VT 0028, Engage Cat, Fire Dies

[mpkeelee]

I have a VT Castings Defiant Encore model 0028. I bought it from a guy who rebuilt the stove 2 yrs ago and rarely used it so its in pretty good shape. It burns great in non-cat mode. I can turn the air way down and have a small hot fire for hours and hours.

When i load the stove and get it nice and hot i engage the cat. The fire just dies out like no air is getting in even though i have the air turned all the way up. I just bought a brand new cat and my chimney was cleaned on monday. The stove vents up into 8 inch pipe, 90 degree turn into my chimney which is lined with clay. Anybody have any experience with this issue?

 

[begreen]

By the description it sounds like something is blocking the flue gases. I'm wondering if ash is plugging up the system or if the rebuild was done incorrectly?

 

[mpkeelee]

I ordered an ash vacuum to attempt to suck any ash out that may be blocking the air flow.

The re-build could be the cause, but I really hope its not. I do not know how to disassemble and re-assemble this stove yet. Right now we have it burning nicely in bypass nice but I would really like to burn with the cat.

If anybody else has any ideas please post. I will post again after the vacuum arrives. Hopefully ill be able to clear out any ash blockage.

 

[BrowningBAR]

First, are you absolutely positive the wood is dry and the air controls are open?

If so, inspect the cat. You can access it from the back panel of the stove.

If the cat is in good shape and not clogged, then you will need to remove the two piece fireback inside the firebox. This is a bit of a pain in the ass.

 

[BrowningBAR]

Another thing, when are you closing the damper to engage the cat? What is the temperature on the griddle when you do this?

 

[BrowningBAR]

I ordered an ash vacuum to attempt to suck any ash out that may be blocking the air flow.

The vacuum is not needed. Use the back access panel to inspect the cat.

The re-build could be the cause, but I really hope its not. I do not know how to disassemble and re-assemble this stove yet. Right now we have it burning nicely in bypass nice but I would really like to burn with the cat.

The rebuild isn't very complicated and there isn't any magic going on behind the firebox. It is just the cat assembly and the cat, with some thin sheet metal looking pieces that support the assembly.

The rebuild is more heavy lifting and scraping out old gaskets and cement than it is "rebuilding" anything.

 

[webby3650]

Is the fire going out? or, are the flames just going out? Does the stove temp. continue to rise? Cat stoves often have no visible flames, but the cat is pumping out some serious heat.

 

[BrowningBAR]

Is the fire going out? or, are the flames just going out? Does the stove temp. continue to rise? Cat stoves often have no visible flames, but the cat is pumping out some serious heat.

Not the case with VC Cat stoves. You will have some flame. When the cat is working the flame on a VC cat stove will become slow and thick looking. Almost like it is liquid.

 

[slindo]

THe fact that you haven't just routinely checked and cleaned the cat before posting here suggests you may not have been doing it twice yearly as VC calls for. If this is the case, it is highly likely the cat is clogged, possibly so bad that you will have to replace it (though you can sometime clean a badly clogged one by soaking it in vinegar, see the Condar website for details).

You got to be very careful removing the cat not to damage the soft refractory box that holds the cat - the cat can warp after years of use and be hard to remove since there is no way to grip it. If you don't have the manual, get a copy (I think you can download one at the VC site) and follow the directions. The two-butter-knife method works well. Oh, and the insulating panel behind the door is very easy to break.

Have you had any episodes of overfiring? If so be prepared for the possbility that you will find no cat at all behind the panel, just some twisted pieces of metal from the metal frame of the cat and the metal sheet that supports it - the cat will have disintegrated and the pieces fallen in to the bottom of the refractory box, often damaging it badly enough that a full rebuild will be necessary.

 

[BrowningBAR]

the cat will have disintegrated and the pieces fallen in to the bottom of the refractory box, often damaging it badly enough that a full rebuild will be necessary.

How would a damaged cat and assembly require a full rebuild?

 

[mellow]

Sounds like a draft issue, explain more on your chimney setup.

 

[BrowningBAR]

Sounds like a draft issue, explain more on your chimney setup.

I thought that as well. The chimney appears to be unlined.

But, we need to know more about how the stove is burning before he/she engages the cat.

 

[Ashful]

webby3650: not the case with Jotul, either. Why would you not see flames when the cat is engaged? I would think any cat stove would continue to show flames as long as the primary air control was open sufficiently. The comments you have seen from cat stove owners about no visible flame only pertain to when you're burning slow and low for max burn times.

mpkeelee: an experienced cat burner should be pulling the cat to inspect and clean once or twice per year. Someone who is new to it, or having trouble with it, should be inspecting their cat much more frequently. You seem to be having one of two problems: (1) cat is clogged, or (2) fresh air supply to cat is somehow blocked. You can see if the cat is clogged by simply pulling the cat, as BAR suggests. A VC owner will have to tell you how to check the fresh air supply, although it sounds like that's why BAR was suggesting possibly pulling the two-piece fireback.

slindo: how would a failing cat damage the stove or refractory? I'm not familiar with the Defiant, but I cannot see how this could possibly happen on my Jotuls.

mellow: draft was also the first thing that crossed my mind. However, it seems he can burn very low in bypass mode, and I'd expect even that to be a problem, if his draft were so poor that he can't burn in cat mode at wide open throttle.

