New Installation Temp and Pressure Gauge Location Questions

[davidmsem]

Hello I'm working the install of my Pacific Energy LE Insert. I'm looking for help on where to place my temperature sensor, and what type. If I use a probe, it will be located only 5 to 8 inches above the unit (just above the damper, path notated). Not much room above this unit with the block off plate.

I'm wondering if i should use a probe or just face measurement with an Auber Instruments unit either way. Opinions on this welcomed.

I am installing a Dywer Magnehelic as well, and that will have to be above the damper. I'm hoping static pressure above the damper will be very close to below the damper. Can't remember if i did this experiment in the late winter, believe I did. This is a static pressure measurement, perpendicular to try he airflow, to remove the pressure effects of gas velocity.

Hoping I can keep the new unit in the specification limits, <= 0.12 for draft, with the pressure gauge, damper, and temperature gauge.

Thoughts? Opinions?

Thanks.

 

[brenndatomu]

I'm hoping static pressure above the damper will be very close to below the damper.

It will when the damper is open, but not when its closed...that's the whole point of the damper.

 

[davidmsem]

It will when the damper is open, but not when its closed...that's the whole point of the damper.

Need to convince myself this is correct. Total pressure will be different, but I'm not sure about static pressure.

Damper will reduce static pressure on both sides I believe.

 

[bholler]

Need to convince myself this is correct. Total pressure will be different, but I'm not sure about static pressure.

Damper will reduce static pressure on both sides I believe.

It will not

 

[davidmsem]

It will not

I'm not entirely sure. An explanation to support would be helpful so I can gain understanding. Hard to believe there would be zero change on one side of that flow. Perhaps you are correct. I work with lots of physicists, so I'll see if they can help explain.

Any opinion on the type and location of the temperature sensor?

 

[EbS-P]

Damper is a pressure regulator of sorts. I think you want to read it below. The pressure that is above the stove. The Bernoulli effect in regions of fast velocity will effect the reading. damper really increases velocity in the open areas. So I would not consider the readings as “calibrated” but as a reference.

I think the same goes for probe flue temps. That close to the stove and given the radiation from the cast damper of the probe is close I think give a reading that is useful but not comparable to others flue temp readings 18” off the stove.

Probe or surface? Probe gives a much faster reading and once you learn the calibration you can adjust the air and see the effects without waiting. The surface measurements take longer to see effects.

Short none of your readings will give others useful info but couple with visual observations will be very useful for you learning and running a new set up.

Just my thoughts

 

[davidmsem]

Damper is a pressure regulator of sorts. I think you want to read it below. The pressure that is above the stove. The Bernoulli effect in regions of fast velocity will effect the reading. damper really increases velocity in the open areas. So I would not consider the readings as “calibrated” but as a reference.

I think the same goes for probe flue temps. That close to the stove and given the radiation from the cast damper of the probe is close I think give a reading that is useful but not comparable to others flue temp readings 18” off the stove.

Probe or surface? Probe gives a much faster reading and once you learn the calibration you can adjust the air and see the effects without waiting. The surface measurements take longer to see effects.

Short none of your readings will give others useful info but couple with visual observations will be very useful for you learning and running a new set up.

Just my thoughts

Thank you. I appreciate the input and thoughts as I try to navigate a new setup. Really had a tough few months after the overfiring of my other unit from overdraft. So I'm really trying to do my best to avoid a repeat of a failed unit.

As far as the effects of the increase velocity from the damper, the static pressure probe is perpendicular to the air flow which removes the effect of velocity from my understanding. Reading parallel to the airflow would take into account the effect of velocity as the probe would sense and experience that velocity. I'm going to run some simulation experiments on my work computer and see if I could learn more.

Thank you again..... I'm just trying to get the best set up after losing thousands of dollars and learning about my unit overdrafting. It's taken many hours to get this thing installed correctly.

