Gasifier Quick Start

[Nofossil]

I always run my gasifier flat-out. I let it heat the house and storage, then let it go out. That means I build fires a lot - every day in cold weather. I've been looking at how to get from lighting the match up to 'safe' inlet temperature, then up to 'usable heat' as quickly as possible. I've made some progress, but I'm looking for any tricks, techniques, or ideas from the vast collective wisdom of the forum. How can I improve on this?

Here's what a fresh fire looks like on my system now:

1. At about 5:47, I turn off the 'Fan Enable' switch in preparation for fire building.
2. At about 5:54, I light the fire and enable the fan. At this point the bypass damper is open. Several things happen:
   • The wood boiler fan comes on at full speed to get the fire going.
   • The Vesta starts a preheat cycle:
     • All the heat loads (Main Floor etc.) are inhibited
     • The storage tank zone valve opens
     • The wood boiler circ comes on at full speed to heat the wood boiler from storage
3. The fire is starting and the boiler inlet temperature is rising due to circulation from storage.
4. At 6:01, I close the damper. That causes combustion temperature to spike.
   • The Vesta recognizes that a fire has started
   • The Vesta switches to 'Wood Mode'
5. At 6:04, the Vesta preheat cycle ends and the wood boiler recirculator is enabled (inlet protection), aiming at 140 degree inlet temp.
6. At 6:11 'Fire Near Target' is achieved - the combustion temperature passes 1000 degrees. The wood boiler fan switches to PID control, aiming at 1100 degree combustion.
7. At 6:14, inlet temperature reaches 140. Elapsed time since start: 20 minutes.
8. At 6:19, boiler outlet reaches 155, my minimum usable heat value. 'Wood Boiler Active' becomes true. Elapsed time since start: 25 minutes.
   • Zone Inhibit is canceled
   • Heat load zone valves are allowed to open
   • Wood boiler circulator switches to PID control, aiming at a boiler outlet temperature of 180.
9. At 6:25, outlet temp reaches 180. Elapsed time since start: 31 minutes.

 

[maple1]

I can't think of anything that would improve that start up.

I was thinking it takes me about 20 minutes from lighting (with a torch - so, there's an improvement for you - use a trigger start torch! ), to get useable water out of the boiler (160). I will try to time it later on today when I light - I might be off a bit. I am somewhat hampered on startup by not having a draft fan, so my draft needs to build on its own. 'Spooling up the turbo', I say. I have a couple of little things I do to try to make that happen as fast as possible, particular to my boiler.

Good idea on the preheat cycle. I would need to turn all my zones up and temporarily jump the speed up on my Alpha, I think, to get that to happen. Turning on the boiler pump (loading unit) would I think just circ around the bypass. So I don't bother trying it. But maybe I should try just turning all my zones up & see what happens - I think though that I would just get flow through storage rather than the boiler. You have a bit more control at hand than I do - lol.

But - I have to wait for the first complete lap through storage before I see water that hot out. That means the first couple of hours, I only get 165 or so coming out. Which works fine for me and the baseboard I have.

 

[stee6043]

Your timeline seems similar to my average. However, I generally reported my elapsed time from lighting of fire to useable heat as approximately one beer. Seems consistent with your results on all but the most stressful days at work.

The only way I've found to speed my startups even just a little was to throw in one or two very small pieces of fire starter with each load. I buy a box of these each year and use about 1/8 of a stick for each fire. For me at least this takes several minutes out of the startup process and also ensures I don't have any misfires (which happen on occasion when trying to be too frugal with kindling late in the year).

Have you tried starting the fire with no fans (just a lower door open) to see if your fire builds faster?

 

[Nofossil]

Have you tried starting the fire with no fans (just a lower door open) to see if your fire builds faster?

I have. It actually might be a bit faster - 4 minutes to damper-close rather than 6 minutes. However, it smokes like an OWB if I start it that way. With the fan, there's very little smoke even during startup.

By the way - my timer for closing the damper is shooting a rack on the pool table.

 

[jebatty]

Your system controls may do this, but I think my start procedure may be just a little different and that may make a difference. My boiler via a circulator only heats storage, hot supply to top of storage, return to boiler from bottom of storage. All loads draw from storage and are independent from boiler operation, supply to loads from top of storage and return to bottom of storage.

Boiler return protection is with a Termovar. Boiler circulator is set to "on" when boiler temp reaches 145F. The Termovar then regulates return water protection, dividing boiler supply between supply to storage and supply recirculation to boiler. The Termovar maintains minimum boiler return at about 140F.

On fire startup, if storage bottom of tank temperature is at least 10F higher than boiler water temperature (a near certainty), then I manually turn on the boiler circulator and manually open a Termovar bypass valve to preheat the boiler. I start the preheat before starting the fire with the goal of substantially preheating the boiler before I start the fire. When the boiler is preheated to about -5F from bottom of storage tank, I manually turn off the boiler circulator, manually close the Termovar bypass valve, and start the boiler fire. Boiler heating then progresses, and the boiler control turns "on" the boiler circulator at boiler temp of 145F.

