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2nd Heat Source For Hot Water Production


UlsterRugby1999
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Hi all. Firstly Bonne Fete à tous. I’m planning a wee thing with my solar hot water system and I’d like your thoughts on where I am with it if you will.

Presently I have a 36 Evacuated tube set up with a 300ltr tank. The tank has the main heat coil for the solar link along with an additional heat coil which can be linked to a secondary heat source. Also, there is an electrical water heater element. The system seems to be set up fine but obviously at this time of the year isn’t giving me as much hot water as I’d like. So, I have a plan (which I have taken from another person so its not my scheme).

I want to augment the hot water I produce to try to maintain as much hot water as possible. So, my plan is to introduce a 2nd heat source. To do this I will wrap copper around the flue pipe to a height of approx 1m. This will then be pumped, as any other heat source would, to the HWT using a circulating pump. BUT – the secondary heat coil is located in the upper half of the HWT and this seems an awful waste, to me, to be heating only half the tank in the winter time when the solar aspect of the system isn’t achieving full hot water production.

So, I know that the use of the flue as a heat source works but can I tap into the lower heat coil in anyway and how can I do this and how can I do it safely.  Thanks folks for any responses and thoughts you might have. Regards. Paul

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Hiya Quillan - Ive been out of action for over a year now and only just getting back into things. Yes I did buy the Airton kit from BricoDepot and I couldnt be happier with it all. Of course it struggled during the very cold spell last February but it worked well and we gave it quite a bit of use during August in the hot spell. Great value for money.

How are you keeping? Well I hope.

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Mine is in use most colder evenings now to top up my main storage heating.

It probably doesn give out as much heat as in warmer weather but then I dont need it then, probably not as efficient a heat pump as in warmer weather but it definitely gives out a lot more than it consumes.

For me its the perfect balance, having cheaper off peak  background heat without oversizing the storage heaters and having an economic back up source on the coldest of days and it has worked at the lowest of temps we have had here, -12° and some, plus I have the cooling facility in summer although the ventilator alone is quite good.

If I were considering it as my sole means of heating then I would oversize the units and have a standby fan heater or something just in case.

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Not to bad Paul, up and down like Tower Bridge but in general OK.

Glad you have both enjoyed your units and hope they are saving you loads of money. Its always nice to help people and find them happy with your advice afterwards. The problem, if you could call it that is that we always managed OK before in the summer and I started off determined not to waste the money I had saved by using them to cool the pace down. Unfortunately you sit there looking at the remote and it's like your fingers have a life of their own and before you know it the units are on and you wonder how the hell that happened but then it's so nice to be cool that you leave them on. It's like heated windows on cars, stupid idea, who would want them? Once you have them you can't quite imagine life without them.

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Great link Dave and thanks. The folks there have, more or less, sorted me out. Here's where we have got to if you are interested.

I'm going to use the flue pipe heat source and connect it into the upper heat coil in the solar hot water tank. In addition, I will install a radiator close by as a heat leak. The feed from the flue will, at the point of entry into the SHWT have a thermostatically controlled motorised diverter valve so that when the tank temperature reaches a preset temperature the valve will divert the flow to the radiator. Once the temperature drops below the preset level the valve will re-divert the flow to the tank and so on. All the usual suspects will be installed too, of course, as in relief valve, expansion vessel etc.

What do you think?

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  • 1 month later...

This is just a quick post to, firstly, thank everyone for their input to this post and to, secondly, just to let you know that I have installed the system and that I am producing all the hot water me and my family need. Basically, I made two coils of flexible copper and fixed them to the top and rear faces of the fire. I did this as there was concern that attaching them to the flue might reduce the draw potential. I connected the flow and return to the secondary heat coil in the Solar hot water tank and after some adjustments I am now producing water temperatures of between 50 & 55 degrees C. I would estimate that the electrical heating element in the tank has been used for approximately 2-3 hours over the past two weeks. Result I think. Thanks again for all your help, advice and input. Regards. Paul.

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