Esse wood fired kitchen range -a problem

[Deadcalm]

We are the proud owners of (apart from our Jotul F600) an Esse WN kitchen range wood burner. We lit up this unit for the first time two weeks ago, and generally it has been great - the kitchen has been warm, and it cooks fabulously.



However, occasionally we are experiencing what can only be described as a muffled explosion from the firebox, the unit rattles, the hotplate appears to lift, and smoke and soot belches out from around the edges of the hotplate. This is alarming, and frightens the cats, the wife, and me! I am guessing that unburnt gases in the firebox are igniting suddenly, and the increase of pressure cannot be handled by the flue - but it is only a guess. It has been suggested that this may be due to downdraughts in the flue, although when it happens it is irrespective of windspeed and direction - indeed it has been dead calm on one occasion.

The Esse is installed in a single storey kitchen, where there wasn't initially a chimney. We have built one of earthenware segments designed for the purpose, and it terminates at about ridge level (about 20 feet from ground level). The flue is single-walled Poujoulat (French flue specialist) stainless steel flexible tube, which passes into a 45 degree "T" piece with a rodding cover. The flue itself is insulated between the stainless-steel tube, and the walls of the earthenware segments with rockwool Flacon loose fill. The flue then passes through a 12" stone wall, and a 45 degree bend (with access cover) returns it to the vertical, and thence into the cooker via the oven damper. All internal flue parts are black gloss enamelled, and single wall.

The flue draws well, the fire burns hot, and is fairly controllable via air controls and an oven flue damper. Our wood is a mixture which I trim to 40 cm logs, seasoned for about 3 years, and dry - the moisture content is quite low. We use the same wood on the Jotul without problems (but 50 cm lengths).

I have removed, cleaned and examined the hotplate unit, which is held on the stove by screws passing into brass "H" blocks, supported by a fork either side on the cooker body. One of these "H" blocks is badly deformed (see photos) compared with its partner. The damage suggests considerable stress, and is in keeping with high momentary pressure from below - this could support my theory of an explosion. I can't honestly see any other way this component could suffer such catastrophic damage.








Has anyone any ideas supporting or refuting my feelings about this?

I have contacted Esse, who are sending new "H" blocks, but who are reluctant to enter into correspondence concerning the possible cause of this phenomenon, and the possible safety implications involved. I could really do with a second opinion, and will give further information if required.

Esse are a British company, and the foundry has been making this type of range since 1854, and compare favourably with the likes of AGA or Rayburn. However, their customer service has been reportedly poor, an experience with which I concur.

Thanks

Chris

 

[Slow1]

Sounds like "back puffing" to me - which is exactly what you described. Wood gases and air mixed and hot suddenly igniting in a puff or explosion.

Solution? Well - improve draft and/or increase airflow to the firebox to insure that you always have a flame in there. You may also want to decrease the amount of hot fuel that is out-gassing at one time. Your dry wood is good but will put out a lot of wood gas if put onto hot coals and needs to burn that off - if you choke it off from oxygen and allow it to collect without burning you will build up the hot gas and eventually enough 02 will mix in and once a flame is there (or a spark) it will ignite and poof!

I don't know this stove at all so I don't know how to control the air or verify a flame in the box. I have had experience with backpuffing though so I know what it is like. I have read up on it and heard some pretty amazing descriptions of just how powerful it can get as well. If you keep a flame alive in there at all times your chances of a puff decrease dramatically although that may not be foolproof depending on stove design.

I would start out with observing how the fire is burning before and during these events. Pay attention to how you are feeding the stove and what stage of the burn you are in - did you just feed new wood on? How how is the firebox? Do you have a large bed of coals? etc... Share these observations and others here may be able to help more too.

 

[savageactor7]

That's a pretty stove. A couple of things deadcalm I can't see your flue damper am guessing a stove with that heritage has one... never, ever close a working stove damper more than 45 degrees. This will assure a constant draft and help eliminate back puffing. OK...you can close the damper if you're locking down a chimney fire.

For cooking you don't want a smoldering type fire so way smaller splits are called for ...like a broom stick handle, even branches work well. also soft woods like willow work better. Save your harder woods for heating the kitchen, then again with an established fire you can cook anytime you want even with hardwood. For the occasional cook fire use seasoned soft woods aka junk wood, and make it easier on yourself.

 

[Deadcalm]

Thanks, both, for your comments. It seems I have to better manage my fire. It's a shame that the manufacturer isn't more forthcoming with information like this!

Savageactor7, the flue damper is the small lever to the right of the "smokebox" in the lower picture. Its primary purpose is to divert flue gases around the ovens, rather than straight up the chimney. However, the top oven gets pretty hot with it open anyway, so we tend not to use it in that way. It is either open or closed - there's no way to park it at 45 degrees, it's either or.

Esse recommend that at night, the firebox is banked up with fuel, the damper closed, and the plate at the front of the smokebox screwed open to kill the flue pull. This seems to work, as there are always sufficient embers left to reignite splits in the morning. Maybe I should make sure that I have a "flaming" fire before I shut it up for the night.

