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Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Fri. Nov. 08, 2013 12:22 pm
by titleist1
lightning, one suggestion i'd make on your mano is to put a short piece of tubing on the other port looped toward the floor to keep any dust or dirt from getting in that open port. probably not a big issue, but just something that was suggested to me way back when and I thought i'd pass it along for others to consider.

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Fri. Nov. 08, 2013 12:30 pm
by Stanb999
Lightning wrote:Oh yeah lol right. It's hooked up backwards to read the negative value on the positive side of the scale. Sorry :lol:
He was thinking your stove blew, when really it's your chimney sucking. :lol:

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Fri. Nov. 08, 2013 2:13 pm
by Lightning
Stanb999 wrote:
Lightning wrote:Oh yeah lol right. It's hooked up backwards to read the negative value on the positive side of the scale. Sorry :lol:
He was thinking your stove blew, when really it's your chimney sucking. :lol:
Right hahaha, I didn't name her Ashley cuz she blows but because she's hot. :lol:

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Fri. Nov. 08, 2013 2:16 pm
by Lightning
titleist1 wrote:lightning, one suggestion i'd make on your mano is to put a short piece of tubing on the other port looped toward the floor to keep any dust or dirt from getting in that open port. probably not a big issue, but just something that was suggested to me way back when and I thought i'd pass it along for others to consider.
Yes sir, I actually folded a little piece of news paper over the open port for any dust to settle on. It's not tight against the port so it can't alter the reading. Your suggestion is excellent too :D

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Fri. Nov. 08, 2013 2:32 pm
by titleist1
yes, I noticed the paper in the pic when I zoomed in that is what made me think of passing along the tubing suggestion.

by the way, I figured out how to get you the info on the mano reading at different baro opening points you were asking about. I must have had brain lock when trying to think about it the first time through. what i'll do is wait to see the baro steadily open about halfway (and other points) and then manually close it while noting the new reading on the mano with the baro closed. I will find the other thread and add the data in case it helps.

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Fri. Nov. 08, 2013 2:47 pm
by ddahlgren
Lightning wrote:
titleist1 wrote:lightning, one suggestion i'd make on your mano is to put a short piece of tubing on the other port looped toward the floor to keep any dust or dirt from getting in that open port. probably not a big issue, but just something that was suggested to me way back when and I thought i'd pass it along for others to consider.
Yes sir, I actually folded a little piece of news paper over the open port for any dust to settle on. It's not tight against the port so it can't alter the reading. Your suggestion is excellent too :D
A small piece of foam makes a great filter though keep it away from the heat and keeps all the trash.
Whenever I have to tap into something that is hotter than the melting temp of the rubber or plastic tubing connected to the sensor I always uses a couple of feet of copper tubing wound in a coil to cool the end of it and not melt the plastic or rubber tubing. I know it works with 1800 to 2000F temperatures quite well on the exhaust of a turbocharged race engine measuring exhaust back pressure.

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Fri. Nov. 08, 2013 9:27 pm
by Lightning
titleist1 wrote:by the way, I figured out how to get you the info on the mano reading at different baro opening points you were asking about. I must have had brain lock when trying to think about it the first time through. what i'll do is wait to see the baro steadily open about halfway (and other points) and then manually close it while noting the new reading on the mano with the baro closed. I will find the other thread and add the data in case it helps.
Cool Thank you! Basically, I was trying to relate mano readings with how far open the door was. I should have gotton a reading with the baro held closed too but didn't think of it at the time :D

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 7:48 pm
by Lightning
Hi Fellas.. I'd like to resurrect this thread for opinions on stove vs pipe temp and what they imply or if they are really very valid at all.. :shock:

Its just that there are SOOOO many variables that contribute to the spread between the stove and pipe.

Lets start with location. My pipe can be 200 degrees 12 inches from breech and 2 feet further up the pipe I can lay my hand on it. Then at the thimble its hardly luke warm. Then there is the location on the pipe itself. The top side of a horizontal pipe can be hot while the underside is much cooler. How does that work for a vertical pipe?