 

[BrowningBAR]

slindo: how would a failing cat damage the stove or refractory? I'm not familiar with the Defiant, but I cannot see how this could possibly happen on my Jotuls.

The cat exanding and/or warping could cause the refractory to break as the cat is seated inside the assembly. Also, excessive heat can break down the assembly more quickly.

 

[Ashful]

Seems like a poor design. In my older Jotul, a badly warped / overfired cat (previous owner) had indeed compressed / slightly damaged the refractory cat chamber. But this did not make it unusable at all. A squirrel did that for me, so it got replaced anyway.

It seemed like slindo was stating that pieces of the crumbling cat would fall into the chamber, thus damaging the chamber. That does not seem likely to me.

 

[firewoodjunky]

I wonder what "nice and hot" means? I know that on my VC if I engage the cat below a 475 stove top she will often stall out.

 

[mpkeelee]

My wood is ok. It burns fine in bypass mode.
My cat is brand new. I just got it a couple days ago.
I let the stove burn for almost an hour and let it heat up to 550-600 slowly. Then I engage the cat.

My fire actually goes out the second I switch to the cat, and yes the air is wide open. The griddle temp begins to drop immediately and doesn't rise again. I don't see any flames or embers.

Chimney is lined. A lot of the answers u asked for are in my original post.

 

[firewoodjunky]

My next guess is that it's full of crud behind the fireback? That could be stopping or reducing the flow of smoke up and through the cat...maybe.

I would defer to BrowningBar on this one though, he has a ton of experience with various VC's.

 

[BrowningBAR]

My wood is ok. It burns fine in bypass mode.

There is a difference from okay to dry. It is far easier burning with the bypass open.

I let the stove burn for almost an hour and let it heat up to 550-600 slowly. Then I engage the cat.

You have wet wood. It should not take that long to get the stove up to that temp and you should easily be able to achieve hotter temps from the griddle.

My fire actually goes out the second I switch to the cat, and yes the air is wide open. The griddle temp begins to drop immediately and doesn't rise again. I don't see any flames or embers.

Chimney is lined. A lot of the answers u asked for are in my original post.

I'm going with wet wood.

 

[rideau]

Fortunately, that is easy to check. Just burn some ends of dimensional lumber or other known dry wood. See if the same thing happens.

 

[Ashful]

A lot of the answers u asked for are in my original post.

I'm out. Sorry for trying to help. Good luck.

 

[BrowningBAR]

my chimney which is lined with clay.

A clay lined chimney is not a 6" or 8" liner. This is an unlined chimney. Unlined chimneys have also been know to have poor drafts and increase the possibility of back puffing.

 

[begreen]

Let's consider the draft question. We'll need to know more about the flue system. What is the size of the clay liner in the chimney? How tall is the chimney above the thimble entry into the chimney? Is there an unsealed cleanout door or other potential air leak in the chimney system like another takeoff that is unsealed?

 

[slindo]

Depends on what you mean by full rebuild. But time and heat cycles eventually can cause the cat and the flimsy "heat exchanger" that partially supports it to flex and distort, and this flexing eventually tears up the delicate refractory box. Overfiring will vastly accelerate the process. Those two items alone will cost about $400 to replace, to which one must add the cost of a new $150 cat and a few other odds and ends. At that point it becomes more cost effective to install the whole $650 firebox kit and replace all the "wearing" parts, since the damper assembly and firebox have also probably warped too. Which I would consider to be a full rebuild, or pretty close to it.

Oh, as to comparisons with Jotul, Jotuls are mostly cast iron, which does not distort and flex the way sheet metal does. And the Jotul engineers seem to know better than support a delicate cat on a .060 sheet of stainless steel on one side, and a box of refractory material so flimsy that you can crumble it between your fingers on the other.

How would a damaged cat and assembly require a full rebuild?

 

[webby3650]

webby3650: not the case with Jotul, either. Why would you not see flames when the cat is engaged? I would think any cat stove would continue to show flames as long as the primary air control was open sufficiently. The comments you have seen from cat stove owners about no visible flame only pertain to when you're burning slow and low for max burn times.

mpkeelee: an experienced cat burner should be pulling the cat to inspect and clean once or twice per year. Someone who is new to it, or having trouble with it, should be inspecting their cat much more frequently. You seem to be having one of two problems: (1) cat is clogged, or (2) fresh air supply to cat is somehow blocked. You can see if the cat is clogged by simply pulling the cat, as BAR suggests. A VC owner will have to tell you how to check the fresh air supply, although it sounds like that's why BAR was suggesting possibly pulling the two-piece fireback.

slindo: how would a failing cat damage the stove or refractory? I'm not familiar with the Defiant, but I cannot see how this could possibly happen on my Jotuls.

mellow: draft was also the first thing that crossed my mind. However, it seems he can burn very low in bypass mode, and I'd expect even that to be a problem, if his draft were so poor that he can't burn in cat mode at wide open throttle.

If you notice I said that "Cat stoves often have no visible flames." I am trying to help the OP with his issue based on experience from working on many different knds of stoves, not just a Jotul.