 

[brenndatomu]

I've messed around with taking the draft measurements different ways...pointing upstream, downstream, and straight in...seemed to make no appreciable difference...I don't think the velocity is high enough to do so, at least not under any kind of normal circumstances.
If you have to take your temp reading that close to the stove, just make sure your probe is capable of taking the temps...some are only rated for 750* or so...and yes, I would really try to take the temp internally, it will be more accurate and responsive than external.

 

[EbS-P]

Thank you. I appreciate the input and thoughts as I try to navigate a new setup. Really had a tough few months after the overfiring of my other unit from overdraft. So I'm really trying to do my best to avoid I repeat of a failed unit.

As far as the effect s of the increase velocity from the damper, the static pressure probe is perpendicular to the air flow which removes the effect of velocity from my understanding. Reading parallel to the airflow would take into account the effect of velocity as the probe would sense and experience that velocity. I'm going to run some simulation experiments on my work computer and see if I could learn more.

Thank you again..... I'm just trying to get the best set up after losing thousands of dollars and learning about my unit overdrafting. It's taken many hours to get this thing installed correctly.

Next time you have a straw in a drink blow across the top. Liquid level will rise a la Bernoulli! Same principle as a wing. Faster velocity separates from low velocity creates low pressure in the slow region.

All of this will help. I regularly see 900 F flue temps above my damper but do not believe it’s over drafting with the damper closed. I can get pretty lazy secondary flames.

You are in a much position to understand how to run the new insert compared to the old one. With the EB2 flapper and a damper and monitoring temp and draft you will establish your safe zone and be able to see when it starts to exceed that.

 

[EbS-P]

I've messed around with taking the draft measurements different ways...pointing upstream, downstream, and straight in...seemed to make no appreciable difference...I don't think the velocity is high enough to do so, at least not under any kind of normal circumstances.
If you have to take your temp reading that close to the stove, just make sure your probe is capable of taking the temps...some are only rated for 750* or so...and yes, I would really try to take the temp internally, it will be more accurate and responsive than external.

But with an insert you really are limited where you can take measurements from. The damper will do funny things to flow. Especially when running closed. Figure what 50? cfm through a closed damper stick your tube in the wrong spot id guess it could effect reading .05” maybe more. No data just feeling and blowing across my magnahelic tube.

 

[davidmsem]

I've messed around with taking the draft measurements different ways...pointing upstream, downstream, and straight in...seemed to make no appreciable difference...I don't think the velocity is high enough to do so, at least not under any kind of normal circumstances.
If you have to take your temp reading that close to the stove, just make sure your probe is capable of taking the temps...some are only rated for 750* or so...and yes, I would really try to take the temp internally, it will be more accurate and responsive than external.

Thank you. This is very helpful. The probe can handle the high temperatures from what I understand. I believe I can get about 8 inches away from the top of the insert.

I had borrowed a draft gauge and took some measurements on the old unit before pulling it out. Much appreciated input from The forum here to do those experiments. I remember moving the probe quite a bit in a given hole and it having no effect on pressure reading. I cannot recall if I read both above and below the damper.

Above in the thread it says there will be no change in pressure above the damper when the damper is closed. I am not thoroughly convinced that is the case, because if you closed it in theory 100%, the flu would not be able to draw and there would be a change in pressure above the flue. So there must be some change in pressure above the damper as the damper closes, correct? Much like the airflow velocity effect being negligible at these forces, I wonder if the same is true for the pressure readings above and below the damper, that they are similar.

I do have the option of using the first inch or so of flu pipe exiting the unit and allowing the pressure probe to stick in there the slightest bit and get a reading. I'm not sure of the accuracy of this based on its location, which could be influenced by it not sticking very far into the flue and ambient air leaking in near the probe tip, influencing the reading.

I appreciate the thoughts.


David

 

[davidmsem]

Next time you have a straw in a drink blow across the top. Liquid level will rise a la Bernoulli! Same principle as a wing. Faster velocity separates from low velocity creates low pressure in the slow region.

All of this will help. I regularly see 900 F flue temps above my damper but do not believe it’s over drafting with the damper closed. I can get pretty lazy secondary flames.

