Parkray multifuel into a...hot tub!

[mallangong1]

Hi,

I would welcome your advice on a quirky project I am considering! - I'm thinking about building a wood fired hot tub using leftovers. I have an old IBC tank and an old Parkray Cumbria multifuel stove/backboiler that I am thinking of repurposing (as well as a stash of of logs). I have read there can be serious explosion risks with running backboilers without a suitable vent, so my plan is for the simplest of open systems, gravity circulation/convection "powered" with no pump.

I assume a pump would lead to the water being heated far quicker but this would seem to be overly complex and increase the risk of the system potentially being sealed and the whole thing going bang.

My plan would be to clad the IBC tank in left over fence cladding, place the Parkray close (but not too close!) and connect copper pipe into the IBC tank at a low point (for the colder water intlet) and at a higher point for the higher temperature water outlet (as a result of convection).

Are there any obvious problems you can see?
The Parkray I have has four pipes outlet/inlet. Can I safely use just two, and if so does it make any difference which?

All a bit bonkers I know but I have a couple of weeks forced leave to fill.

 

[Terrywookfit]

It won't be pretty !!!

This has got to be a fookin wind up !!

 

[mallangong1]

Afraid not! Got the idea from quite a few examples on the internet. Any criticism/thoughts wellcome!

 

[Terrywookfit]

Afraid not! Got the idea from quite a few examples on the internet. Any criticism/thoughts wellcome!

Direct heating of the water will cause corrosion and rust in the water.... You will look like Trump!!

Flue height will be a problem to produce sufficient draught.

Do a sketch of your proposed set up !

 

[polesapart]

why not?

I'd suggest 28mm pipework with at least a meter of (continuous) rise with no more elbows than necessary, possibly a safety blowoff valve on the flow next to the boiler, definately a valve to drain. Possibly a cage to keep the unwary back away from the hot incomer.

Wouldn't pass the health and safety brigade but who cares? I've enjoyed similar lash-ups at festivals and lived to tell the tale.

 

[mallangong1]

Thanks all and sorry for the delay...the project got put on the back burner for a couple of weeks (pun intended!). Below are pictures of the actual IBC tank and the Parkray along with a sketch of my plan. As suggested I'll keep the bends in the pipes to a minimum and try to maximise the height difference.

Can any one advise on the Parkray piping? I'm assuming originally two were for hot water and the other two for central heating.

Am I correct in assuming I will therefore need to connect all four pipes (as shown in my sketch)?
Also, am I correct in assuming that the cold inflow pipes are the bottom pipes either side on the Parkray and the hot outflow are on the top on each side?

Thanks again.

 

[Terrywookfit]

Sketch would work ok.

 

[polesapart]

I'd be inclined to site the tank a bit higher than the stove if possible, to turn the stove so that the flows and returns are symmetrical and to extend the copper stubs on the stove a meter or so before thinking of transitioning to plastic!

 

[mallangong1]

Thanks, it will be difficult to make it much higher (it will need steps to climb in as it is). I had thought about when would be safe to transition to plastic. I assume there is some benefit in less heat loss from plastic but I can't imagine it will be much over such a short distance, therefore I was thinking of keeping it all copper - especially as I will have to buy a length anyway and may not even need any more.

More symmetrical makes a lot more sense. Perhaps something like this.

 

[Terrywookfit]

In order to vent, the flows need to rise continually.... not drop back down.
Less horizontal and bends the better.

 

[endecotp]

I assume there is some benefit in less heat loss from plastic

It's not massively different from copper.

If I were you'd I'd think about how to insulate the tank as well as the pipes. Just wrapping some loft roll around it, for example.
And improvise a warm lid to put on while you wait for it to get up to temperature.