Wood heater not drawing properly - Help

[whitewood]

We have used a Masport wood heater during the last 7 winters, in the evening. Now it is not buring well and I am reasonable sure the flue is 'blocked'. It has never been cleaned since it was installed.

Can anyone offer me some advice on how to clear the flue without filling the house with soot. Is that possible? I would like to do it today if it is a DIY job.

[Barry_White]

Hi Whitewood

I have a Masport heater and had the same problem when I came back from over the coast and it just wouldn't draw.

What I discovered was if yours is the same model as mine there is a removable draught shelf in the top of the fire box and over the years the ash builds up on top of it and gradually blocks off the flue exit and wont let it draw properly. You have to wangle it out because it can be difficult to remove.

Edit: Just as an added point you need an 8" flue brush and push it down from the roof to clean the flue.

[rsser]

Ditto, though the 'shelf' on mine sags and has to be replaced every three years or so.

Apart from that your flue may be blocked with soot or the remains of a bird's nest. Occasionally I burn one of those blocks of gunk that's supposed to convert soot but that prob. wouldn't work with a blockage. Can you lift the flue cap off and poke a broom handle down? Then vac out the shelf and firebox.

[whitewood]

Thanks Bazza and Ern. I wriggled out the baffle and cleaned the build up of ash from it. Don't know what is a lot but but it is clean now. Wasn't a difficult job. Put a stick up the flue for about 40cm and could not disturb any worth while soot. I'll leave the heater for the moment and try it again tonight to see if it works OK. Thanks once again for the prompt replies.
The diverse knowledge that is shared is wonderfull. I wish I had discovered the Forum when I was a lot younger.

John

[DJ’s Timber]

Once you get the fire going again, burn a red hot fire, as hot as you can get it for about 10-15mins using absolutely dry wood only preferably a hardwood. This should clean any soot build up in your flue, if you do this once or twice a week it will keep the flue clean for you.

[Rattrap]

Sounds very similar to the saxon heater i have here. If you haven't cleaned for 7 years then u are defenately up for a full flue clean out. You can either buy a flue brush (match the flue brush size to your flue - mine is a 6 " flue round $40) & do it yourself or hire a dude to come do for u (round $40 - $80). The removable draught shelf will have to come out as Barry mentioned. They are normally a 1/4" steel plate so they weigh a fair bit The plate sits on a cpl of ridges & can be removed by lifting out on an angle. Make sure u put it back afterwoods, it helps to stop too much heat going up the flue.
Its really easy to do & you shouldn't get much ash & soot thru your house at all, i just tie a rope with a weight onto either end of the flue brush, drop 1 weight down then pull the brush down into the heater then back up onto the roof & pull it back up. thats normally all it needs tho you might like to do it a couple of times since its been 7 years since its been cleaned.
I give my flue a full clean out at least once a year but then its a hell of a lot colder & for longer here in Tasmania so it gets much more of a work out than yours probably does.
Getting the heater really hot as DJ suggested is a great idea, the creosote that builds up in flues can set like cement & needs a good amount of heat to make it brittle so the brush can remove. It needs a good couple of hours burning hot to really get into that creosote.
Getting the heater roaring hot might be hard if the flue is really blocked so if u can't then just clean flue as best as u can then get the heater hot after.

PS; that same creosote can actually catch fire causing a flue fire which is bad so its a good idea to keep your flue reasonably clean.

[cellist]

Advice from an expert (and I don't call myself that about too many things!)...

We heat our home with two wood heaters. You said that you haven't cleaned it out since you bought it. Gulp. Danger! Danger!

I clean ours out about once a month through the winter. Here's the deal: There is a section of flue called the "active" flue. It's actually a secondary combustion chamber, and is the first metre or so above the firebox. Typically, flues are insulated (and should be!). There is an inner sleeve and an outer one, separated by about an inch or so of Rockwool. The flue will get blocked up at the point where the heat from below no longer sublimates the emissions. (turns the hot creosote gas into a solid) This occurs in ours about 600 to 1000mm above the box. It actually forms a sort of internal collar in there.

Keep in mind that diameter is everything in a flue, and as the solids build up in there, it does it from the outside-in over the entire surface, so a 1mm build-up is actually a 2mm build-up, and a 5mm build-up is actually a 10mm one. You can see that this process accelerates, and once it gets to a certain point, the lack of efficiency in the burn tends to make it get worse a lot faster. That's why I do preventative maintenance over the winter.

If you buy a brush and pole kit (made in England, they usually are), you'll be glad that you did. The initial expense is amortised over the years, and you and your fire will be best mates. Make sure that it's the right size brush! There are also device sold which are cheaper, such as a brush with two eyelets. For those, you need two people. One in the house (who will get covered in black sh*t) and one on the roof, who will be laughing at the guy inside covered in black sh*t. Two ropes of sufficient length allow the operators to pull it up and down.

One critically important tip: Remember I said something about the inner and outer metal flue components? Well....when you are pulling brushes UP, make sure that you press DOWN on the inner flue, or it will pull out of the rockwool sleeve. If it does get pulled out, you may be in for the unpleasant experience of having to dismantle your entire flue , since the sections inside don't necessarily just fit together easily once disengaged.

Wear gloves! Creosote is a carcinogen, and the flue edges may be quite sharp. Don't forget to clean the hat on the chimney, as creosote also builds up there. Hope this comprehensive post helps a few out there.

[Barry_White]

Just a couple of other points on flues.

Allowing creosote to build up in a flue can be dangerous. The danger comes when you get a flue fire and if you haven't experienced one it can be a bit terrifying. Over the years I have had several in my slow combustion stove which when lit at the start of winter burns 24/7 for the whole winter.

When I have got a bit lazy and haven't cleaned the flue at least every two months I have had flue fires. They start of quietly and then build up to a crescendo and sounds like a 747 warming up on the tarmac. The best part is when they get going the flue begins to glow cherry red.

The last one I had was three years ago three weeks after my heart operation and I had to reef a range hood out to get at the flue. Boy did that hurt my chest. My wife wanted to get the fire brigade in and I said NO because they would come in with a four inch fire hose and do more damage with the water than if I just let it burn.

I wasn't really concerned because the house is steel framed so there was nothing to burn. I just brought the garden hose in and tricked water on the flue to cool it down and just let the flue burn itself out.

Like DJ says it certainly is the best way to clean a flue but can be dangerous with a timber framed house. There have been many houses burnt down from flue or chimney fires.

With a flue brush I have stuck the handle of the flue brush up in 1 1/2 lengths of 20 mm electrical conduit held in place with a 3/16" bolt and nut and then just push that down the flue then pull it out. Hey presto a clean flue with the fire shut up inside you wont get any soot in the house and you will have one happy SWMBO.

Certainly some other good advice posted as well.