You are in a much position to understand how to run the new insert compared to the old one. With the EB2 flapper and a damper and monitoring temp and draft you will establish your safe zone and be able to see when it starts to exceed that.

You make an interesting point about blowing across the tip of a straw. The velocity will be highest right at the damper, as airflow works its way around the damper. So that raises the question in my mind if I should measure very close to the damper, perhaps right at the plane of damper when closed.

Trying to figure the best location before drilling!

Thank you.

 

[brenndatomu]

You have to be an engineer...I have friends who are and I now recognize the "question everything" thinking

 

[davidmsem]

You have to be an engineer...I have friends who are and I now recognize the "question everything" thinking

Yes, guilty as charged. I work at a jet engine manufacturer and do jet engine simulation. I'm actually contemplating building a simulation of a duct with a damper and seeing how the static pressure behaves on both sides of the damper. Engineering is not a career I say, it is a disease.

The craziness actually helps in the development of products like jet engines. When sitting at 30,000 ft I am happy that I work with people that obsess about details. My poor wife has to live with this.

And the last time we installed the unit we did everything per the manufacturers instructions and yet the unit over fired. I've lost thousands of dollars and a great deal of time trying to get a reinstall done properly. I want this unit to last a very long time.

 

[brenndatomu]

The craziness actually helps in the development of products like jet engines. When sitting at 30,000 ft I am happy that I work with people that obsess about details.

Yup, we all contribute in different ways...engineering is an important one for sure...but I'm sure glad that some are perfectly happy doing more laborious jobs...because I HATE doing some things...like painting and roofing...and not much for cooking either...sure glad some love it though!
Sounds like you are all over it this time...if nothing else, much more educated and know what to look for (or at very least, to just be looking/paying close attention) now

 

[begreen]

Trying to figure the best location before drilling!

This is the primary concern. The damper needs to be able to rotate 90º without obstruction. The rest is overthinking IMO.

 

[davidmsem]

This is the primary concern. The damper needs to be able to rotate 90º without obstruction. The rest is overthinking IMO.

Installed the damper today and it rotates 360° without obstruction. It took me two installs to get it to not have interference as I had a couple washers against the inside of the flu where there was a bit of rubbing. Thank you for the encouragement to have no rubbing it motivated me to get those washers in there.

I'm not so sure about the overthinking, last time I was under thinking and it cost me thousands of dollars and gobs of hours since February.

From another post about how to install dampers on inserts you could see the 3/8 threaded rod and the 3/8 threaded nut that was welded onto the damper rod. Truly a custom to set up here.

I don't think trying to understand if the pressure reading above the damper will be a good measure of draft is overthinking it. I want to be able to depend on the reading.

Just trying to understand the true physics of the situation.

Once bitten twice shy.

David

 

[begreen]

Nice progress. How large is the gap between the appliance adapter and the damper?
This has been mentioned before, but anytime the baffle is out, a rag should be stuffed into the secondary supply tube to prevent debris from dropping down there.

FWIW, this is already ahead of the game compared with the past insert. With a flue temp probe above the damper, there should be a good indication of whether the damper has effectively tamed the draft to a tolerable level. The stove flames will also provide a visual guide.

 

[davidmsem]

Nice progress. How large is the gap between the appliance adapter and the damper?
This has been mentioned before, but anytime the baffle is out, a rag should be stuffed into the secondary supply tube to prevent debris from dropping down there.

FWIW, this is already ahead of the game compared with the past insert. With a flue temp probe above the damper, there should be a good indication of whether the damper has effectively tamed the draft to a tolerable level. The stove flames will also provide a visual guide.

Thank you.

The gap between the appliance adapter and the damper saver is approximately 1/4". I used a standard 5.5" damper (Amazon). I placed steel sheets on both sides to plug the holes. I was really shocked that it took plugging the holes in the damper to get the unit with specification. Do you think this is okay? Same damper I used for experiments on the Regency I3100L before removing it.

I was unaware of placing a rag at the top of the secondary I felt the opening and will protect it going forward.

Thank you for the encouragement.

As evidenced by my progress and education, it's a real tribute to hearth. com.

