Advice please: logs or chips

[nick channer]

central boiler from america is what we're installing to heat 2 4 bedroom houses and 2 2/3 bed houses.. the guy selling them local to us already has 2 installed himself.. oneat his old farm house and another at his brickworks where he has it installed to dry bricks in his drying shed... it also heats his offices and runs 24 hours a day 6 days a week... he burns around 2.5 tons of sweet chestnut cord cut to 900mm lengths a week.. and lot less at his house... he'd be more than willing to show you round and explain the incentives the government are offering...

[openspaceman]

I deliver logs to a number of people with large log boilers , they all seem to use a lot more timber than they first thought , and still a lot of hard work

I also supply woodchip which seems to be a lot more efficient , just feed it through the chipper and done

 

The difference is largely down to capital cost.

 

The woodchip is fed into the boiler concurrent with the air supply so easier to get the combustion rigt. Very hard to get chips to a G30 W30 spec, even if the supplier tells you it is. Much easier to stack and dry cordwood.

[openspaceman]

Most of the auger problems are from slithers of chip that cross or bridge the auger not letting the chips into the auger , a bit of a problem when you have a few tonnes of chip sat on top

Another problem has been keeping a large chip store full all the time ie topping up every day keeping all that weight on the drive systems .With some motor failures

Both are easy fixes just let the chip store run low every so often also reducing the chip at the bottom from starting to rot

 

You've hit a couple of nails on the head there, Sweep auger systems under the hopper are a pain it the backside although they are cheap and suitable for grain or pellets.. They always fail when the hopper is full. Points of failure are interesting, the original models I dealt with used the auger to provide power to the gearbox for the sweep auger in the middle. After the auger jams a few times it gets out of true and over then next few weeks gradually fatigue fractures. Welding it up just makes it more rigid and it fails even quicker.

 

The reasons I have seen for the auger failing are also interesting and, to me, counter intuitive. The obvious one is slivers bridging the flights and then being carried forward on top of the auger to be impacted into a mass at the auger exit. G30 specifies no slivers over 100mm and presence of these loses you any warranty claim.

 

The one that confused me most was some dry woodchip from a joinery firm which was dusty. With high mc chip dust is not a problem as it sticks to the bigger chips but in this instance as the silo emptied and was regularly topped up the dust gradually worked its way to the bottom and settled on the bottom of the auger trough where it compacted. As this layer built up the auger ran on it but was bowed upward until it jammed on the top side of the trough and brought the system to a halt with initially a motor thermal trip and later as they fooled about with the current overload sensor, snapping the drive chain.

[openspaceman]

How about looking into geothermal/ground source heat pump to raise the water temperature, thereby giving your existing oil fired system less work to do? With geothermal, you can generally get 4kW of heat out for every 1kW of electrical energy going in. You could retain log burners in each part of the accommodation for the 'ambience', but get the heat for central heating and hot water from the ground source heat pump, enabling you to ditch the oil altogether, and not completely clear your 25 acres while knackering yourself. There are also grants available for this.

 

single stage ground source heat pumps seem to have a COP of about 3 when delta T is no more than 10C, great for spring and autumn. I do think they complement a woodfired system but would still use the boiler for DHW as the heat pump is far less efficient at heating water to 50C.

[slasherscot]

in a perfect world and i had the available buildings for storage, i would buy in 100 tons of chipwood 2m....specifying nothing bigger than 10 inch at butt, store inside, the idea would be to have enough wood in front of u for 4 years, the biggest expense is splitting timber so this would do anyway with it, assuming u use a load a year , u buy in a load every year to refill the stock.......giving 3 years in door to dry before u get to use it and use an outdoor burner that u can chuck 2m lengths into

[Pedroski]

single stage ground source heat pumps seem to have a COP of about 3 when delta T is no more than 10C, great for spring and autumn. I do think they complement a woodfired system but would still use the boiler for DHW as the heat pump is far less efficient at heating water to 50C.

That boiler for DHW wouldn't have to do much work is inlet water is already fairly high.

[Mycoman]

I've looked into a few other forms of renewables but, in my case, the property's listing puts the kibosh on - even means we can't double glaze. Thank you so far to all responses.

[Spruce]

Sell the 25 acres as standing timber, stick with the oil and put your feet up.

[Marko]

A real account of installing a log boiler to power Central Heating and DHW at a B&B can be found on Sustainable heating using wood fuel at Coed Cae B&B, North Wales

 

As others have said, the realisation about the amount of wood needed to be seasoning always seems to be a surprise.

 

Hard work but it is away of converting your own time into cash (or at least a cash saving).