Sealing flue pipe on Kuuma

[motoguy]

Our Kuuma VF100 is entering it's 2nd day of service. I'm going to let the fire die down today, and install a nipple/copper pipe in the flue for the Dwyer manometer. Once that's done, I'd like to seal up the flue as best as possible.

I've read that the silicone stove sealant (I have the black Imperial stuff) is no good, in that it simply gets hot and cracks off. I've read the adhesive backed aluminum tape is no good as well; the metal tape lasts, but the adhesive does not. Granted, I think most of these comments were regarding wood stoves, with their much higher flue temps (the highest I've read on the Kuuma the past day is ~250, right at the outlet). I'm curious if these products would work better on the Kuuma, with the lower temps?

If not, what's the best way to seal up the seam on my flue pipe? I've read of using a fiberglass wrap with straps. I have easy access to the pipe, and it's a relatively short length (with several joints), so a wrap/clamp option would work for me.

 

[velvetfoot]

Is this really necessary? Don't forget too, you have to take some stuff apart to clean.

 

[maple1]

Ya, don't think I'd bother unless you have an issue getting enough draft that leads to sealing up everything you possibly can.

I had thoughts of doing it to my pipes, but once I measured draft & it was in spec, 'to heck with that...'

 

[motoguy]

You may have point. I hooked up my manometer today. I had purposefully let the fire die down since 1) it wasn't going to be overly cold today, and 2) I knew I'd be working in the flu. It's currently low 40's outside, essentially no wind.

As soon as I hooked up the manometer, I saw it bump to .02. I unplugged the hose, made sure 0 was set accurately, and hooked it up again. Yup, .02. I decided to set a small fire, in preparation for a larger one this evening. When I opened the door, it looked like the fire was completely out. I raked all the ash into the pit, and piled the coals up. I had about a softball sized mound of near-black coals on the grate. Cleaned out the ash pan, left the ash door open to liven up the coals, and threw in a half dozen or so small/medium splits. The damper setting had been on "3" all this time.

The fire took off shortly, and the damper closed down to the #2, then #1 position (heat knob on "max"). I figured a #1 or "c" (pilot) position would be a decent place to measure the draft, as it should signify a "settled down" fire.

The barometric damper supplied with the Kuuma was set at .06, per the knob adjustment on the unit. When I checked the manometer, I saw it was pulling between .07 and .08. I had to loosen the damper knob, and slide it to (almost) the .02 position (damper swinging really easily), in order to get the manometer to read approx .055.

Am I testing my unit in an correct manner? I'm surprised to find the supplied barometric damper to be so far off (going from .06 knob setting to .02 knob setting, to keep manometer below .06). I made sure it's mounted level and plumb.

 

[maple1]

Sounds about right. As long as the manometer is level & zero'd, I think the only other blunder that could happen is having it hooked up downstream of the baro. (Needs to be hooked in between the furnace & the baro). Doing that wrong would make it read higher than what the furnace is seeing - likely significantly.

 

[motoguy]

Sounds about right. As long as the manometer is level & zero'd, I think the only other blunder that could happen is having it hooked up downstream of the baro. (Needs to be hooked in between the furnace & the baro). Doing that wrong would make it read higher than what the furnace is seeing - likely significantly.

It is indeed hooked between the baro and the furnace. 90 out of furnace, baro T is attached to the 90. The manometer port is attached to one of the swivel joints on the 90 itself, between baro and furnace.

 

[STIHLY DAN]

It's just a weight on the baron so they all vary a bit. there is no need to test it on high but it's fine to. also no need to seal the pipe.

 

[brenndatomu]

Those marks on the baro are a starting point only...it does sound like yours is way off though. Make sure the baro flapper swings through its full travel freely and is mounted plumb and level...same goes for the manometer, doesn't take much to throw 'em off either. Is that a Fields baro?

 

[motoguy]

Those marks on the baro are a starting point only...it does sound like yours is way off though. Make sure the baro flapper swings through its full travel freely and is mounted plumb and level...same goes for the manometer, doesn't take much to throw 'em off either. Is that a Fields baro?

