Ten things *this* installer will tell you about biomass boilers (Part 2)

To recap: I was Googling ‘biomass boilers’, which is what I do to relax on my days off, when I came across a blog called greenwisebusiness.co.uk that appears pretty high on the first page. The subject of the article is “10 things your installer won’t tell you before you purchase a biomass boiler.” The author, Louise Bateman, had a very bad experience with her pellet boiler and the installer who was supposed to be looking after it.

#4 on the list says how carrying out the ‘weekly checks and clean-outs’ does not prevent breakdowns.

Weekly? Well, I suppose everybody should have a hobby, but boiler maintenance is nowhere near as fulfilling as say Competitive Dog Grooming, or Yarn Bombing, I find. That’s why I like my ETA boilers.

"Come on people, let's get on with this -- I've got a pile of extreme ironing waiting for me..."

“Come on people, let’s get on with this — I’ve got a pile of extreme ironing waiting for me…”

If you look at the maintenance schedule for a Pe-k pellet boiler (see below), ETA recommend that you empty the ash box every 2,000kg.

On a 35kw boiler, if you worked on your Tier 1 RHI allowance of 1,314 hours at full load (1,314 x 35 = 45,990 kilowatt hours per year) and a pellet calorific value of 4.8 kilowatt hours per kg (taken from here), that’s around 9.6 tonnes of pellet a year, so you would have to empty the ash box roughly five times a year. On a 90kw boiler Tier 1 (1,314 x 90 = 118,260 kilowatt hours per year) it would be 24,637 tonnes a year, so seven and a bit times per year you would have to empty the ash box, glance at the pressure gauge, check the seals. I usually suggest people get into the habit of checking it once a month and have a scrape around the inside of the burning chamber while they’re at it.

Not weekly.

Maintenance schedule for ETA pellet boiler

Maintenance schedule for ETA pellet boiler

If you’re particularly averse to doing it, there’s also a bargain bucket sized ash box available as an optional extra with double the standard capacity, so you can be very lazy.

Doing this won’t prevent breakdowns any more than will having your car washed prevent it from breaking down, but then it shouldn’t break down at all, and if it does then there’s a free five year parts warranty backing you up with an ETA boiler.

Let’s face it, you don’t get a free five year warranty with anything else I can think of.

ETA boilers are reliable, too — I can state that categorically because all the faults from the dozens of boilers we have fitted go through me. Apart from a few commissioning faults and a batch of dodgy sensors we had backalong, I can only remember two screens going down, one factory fitted motor working loose, two motors losing phases, two transformer board faults and one igniter element breaking down. All of which were fixed under warranty within 24 hours with no cost to the customer.

Everything else has been down to rocks in the fuel and other similar things beyond our control.

#5 When the boiler breaks down it won’t be fixed within a few hours because there’s no engineer in the area

There aren’t many places in the UK that can’t be reached within six hours. Where there’s a will there’s a way.

On the odd occasions we have had a boiler break down we’ve either had the part in stock at our workshop or it’s arrived on a courier from Austria the following day.


#6 When the boiler breaks down the fuel will be blamed rather than the boiler

Oh, don’t get me started here — I could write a book about the rubbish some people have put through their wood chip boilers.

The bottom line is: Burn wood pellets if you want a quiet life

Even if you’ve got a wood chip boiler — burn pellets. Just make sure you have flue gas recirculation enabled and the firebed sensor set right first.

The least problematic wood chip boilers we take care of are the ones at Savage Cat Farm near Gillingham. The farm buys-in bent wood from the nearby Longleat Estate and seasons it outdoors for a year. It’s then chipped by a local contractor and stored in an open barn.

Two of the four boilers don’t have flue gas recirculation fitted and the oldest of these two has done over six thousand full load hours. It has never broken down, but it’s had some trouble with rubble — see this old post.

Rocks in the Wood ChipWhat’s that funny noise…?

All sorts of crap gets left in telehandler buckets or scooped-up with the chip. A plastic chair leg ended-up getting stuck in the auger on one of the other boilers there. If you have this much trouble with chip you’ve made yourself, just imagine the trouble we get with chip brought in from outside suppliers.

We’ve had to go out to farms where things have gone through such as a lump hammer head, gate hinge spike, roof hook, reinforcing bars, handfuls of nails, chunks of aluminium and glass that melts into the grates, a pair of ten inch mole grips went through one and punched through the side of the auger casing.

mole grips meet ETA boiler

These don’t burn well

Then there’s the wet chip — the worst of which was over sixty percent water content, sold as twenty-five percent chip. this deposits tar all over the place, which jams the cleaning gear, and the moisture rusts the boiler.

Recently one of our customers has been buying and burning this diseased larch that is doing the rounds. He bought it in good faith, but it turns out to be rubbish. It has been ‘standing dead wood’ for a while, so it’s been bone dry and has lost most of its volatiles, but then it’s become saturated with water and rotten. Now it’s like damp compost with next to no calorific value. His boilers send me emails daily, saying the ash box is being emptied (lots of ash) and too much oxygen in the flue gas (where the fire is being starved of fuel), so I can’t imagine he will be getting any more of that.

Foot long spike in the wood chip

One of those nails only farmers and Roman Centurions on crucifixion duty seem to have access to — found in the wood chip

Other people have had loads of freshly felled timber that has been chipped and mixed with very dry material, like pallet wood, in the hope that the moisture will equalise or average out in the burn. It doesn’t work. Dry wood doesn’t take up moisture very easily, so the green wood stays wet and won’t burn until the water has been boiled-off, taking your calorific value out through the flue in the form of steam and depositing tar all over the place, meanwhile the dry wood burns hot and fast. This is confusing for the boiler, which is carefully monitoring how the wood is burning and trying to judge how much air to give the fire.


I fired-up one boiler earlier in the year and checked the quality of the fuel during the setup only to find leaves, bark, and a chunk of road sign — these were hedge trimmings sold as 25% moisture premium quality virgin wood chip. It’ll burn, but there’s little calorific value to be found in bark and leaves, and even less in road signs. It makes for lots of ash, too.

nails in the wood chip

My old man would re-use these

It really is a mug’s game buying chipped wood. If you insist on burning chipped wood the only way to go is to buy the round wood, keep it a year and get somebody in to chip it for you.

If you’re not going to do that, burn pellets!


#7 Continued here