which hot water cylinder for gas / wood burner dual system

[rob123#]

Hi, I am installing a new heating system in my 1930 semi. I am putting in a worcester bosch greenstar 30cdi regular boiler (mains gas) and a hunter 80b boiler stove. Q. can anyone advise which hot water cylinder i am best to use. I was looking to install a dual coil unvented combination cylinder as i am moving the existing cylinder from the bathroom into the loft and due to the lack of height dont have the room for a header tank. I can see dual coil systems but the second coil only seems to relate to solar.  Any help / advise would be greatly appreciated. Many Thanks Rob.

[guydewdney]

you basically can't have an unvented cylinder with a wood burner as the wood burner is not a 'controlled heat source'. You will need a 'thermal store' if you want mains pressure hot water.

You can use a 'solar' coil for the wood burner or gas - its nothing special - its just lower down the tank, and bigger than normal.

i am not a plumber.....

[rob123#]

hi, thanks for your advise,

apologies, i meant vented. if i go down the route of a (vented) combination cylinder with twin coils does this then negate the need to purchase a Dunsley link up or equivalent ?

thanks

Rob

[Nickthegreek]

I have an unvented cylinder running a WBS and electric boiler, the hot water circuit is on a pump as well as a separate central heating pump. There is a valve controlled by a flue thermostat to regulate between the two. Negates the need for a Dunsley and means you can have mains pressure hot water. 

My heating engineer came up with this instead of a thermal store as it heats the rads a lot quicker!

[rob123#]

thanks for your help, am i right in thinking that you have mains pressure feed to the cylinder then with a (direct) heat source being supplied to the cylinder by either the WBS or the boiler. I take it you cant run both at the same time? How does the flue stat work? is it a case of when the WBS is lit the stat turns off the conventional boiler. Does your domestic hot water have priority and once the set temp has been reached the WBS then switches to the rads?

thanks again

Rob

[Nickthegreek]

Thats correct, you cant run both at the same time but it will switch between the 2 as the flue stat on the WBS reaches a high enough temperature it switches the valve to the stove position. The hot water and rads have same priority unless I switch the rads off in which case it heats the water until full and dumps excessheat into the rads.

If you want to let me have your email address I can mail you my piping diagram. Tried to attach to this but the file is too big!