New wood boiler outside in a new shed

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Devon
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Having removed the Rayburn last Summer due to on going building works I didn't envisage still having no means of making hot water or heating the rads. Using fan heaters and immersion heaters is worryingly expensive so desperate to get something sorted quick.
As a stop-gap I am thinking of building a timber shed against the house, picking up a pair of 22mm tails left for future connection and installing a wood burning boiler, approx. 25kw o/p. The empty heating system is fully pumped and vented. I can pick up a log boiler cheaper than an oil one and as I have about 4 years worth of logs and wood in the barn I may as well use it. The boiler needs to go outside as it will be out of the way and not hinder the next stage of building work. It will have a place inside on the next extension.
Would I need to use a fire proof lining inside the shed covering timber? I reckon there will be about 15-18 gap between boiler and shed wall.
the lean to type roof will have slate covering, I'll use the correct metal slate tile to take the flu through the roof but I cannot find anywhere on the www a required height for the flu. Also I can only find flu pieces in 1mt sections, are these things strong if I had to have a free standing structure consisting of 3 or 4 sections? I have my doubts. There are no nearby doors or windows where the shed will be sited but there is a cooker hood outlet with back draught shutters.
I have installed gas and oil boilers in the past and done complete central heating systems in my own houses but that was over 15 years ago and I am not too sure of the legal side of this job now, things have changed. I have looked on various sites but nothing states in black and white that I am not allowed to install an external wood boiler on my own property. It only seems to mention internal log burners.
I was going to get a contractor in but they are all more interested in supplying the stuff themselves at vastly inflated cost and some local suppliers only want to advise on stuff they want to sell you. This thing only has to last until April/ May when the weather warms up so I don't want to throw too much money at it.
Advice greatly appreciated. Thanks.

PS - what I forgot to add is, having read up on some websites I realised that as the log burner has no instant safety shut down device if there is a power cut then the pump must stay running so I will have to run the pump via a small UPS. This will cost about £120 and give about 4 hours run time.
 
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If the pump beaks down then the UPS won't be much use.
Its usual practise to create a gravity circuit to dissipate excess heat.

Picking up f&r at floor level will present a few problems for a boiler stove.
 
MMmmm, good point, missed that one out about the pump, cos oddly enough that is my 2nd pump in 3 years.

Did wonder about the gravity bit, the Rayburn was gravity to the cylinder when I first moved in but pumped for the heating. 28mm pipe not accessible to outside. Have a bad feeling about this now. Some one mentioned about a 300lt accumulator sitting beside the boiler in the shed but again I didn't want to throw too much cash at this as it will be ripped out later in the year and relocated. Would an accumulator solve this problem do you think?
 
The stove would need its own feed and expansion cistern.

Then a plate heat exchanger could be used to make the transfer without an accumulator.
Being outside in a shed and boiling is not a major problem at the end of the day.

Fitted a 40kw unit for the brother and it boils over occasionally if he over fires it.
Garage becomes a steam room. LoL.

It's a different issue when it becomes part of the house however.
Then you have to think about pipes rising vertically from the stove.
 
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Whether it is pumped or not the primaries need to be 28 not 22... A 15mm bypass round the pump should offer enough flow for the boiler to cool in the event of a power outage...

Metal F&E tank and metal valve float for SF.. Minimum height for your flue is 4.5 metres from the highest air vent in the boiler but it must clear the building that it is next to... Schiedel make twinwall in 2 meter lengths , it must be supported every 3 metres and the boiler must not have to support the weight of the flue, so a lower support is needed...

A 25kW boiler is going to keep you busy filling it up, enjoy living in the shed... 15-18 what? millimetres or metres gap between the boiler and combustibles...The distance will be set by the manufacturer, ignore at your peril...

By the way, you do realise that with a lot of cheap boilers roughly half of the output will go to heating, the other half will be heating your shed..Toasty!
 
Norcon, if your brothers boiler boils, then you phucked up the design!...Doh!
 
Norcon, if your brothers boiler boils, then you phucked up the design!...Doh!

Its a bit oversized thats all.
Plus several of his rads were filled with air last time I was over. And it didn't help when he opened up the lock shields on most of the rads thinking that would boost the output to each rad.

It also doesn't help when his missus covers just about every rad in the house with wet clothes and garments to dry them and they seem to park there permanetly. :rolleyes:
I explained the issues he will have with that.
He was convinced the phe was undersized.
:rolleyes:
Every now and then I fit a new rad for him about twice the size of the previous one. He knows best.
Its been running about 5 years now with little issue other than the odd boil over. He even runs it in the summer to generate hw.
f&e is plastic as is float.
 

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