thermal store/rayburn what else do i need?

[igotalake]

Hi to all you,

i am planning to install a thermal store which will work in conjunction with my rayburn and oil boiler to heat the DHW and maybe some rads. the current DHW vessel is pressurised but i know the rayburn shouldn't work with unvented systems so that's why i am thinking the thermal store is the answer, plus i can add a solar source later if i want.

please have a look at this:

thermal store system

• igotalake
• 11 Feb 2012
• 1

the items in it should be straight forward to identify but 'p' means pump and 'v' means thermo mixing valve. oh and 'adolf' is the viessmann boiler who seems to want to dominate me and my house. it takes no notice of what program i set it to, it just does what it feels like doing at whatever time it feels like doing it. i believe it has further sinister plans for the world in general.

anyway, what i would really like to know from you guys is what else do i need to buy to make this system workable and safe? i want a controller that will pump to DHW vessel until that is satisfied, then pump to rads if thermal store has over a certain temp. if neither of those functions is enough to keep thermal store temp under control then the heat dump rad will hopefully provide safety.

please do point out any errors that you can see although the drawing is only a quick sketch.

cheers,

john.

 

[snb]

have a lookk at the H2 site. There is a way of linking various heat sources

 

[igotalake]

thanks for that, that is a useful link but i was looking at the set-ups they have on their website and they are different to mine in that i want to have a separate dhw cylinder, partly because i already have a good quality cylinder to use. the main reason though is that i want the hot water to be heated as a priority when the store is hot and only residual heat sent to rads. if i was to rely on the store to heat dhw on demand, as the H2 site and most other examples show, i would have to keep the store up to temp at all times and i don't want to do that. i only want to heat the dhw with the rayburn but take advantage of when the rayburn is going well and maybe heat a few rads as well but the rayburn cant work with my existing dhw system so i need the TS.
if the heat is not available from the rayburn at any particular time then the oil boiler will do what it normally does and heat the dhw and rads.

 

[dcawkwell]

My advice would be chuck the inefficient rayburn
and get yourself a nice modern range gas/electric oven
isnt it cheap electric in france?
Air source heat pump is a much better secondary heat source

 

[mysteryman]

Are you comfortable without being too hot, and do you have hot water as required?

If 'yes' then Adolf is doing an excellent job as economically as possible.

Changing to a Rayburn will cost you more in fuel because it won't be as well controlled.

 

[igotalake]

ha! all advice is appreciated but let me tell you how things are at the moment:

the previous owner fitted the viessmann and it's dhw vessel in a outbuilding and, to be fair Mysteryman, it is good apart from it's expensive to run and arrogant.
Dcawkwell, electricity is maybe a bit cheaper than in the uk but not that much. the need for electricity is my reason for not having a heat pump as they may output 3 times the input but the input has to be electricity which is ususally much dearer than the heating fuel that the heat pump is replacing. not to mention a biggish capital outlay at the start. also, air source heat pumps aren't great in the really cold weather which is when you need it most.

i've got the rayburn already...it does most of the cooking from september to april and heats the kitchen and the wood that runs it is by far the cheapest heating fuel available over here.

i've always wanted to move the dhw vessel out of the shed and into the house to reduce the 'dead leg' but this last week we've lost hot water as the cold supply going to the shed has frozen so i'm definitely moving the vessel this spring (to a room practically above the rayburn) and i'm thinking why not put a thermal store there at the same time and include the rayburn and maybe solar at a later date.
i've got a 600 litre steel tank which will serve as the store so my outlay will only be for the pumps/controls etc. and the usual copper and brass.

 

[mysteryman]

OK, I was just concerned that you do not compromise the controllability of the existing system. Take a look at the kW output of your existing boiler, and you need to be sure that your alternative is up to the job in severe weather.

Adolf may seem arrogant, but he will do what you tell him and make your system as efficient as possible.

 

[igotalake]

i see your concerns but i am keeping adolf for heating both the dhw and rads whenever its needed but it won't be heating the thermal store. the store is only there as the rayburn needs to be non-pressurised and it also makes adding solar easy.

i cannot let your last statement pass without comment..this particular Chancellor of the boiler house and Great Leader rarely does as he's told although he is effective in his own way. I think i heard him murmuring yesterday that the Patio was really a part of the Greater boilerhouse.

 

[igotalake]

Just to press you all a bit for more answers, can anyone tell me whether the separate dhw tank being heated via a coil is sensible? i have seen lots of examples where the mains cold water runs directly through a coil on the thermal store but that would only work if the store is kept up to a high temperature 24/7. my set up will be controlled to only pump through the dhw coil when there is a good temp in the store. i'll work out through experience when that would normally occur and set the oil boiler to heat the dhw at a later time of day as back up.

 

[1mowbrayfireplaces]

Look at a xcel heat bank, great with an uncontrolled heat source.

 

[mysteryman]

An uncontrolled heat source can't be as efficient as an Adolf controlled one.

You could spend a lot of money adding great complication and end up with more work AND higher costs. Or it could be brilliant. Take care!

 

[igotalake]

mowbrayfireplaces, an xcel heat bank would require me to keep it constantly hot to ensure a hot water supply so it's not suitable for my needs unfortunately, and it probably costs a fair bit..

mysteryman, i agree with you but i will be keeping adolf and all his associated equipment. the change to my system is that there will be an additional coil in the dhw tank so that the thermal store can heat it as well if it gets hot enough. take another look at the drawing at the top of the thread and you'll see what i mean. my only questions are 1)what devices are needed to make it work and be safe and 2) will the coil heat exchanger in the dhw tank which is pumped from the store be effective or not?

 

[Norcon]

the rayburn shouldn't work with unvented systems

H2 control panel will let you go direct to the unvented cylinder with the solid fuel and no wasted heat in an intermediate sludge collector.

 

[igotalake]

it looks like the unvented cylinder/motorised valve combo is one of their products or is it possible to use an existing unvented cylinder?

 

[ALEC1]

i would use a thermal store from the raeburn to pre heat mains water to the unventd controlled by the viessmann boiler. It coild have a solar coil to preheat the water in summer

Leave the boiler doing the heating, but if you wanted you could do some extra rads from the raeburn

If you try to redesign the viessmann system you will regret it, I can guarantee it...