Fire bricks

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Fire bricks

Postby jimbo » Sun May 26, 2013 9:29 pm

Our house uses an Ultimate Elite 30 wood heater and despite the many negative reviews, seems to do a good job. It has a huge firebox that we rarely fill right up so I decided to add some fire bricks that were given to me as it doesn't use any in the hope of running it more efficiently as most of the more expensive units use them. To my surprise the bricks have had the opposite effect and I'm struggling to get the house up to temp.

What are people's thoughts? I have always thought that less insulating material is better as you want to transfer as much heat to the room as possible before it escapes up the chimney!

Cheers

James
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Re: Fire bricks

Postby Cherokee Solar » Mon May 27, 2013 8:05 pm

jimbo wrote:To my surprise the bricks have had the opposite effect and I'm struggling to get the house up to temp.


I don't know about why that would be as it doesn't make sense. Someone here will probably know though.

Yeah it's a big heater. I broke the glass on my heater a few years back by jamming in that last extra log, so be careful with it as it is massively expensive to replace (yours is curved as well). About $1,000/m2! :shock:

Most of the heat here from the wood box is felt at the front of the heater, not at the sides.

A couple of thoughts though about wood heaters not burning very hot come to mind:

- You've gotta leave some ash in the bottom of the fire box as the fire burns hotter. Someone at the Pivot wood heater dealer explained this to me years ago and I've long since forgotten the why of it, but it is a noticeable effect. By all means clean out the ash and spread it around an orchard, but remember to always leave some. I only ever remove half and then spread the rest back over the floor of the wood box.

- Unseasoned timber (ie. less than 12 months since it was cut and stacked to air dry) doesn't burn as efficiently as seasoned wood. Generally, firewood is best if seasoned for at least 24 months. The difference is noticeable. Burning unseasoned firewood can also lead to your flue getting blocked which is a major fire hazard (the stuff in the flue can ignite in the flue and potentially burn the house down!) and also further reduces combustion efficiency. A good hot burn every week or so will keep it mostly clear. If the fire is going hard with the inlets full open for a few hours and you see lots of smoke coming out of the chimney, then your timber isn't seasoned (or something is restricting the flow of air to and/or in the heater). Most Australian hardwoods can't be easily burnt green, those that could be have been over selected by the early settlers.

- Wet timber uses up energy in the combustion process so although the wood is burning, you just won't get the heat out of it.

- It may possibly be that the air vents are blocked and this will reduce the oxygen supply and reduce the combustion efficiency.

- The heater here has an ash tray at the bottom of the heater below the oven which must be kept clean as the warm air flows around the back and sides of the oven and wet back. There are also side ducts which need to be kept clean too. It may be possible that there is some sort of circulation flow for the hot air around the heater and this may be blocked? Keeping this stuff clean makes a huge difference here.

- Chimney brushes are cheap and easy to use. Just try not to breathe the toxic black brew in.

Wood heaters are great. Mine is currently: heating the house plus a few dogs; heating the hot water; cooking some toasted muesli; and continuing the production of apple cider and mead. Tidy work for a few chunks of well seasoned messmate (eucalytpus obliqua). :D

If you've got lots of unseasoned firewood, the trick is to start the fire with the seasoned stuff and then once you have a bed of hot coals, start adding in the unseasoned stuff, but keep the oxygen levels high through the inlet vent when burning the wet and/or unseasoned fire wood.

Chris
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Re: Fire bricks

Postby jimbo » Mon May 27, 2013 8:45 pm

I don't burn any unseasoned wood in my heater and have put a brush through the chimney last week as well as changing the baffle so it should be roaring.

The way i see it is My heater uses a fan to blow air around the fire box so if there is insulation from the bricks it is transmitted to the walls slower and has more chance to go up the flue. The only thing stoping heat going up the flue is the baffle as the modern EPA heaters don't seem to use a flue choke.
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Re: Fire bricks

Postby Cherokee Solar » Tue May 28, 2013 9:14 am

jimbo wrote:I don't burn any unseasoned wood in my heater and have put a brush through the chimney last week as well as changing the baffle so it should be roaring.