Yes, Fields baro.

 

[motoguy]

Sounds about right. As long as the manometer is level & zero'd, I think the only other blunder that could happen is having it hooked up downstream of the baro. (Needs to be hooked in between the furnace & the baro). Doing that wrong would make it read higher than what the furnace is seeing - likely significantly.

Photo of install

 

[maple1]

Looks good!

 

[brenndatomu]

Looks like a nice setup moto.
About the only (potential) issue I see is that the manometer port is cut in right where the flue gasses are coming 'round the bend so to speak. For myself I would have put the port in on the side (facing the wall) to get it a little more out of the flow comin around the corner there...but honestly I can't say if it will change your readings or not.
Typically they want it in a straight section of pipe to limit turbulence that could affect the draft reading.

 

[JRHAWK9]

I think that surface temp gauge will be useless so close to the BD. I don't like surface temp gauges to begin with, but being so close to where flue gases are being mixed with fresh air may make it even more inaccurate.

I'd look into some sort of probe type gauge if you want to monitor your actual flue gas temp. I use a Bacharach Tempoint gauge and have it inserted right after the flue collar..

 

[motoguy]

I think that surface temp gauge will be useless so close to the BD. I don't like surface temp gauges to begin with, but being so close to where flue gases are being mixed with fresh air may make it even more inaccurate.

I'd look into some sort of probe type gauge if you want to monitor your actual flue gas temp. I use a Bacharach Tempoint gauge and have it inserted right after the flue collar..

I have an IR thermometer that I shoot when I want to know actual temps. Comparing the IR reading to the display on the surface temp gauge gives me a "ballpark" reading on the surface gauge. Was shocked to see temps at the elbow in the 250 range, and down to 175 or so by the time you get above the baro damper. I was used to seeing such high temps when using the Arbor Avalon wood stove (which the furnace replaced).

 

[JRHAWK9]

Those are not going to be accurate either...at least of giving you the actual temperature of flue gases. Flue gases inside the pipe can be 2 - 2.5 times the surface temp of the stove pipe. I have an IR one as well, and my flue gases are always much higher than what the IR reading is. You don't want flue gas temps too low, as you will then start to have condensation issues. In this mild weather, with the furnace on low and on pilot, I've seen my flue gas temps as low as a hair under 300°, sampled right at the collar. Daryl has told me he doesn't want to extract any more heat out of the flue gas because of the possibility of condensation on some setups.

 

[maple1]

I have one of those magnetic guages, right beside a probe one. The magnetic reads 100°c less than the probe does, when I'm burning. They're almost useless - approaching dangerous depending how much one relies on one to guide their burning practices.

 

[STIHLY DAN]

It really doesn't matter, your flue temps are what they are, its not like you can throttle down the air. The computer does it for you. Throw the magnet away and don't worry about the temp, unless you are a furnace nut like some of these guys.

 

[JRHAWK9]

It really doesn't matter, your flue temps are what they are, its not like you can throttle down the air. The computer does it for you. Throw the magnet away and don't worry about the temp, unless you are a furnace nut like some of these guys.

I'm just a nut, period. I just like knowing. This way you know what the norm is and if there ever comes a time where one must trouble shoot something you will now have the data to properly try to diagnose or you can make changes to something to see how it affects other things. I monitor my flue gas temp, draft, plenum temp and return air temp.

 

[motoguy]

It really doesn't matter, your flue temps are what they are, its not like you can throttle down the air. The computer does it for you. Throw the magnet away and don't worry about the temp, unless you are a furnace nut like some of these guys.

Honestly, I just threw the gauge on there because I had it left over from the wood stove. I can't say I look at it much, other than initially establishing a "normal zone" after running the Kuuma for the first week. I'll just use it for trending data, really. Not specific readings. I spend far more time dinking with the baro damper, and scrutinizing the reading on the Dwyer.

 

[STIHLY DAN]

I get it, did the same thing myself.