Crazy Secondaries!

begreen · Dec 19, 2013

The old EBT fed air into the boost manifold. When conditions were right, typically on a hot reload, you could get a large bloom of wood gas and extra air fed by the EBT opening. This could produce an unusually high peak temperature. Closing off the EBT on the older Summits/T6 effectively closes off the boost manifold. That has given us a more controllable top end but not a lot of change with flue temps. The new Summits have a smaller boost manifold opening and PE has moved the EBT to the secondary manifold. It is no longer temperature driven. Now it operates on draft strength, similar to a barometric damper. They have also added a lot more secondary ports. I would be curious to know what flue temps read on the new Summit with these changes. FWIW, our flue temps track pretty closely with stove top temps -100 ::F

at the peak of the burn cycle. This is with a probe thermometer on double wall pipe.

Todd · Dec 19, 2013

oldspark said:
I had it in there for one year and it did not help, I thought it did at first but as time went by I don't think it helped.
Many have reported the same flue temps as me and the same concerns.
Some posted the other day their flames did not wrap around the baffle with their 30, different placement of the holes for the secondaries?

Well if there are many others with Summits reporting high flue temps maybe it's the way it is and has to be to pass the EPA test. Maybe that EBT is there for that purpose, I know they just recently made an EBT mod so maybe they new they were wasting heat? It will be interesting to see if disabling it helps.

oldspark · Dec 19, 2013

begreen said:
FWIW, our flue temps track pretty closely with stove top temps -100 at the peak of the burn cycle. This is with a probe thermometer on double wall pipe.

I hate to ask because I am rubbing several people the wrong way lately but if your flue temps are tracking your stove top (give or take) with a probe that means your flue temps are way way, way, lower then mine.
For example.
600 stove top for you=600 probe which would be 300 surface.
600 stove top for me=at least 600 surface which would be 1200 probe
Is this correct or I am confused?

BrowningBAR · Dec 19, 2013

oldspark said:
I hate to ask because I am rubbing several people the wrong way lately but if your flue temps are tracking your stove top (give or take) with a probe that means your flue temps are way way, way, lower then mine.
For example.
600 stove top for you=600 probe which would be 300 surface.
600 stove top for me=at least 600 surface which would be 1200 probe
Is this correct or I am confused?

How tall is your chimney? Your surface temps on your pipe seem really high.

oldspark · Dec 19, 2013

Yes they are but some others have reported the same thing, flames are wrapping around the baffle only a short distance form the flue exit.
Its only 18 feet.

begreen · Dec 19, 2013

oldspark said:
I hate to ask because I am rubbing several people the wrong way lately but if your flue temps are tracking your stove top (give or take) with a probe that means your flue temps are way way, way, lower then mine.
For example.
600 stove top for you=600 probe which would be 300 surface.
600 stove top for me=at least 600 surface which would be 1200 probe
Is this correct or I am confused?

Correct, your pipe temps are high. Our stove top temp of 600F = 500-600F probe temp measured about 24" above the stove top. FWIW, I don't believe that the flue internal temps are necessarily double the surface. I have seen them measured at only 50% higher or 900F. This appears to be particularly true with straight up configurations. FYI we have an offset at the stove that does slow things down a bit. There are two mods on our stove. The style A EBT is blocked and the air control stop tab has been slightly bent to reduce the fully closed opening from about 3/8" (stock config) to 1/4".

oldspark · Dec 19, 2013

begreen said:
I don't believe that the flue internal temps are necessarily double the surface. I have seen them measured at only 50% higher or 900F. This appears to be particularly true with straight up configurations. FYI

You may be correct but I thought Pen did a bunch of testing and he's the one who came up with that figure.

begreen · Dec 19, 2013

Pen's stove IIRC has an elbow above the thermo. My theory is that makes the pipe hotter below the elbow as gases slow down, similar to how a key damper does.

oldspark · Dec 19, 2013

begreen said:
Pen's stove IIRC has an elbow above the thermo. My theory is that makes the pipe hotter below the elbow as gases slow down, similar to how a key damper does.