Yeah, that's a fair call. Sometimes here for all sorts of reasons some firewood seasons quicker than others in the same wood pile. It usually has to do with them being stored unsplit so they are usually larger with less surface area (from very big trees though, which is not a problem for most people).

jimbo wrote:My heater uses a fan to blow air around the fire box


I don't have any experience with these types of fans in a wood heater. I would have thought they'd blow air over some sort of heat exchanger rather than directly into the combustion chamber? Dunno, it's beyond me.

Take the bricks out and see what happens?

The other thing maybe is that the seals on the door maybe broken or crushed beyond use? This can allow too much air to get into the combustion chamber. They're pretty easy to replace as they just sit in a channel on the door. They're easily damaged by having burning material in the door when it is closed, so it's worthwhile checking out too.
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Re: Fire bricks

Postby FarmerJohn » Tue May 28, 2013 8:48 pm

Cherokee Solar wrote: I would have thought they'd blow air over some sort of heat exchanger rather than directly into the combustion chamber? Dunno, it's beyond me.


I think that is what he means. Mine is the same kind (Norseman), it's just a blower to increase convection around the outsides, but its ducted, the idea is to get the heat out the box as fast as poss.

I never understood the firebricks, I thought they were there to help the sides last longer and increase the stored heat to smooth out heat delivery between refueling.

What is a baffle? Is it that plate at the top that forces the exhaust gasses to take a detour before they go up the flue? Mine is massive - I would think it needs a clean, but actual replacement? I hope not it would no doubt cost a bomb. I never even tried to get mine out.

I need a pro to come and clean it and explain more about it to me I think.
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Re: Fire bricks

Postby jimbo » Tue May 28, 2013 9:03 pm

Yes the baffle is the steel between the flu and the firebox. Mine was all warped and burnt through in some sections so I went to Ultimate heaters and they told me I was lucky to get 4 years out if it and many due after 2!!! They also wanted $250 for a replacement. BBQ Galore has aftermarket version (slightly thicker steel) for $150.

My old man had a Kent wood heater. It had the normal air control but instead of a baffle had a slide valve in the flu. When ever you started the heater or needed to open the door the slide would be pulled open and during normal operation it was closed and only left a small gap for flu gas. It could be choked all the way down to killthe fire if needed. I think this design is far superior to the modern EPA heaters and very little heat is lost up the flu.
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Re: Fire bricks

Postby Smurf1976 » Tue May 28, 2013 9:50 pm

Just a few things I've generally learned through using solid fuel heaters over the years.... :D

Baffle - yes they do wear out and not having one (or having one with a hole in it) will kill the heater's efficiency. Options for replacement are either buy a new one as such, get an after market one, or just get a thick piece of steel cut to the right size. It's just a steel plate, doesn't have to be precise down to the mm.

Door seals - it's just a fibreglass rope and pretty easy to replace. Professionals tend to glue the new one in place with PVA glue (woodworking glue - get it from any hardware store). You can get the rope at Barbeques Galore.

Some heaters (notably the older Saxon heaters) have an air tube inside the heater in front of the baffle which provides air for combustion of gases not burnt in the main fire itself. This tube will burn through eventually and if left in that condition eventually you'll end up literally melting the heater itself. It's a professional job to replace unless you're reasonably competent at DIY (first step being to remove the outer cover of the heater to get the old tube out).

Firewood - believe it or not, it will season just fine sitting out in the open getting rained on if you leave it there until it goes grey. Alternatively you could put it under cover, but it's not essential. Mine is stored in the open.

