VC downdraft encore

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heffergm

Member
Nov 24, 2009
162
South Shore, MA
So it occured to me when I got my encore nc that measuring stovetop temp on the griddle when in downdraft mode isn't really indicative of what's going on. After all, most of the combustion is going on in the rear burn chamber at that point. So, I run two thermometers. One on the griddle and one on the rear collar (mine is set of rear exit).

When things are really humming with the bypass closed, the griddle temp will plumet to around 400 or 450, but the rear collar temp will be up around 650 plus depending on the load... And this with the air closed all the way down.

It seems to me all the reports about glowing stove backs were directly related to this... If you're only measuring griddle temp with the bypass closed, you're not really getting the right story. If you're only looking at griddle temp and see the temps plumet, you're going to leave the air wide open. At which point things go thermonuclear in the rear burn chamber.

Clearly, VC hasn't been very good about directing people how to operate this stove. I think Ive got a pretty good handle on it now with my dual thermometer method.

I'm curious if the few of us still using this stove have come to any kind of similar realizations.
 
Yap, I have one on the flue collar as well. At the beginning of the burn cycle the griddle temp will drop to (same as yours) 450*. The flue thermo will read 600* & my new probe thermo 18" up (DW) will also read 600*. Couple of hrs later I will see the griddle temp slowly go up to 600-650* & the flue thermo will drop to 400* but the probe will only drop to 500*.

Reading the other thread about the accuracy of these thermometers.....I think they should all be tossed in the trash. Use common sense i.e. no smoke out the chimney & no glowing parts + toasty room ...you're burning just fine!
 
That's exactly the same behavior I see. I check my thermos in the oven so I know they're at least in the right ballpark ;)
 
So, is the magnetic therm. on the flue collar just above the heat shield? Do you use this as an indication of good combustion? If so, what temp. indicates failure?

In the Leyden, I've noticed that with too much air going through the combuster I still get smoke, like it cools it down too much. If I back the air to almost nothing, she'll combust. I just wish I didn't have to go outside and look for smoke to know that.
 
I don't worry about it to that extent. Essentially I use the thermos for two thing: making sure nothin is too hot and telling me when to close the bypass.

What I basically do is this:

burn the first load with the damper open. When there's a nice coal bed, reload. Let it burn until griddle hits 500F. Close bypass. It should roar like a bastard at this point. Leave the air open for a bit until temps at the collar start climbing, then close the air in maybe 3 stages.

Two things clue me in to things not working right: backpuffing, which will happen if I haven't let a good draft establish, or te collar temp drops like a stone and Ive got no visible flame. In both cases I open the damper back up, let the griddle temp hit 500, and repeat. I usually don't have an issue the first time around, but if I did, second times the charm.
 
I've only seen the red glow on two occasions; when the outside temps were -10 and the coal bed was thick, resulting in a jet of a draft. There is no doubt that when that Everburn goes into overdrive there is the risk of overheating the flue collar and the back of the stove (behind the heat shield) and you have no way of knowing based on the stovetop placement of the thermo.

Question: Is the griddle a different metal than the cast iron of the stove body? Would that make a difference in the temp reading? I place my thermo (Kel Kem Imperial) on the cast iron next to the griddle.
 
Of I recall correctly VC recommends measuring off the griddle. I believe the griddle reading is about 50F or so higher than off the cast iron directly.
 
heffergm said:
Clearly, VC hasn't been very good about directing people how to operate this stove.

I agree 100%. I've learned more about operating the Encore via this forum than from the VC manual, website or the local dealer (who knows next to nothing).

I'm gonna break down and order an IR thermo sometime soon. :-S
 
heffergm said:
Of I recall correctly VC recommends measuring off the griddle. I believe the griddle reading is about 50F or so higher than off the cast iron directly.

so I checked today and the griddle actually measures a solid 100F higher than reading off the iron behind it. That's a pretty bog gap, and judging by how the stove likes to burn, it seems to make more sense to measure off the cast iron directly.
 
If you put the thermo. dead center on the cast, north of the griddle & you have the everburn rocking that thermo will read higher than the griddle one for couple of hrs or so. (couple of yrs back I did that test)
 
I've been putting the thermo. dead center in front of the flue collar. Just back of the griddle, which yes, does tend to run about 100deg. higher than the iron.
When I start combusting, that temp. will tend to be around 600 and will stay there for a good while after liftoff. I can only assume that means I'm at least combusting something in this downdraft, or else it would plummet, I'm guessing.

I've not been able to get good combustion at any lesser temp. Could be the wood.
 
Gotta put my 2 cents in. For years, my VC reps have advised to put a the thermometer at either of the top rear corners. This spot, as well as others, will give the operator an overall stove temp as opposed to the thin griddle temp. Be cautious of your placement. Stack temp, flue collar temp and griddle temp are most often 200 degrees higher when bypass is open and then read "normal" when closed. Of course, you may find different readings because each installlation is different as is wood, draft and moisture content. Very few will get the same results. Please, be "Vigilant."
 
Well, as you say, the temp will read lower in the corners. So of anything we're being more conservative measuring off the griddle or directly behind it in front of the collar.
 
lakside said:
Gotta put my 2 cents in. For years, my VC reps have advised to put a the thermometer at either of the top rear corners. This spot, as well as others, will give the operator an overall stove temp as opposed to the thin griddle temp. Be cautious of your placement. Stack temp, flue collar temp and griddle temp are most often 200 degrees higher when bypass is open and then read "normal" when closed. Of course, you may find different readings because each installlation is different as is wood, draft and moisture content. Very few will get the same results. Please, be "Vigilant."

I'm a little confused by this. Are you saying that when the bypass is closed all parts of the stove top tend to "equal out"?
The leyden manual says to put the therm. over the front door. That temp. is a good 150deg less than back of the griddle (with bypass open at least). I figure if I put it in the hot spot, I'll never over-fire.
 
I guess my next question is what temp do we actually want to be measuring or what is the most important component to watch for overfiring-the box or the Everburn chamber? Or should we be rigging a thermo with a probe into the flue to measure flue gas temp? Sooo complicated :-S

That being asked; I am checking out the accuracy of my thermo by comparing it to my oven temp while cooking a roast beef. At oven temp 475 the thermo read 600. At oven temp 350 the thermo is reading 425. So I have a 75 to 125 discrepancy. That IR thermo is sounding better and better everyday.
 
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