Basic Blower Question

[Sugardaddy]

This is my 2nd year and I'm expanding (doesn't everyone?). Going from under 20 taps to about 90 and my cooking pot is being retired in favor of a 20x30 SS pan a friend is fabbing for me.
I boil on a modded BBQ pit in the backyard. I plan to raise the fire closer to the pan bottom and am trying to figure out the blower. Does the blower bring air into the fire to make it burn hotter? I'm a bit confused, as I'm reading posts here that talk about mounting the blower at the back.

[RileySugarbush]

Most of the basic draft blowers are just blowing air up through the grate to increase the combustion rate and therefore the temperature at the top of the fire and in the flue gases that run through the flues of the sap pan. A very real benefit is complete combustion of all the coals so you don't end up with a fire on top of a pile of coals after a few hours. That is likely the case in your setup. When people describe the blower as coming in the back, that just means it is connected to the back of the area below the grate, and out of the way. It could be in the front just as well, but would get in the way of firing.

There are more complicated combustion air setups, but just adding some through the grate can make a huge difference.

[Sugardaddy]

Ahhhhhh....

Like opening the air intakes wider on the front of a woodstove? I get it. I'll have to see what I can devise for my set up. I'm using cinderblocks to raise the fire grate, so maybe I'll put them on thier side and run a duct thorugh the holes. Connect to a blower and off I go!

[RileySugarbush]

That will work, but hook it up as tight as you can and only have one hole open or you will be blowing unpleasant stuff everywhere! And shut it off before you stoke the fire. My last year on a block arch was pretty efficient when I added forced air with a cheap leaf blower through some galvanized ducting.

John

[Brent]

a small variable speed switch on the power line is a big help. depending on how well you seal everything you will get varying amounts of stuff blowing everywhere as noted above.

With the vari speed you can crank it up to the point of too much and then back off a bit.

Good luck wiith it.

[Sugardaddy]

a small variable speed switch on the power line is a big help. depending on how well you seal everything you will get varying amounts of stuff blowing everywhere as noted above.

With the vari speed you can crank it up to the point of too much and then back off a bit.

Good luck wiith it.

Is a vari. speed switch something I need to splice in, or is it a plug in tye of item that the blower then plugs into? I'll go shopping this weekend, but it would be helpful to know what to look for.

Thinks I'll seal the other cinder block holes with ref. cement and pieces of brick.

[Brent]

some blowers come with them built in. The blowers on our wood stove that heats our house have them built in. You won't get the best deal in the world at at a fireplace shop but they might have a package that works out of the box.
I had a small blower that pulled about 4 amps and it made a huge difference on our Leader Half Pint evaporator and it sounds like yours is going to be about the same size. When selecting, go larger and then dial back the speed to suit. If you're like the rest of us there's a good chance in two years you'll be upgrading again and the larger blower will save you doing it all over again.

Depending on the size blower and the current it draws you might be able to get away with a dimmer switch for a light.

[maplehound]

Another reason most put the blower at the back of the fire pit, is that the air will then reverse direction as it comes up through the fire sue to the pull of the draw from the stack. If you put the blower at the front it could blow the air and any heat with it, past the front of the pan. Thus making it hard to get a boil on the front bay of your pan. Wich is where most are finishing there syrup.

[RileySugarbush]

You should be able to find a cheap ceiling fan speed control at Home Depot or Lowes.

[mfchef54]

I have a cider block arch. Front doors (two pieces of tin) are not air tight. also my grate is a standard fire place grate. my feeling is that if I have it blowing forward it's just going to blow the fire forward and out the doors . My plan is to have the blower on the side in the front. I did a test run last week and it seemed to work fine. I picked up my blower (leaf) at Lowes for 29.97. Now to incorporate the dimmer switch. thanks again for all the great ideas.

[Brent]

The firebox is going to get pressurized a bit when you put the blower in no matter where you aim it. This is going to cause some smoke/fire to blow out where ever there are leaks. So put the blower where it is most out of the way of getting kicked.

This is why you see air tight arches fronts and doors for $2700 on the dealer's web sites.

Keeping this to a tolerable level is the second reason for having a variable speed.

You will likely spend some time trying to figure out how to put some gaskets around the doors to minimize the blow by.

I stood some fire bricks on the floor of the arch to direct the air from the blower around the base of the fire. After you run it a few times you will be able to see what areas are getting more air and re-direct some of the blast from the blower.

