# Jotul GF 400 Surface Temperature



## Malachi (Dec 4, 2018)

I have a newly installed Jotul GF 400 LP Gas Stove.  I would like to know if the stove is getting to the correct heat level.  Once it is up to normal operating temperature, what should the approximate surface temperature be on top?   I would be testing this with an Infrared Laser Thermometer.  Thanks!


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## wooduser (Dec 4, 2018)

Gas stoves don't have their BTU input measure by temperature,  typically.  With natural gas fired stoves,  input can be measured by clocking the gas meter. and calculating the amount of gas used by the appliance.

Does the stove use natural gas?


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## Malachi (Dec 4, 2018)

The stove is propane.  It had the conversion kit installed when it was delivered.  I did a few temperature reads on it tonight at different locations.  After about an hour of run time on the lowest setting (16,000 btu's), these were the following temps:

top plate = 240
stove front (upper right where JOTUL is stamped into the cast iron) = 190
flue pipe (at the base near restrictor plate) = 260
flue pipe (at top of elbow right before horizontal termination through wall - two foot rise) = 205

The stove seems to be putting out a good amount of heat.  I just wanted to make sure these numbers were within a normal range and that I'm not losing to much heat up the flue.   The exhaust vent restrictor is set to "D" (factory setting).  I was contemplating trying it at "C" since the flue was a little hot compared to the stove. 

On my wood stove, the flue is always cooler than the stove, whereas with this propane stove, they're more equal.  That doesn't seem correct.


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## wooduser (Dec 5, 2018)

To determine the efficiency of your stove,  you'd need to have a combustion analysis of the flue gasses performed.  Things that would be measured might be the stack temperature, oxygen level, carbon monoxide level and draft.   Many of these would require specialized instruments,  and the ability to analyze and make judgements about the data collected.

Your stove dealer might have someone who could do that for you,  probably for a price,  or refer you out to someone who could do that.  You could shop around among gas appliance repair services for someone to do that for you.

I don't know anything you can do with your temperature data. Nothing you report is obviously out of line. The main defects you might observe that would indicate a problem would be #1  ---black soot  #2  floating flames  ----  flames burning above the logs,  and perhaps being snuffed out altogether due to impaired flow of combustion air through the stove.#3  Noticeably loud hissing from the main burners,  suggesting the primary air shutters need to be adjusted. #4  burners not lighting promptly and smoothly ---- causing a WHUMP noise when they finally light. 

But frankly,  these problems would be unusual on a new stove.


I find this an interesting question and I wonder how Daksy would reply to it...


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## Malachi (Dec 5, 2018)

wooduser said:


> To determine the efficiency of your stove,  you'd need to have a combustion analysis of the flue gasses performed.  Things that would be measured might be the stack temperature, oxygen level, carbon monoxide level and draft.   Many of these would require specialized instruments,  and the ability to analyze and make judgements about the data collected.
> 
> Your stove dealer might have someone who could do that for you,  probably for a price,  or refer you out to someone who could do that.  You could shop around among gas appliance repair services for someone to do that for you.
> 
> ...


Actually, a friend of mine who is an HVAC Tech, was checking out this stove, out of interest, and happened to have his work van and tools.  The analyzer you are speaking of, had a long metal probe.   He did a quick check of the flue gases at termination.   The readings I recall him saying were flue temperature and carbon monoxide level.   The stove was on high and the exhaust gases coming out of the flue were near 700 degrees.  The carbon monoxide was near 40 ppm.


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## DAKSY (Dec 5, 2018)

***I find this an interesting question and I wonder how Daksy would reply to it...***

Actually, I've never been asked this question on the stove BODY temps.
The GLASS will EASILY get to 450 Deg. F., but the body?


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## wooduser (Dec 5, 2018)

Malachi said:


> Actually, a friend of mine who is an HVAC Tech, was checking out this stove, out of interest, and happened to have his work van and tools.  The analyzer you are speaking of, had a long metal probe.   He did a quick check of the flue gases at termination.   The readings I recall him saying were flue temperature and carbon monoxide level.   The stove was on high and the exhaust gases coming out of the flue were near 700 degrees.  The carbon monoxide was near 40 ppm.



The CO level sounds fine,  the stack temperature sounds unusually high.  I would expect something more like 400m degrees.  The high stack temperature suggests that the draft is too high,  causing the combustion gasses to travel through the stove too fast to give up much of their heat,  so it goes up the chimney.

