Two open vents on same system?

[Kenny.5]

Is there any reason why you can't have two open vents on the same system?

Under normal conditions the pumped circuit from the stove would feed the cylinder directly and in a power cut the gravity circuit could continue to operate via a coil, unaffected by the pump circuit, least that was the idea.
Any advice or comments appreciated.

P.S excuse the drawing!

 

[Ermintrude]

This looks a wee bit of a mess. That heat leak looks like it's in the wrong place tho!

It might not be upon closer inspection ! c

 

[Kenny.5]

As said, please excuse the rubbish drawing!
The heat leak should be lower down on the flow from the stove.

I'm open to any suggestions for a better way to have both gravity and pumped circuits feeding the cylinder. Not sure if an injection Tee would work?

I was trying to avoid having a cylinder full of DHW that we might not use so the storage route seemed like the better option and then we can use it for what ever we need at the time.

 

[Worcester]

You need a thermal store simples

:: AKVA

For example hydraulics (yep I know it has a solar coil, just be open minded, its an EXAMPLE : :: AKVA SOLAR

 

[Nostrum]

Your pump should on the return and then take the vent from the highest point ie the coil, but I'm struggling to understand what your purpose for such a complicated set up is?!

 

[Nostrum]

You could lose the gravity coil unless you are expecting frequent power cuts. Take a gravity feed to heat leaks through a 28mm normally open MV which is powered closed by the pump call signal.

That way the heat leak will only circulate in a power failure and you can put them anywhere you like. You'll need to notify building control about this installation as its a controlled service.

 

[Nostrum]

Sorry, to answer your question. There is no reason you can't have 2 open vents, it's just not required!

 

[Kenny.5]

I was just trying to devise a way of making best use of the stove, both in normal circumstances and during power cuts, we're out in the sticks and get several through the winter.

If I could be sure that the gravity circuit would be able to transfer all of the available output from the stove to the cylinder/store then I would forget the pumped circuit, but i'm not sure it would?
Or as you say, just have a heat leak on the gravity circuit to deal with the power cuts, but as mentioned, the idea was to try and cover all eventualities and have some means of heating and hot water during a power cut. If however it's going to prove overly complicated we may need to go back to the drawing board.

 

[SimonG]

Gravity only on the primaries, correctly sized and located heat leak in conjunction with a normally open and normally closed valve.

what kw to water is the stove?

 

[Kenny.5]

The stove was already installed when we moved in but due to how it had been piped, tight radius 90deg elbows directly off the back of the boiler, it would not circulate by gravity in the event of a power cut. It was 28mm all the way to the neutraliser but it didn't work very well.

There were Several times last winter when I had to put welding gloves on and shovel the fuel into and a big metal bucket! Then close all the vents down to stop it kettling during a power cut.

On wood, its supposed to put out about 8.5-9kw to water. The new heat leak radiator we've got is rated at 2.4kw with a 50'c delta