Then there is the burn rate issue. At lower burn rates I see a closer gap between stove and pipe. Is this because the top of the coal bed is cool and not producing radiant heat? At higher burn rates I see a more dramatic spread. Is this because the top of the coal bed is glowing and throwing massive amounts of radiant heat that the steel is absorbing?

And how about that secondary air? When I close my secondary air, the pipe cools.. Open secondary air and the pipe temp rises.. but, in both cases the stove temp stays the same.. Is this because more heated air MASS is running across the inside of the pipe surface by opening the secondaries?

And what about heat loss of the pipe itself? Last year I held my probe against the pipe with magnets. I could blow on it to cool it down. This year I secured the probe under a thin layer of insulation and blasted foil tape over it. Since the pipe isn't exposed where the probe is, it sees a higher temperature.

With all these variables and inconsistencies from one set up to the next, how can we justify any amount of efficiency based on these numbers?

Any comments are appreciated..

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 7:53 pm
by lsayre
Lightning wrote:With all these variables and inconsistencies from one set up to the next, how can we justify any amount of efficiency based on these numbers?

Any comments are appreciated..
You are of course quite correct. We can't make heads or tails out of anything when there are no standards or controls being adhered to.

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 8:00 pm
by franco b
Without a fixed method of measurement , you are right that most value is lost.

Stack temp. ideally should be measured within a foot of the stove breech and with a probe into the pipe. Even surface temp. would be useful if everyone measured at that point, but many measure at the thimble or after a baro and the measurement is useless.

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 8:18 pm
by windyhill4.2
380* stove top,top end of the elbow on stove is 180*,right b4 the elbow b4 the thimble is 118*,the thimble end of that elbow is 105*. If these measurements turn out to be invalid because they have no scientific merit,how about this measurement............. We are WARM,does that one count ? :)

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 9:32 pm
by dlj
lsayre wrote:
Lightning wrote:With all these variables and inconsistencies from one set up to the next, how can we justify any amount of efficiency based on these numbers?

Any comments are appreciated..
You are of course quite correct. We can't make heads or tails out of anything when there are no standards or controls being adhered to.
It's my understanding that this is not a field that has been completely defined yet at any level. Methods of measuring temperature and constituents within the exhaust/chimneys are still being developed. I believe the current methods being pursued in research are using LASERs to shoot through the exhaust stream enabling the measurement of the complex temperature profiles within the exhaust stream, volume, flow rates, as well as measuring the various constituents within the exhaust gases.

This all being said, knowing that your stove pipe has much less going up it in heat, per a surface measurement, can give a nice warm fuzzy feeling... :D

dj

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 9:49 pm
by Lightning
dlj wrote:This all being said, knowing that your stove pipe has much less going up it in heat, per a surface measurement, can give a nice warm fuzzy feeling...
Yes, I suppose it does.. 8-)

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 10:45 pm
by 2001Sierra
How you measure does matter. Here are my stove pipe readings. The large white gauge has a probe into the flue, about 2 inches.

Re: Comparing Temps Between Flue Pipe and Stove Body

Posted: Sun. Jan. 04, 2015 11:13 pm
by titleist1
I don't use the comparison of the two temps to make any claims on efficiency percentages. I don't really even look to them to be extremely accurate temperature readings for all the reasons already stated.

What I do expect is that the flue & stove body gauges are repeatable in the measurement so they are useful when viewed individually from time to time or compared to each other. I am used to looking at the temp probe on the flue pipe and seeing about 130* when idling and 275* when at full burn for at least 30 minutes. I am used to seeing about 200* on the stove body when mostly idling and 600* when at full burn for at least 30 minutes measured with an IR gauge at the same point each time.

Because of that I can tell when I first look in the morning if it has been firing or idling for a while just by looking at the flue temp. And I can tell if something may be wrong if the temp spreads are not their usual values. For instance, if the flue temp looks too high compared to the stove body temp I look at the manometer & check the baro to make sure it is open as far as it should be since it seems I am sending heat up the chimney. Last year a couple day long chronically low stove temp led me to notice a smaller fire than normal (glass is frosted too badly to see flames clearly) which led me to find the combustion fan not seated properly and only supplying about 2/3's the normal air.

So other than giving somebody new a little reassurance that their temps are 'in the ballpark' I view the temps I measure as useful to myself only.