I found the fire starts and heats faster with preheating before firing the boiler.

 

[maple1]

How cold is your boiler when you start a next day burn? (Anyone?).

I just lit, and my boiler was 100/90. My storage is 135/120. So I only had 30° difference between them. Or maybe less - that lower storage tank is in the middle of my bottom tanks. So preheat wouldn't have been huge for me today at least - but would likely help some.

EDIT: I am liking these damper timing methods.

 

[huffdawg]

Heres my start this morning with Storage and house loop pump on. Storage temp looks to be about 130 on top and a couple of degrees colder on the bottom. My pump launch is set at 170f , danfoss 140f. I could have usable heat quite fast if I switch off the storage pump as the boiler out flows into buffer tank which is a basically a 150 gal manifold.

Boiler was 105f.

 

[maple1]

OK, will give the rest of todays start details.

This was one of my faster starting burns I think. It seems to vary depending on outside conditions (not cold here today, just below freezing, but a bit breezy & overcast), and the particular fire starting stuff I pick off my pile. Must have grabbed really dry stuff today. I start with small load, of a couple of pieces of softwood on the sides, newspaper crumples on the bottom, handfull of kindling, few very small pieces on that. One crumple of paper on the top. I light that, close the top door, then light underneath after a few seconds. Gets my draft going.

I also leave my secondary glass door out all together until I close my bypass damper - also helps the turbo get spooled up.

I put the door in & closed my bypass damper at 2 minutes after lighting and had immediate good gasification.

At 18 minutes after lighting, I had 170 water coming out the top of the boiler. 115 going in the bottom. Loading unit had not kicked on yet, it was convecting. No idea with how much flow but not much. Loading unit kicked on then (at 18 minutes), flow settled in. Return to boiler jumps to 150 when the pump starts, then smooths down to 140. Top out was still about 170. It will likely be down to 165 when I go back down and load the rest of the way up for the burn.

I wasn't expecting it to get up to temp that quick - was expecting it to take another 5-10 minutes. Hadn't timed it before though - tomorrow could be different.

 

[huffdawg]

Looks like mine was up to 170f in roughly the same as yours Maple. I do run with my secondary door open for 5 mins or so though.. NoFo is right smokes like a bugger. I wonder if it is better to totally charge my buffer tank first before sending to storage?

 

[ewdudley]

At the end of the burn cycle, switch off the draft fan when stack temperature has fallen because of end of gasification. This will leave a good bed of charcoal ready for starting the next fire. Re-starting with charcoal allows gasification to resume rapidly after just of a couple dozen seconds.

Ideally you would also want to valve-off the combustion air inlet automatically when stopping the burn to minimize burning of the charcoal due to natural draft.

 

[woodsmaster]

I'm usually gassing within two minutes of lighting.. I always leave secondary door closed. I light the fire, leave damper open for a minute or two. Sometimes I close damper for 30 seconds or so at beginning to suck the flame to the middle as I light the front, then open it for a minute or so to get wood off the bottom burning a little and close again. I leave the primary door cracked a little until flue temps get to 300F then close door and walk away. rarley does it take more than five minutes from the time I light it. My storage is almost hallways too cool to warm the boiler. i COULDN'T WARM IT WITH STORAGE ANYHOW BECAUSE MY boiler circ is also my storage circ and don't come on until boiler is up to temp. It's a very simple system without a lot of controls. Sorry about the caps. lol Ill try to post a video of how I light it tomorrow. Already did today's fire.

 

[Nofossil]

I've never been able to get solid and sustained gasification any quicker than 4 minutes after lighting. It seems like I have to have at least a few coals.

My storage is always at least 120, and usually 130 to 140. My boiler is usually down to 90 or less.

I do in fact shut down everything to preserve some coals, but I don't have a way (yet) to valve off the air supply, so I do get some natural draft combustion.

 

[huffdawg]

I'm usually gassing within two minutes of lighting.. I always leave secondary door closed. I light the fire, leave damper open for a minute or two. Sometimes I close damper for 30 seconds or so at beginning to suck the flame to the middle as I light the front, then open it for a minute or so to get wood off the bottom burning a little and close again. I leave the primary door cracked a little until flue temps get to 300F then close door and walk away. rarley does it take more than five minutes from the time I light it. My storage is almost hallways too cool to warm the boiler. i COULDN'T WARM IT WITH STORAGE ANYHOW BECAUSE MY boiler circ is also my storage circ and don't come on until boiler is up to temp. It's a very simple system without a lot of controls. Sorry about the caps. lol Ill try to post a video of how I light it tomorrow. Already did today's fire.

only one fire? must be nice

 

[Nofossil]

For me, an average winter day takes 5 or 6 hours of fire. The last 24 hours here were cold - high of 7, low of 0. It took a burn of about 8 hours to make up the heat loss for the day (starting and ending with the same amount of heat in storage). 8 hours heating the house and storage from the boiler, 16 hours heating the house from storage.

