not be heating a large tank which is the main point of having a cimbi boiler
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Unless you can site a combi boiler close to the tap, you will still have that problem of the water sitting in the pipes running off before the heated water arrives at the tap. The kitchen is a popular area to install a combi as the kitchen sink is the place where you most often use small quantities of hot water. Boiler very close to the tap means less waste.

However, feeding a combi boiler in the kitchen from a hot cylinder some distance away will mean you just end up wasting lots of your solar heated water as the hot water from the tank will only start arriving at the tap as you're turning it off, leaving the heated hater to cool in the pipes.

If the kitchen sink is the main issue, have you considered a tap with combined heating unit?
 
The kitchen is near the boiler house which would solve the problem of running the hot water from the hot water tank, but also I don't want to waste my solar heated water which is mainly in the summer
 
Thirsty said:
Second shower can be electric - which I would recommend as back up in a house anyway
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If you mean immersion it still requires a hot water tank
Presently I have a electric shower, and from the hot water tank, a pumped mixer shower and mixer taps, which work off the solar heating in summer and boiler in winter
 
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@roker I believe my understanding of the term 'electric shower' is the same as the commonly understood meaning; being a shower with cold water in feed where the water is heated by an element inside the device.
 
Yeah, electric shower here refers to a shower fed with only a cold feed, either mains or gravity (tank in attic).

The other options are mixer shower or power shower, both of which take a hot and cold feed, the latter variety having an internal pump to boost pressure.
 
I have both, a pumped shower with hot and cold feed from the H water tank and a pumped shower with a heater, and also bath mixer taps for a shower, so unless and can put a auto valve to shut off the HW tank when it is hot from the solar system and isolate the combi boiler.
I don't think a system has been thought out yet to do this
 
roker said:
so unless and can put a auto valve to shut off the HW tank when it is hot from the solar system and isolate the combi boiler.
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Normal practice would be to feed the combi from the solar tank, thus even a little heat from the solar will save gas.
 

Leo said:
Normal practice would be to feed the combi from the solar tank, thus even a little heat from the solar will save gas.
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That could work in the winter but the solar hot water can get up to max 60 deg in the summer that is max temp the solar system switches off
 
roker said:
That could work in the winter but the solar hot water can get up to max 60 deg in the summer that is max temp the solar system switches off
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It works all year round. If the water is at 60° it will likely just pass through the boiler without firing as combis usually supply hot water at 60°). But, the boiler must be specified correctly, not all can take the high temp input.
 
Combi solar dilema.
Could some one please advise me. 2 years ago we had 2 electric showers in the house and an 18yr old boiler. So as electricity is more expensive than Gas to heat water when we opted for a new boiler we decided to get a combi (Ideal logic Max combi C 30IE) but when the plumber went to connect the combi in the main family bathroom he said there was a leek under the bath, and replacing the bath etc, lead to a decision to eventually replace the bathroom, we did not have the money to do so at the time so we left it electric and replaced the small ground floor bath room to combi and we have used this ever since. However now my husband is determined to get solar power and we can afford to do the bathroom. However it is killing me that with an investment of 12 pv panels we can not benefit from the hot water, so my question is this, could I install an immersion tank run a feed of it to the new bathroom but also on the same wall have a feed for the combi ( the pipes are there ready to be connected ) so yes that means 2 shower hoses in the one shower and kind of 2 systems, my plumber says it can be done, but he also says I am mad ! But at the same time the solar and bathroom will be in place for the next 20years and it would kill me not to benefit from the free hot water, we have a superb south west orientation. Opinions please thanks so much. P.S Unfortunately no informed us at the time that combi was not compatible with solar.
 
Solar PV produces electricity, not hot water, unless you pay extra for a diverter to use excess electricity to heat your hot water tank via the immersion.
If you have a combi boiler, you more than lilkely do not have a hot water tank. So if you wanted to use the excess to heat water, you would need to pay extra for a hot water tank and diverter and this would be a headache for a plumber also. You'd never financially recoup the cost through the "free" hot water.
Instead, just let any excess electricity go to grid, where you are now paid a half decent rate for it, which is further offset against your electricity bill.
Otherwise, your post is hard to understand.
 
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