Kuuma burn times and draft question

[Micdrew]

I’ve been scrolling through the forum here lately and have noticed that some of you with the VF100 are saying you’re getting 10-12 hour burns on a load of 25-35lbs, is that from the time you load to the time the blower shuts off? I’m burning maple and I’ll load 35lbs before bed about 10 when I wake up at 6:30 the blower is off and I have enough coals to load on, not sure when the blower is shutting off but depending on outside temps when I wake up the house is usually between 68-70 when the blower is running the house is staying around 72 with computer on low. Also I’ve been wondering about how the draft affects the heat output/efficiency of the furnace, more draft more heat?

 

[brenndatomu]

more draft more heat?

Yes, but shorter burn time too.

noticed that some of you with the VF100 are saying you’re getting 10-12 hour burns on a load of 25-35lbs, is that from the time you load to the time the blower shuts off?

Like who? Keep in mind some of us have some mods goin on too...

 

[Micdrew]

Yes, but shorter burn time too.

Like who? Keep in mind some of us have some mods goin on too...

Yes, but shorter burn time too.

Like who? Keep in mind some of us have some mods goin on too...

Actually it was you

 

[brenndatomu]

Actually it was you

I thought maybe...
On those small loads I am shutting the computer off once things are burnt down enough that the computer is back on "3"
And I have the blower speed controlled too.
25-35# loads would probably not keep the blower on for much more than 6-8 hours without these mods...of course that depends if you are doing a cold start, or loading on a mountain of hot coals though too...

 

[Micdrew]

I thought maybe...
On those small loads I am shutting the computer off once things are burnt down enough that the computer is back on "3"
And I have the blower speed controlled too.
25-35# loads would probably not keep the blower on for much more than 6-8 hours without these mods...of course that depends if you are doing a cold start, or loading on a mountain of hot coals though too...

Ok that makes more sense 6-8 hours is about what I’m getting with blower on low, thought I was doing something wrong!

 

[Highbeam]

Wow, those are small loads for a furnace. I get 45-50# loads of softwoods into my little 3 cubic foot woodstove.

 

[brenndatomu]

Wow, those are small loads for a furnace. I get 45-50# loads of softwoods into my little 3 cubic foot woodstove.

But that's a stove...this is a furnace with a proper heat exchanger, so the flue temps are much lower...which equals the house ending up at 95* if you load the firebox clear full in weather that doesn't warrant it...

 

[JRHAWK9]

Yeah, those of us who are speed controlled will see longer blower run times vs running the out of the box blower setup. I have my blower running very slow and speed controlled, so it doesn't turn off until there are very few coals even left. Couple that with turning the computer off once it reaches the coaling stage you are going to see even longer blower run times.....but at reduced BTU/hr output.

I've done a handful of 24 hour blower run times loading the firebox full of BL.....90-100lbs worth.

 

[JRHAWK9]

Wow, those are small loads for a furnace. I get 45-50# loads of softwoods into my little 3 cubic foot woodstove.

I've already done 10-15 lb loads.

 

[brenndatomu]

I've already done 10-15 lb loads.

I did a 20# load this evening...was shocked to see it go to pilot rather quickly, and stay there for quite some time...and this was with very few coals left too.
This was basically just a "kicker load" to get me to bedtime...its in the upper 30s out now, but will be dropping rapidly after midnight...so I wanted to wait until the house temp and the outdoor temp dropped a lil more to do the overnight load...

 

[Micdrew]

Yeah, those of us who are speed controlled will see longer blower run times vs running the out of the box blower setup. I have my blower running very slow and speed controlled, so it doesn't turn off until there are very few coals even left. Couple that with turning the computer off once it reaches the coaling stage you are going to see even longer blower run times.....but at reduced BTU/hr output.

I've done a handful of 24 hour blower run times loading the firebox full of BL.....90-100lbs worth.

Wow that’s impressive! What kind of supply temps do you get with the lower speed?

 

[JRHAWK9]

Wow that’s impressive! What kind of supply temps do you get with the lower speed?

Sounds like you may have not seen my threads. The first link also has links to a couple other posts from past years.

Here's some reading for ya.

EPA 2020 Wood Furnace Intertek Data Comparison

I made up a quick reference comparing the main EPA hot air furnaces in the category by combining the tables from three furnaces. I did this so I could see where I wanted to put the most effort in when building my furnace controller and furnace shed project. I thought it might be useful for...

www.hearth.com

EPA 2020 Wood Furnace Intertek Data Comparison

I made up a quick reference comparing the main EPA hot air furnaces in the category by combining the tables from three furnaces. I did this so I could see where I wanted to put the most effort in when building my furnace controller and furnace shed project. I thought it might be useful for...

www.hearth.com

EPA 2020 Wood Furnace Intertek Data Comparison

I made up a quick reference comparing the main EPA hot air furnaces in the category by combining the tables from three furnaces. I did this so I could see where I wanted to put the most effort in when building my furnace controller and furnace shed project. I thought it might be useful for...

www.hearth.com

 

[JRHAWK9]

its in the upper 30s out now, but will be dropping rapidly after midnight.

Right now, was a high of 10° today:

Supposed to be dropping to -7° tonight with 20mph wind gusts. We are almost always colder than the forecast here in the morning due to being in a lower lying area though.