All in all, it's a brilliant cooker, it's just this niggling "puffing" problem, plus the fact that the door catches are not that good. Very efficient, too, as it uses very little fuel (far less than the F600!)

Chris

 

[savageactor7]

Cris you don't have a pipe extending off the top of the stove with a handle illustrated by whats painted white above that only moves 90 degrees? forgive the crude attempt at 'paint'.

 

[Deadcalm]

That photo is probably a bit misleading, as it was taken just after the stove had arrived and been placed in situ. We hadn't even built the chimney then!
This photo is with the flue in situ:

These photos show the smoke box at the base of the flue - the damper is on the right:

Hope that makes it clearer - the damper is in the closed position (for oven circulation), to open it we push it towards the wall. it's very light, and you can't have it half way. All or nothing!

Chris

 

[savageactor7]

Cris if you can't get satisfaction from the companies toll free help# or find a solution on line among other stove owners consider this as a last resort...

...install a traditional damper like what's pictured here. Leave the stove damper fully open and use this inline damper to allow more of a draft to take place. Leave it open like pictured until you have a working fire then try closing it 50 or so degrees or so. Maybe with more experience you can bring it down to 45 if it rumbles like before you closed it too much. Keep in mind smoke always has to rise and get out of the way of fire or your going to have these minor puffs or smoke pouring out of the stove.


EDIT whoops rather than dicking that beautiful stove up with an inline damper I bet you take apart your damper and remove a spring or modify it in such a way that it can be more opened when closed...if that makes any sense.

 

[Deadcalm]

Thanks, Savageactor7, I'll have a look and see what (if anything) can be done

Chris

 

[ashpanannie]

Interesting thread. I am considering a wood cook stove someday. I wonder if this phenomenon is why my granny always left one plate slightly ajar on top of her old stove? I remembered that suddenly while reading this.

 

[newflue]

deadcalm,

Your stove is exactly the same as what we have just installed. We are having problems with our installer regarding the flue which should look exactly the same as yours. The installers say they don't have this style on flue in Australia. Australia's flue standards would be similar to Europe but here they mainly just use straight stainless steel in three layers. It comes in sections which are fitted together. Single flue is allowed but anything but straight up is ugly spot welded pipe. So whereas your kitchen flue section is attractive ours will look industrial. I can't help thinking that I need to source the same parts, that you have, myself.

Can you tell me exactly what brand of flue components and if possible the exact parts used in your photos including the oval ring on the wall? Do you have a photo of the angled T piece behind the wall? Does it have a soot trap?

After the T piece I can use the standard local product up to the sky.

thanks,

David Allen
Melbourne, Aus.

 

[begreen]

Awesome stove. By the problems described it sounds like the air supply to the fire was shut down too early, or the oven bypass was engaged too soon, or the wood used was a bit damp and made it smoke alot and cranky to start. You want to be sure you have a good strong fire before engaging the flue damper. Do not engage the oven bypass after a fresh load of wood. Let it burn off the fresh wood gases first. Otherwise, if the wood smolders, the passages can store a lot of unburnt wood gas. When that ignites, kawhumph!

I would not add a flue damper quite yet. Live with is a little more. A flue damper could actually complicated things and make the chance of a puffback even greater.

 

[Fake coal burner]

Go to this ESSE cite fill out form ask for David the ttechnician. He fixed me up with the problem I was having on my gas coal effect heating stove.

(broken link removed to http://www.esse.com/stoves/question.html)

 

[benjamin]

I'm one of many that nearly had a heart attack when I first saw that pink behind your stove. Pink board is a little different product over here.
Then you'd have some real huffing to complain about!

Nice stove, by the way.

 

[snowtime]

Old thread but as a current user of 2 cook stoves I feel I should correct one thing. I am sure most know this so I will make it short.
Savageactor has got it wrong do not modify your stove damper. This damper is for cooking and is not a chimney damper. If you modified it so it was open partially then your oven would not cook properly.
A chimney damper is a whole different animal mainly for controlling flue draft. I know this is obvious but I thought it ought to be on this thread.

 

[Deadcalm]

Thanks for the interest in this, I see the thread has become resurrected!

David Allen, I've E mailed you...

For all those who took an interest, we have been in contact with Esse throughout. It took a while, but we established several problems with the stove - the oven door handles needed a modification, as did the firebox door handle - the catch of which had been fitted so off centre, that Esse had to make a special offset latch (the door kept popping open). We also extended our flue by about 1.5 metres, and the result is a vast improvement, draught-wise and the stove is a pleasure to use. It heats the kitchen nicely, and cooks really well. We never had problems with our wood, it was always well-seasoned and from the same source as that for our Jotul F600. (The only problem being that we have to lop 10cm off the ends of all the logs that we use in the Esse).


Here's a photo of the unit with the surroundings tidied up a bit...

Chris

 

[savageactor7]

So you have it mastered now, that good to hear...it's a real beauty.