If he's got a reading of the oxygen level in the combustion gasses,  we'd be able to tell better if that was the case.  If oxygen levels were high,  that would document excessive combustion air.  Low to moderate levels of oxygen would document that excess combustion air was moderate,  and most was being used up burning the gas.  You need some excess air to insure that the gas is burned properly,  but too much is too much and inefficient.

Also,  it would be useful to know if he got a reading on the draft at the stack.  A cause of high excess air might be a stack that has too much draft and is therefore sucking too much air through the stove and up the chimney.  That could explain the high stack temperature.

Perhaps he just had a carbon monoxide detector and not a combustion analyzer that measures a lot of things including draft and oxygen levels.  That's what I carried in my days as a gas fireplace/gas furnace/gas appliance repairman.  I would have been able to measure the carbon monoxide level and stack temperature,  but not other parts of a combustion  analysis. 

You might ask your friend if he a measurement on the draft and the oxygen levels in the flue gasses,  and if he didn't perhaps he'd can borrow the instruments needed to take those measurements and do that for you.  He'd probably be VERY impressed with your asking those questions!

And if he's not used to doing those kind of measurements,  it might well be a valuable experience to do that for you if he can get the instruments to do so.   

But your friend is the Xpert with his equipment,  what did he have to say about the reads he got?

And what do you mean when you say he took the reads "at termination."  That could mean several different things.


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## wooduser (Dec 5, 2018)

DAKSY said:


> ***I find this an interesting question and I wonder how Daksy would reply to it...***
> 
> Actually, I've never been asked this question on the stove BODY temps.
> The GLASS will EASILY get to 450 Deg. F., but the body?




I never measured stove body temperature with gas stoves or fireplaces either.  But the reads given on the stove body don't seem like they'd be unusual.   However the 700 degree stack temperature sounds quite high.

Off hand,  that suggests to me too high draft that's sucking the hot combustion gasses out of the stove too fast.  That might produce a moderate temperature on the stove itself and high flue gas temperatures.

But without a measurement of the draft and oxygen level in the flue gasses,  you can't really tell,  or at least I can't tell.  .


As I think about this more,  excessive draft and and too much excess air ought to cool down those flue gas temperatures by diluting them,  not raise them to 700 degrees. 


At this point I don't really know what would cause the low carbon monoxide levels,  high stack temperature and moderate stovetop temperature.  It's a puzzlement to me!

Those oxygen and draft measurements might help to clear up the mystery.  If your friend has an actual combustion analyzer or can borrow one,  it would probably provide quite a few additional measurements as well.  If your friend can get one of those and run it for you,  having all those additional measurements would be useful.


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## wooduser (Dec 5, 2018)

Here is the installation manual for this stove::

https://www.manualslib.com/products/J-Tul-Gf-400-Dv-Sebago-3482248.html


It's a direct vent stove,  so that answers my earlier question as to where the reads were taken.  They were taken at the termination vent outdoors,  which is fine.  With some equipment,  reads might have been taken by drilling through the vent pipe,  but that wasn't necessary here.


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## Malachi (Dec 5, 2018)

wooduser said:


> Here is the installation manual for this stove::
> 
> https://www.manualslib.com/products/J-Tul-Gf-400-Dv-Sebago-3482248.html
> 
> ...



WoodUser,

Thanks for taking time to think and post some possible solutions.   I will check with my buddy to see if what he used was a combustion analyzer.  I'll see if he can stop by again soon and check those other levels, too.

In the meantime, I'm looking at the manual.   To be clear, my stove has a horizontal termination (*not snorkel*) and is a corner installation as illustrated on page 14, figures 16 and 18.   I have a 24" straight rise to a 90 degree elbow, then an 18" horizontal run to the end of the termination cap.   Based on what you posted above, I'm trying to determine if the intake and exhaust restrictors are set correctly.   Currently, the intake restrictor is set to fully open as seen on page 9 figure 6 and the exhaust restrictor is set to "D" as seen on page 9 figure 7.   Based on the Vent Termination Zones for Propane Graph on page 11, figure 11, I'm wondering if the intake restrictor needs to be closed 25% to 50% and the exhaust restrictor set to "C."

If my stove was natural gas instead of propane, according to the Vent Termination Zones for Natural Gas on page 10, figure 9, the exhaust restrictor would be set to "C" for the rise and run of my stove's termination.   What's odd is "C" is *not* in the graph for Propane on page 11.  It goes from "B" to "D."   Perhaps it's a flaw in the manual.


