Pre heating water into combi boiler?

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Hi,
I have a Worcester Bosch Greenstar 35CDi combi boiler running on LPG. This works very well providing both hot water and central heating.

I have recently installed a PV solar/battery system and expect to have more electrical power than I need for about 8 months of the year. I am looking at ways of making use of this excess.

One option I am exploring is to fit a large pressurised hot water cylinder with immersion heater “upstream” of the combi boiler and use it to pre-heat the water in the summer months when I have spare power. I am hoping that this would result in the combi not kicking in at all when fed with hot water in the summer and working as normal in winter when the immersion heater was switched off.

I would appreciate your thoughts on whether this would work, problems to look out for or generally better options to achieve the same end!

Thanks in advance
 
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Reversible aircon to heat/cool your home coupled with a bigger power wall is easier.
 
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Hi Motorbiking,
Thanks for coming back to me.
I’ll have a think about it but not sure that’s going to work for me. Not much call for aircon in the summer up here in North Yorkshire and in the winter when I do need heating I don’t have a reliable surplus of solar power.
 
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Surely easier to just use the cylinder for all of the hot water, with the immersion for the solar and the combi to heat the cylinder at other times.
 
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There's usually a limit on the temperature of water you can feed into a combi. WB will be able to advise.
 
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There's usually a limit on the temperature of water you can feed into a combi. WB will be able to advise.
Alpha done a solar system years ago and it was thermal solar as opposed to solar PV, on the cold water inlet there was a solar thermal valve, basically a wax stat, if the water coming from the solar cylinder was above 55 C then the water went straight to the open tap, if below that it was diverted through the combi to top it up
 
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Hi,
I have a Worcester Bosch Greenstar 35CDi combi boiler running on LPG. This works very well providing both hot water and central heating.

I have recently installed a PV solar/battery system and expect to have more electrical power than I need for about 8 months of the year. I am looking at ways of making use of this excess.

e
can't the excess be sold back to the grid ? or are you off grid:idea:
 
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Thanks for all the replies.

To answer a few questions:
  • I can’t sell the excess back to the grid as, at the moment, I can’t get a new smart meter so no access to cheap overnight rates and no option to sell back to the grid. Still working on this one but 6 months of trying hasn’t got anywhere yet.
  • I will have another look at heating the cylinder with both an immersion heater and coil from the combi. I think the plumbing will be more challenging but worth another look - thank you.
  • I have an enquiry in with Worcester Bosch to find out the max temp I can feed the combi with. Waiting to hear back on that one.
  • Ianmcd -thanks for your suggestion of a thermal valve. I’ll look at that as an option.
Many thanks to all of you who have contributed!
 
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Thanks for all the replies.

To answer a few questions:
  • I can’t sell the excess back to the grid as, at the moment, I can’t get a new smart meter so no access to cheap overnight rates and no option to sell back to the grid. Still working on this one but 6 months of trying hasn’t got anywhere yet.
  • I will have another look at heating the cylinder with both an immersion heater and coil from the combi. I think the plumbing will be more challenging but worth another look - thank you.
  • I have an enquiry in with Worcester Bosch to find out the max temp I can feed the combi with. Waiting to hear back on that one.
  • Ianmcd -thanks for your suggestion of a thermal valve. I’ll look at that as an option.
Many thanks to all of you who have contributed!


Did you ever get any update? I’m in TBF same situation looking to feed preheated water into a Combi
 
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Update:
I contacted Worcester Bosch who advised that my particular model of combi wasn’t suitable for pre heated water.
I’ve decided to go with a direct unvented cylinder plumbed in such a way that in summer when I have spare power I can bypass the combi and draw hot water from the cylinder and revert to the current combi fed system in winter. Simplest option in terms of plumbing and should be pretty fail safe - if either the combi or the immersion fail I can switch to the other.
 
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Update:
I contacted Worcester Bosch who advised that my particular model of combi wasn’t suitable for pre heated water.
I’ve decided to go with a direct unvented cylinder plumbed in such a way that in summer when I have spare power I can bypass the combi and draw hot water from the cylinder and revert to the current combi fed system in winter. Simplest option in terms of plumbing and should be pretty fail safe - if either the combi or the immersion fail I can switch to the other.

Nice, I might need to do the same I think
 

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