Ahhh yes... the annual Hot Blast thread.
Your gonna' get two thought lines... but not much in between the two extremes.
1) I absolutely hate/hated that wood-gobbling, creosote-making, short-burning POS‼
2) I absolutely love/loved that workhorse heat-making machine.
I've never owned a Hot Blast, but I know of a few around the area... I don't hear the same complaints about them as I read on this board. Excessive creosote don't seem to be an issue, likely because the further north you live the more often you'll be running it hot(er) 'n' heavy(er). Wood-gobbling and short burn times is a perception thing... I mean... if ya' need more heat, ya' need to burn more wood at a faster rate (shrug). Most of the complaints I hear are about the thermostatic/bi-metal control and noisy, ineffective circulation blower(s).
That thermostatic control probably has more to do with creosote formation than anything; more wood in the firebox means more heat, so a low or medium setting with a full fuel load is gonna' smolder more than a smaller fuel load. In other words... they make creosote because they're being over-loaded relative to heat demand. In any old-school(?), non-secondary combustion box there's a "sweet spot" where they run best... and that spot sort'a floats as conditions and demand change. Over-loading the box is worse than under-loading but you'll never get the "haters" to understand that... the "lovers" have figured it out. Running a box like that is more about loading technique, and near nothing about settings (once established)... how much, how often, and what type of fuel depending on conditions and demand. I've used boxes of that sort for decades (without the thermostatic control); once the flue damper and combustion air inlet is set I rarely touch them, maybe slight adjustments a couple times a year... "control" of the box is done with loading technique.
The circulation blowers supplied with those type of furnaces are a joke... if you're gonna' use it as a furnace it should have a large (full-size), multi-speed blower so it can be matched to your entire system. Short-cutting the install is another mistake. The "system" needs return air connected for efficient heat transfer and air flow... and back-draft dampers are a must to keep air (100% of it) moving correctly if it's installed as an add-on. And, a wood furnace ain't like a gas or oil furnace, it never "shuts off" completely or recovers as quickly, you need dampers installed in the individual ducts running to different rooms so you can "balance" the flow... especially to bedrooms and smaller rooms like the bathroom. It takes a bit of trial 'n' error, but once they're set you'll never need to touch them again.
My current wood furnace (DAKA) has a induction draft blower, which (in my opinion) is a much better approach than the thermostatic control on the Hot Blast. Rather than being controlled by furnace temperature, the induction blower is controlled by a (programmable) wall thermostat in the area being heated... controlled by demand rather than output. It rarely runs during the day unless it's extremely cold... it runs in the morning for a little bit, and sometimes again in the evening shortly after sunset (due mostly to the programmed settings of the t-stat). One problem I see with the Hot Blast is with the accessory add-on induction blower (if you choose to get it). From what I see by looking at them, it appears to blow air over the fire rather than under it. That's a poor and inefficient design in my opinion. After using it for a couple years now, I really love the induction blower set-up I have that forces air under the fire. So, because the Hot Blast induction blower is set-up the way it is, the Hot Blast would be a non-starter for me.
And speaking of non-starters... any furnace that requires letting the fire burn out to empty ashes, or even requires shoveling ashes, or requires special maintenance techniques such as cleaning heat exchanger tubes and such... would be a non-starter for me. I've always said... makin' firewood should be the hard part, burnin' it should be the easy part. But that's just me...
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