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## Malachi (Dec 5, 2018)

DAKSY said:


> ***I find this an interesting question and I wonder how Daksy would reply to it...***
> 
> Actually, I've never been asked this question on the stove BODY temps.
> The GLASS will EASILY get to 450 Deg. F., but the body?


Well, you never know...there's always one in the crowd that asks that first question.


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## k0wtz (Dec 6, 2018)

Malachi said:


> Well, you never know...there's always one in the crowd that asks that first question.


Our gas stove will get hot to the touch about everywhere not where you cant keep your hand on it.  The stove has a cast iron liner where the burner is and it is hot really hot.  With the fan running it holds it down the decoritve outside is just that decoration.  You don't want to touch that inner liner when the burner is running!

Our flue is b-vent and it gets very hot but I am not worried about that it is supposed to get hot.  What I have read the stove draws inside air to create combustion pas that the fire is burning correctly I am not going to worry about anything else.


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## Fake coal burner (Dec 6, 2018)

My Nat/gas coal affect stove runs 275 deg f on top stove body on high. It b vented .


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## k0wtz (Dec 7, 2018)

Fake coal burner said:


> My Nat/gas coal affect stove runs 275 deg f on top stove body on high. It b vented .


our v/c startdance will get that hot if the fan isnt blowing but not near that hot when the fan is running!  I dotn know if i would want that much heat there our stove also has a cast iron innerbody!


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## Malachi (Dec 7, 2018)

Fake coal burner said:


> My Nat/gas coal affect stove runs 275 deg f on top stove body on high. It b vented .


Since my stove currently gets 240 degrees on the inner top plate on low (16,000 btu setting), I'm sure it would hit 300+ degrees on high (32,000 btu's).  Jotul does not indicate in the manual or anywhere else how hot their stoves should be.   That would be a good specification to have and know.


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## Malachi (Dec 7, 2018)

k0wtz said:


> our v/c startdance will get that hot if the fan isnt blowing but not near that hot when the fan is running!  I dotn know if i would want that much heat there our stove also has a cast iron innerbody!


When you consider a wood stove made of plated steel or even cast can normally handle heat in the 500 to 600 degree range with no problem, why couldn't gas heating stove easily handle 300 to 400 degrees or more...just a consideration.


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## k0wtz (Dec 7, 2018)

Malachi said:


> When you consider a wood stove made of plated steel or even cast can normally handle heat in the 500 to 600 degree range with no problem, why couldn't gas heating stove easily handle 300 to 400 degrees or more...just a consideration.


got me i dont know!  our v/c stove has a cat iron inner body I dont think 300 or 400d would be hard for it to handle but i havent let it get that hot as our fan runs.  It is made to run either way just seems wasteful to me to run it without a fan!!


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## wooduser (Dec 7, 2018)

Malachi said:


> When you consider a wood stove made of plated steel or even cast can normally handle heat in the 500 to 600 degree range with no problem, why couldn't gas heating stove easily handle 300 to 400 degrees or more...just a consideration.




Gas fired stoves typically 


Malachi said:


> When you consider a wood stove made of plated steel or even cast can normally handle heat in the 500 to 600 degree range with no problem, why couldn't gas heating stove easily handle 300 to 400 degrees or more...just a consideration.




This gas stove has a listed BTU input on propane that can be adjusted between 16,000-32,000 BTUs/hour of gas input (page 4 of the manual referred to earlier)  Gas stoves get hot,  but not nearly as hot as wood stoves are designed to get.  

This stove is listed to have 3" clearance to combustibles on the sides o0f the fireplace,  no doubt as a consequence of the lower stove temperature.  

So the short answer to your question is that gas stoves are typically designed to handle much lower temperatures than wood stoves.  For this stove that allows direct venting out the side of a house with a relatively simple venting system,  while a wood stove must be vented out the roof with a Class A vent system designed to handle much higher flue gas temperatures.  These are considered to be advantages of gas stoves compared to wood stoves.


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## Malachi (Dec 7, 2018)

wooduser said:


> Gas fired stoves typically
> 
> 
> 
> ...


Yes, I did see that in the manual.   I have about a 5" minimum to the wall (corner installation) and about 12" to the nearest combustible (curtains).   It would have been a useful specification had Jotul indicated approximate temperature outputs of their stoves.   My wood stove manual says 500 degrees for the top.  That's good to know.   We are only guessing what is acceptable for the Jotul.


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