An 8 hour burn for me means visiting the boiler three times:

1. Build the fire (includes about 1/3 load of wood)
2. Come back in an hour and refill to about 2/3 full
3. Come back in 3 hours and pack it to the gills.

A full load in a hot boiler will burn for about 4 hours. Since I don't have enough storage, I try to time it so that my third visit is just before bedtime. That way the boiler heats the house as far into the night as possible.

 

[woodsmaster]

only one fire? must be nice

It's been above average temps here until last couple of days. My boiler is a little oversize for my heat load and I haven't been putting much heat into my work shop to conserve on wood. Last night was are coldest night of this winter. It got down to 11 F. One reason I picked the biomass 60 is the
length / amount of wood it holds. I had about a 1/4 of a load of wood left last night when my timer shut the boiler off so I topped it off this morning and reset the timer. Ill have to do another fire tonight before bed and put a little heat in the shop also.

 

[Nofossil]

I hadn't thought of leaving that much unburned wood in the boiler at shutdown. I think if I did, I'd have two problems:

1. I'd have continuing (maybe smoky) combustion due to natural draft
2. The boiler would generate enough heat to periodically switch the system back to boiler mode from storage mode, but not enough heat to actually keep the house warm.

Guess I'll stick to building a fire every day or two.....

 

[JohnDolz]

only one fire? must be nice

I am pretty new here and haven't added any info to my User name but when I do I will add square footage being heated as well. SqFt would help to better understand the meaning of 1 fire today with 1000 gal of storage. I will do 2 fires today (with a little extra wood thrown into each burn. Heating 3300 sq feet of Living Area to 72 and 1500 sqft of unfinished basement to 67 degrees. Of course you can then wonder how much wood goes into each burn......

 

[Nofossil]

I am pretty new here and haven't added any info to my User name but when I do I will add square footage being heated as well. SqFt would help to better understand the meaning of 1 fire today with 1000 gal of storage. I will do 2 fires today (with a little extra wood thrown into each burn. Heating 3300 sq feet of Living Area to 72 and 1500 sqft of unfinished basement to 67 degrees. Of course you can then wonder how much wood goes into each burn......

I'm heating 3500 square feet in Vermont along with DHW (and sometimes a hot tub). I use a bit over 4 cords a year. My heating season starts in October and ends in April, plus or minus.

 

[huffdawg]

Im heating two dwellings one two level with 2800 ft of heated space with lots of windows. and a 50 gal DHW TK, infloor over pour on main level , all conventional baseboard in series upstairs.

Upstairs heated to 69f . main floor 72f.

Second dwelling 900 square ft shop on main floor with 900 sqare ft suite on second floor , 40 gal DHW TK.
Heated to 69f

All with r19 walls. house - r30 attic Suite r22 cathedral ceiling.

House Heat Loss 38,000 btu per/ hr.
Shop and Suite Heat Loss - Unknown

Burnin just over two loads per day,was -9c last night ,just over 0c during the day.

 

[maple1]

Just lit again, a bit different results today.

Took 20 minutes to get to 160 at top of boiler. 25 minutes to 170. At 28 minutes the loading unit kicked in at 180.

As soon as the boiler starts heating it starts convecting some to storage, before the loading unit kicks in - that affects time some.

Gasification was slower building, it was going in spurts for the first few minutes. It was 10c colder today so should have had better chimney draft, but I also added a turb before I started. Also think I used a piece of juniper that was only a year seasoned for kindling, instead of my 2 year old windfall spruce kindling material stash. I also could have crumpled the newspaper a bit tighter and held my head a bit differently - who knows.

 

[huffdawg]

Looks like 30 mins this morn with the storage circ off

 

[Nofossil]

Reading through all of this, it seems like more kindling might shorten the time to gasification, and maybe the blower should ramp up during damper-open start rather than run full speed the whole time. Regardless, 30 minutes isn't out of line.

More experiments....

 

[huffdawg]

Reading through all of this, it seems like more kindling might shorten the time to gasification, and maybe the blower should ramp up during damper-open start rather than run full speed the whole time. Regardless, 30 minutes isn't out of line.

More experiments....

I used two good handfulls of cedar kindling and then chopped up 4 or five splits. I lit from the secondary chamber with map gas torch , then left secondary door slightly open approximately 5 mins. shut bypass and get instant gratification. Using douglas fir for wood.

 

[maple1]

shut bypass and get instant gratification.

Now there's a Freudian slip if I ever saw one. Or maybe not a slip?

 

[huffdawg]

shut bypass and get instant gratification.

Now there's a Freudian slip if I ever saw one. Or maybe not a slip?

Lol. trying to see how long it would take someone to notice that. It was quicker then Gasification.