Opening arch door with forced air

[tonka]

On an evaporator that has aof and auf, dose one need to shut the auf off before opening the door to fire while aof is still on?

[RileySugarbush]

On my system, yes. It would be a big mistake to have your face near the open door with the blowers on. Some others can fire with the blowers on.

I put my blower in a box with a inlet flap door that opens and closes very fast. If you turn the blower off and on electrically, you will have to wait a second or so before opening and again for the blower to spin up after firing.

[Sugarmaker]

I don't shut either the AOF or AUF off during firing.
Regards,
Chris

[Bruce L]

Don't think I would want to try it,I find ash at the bottom of the door,pretty sure there would be flames shooting straight out the door if I didn't shut off the aof and turn down the auf.

[RileySugarbush]

It must have been you I was thinking of,Chris. I've seen you mention not shutting down the air when firing. I have turned my air on with the door open and its pretty spectacular. You must have some great draft!

[maple flats]

When I first installed my AUF/AOF I started shutting off the blower to fuel, then one day my grandson was helping and he forgot to shut the blower off. Ever since we no longer shut ours off. We never see any flame or ashes/sparks coming out the front while fueling. Our blower now stays on all the time from about 2-3 minutes after lighting the fire until all the coals are burned up. We do not start our blower until the fire starts burning, which takes very little time since we use a 500,000 BTU weed burner torch at about 1/2 throttle to light the fire. 2-3 minutes and it's going good, no kindling, just wrist sized wood stacked criss crossed and 3-4 layers high.

[ennismaple]

We need to shut down the primary air on the Force 5 to fire. If you don't there's waaaaay too much heat getting blown back and you can't get close enough to load it. The secondary air stays on from first fire until shutdown.

[Russell Lampron]

I have AUF and don't shut my blower off either. My blower and my bubbler are on the same breaker and get turned on when I light up and turned off when I shut down.

[GeneralStark]

You guys are all comparing apples and oranges....

[wiam]

You guys are all comparing apples and oranges....

And bananas maybe.

[Ghs57]

I do not turn off my forced air when firing. However, I would not put my face or any other exposed skin in front of the open door. I get a few sparks out the door, but no smoke.

As always, "your milage may vary"

[doocat]

Ennis if you don't mind, is primary air under fire, and the secondary air over, behind, door, etc?

Thanks, Craig

[GeneralStark]

And bananas maybe.

Good point...

With my rig, and likely most other commercial forced air arches, I would be risking serious bodily harm or burning down my sugarhouse if I did not close the auf damper when opening the door. The door air damper can stay open as can the rear aof damper, but I still choose to turn them down because they can still blow sparks out the door.

I have to be very careful when the door is open to not burn myself. The first season I had this rig, the left side of my face was bright red after the first couple times I used it. I quickly altered my technique and started using safety glasses when loading...

[ennismaple]

Ennis if you don't mind, is primary air under fire, and the secondary air over, behind, door, etc?

Thanks, Craig The air under fire blows up through a grid of holes in the fire bricks under the logs and also blows through an opening above the door, through the door and then out a slot in the bottom of the door (when the door is closed) under the front of the logs. If the primary air was left on you'd have pre-heated air blasting in your face plus tons of sparks blowing out onto the floor. Guaranteed you'd start a fire in the sugar camp.

I've accidently left the primary air (AUF) on when I opened the door and I'll never do that again. It's the fastest way to remove your eyebrows, eyelashes and all other exposed hair.

[tonka]

That explains it! I've seen videos on youtube of certain evaporator models and they have the door wide open and still have the air still on which made me scratch my head seeing that. They have the AUF damper on but still have AOF damper open. So my next question: how important is stack hight while running forced air? I know the stack needs to be twice the length of your cooker in order to create natural draft, is it the same rule of thumb when your mechanically creating draft?

[Russell Lampron]

I'm thinking that when you use aof and auf that stack height doesn't matter but with that being said I have a 2x6 evaporator with 17' of stack. I think that the natural draft created by the tall stack is the reason that I don't have to turn my blower off when firing. I can see the flames being pulled into the arch with the doors open.

[Super Sapper]

I think it has to do with the amount air added compared to the draft. If you have more total air coming in than the stack can handle it will come out the door when opened. I just have auf and it is adjusted to where I can open the door and add wood without shutting off the auf, but will come out the door if I do not load quick enough. I tried more air but it did not change my evaporartion rate and just blew heat up the stack and I had to shut it off when firing.

[Daveg]

On an evaporator that has aof and auf, dose one need to shut the auf off before opening the door to fire while aof is still on?

Several factors come into play. It depends on the draft and chimney size in comparison to the size of the firebox and the cfm capacity of your blowers, whether the draft is near maximum at the time the door is opened, whether it is a windy day, and even the barometer can have an affect. Trial and error may be your best recourse.

[ennismaple]

That explains it! I've seen videos on youtube of certain evaporator models and they have the door wide open and still have the air still on which made me scratch my head seeing that. They have the AUF damper on but still have AOF damper open. So my next question: how important is stack hight while running forced air? I know the stack needs to be twice the length of your cooker in order to create natural draft, is it the same rule of thumb when your mechanically creating draft?

For a sealed front forced air unit like ours the stack height doesn't matter. Our stack barely clears the peak of the roof.