I lost 2 90's with the new chimney and flue temps are as high as before if not higher, I will find out if I have to buy a probe my self.

begreen · Dec 19, 2013

A regular probe is calibrated for double wall pipe. You would need a thermocouple and remote instrument like a Fluke meter or similar. I would put in a key damper and then measure surface temp above and below the damper when the damper is closed.

oldspark · Dec 19, 2013

begreen said:
A regular probe is calibrated for double wall pipe. You would need a thermocouple and remote instrument like a Fluke meter or similar. I would put in a key damper and then measure surface temp above and below the damper when the damper is closed.

Been down that road before, played with it for a year before I took it out.
Too early to tell but the first fire with the EBT taped had lower flue temps then before.
Planned on going with a RTD set up.

Todd · Dec 19, 2013

I also did lots of tests and found internal temps pretty much double the external temps on single wall pipe. I used a Teltru probe which seemed quicker to react than a Condar and the Condar was more inline with the Teltru if I pulled it out about an inch from the pipe. A thermocouple would be much more accurate but I still think your way to high.
IMHO I think your stove sucks too much air for your set up. Pipe damper or a mod to the air intake is prolly the best thing you could do or get a more controllable cat stove.

oldspark · Dec 19, 2013

Todd said:
IMHO I think your stove sucks too much air for your set up

I can fix that!

pen · Dec 19, 2013

oldspark said:
I posted wh

Don't think I need it do to the problems are when it bitterly cold and or a strong south wind, other wise the stove works great.
Stuck with the 6 inch flue, have thought about trying a NC30 (stove BB has) because it is more radiant and has lower flue temps, not sure how they compare in a side by side heat test. Common sense would tell me that if they can put out 600 degree stove top and a 300 flue they are wasting less heat.

If you weren't so far away, I'd honestly be willing to shut my 30 down and swap it out for your summit for a time just to try things out as this has always boggled me.

Assuming your temp readings are accurate, and that you tried a pipe damper for a year and thought it helped at first, but apparently it didn't, and that your chimney is under 20 foot if I remember, it sounds like you really have an ideal setup.

I'd be curious to see what a manometer would read for draft on that stack. Somehow, whether there is a black hole over Iowa or some such thing, it does sound like this drafts way better than it should.

I just can't see how a manufacturing defect could cause this, but it is curious. Also since I've never heard you complain of shorter than expected burn times, which should come in an overdraft situation,,,,,,, there is more confusion.

In all, it is perplexing, as the situation sounds perfect, but obviously, the results are not adding up. After four years, I really can't tell if there is a problem with this stove or not!

oldspark · Dec 19, 2013

pen said:
If you weren't so far away, I'd honestly be willing to shut my 30 down and swap it out for your summit for a time just to try things out as this has always boggled me.

Now that would be fun. :cool:

pen · Dec 19, 2013

oldspark said:
Now that would be fun.

I'd love to give the summit a try, but it would cost us both too much to do it with a swap.

My 30 was used 1 season when I bought it. Can't remember if I paid 400 or 450 for it now, but the point is I bought it as an experiment. The wife didn't want me to as my old fisher heated this place well. She grew up burning wood in her home, and it always smelled of smoke. She didn't want me to change the stove for fear the new one would cause our house to have a smoke smell, and with the fisher (and of course the way we operated it) that wasn't an issue.

Long story short, I kept both stoves until I proved that the 30 would work for us then sold the fisher.

Maybe you could be lucky if you look and find a cheap 30 like I did and try it out. If you buy one for around 500 and do not like it compared to the summit, I don't see you having a problem selling it again for the same money you paid.

pen

BrowningBAR · Dec 19, 2013

pen said:
Maybe you could be lucky if you look and find a cheap 30 like I did and try it out. If you buy one for around 500 and do not like it compared to the summit, I don't see you having a problem selling it again for the same money you paid.

