Direct or indirect?

[WendyH]

Thanks Reg Man. What's your reasoning for suggesting indirect for the solid fuel? Yes, that circuit will be gravity fed and no, I wouldn't dream of using plastic for the expansion/header tank. This installation isn't in the UK, so I can't phone my local HETAS-registered engineer, but I will probably be sourcing the hot water cylinder here because of price and availability. How do I tell whether a cylinder is suitable for a gravity circuit?

 

[SimonG]

Forget my last post, not in the uk, crack on.

 

[WendyH]

SimonG - see my original post, viz " The solar will be indirect as it makes most sense in the context."

 

[SimonG]

WendyH - make contact with professionals in the country of install they'll be able to answer your questions accurately with the rules and regs pertaining to that country. Might even have been a good idea to mention this in your original post. Although with being on here you intend to biy?

 

[WendyH]

What's biy? Bodge it yourself? Yes, we intend to bodge it ourselves, LOL. (And BTW, just because we're not plumbers doesn't mean we're not engineers. Like I said, we're not looking for input on the system, but would just appreciate a bit of advice from those for whom plumbing is more of a speciality.)

 

[Nostrum]

Steel heat exchanger = indirect.

 

[SimonG]

Engineers, say no more.


Honestly though just watch what you're doing, it's not quite as easy as some people make out.

Have a look at the dunsley site (I know it's a neutraliser but have some good diagrams and also the heating innovations web site about the h2 panel. Both overkill but give good diagrams of the layouts.

 

[Pipes Plumbing]

Indirect through a 1" coil for the stove heat-ex (which can be a bad idea for flue gas temps, as has already been said), to stop the the steel exchanger contaminating the water.
You'll want a gravity circuit in min 28mm tube and a heat leak rad @20% of the stove output to sync excess heat. you can valve this off with an N.O 2 port set to spring open when the cylinder is satisfied...

Be careful with this, although Solid fuel and thermosyphons are relatively simple they do need careful planning and installation.

 

[AWheating]

in the uk you would want an indirect grade 1 cylinder, with a coil suitable for gravity. most modern cylinders have coils that are designed with small bore high output, gravity requires a different design. grade 1 because its made better, stronger.

you would also need hot water temp controls,(cylinder stat and zone valve) on the gravity circuit and heat leak rad/s.

you will get corrosion from the heat exchanger.

id fit a large thermal store cylinder. your solar will work in the winter to, you wont need much from the solid fuel.

 

[WendyH]

Thanks Pipes Plumbing and AWheating. Solar will contribute in autumn and spring but not for around 10 weeks in winter as the sun disappears behind a mountain ridge to the south. We're aware we won't need a lot of input from the solid fuel, hence designing the heat exchanger into the cook stove rather than space heating, because it will only be run for short periods.