Good luck

[WESTVIRGINIAMAPLER]

Unless you have an airtight front or semi-airtight, you are much better off mounting it at the front of the arch. It will help a lot and cut down on blowing ash around. Mounting it behind is going to make a big mess unless you crank the blower down to the point it is not doing you much good.

[Sugardaddy]

Since I'm boiling on an old brick BBQ pit I'm nodding, i am going to have to mount this from the front. I can't put an opening anywhere else without possible making this thing collapse (it's not in great shape now!). I'll play around with ths and see what I can do to make it work best. I wonder if I can use threaded iron pipe to direct the air flow inside the firebox area itself?

It will take some playing, but I'll get it. Thank you all!

[RileySugarbush]

You can blow through a steel pipe, but if it is stuck in the coals, you may burn the end off of it. That makes a forge and the temperatures where the air hits the coals is incredible. We know this from experience.

It's is not a problem when you have a high volume blower routed up through the grates, because the coals never drop through, they burn up on top and that's the extra heat that speeds up the boil.

Here is something you might want to try:

Get some firebricks and make a ring around the base of your grate, leaving a small gap for some duct to go through. You can use an elbow or two in the duct to move the leaf blower out of the way. They can be kind of loud, so move it a few feet away. I uses about 10' on my old set up. Out there, een the flex duct will work since it is in the cool. Just jam the snout of the blower in the duct.

Put a grate over the top of the brick ring. A flattened grate would be best but a fireplace grate would work too. You may want to put a firebrick in front of the air inlet to diffuse the air flow a bit.

The goal is to get a medium velocity flow of air evenly through the grates by boxing in the area below them.

When I did this, the results were fantastic. A constant steady boil, none of the old simmering.

Good luck!

[sweetwoodmaple]

I've had good experience with mounting at the back. Whether front or back, you still have to duct or use bricks or whatever to get the air flow below the grates and up into the fire.

As Brent said, Once you fool around for a while, you should be able to balance the air flow such that you can fire the evaporator and not loose the boil. The reason is that when the air is balanced right, opening the front doors to fire has almost no effect because the fire is being fed the right amount from the forced air.

With my old 2 x 6 setup, I would only have to kill the fan motor to fire when I was first getting the fire going. After that, I could turn the fan down a little bit and leave it there.

Good Luck.

[Sugardaddy]

This is all very helpful. I like the firebrick below my main grate. The extra grate on the firebrick will keep the coals off the end of the pipe/duct, right?

There's a lot I still don't understand fully in the sugaring process, but I've learned more this year than I thought possible. Good thing, since we're upping our production approximately 1000%! Producing 3 gallons on a very inneficient open fire is very different from 30 gallons on a better thought out rig.

[Father & Son]

One way to adjust/control the airflow is to put a damper in the plenum, that way you can run the blower wide open (the way they are meant to be run) and adjust with the damper.

Jim

[mfchef54]

what is a plenum?

[danno]

Just about any arch can be made air tight:)

I put fire brick around the exterior of the arch at the bottom - where the older archs were about an 1" off the ground. Also, leave some ash in the fire box and bank the sides. Stuff insulating blanket wherever needed. For smaller cracks, use high heat caulk (the red stuff).

Where the two arch doors don't quite come together - I take a peice of steel plate and bolt it to the inside of one of the doors. Can only open one door at a time, but it works great.

Also have used woods stove door rope around both arch doors and ash door.

I like forced air, but not smoke and ash in the sugarshack!

[Father & Son]

A plenum is the duct that runs from the blower to the evaporator.
Here is a picture from a recent ebay auction that shows it.

Jim

[lpakiz]

Hello,
I rigged up a fan on my unit and used pieces of my old truck exhaust pipe. I cut out the bends, straights, etc and tacked them back together in the configuration I needed. If you can't find these pieces, an auto parts store will sell you elbows and straight tubing. As to the issue of controlling the amount of air, just cover the intake (partially) to get the correct output. Contrary to popular opinion, this will not over work the moter. In fact, the motor will draw less amperage when the intake is restricted. The motor is worked more when you restrict the outflow. (the impeller runs in a partial vacuum, so not as much to pump).
Larry

[Brent]

Larry

it may not overwork the motor but depending on the design it may need the air flow for cooling the motor itself.

[tapper]

I have used many smaller squirrel cage fans over the years and some are made with the damper on the intake. As long as they were kept oiled they lasted for years.