If you burn unseasoned ("green") wood then there are lots of problems. Firstly it won't actually burn well since the volatile components won't ignite. Secondly you'll end up with all these volatiles deposited as a black mess (which is highly flammable once it dries) on the inside of the flue. Thirdly you'll be making unnecessary smoke. Fourth is the fact that you'll be sending an awful lot of steam up the flue, and it will actually carry a lot of the heat up there with it (due to the latent heat of evaporation). In short, don't burn green wood. Since most commercially available wood is only partly seasoned at best, you need to buy well before you use it - I get mine in Spring and leave it outside over Summer.

Loading the wood - some heaters, including the Saxon I have, work a lot better if you put the wood "end on" into the fire box. That is, with the ends of the logs facing the door rather than placing them across. The airflow works better this way, hence the wood burns more effectively. Experiment with your own heater to see what works best.

How much wood to put in - another "it depends" situation. Personally, I've found that I can get good performance and minimal smoke by loading it fully up (literally full) before it's lit. Most days I don't need to add any more wood, and it burns without smoke when turned down since after the initial hot burn it's basically full of charcoal. Works for me but you'll need to experiment to find what works best in your heater.

Coal - don't even think of using this in an ordinary domestic wood heater without a grate. Just don't do it. Been there, done that and won't be doing again. It works brilliant in a pot belly stove, but it's a disaster in a slow combustion heater. Don't put yourself through the misery of burning coal in a slow combustion heater not designed for it. :cry:

Manufactured compressed wood blocks - nothing wrong with them as such (apart from the cost) but be aware that they expand significantly once they start burning. Don't, whatever you do, cram the heater full of the things :!: I don't use them normally, but a couple of years ago they were an end of season clearance item being sold for $1 per bag in a supermarket. I bought the entire stock they had.
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Re: Fire bricks

Postby Cherokee Solar » Wed May 29, 2013 8:21 am

Smurf1976 wrote:Firewood - believe it or not, it will season just fine sitting out in the open getting rained on if you leave it there until it goes grey. Alternatively you could put it under cover, but it's not essential. Mine is stored in the open.


Too true. Rain has very little effect on the seasoning of firewood. I usually leave piles out in the rain on either old corrugated gal sheets (or tarps) for at least 2 years. The piles are made up of ready to go pieces so there is little further splitting to do. The firewood does get stacked for a few weeks to a few months in a covered storage area under the car port so that they aren't too wet to burn properly.

You can stack firewood directly on the ground, but here I find that the pieces in contact with the ground start turning into soil through the actions of the local fungi population regardless of the weather conditions.

When you have really large discs of timber from big trees, when they season, they split themselves as the sugars leave the timber so it can save a lot of work splitting by letting nature do it for you.
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Re: Fire bricks

Postby Gusnella » Sun Jul 14, 2013 11:31 am

Hello, The bride & I have moved to the country & now have a combustion heater, It is a lucifier with an electric fan and we can not find any information about this unit online, Any help would be appreciated. I found that the baffle in the unit has been modified somewhat, Can i get away with just putting a bigger piece of flat steel in its place without any ribbing on top of the baffle???

We have been trailing different wood,Blue Gum, Red Gum & Mallee tree, We found Mallee burns better than both Gum but suspect its because the mallee is seasoned. What do you think folks?
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Re: Fire bricks

Postby Smurf1976 » Sun Jul 14, 2013 5:08 pm

The baffle (in most heaters at least) just needs to be a steel plate. The "ribs" on the top are just to add strength.

Any solid steel plate will do as long as it's thick enough to be self supporting when it's hot (noting that the heat greatly reduces the strength of steel). As a general rule, I'd recommend using steel that is at least 8mm thick - too thin and it will either buckle or burn through rather quickly.

Any engineering workshop that cuts steel plate will be able to make one that fits, you don't need to get the manufacturer's original part unless you want to. Assuming you're in a city or a large town, there will be a workshop (business) around that can supply you with a steel plate cut to the right size. Either measure it yourself, or take the existing one to them.
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