Kuuma Vapor Fire 100: Supply and Stack Temps vs Time over 20 hours

[sloeffle]

Thanks for the info guys.

When the computer opens then damper does it open it to set positions or are positions variable based off of the firebox temp ?

Is the computer always adjusting the damper for maximum efficiency too ?

 

[JRHAWK9]

Thanks for the info guys.

When the computer opens then damper does it open it to set positions or are positions variable based off of the firebox temp ?

Is the computer always adjusting the damper for maximum efficiency too ?

It's a stepper motor, with four positions....fully open (3), ~2/3rds open (2), ~1/3rds open (1) and fully closed (c or what we call on pilot). Those positions are dependent on firebox temps. The computer is always monitoring firebox temps and adjusting the primary air stepper motor appropriately. The parameters at which the computer adjusts the damper is based on many years of test burns for efficiency and clean burning. I can't speak on that, as I have no knowledge of that.

 

[sloeffle]

Thanks for the info @JRHAWK9

I’ve often thought about hooking up my temp probe to an Arduino. The Arduino would then control a stepper motor on the damper based off of the exhaust temps.

It sounds like the kuuma is doing the same thing but based off of firebox temps.

 

[brenndatomu]

The Arduino would then control a stepper motor on the damper based off of the exhaust temps.

It sounds like the kuuma is doing the same thing but based off of firebox temps.

Thought about doing something similar on my old Tundra at one point too.
Wait a few months and you will be able to buy a new Caddy with this setup (IMO)
I found it interesting when I had my first Kuuma...firebox temp and flue temp aren't completely tied together...makes sense once I thought about it...flue temp is a combination of firebox temp and damper position (among other things)

 

[JRHAWK9]

I found it interesting when I had my first Kuuma...firebox temp and flue temp aren't completely tied together...makes sense once I thought about it...flue temp is a combination of firebox temp and damper position (among other things)

yep, they both can be moving in opposite directions. This happens mostly when the damper closes (flue temps immediately start dropping while firebox temps continue to rise a bit before coming back down) and when the damper opens (flue temps immediately start to rise while firebox temps still continue to drop for a bit before starting to rise).

 

[sloeffle]

Wait a few months and you will be able to buy a new Caddy with this setup (IMO)

I'm too cheap to buy a new furnace.

For about $25 in parts in and some time writing some code I think you could get the arduino setup and working. The damper actuator is what I'm struggling to find. Wouldn't it need to be DC since it is a stepper motor ? I am interested to see what kind of damper actuator they do use on the new 2020 compliant furnace.

Sorry to railroad your thread JR

 

[JRHAWK9]

This is from a few days ago. Computer was set to medium burn the whole time. It was doing the c-1-c thing most of both burns keeping firebox temp at a minimum of ~1,190° (medium). Stack temps were going from ~330° to ~420° during the c-1-c cycling. Draft is set at -0.06"/-0.065".

1 - Loaded 47.5 lbs in the morning at 8:30am
2 - Raked coals forward
3 - Loaded 42.7 lbs at 3:45pm
4 - Loaded the night load at 10:30pm

Loaded each time with similar amount of coals.

The mornings load was consumed at a rate of 6.55lbs/hr (~42,000 BTU's/hr -gross- on average over the burn)
Afternoon load was 6.33lbs/hr (~41,000 BTU's/hr -gross-)

I knew once I started turning the computer up I'd start seeing some flatter plenum temp curves, with the middle of the burn temps bumped up some. I also suspect when I run the Kuuma wide open I will see a more typical slightly bell shaped curve with the plenum temps being similar (maybe slightly higher) at re-loading, but consistently higher during the middle of the burn due to the computer keeping firebox temps higher.

The even/consistent heat output of the Kuuma throughout the burn coupled with the speed controlled blower really helps with maintaining consistent plenum temps throughout the burn.