I'm thinking the temperatures in the flue (gas path) will be the most valuable.

I did order a Magnehelic and will install it for the learning and entertainment. It looks cool too! Not sure on the location of the Magnehelic probe. Can fit the probe just below the damper plane but it will only insert about a bit over the 1/4". There will be high gas velocities at that location, so that might not be a good spot.

I just want the best possible install I can have.

In a few months the fun will start. I'm very curious about the heat output of the Pacific Energy Summit LE Insert versus the older Regency I3100L. The 3100 was amazing! The PE Summit will benefit from (Hopefully) slightly longer and more efficient burns. I had to be losing a great deal of energy up the flu due to over draft.

David

 

[begreen]

The gap between the appliance adapter and the damper saver is approximately 1/4". I used a standard 5.5" damper (Amazon). I placed steel sheets on both sides to plug the holes. I was really shocked that it took plugging the holes in the damper to get the unit with specification. Do you think this is okay? Same damper I used for experiments on the Regency I3100L before removing it.

A standard damper blocks about 75% of the flow of flue gases when closed. This is intentional because a zero draft situation would be quite undesirable, especially if flue gases backed up in the firebox. If there is a 1/4" gap then it is blocking off around 84% of the flow. If the gap is 3/8" then the blockage is about 77%. With the very tall chimney, 84% may be necessary.

I was unaware of placing a rag at the top of the secondary I felt the opening and will protect it going forward.

This is particularly important when cleaning the liner. A pile of sote down the tube can mess up the EBT which might require pulling the insert to clean out.

It will be a new wood-burning experience with the new insert and damper installation. Hope it's a great improvement.

 

[davidmsem]

A standard damper blocks about 75% of the flow of flue gases when closed. This is intentional because a zero draft situation would be quite undesirable, especially if flue gases backed up in the firebox. If there is a 1/4" gap then it is blocking off around 84% of the flow. If the gap is 3/8" then the blockage is about 77%. With the very tall chimney, 84% may be necessary.

This is particularly important when cleaning the liner. A pile of sote down the tube can mess up the EBT which might require pulling the insert to clean out.

It will be a new wood-burning experience with the new insert and damper installation. Hope it's a great improvement.

Thanks. Great information on the percent blockage!

I'll follow up with some photos when the install is complete and then provide some data from the instrumentation when the season kicks off.

I already purchased the draft gauge. Would you install it above the damper or even with the damper if you were to offer an opinion.

Thank you and everyone for the help.

 

[bholler]

Thanks. Great information on the percent blockage!

I'll follow up with some photos when the install is complete and then provide some data from the instrumentation when the season kicks off.

I already purchased the draft gauge. Would you install it above the damper or even with the damper if you were to offer an opinion.

Thank you and everyone for the help.

Above the damper won't tell you anything about what suction the stove is seeing

 

[davidmsem]

Nice progress. How large is the gap between the appliance adapter and the damper?
This has been mentioned before, but anytime the baffle is out, a rag should be stuffed into the secondary supply tube to prevent debris from dropping down there.

FWIW, this is already ahead of the game compared with the past insert. With a flue temp probe above the damper, there should be a good indication of whether the damper has effectively tamed the draft to a tolerable level. The stove flames will also provide a visual guide.

Begreen, there is much written about flue gas temps, but I'm wondering if you could offer a guess a range you would want to see my install at. I will be approximately 8 inches above the unit. Best I can do with an insert. I understand best is 18 inches above.

 

[davidmsem]

Above the damper won't tell you anything about what suction the stove is seeing

Thanks bholler.

My other option is right at the height of the damper. The probe will only stick in about 1/4 inch and be right at the location of the highest gas velocities (I think) as the flow is directed through the annulus around the damper.

What are your opinions on that location?

 

[bholler]

Thanks bholler.

My other option is right at the height of the damper. The probe will only stick in about 1/4 inch and be right at the location of the highest gas velocities (I think) as the flow is directed through the annulus around the damper.

What are your opinions on that location?

It's really your only option it won't be the best measurement but the best option available