If I can find a used BK King, I may be able to supply a cheap 30...

lillyrat · Dec 20, 2013

I haven't been on here for a while but still lurk around. I have the exact same issues as OldSpark with the same stove. My flue temps are always high if I want to get my stove top to 550. 550 is really as high as I can get the stove without getting the pipe over 600 (external). I have just decided to live with the high temps, got tired of being consumed by it.

oldspark · Dec 20, 2013

lillyrat said:
I haven't been on here for a while but still lurk around. I have the exact same issues as OldSpark with the same stove. My flue temps are always high if I want to get my stove top to 550. 550 is really as high as I can get the stove without getting the pipe over 600 (external). I have just decided to live with the high temps, got tired of being consumed by it.

There you are, I knew some one had the same flue temps as me but could not remember who it was.
I been living with it for 3 years trying to get an answer and no one had much of an idea.
I have cooler flue temps and more heat from the Nashua (in shop now) so I know something is not right.
Getting close (real close I hope) to retirement and I want this stove fixed, I have the money right now to buy a different stove now (really don't want to put in a 8 inch chimney) so if I have to buy a different stove I will.

BurnIt13 · Dec 20, 2013

I experience this more often than I would like with the 30 as well, but only with hardwood....and I've started a few threads on it. It always seems to happen when you least expect it as well. Usually when I wake up early I get the fire started and shut the primary air down as early as possible to stay ahead of a too hot stove. Things appear to be dialed in so I go and take a shower. Then I come downstairs to find nuclear secondaries and an 850F stove top. The firebox is full of secondaries even though the primary air is shut down 100%. No choice but to pucker up and turn the fan on high and wait.

I find that this happens when conditions are ripe for excessive draft and I have a full load of wood in there. I have 23' of stove/chimney pipe and that may be the issue. When the stove gets hot and running and the air is shut down all the way....it draws all the air it wants through the secondaries and off it goes.

A magnet over the half of the secondary air inlet might help.

I'm not experiencing this phenominon with the pine I'm burning. In fact it is a much more controllable stove. It just comes down to BTU's. A full load of oak has a bazillion BTU's compared to the same load of pine. The oak would be shut down all the way to keep the stove at 650+ with high flue temps. The pine can be dampered down for whatever temp I desire.

oldspark · Dec 20, 2013

BurnIt13 said:
I'm not experiencing this phenominon with the pine I'm burning. In fact it is a much more controllable stove

Thank you for that information Burnlt, and it brings up a valid point, some who give advice on here might be burning a different type of wood, from BG's posts I think he only burns hard wood a small part of the time.

Dairyman · Dec 20, 2013

I've had decent luck with a flue damper. I find it drops temps 150-200° measured on a probe at 36". But I hate that I need it with only 15' of flue.

mfetcho · Dec 20, 2013

begreen said:
Correct, your pipe temps are high. Our stove top temp of 600F = 500-600F probe temp measured about 24" above the stove top. FWIW, I don't believe that the flue internal temps are necessarily double the surface. I have seen them measured at only 50% higher or 900F. This appears to be particularly true with straight up configurations. FYI we have an offset at the stove that does slow things down a bit. There are two mods on our stove. The style A EBT is blocked and the air control stop tab has been slightly bent to reduce the fully closed opening from about 3/8" (stock config) to 1/4".

Begreen - Where are you measuring your stove top temp?

begreen · Dec 20, 2013

To the front and left of the flue collar under the back slats of the trivet so that I can read the thermo with the trivet closed.

begreen · Dec 20, 2013

oldspark said:
Thank you for that information Burnlt, and it brings up a valid point, some who give advice on here might be burning a different type of wood, from BG's posts I think he only burns hard wood a small part of the time.

It's not the wood. Doug fir burns hot and I have cherry in the stove right now. Locust is the hottest wood I burn. Put the damper back in and try again.

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