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burning pellets for newbees

May 2, 2013
burning pellets for newbees
  • So you just bought your new pellet stove & had it installed & fired it up for the first time and maybe smelled a little
    paint burning off. Dont worry, pellet stoves do that for the first 3 or 4 runs, until the paint cures.

    But now, you have the dreaded "BLACK WINDOW".

    Pellet stoves have an air wash system that is susposed to keep the window from getting black, but, if you turn down the primary combustion chamber outside cold air control, because you mistakenly think you are keeping excessive heat from blowing out the exhaust vent,
    you not only dont give the fire enough air to burn clean but also dont give the window air wash system enough air to wash the window.
    You end up with a dirty fire that causes clinkers to form in the fire pot and dirtys up the window all the faster as well as an air starved window air wash system that is no longer powerful enough to keep the window clean.

    The simple cure for all these woes is to meerly open up the cold outside primary combustion air control.

    Terms for newbees:

    Black Window---- Your window turns black with soot caused by incomplete combustion caused by not enough intake air. Cure is to open primary air .

    After the heating cycle is over & then only when stove is off and well cooled,spray windex &
    paper towell the sooty window.
    NEVER SPRAY WINDEX ON A HOT WINDOW, WINDOW MAY BREAK FROM THERMAL SHOCK.

    CLINKERS -- A mound of half burned Pellets stuck to your fire pot usually because there was not enough enough combustion air for clean burning. The cure may be to open primary air to combustion chamber or otherwise adjust your combustion.

    Cold Outside Air to Combustion Chamber - This is the major air supply that the pellet stove picks up from outside the house, pulls into the combustion chamber & burns. It is also responsible for providing enough air to the air wash system to prolong the time needed for formation of enough soot to eventually blacken the window. You should be pulling your primary combustion air from outside through an OAK=Outside Air Kit , otherwise, your pellet stove creates a vacuum inside your room and pulls outside cold air under the doors & around the windows , needlessly chilling your house.


    NOT ALL PELLET STOVES HAVE manuel primary air controls. Some pellet stoves have factory preset primary air control settings selected by computer. IF YOU HAVE ONE OF THESE MORE EXPENSIVE PELLET STOVES,much of the above discussion does not really apply to you as the setting is automatilly selected by your stoves computer. But just because something does not at this moment, directly apply to you,is no reason to not learn about it. You may later have to know how to opperate a cheaper pellet stove with a manuel primary air control .

    SHUT DOWN CYCLE, LENGTH OF,

    The shut down cycle is responsible for cleaning out the firepot of any clinkers, tar , creosote as well as providing fresh air to burn up any smoldering Pellets that popcorned out of the fire pot & are laying on the inside floor of the stove smoldering.

    ON SOME PELLET STOVES, THE LENGTH OF THE SHUT DOWN CYCLE DEPENDS ON THE HEAT OF THE HEAT EXCHANGER. The hotter the heat exchanger,the longer the shut down cycle. Thus , turning a stove on ,letting it burn for 5 minutes and turning it off, will result in a cold heat exchanger, a short shut down cycle, smoldering Pellets on the floor of the stove stinking up the room & clinkers in your fire pot that take forever to clean out by hand.

    FOR EASE OF CLEANING AND MAINTAINANCE , always let your pellet stove run long enough for the heat exchanger to get good & hot & when you go to shut down the stove, put the room air circulator fan motor on its slowest speed. The slow speed of the room air circulator keeps the heat exchanger hotter for longer & gives you a nice long shut down cycle.

    DO OPEN THE PRIMARY AIR UP FULLY ON STOVES WITH MANUAL PRIMARY AIR CONTROLS, DURING THE SHUT DOWN CYCLE, ABOUT 2 to 3 MINUTES AFTER THE FLAME GOES OUT.

    The idea here is to clean out the fire pot grate, but only after most of the glowing Pellets have gone out. Some glowing Pellets are stickers, they stick to the fire pot but the extra air of a full open primary control (on Stoves so equipped) will blow these stickers out of the fire pot or cause them to glow hotter, until they expend their fuel. You don't want to blow out onto the stove floor all the glowing Pellets because they could fall onto unburned Pellets on the stove floor & cause smokers.(long smoldering Pellets 1/2 buried in ashes.) So, let most of the glowing Pellets in the fire pot burn out with normal primary air & then after most are dead, clean out the stickers with maximum primary air.

    This blows out or POPCORNS OUT all the glowing Pellets and leaves you with a nice clean fire pot ready for the next burn cycle. The glowing Pellets will fall to the inside floor of the pellet stove where they will glow for another 2 or 3 minutes. As long as the shut down cycle continues longer that the Pellets glow,you will never have smoke smells in your room.

    Clean the inside floor of the stove as soon as you see an accumulation of unburned Pellets so that you don't get any smokers.(long smoldering Pellets on the stove floor).

    POPCORNING-- reference to hot air popcorn machine & Pellets blowing out of the fire pot, usually caused by too strong a primary air flow caused by too open a primary air setting. As Pellets burn ,they become lighter in weight and will popcorn even with a proper primary air setting.

    FIREPOT OR FIRECUP -- This is the stainless steel box ,pot or cup that the Pellets burn in. It must be keept clean with all air holes/ air slots opened up of ash or soot or partially burned Pellets.PAY CLOSE ATTENTION TO HOW TO REMOVE AND REPLACE THE FIREPOT ON A NEW STOVE UNTIL YOU GET USED TO THE PROCEEDURE.

    ASHTRAP---- UNDER THE FIRECUP is the ash trap. THE ASH TRAP MUST BE CLEANED OUT AT THE END OF EVERY BAG OF Pellets, or every 2 or 3 bags of Pellets, depending on your particular stove. Ash trap design & capacity
    varies from stove to stove, so some stoves will go longer without cleaning.

    A HALF FULL ASH TRAP BLOCKS OFF HALF OF YOUR PRIMARY AIR FROM THE COMBUSTION CHAMBER, FIREPOT AND AIR WASH SYSTEM.

    Up to a point, you can compensate for a dirty ash trap by opening up your primary air control, but the point will be reached when the ash trap ashes clutter controls the air flow to the combustion chamber and not the primary air control system.

    HEAT EXCHANGER--------- ,these are the pipes that go through the combustion chamber above the fire pot & just below the hopper.Cold room air is blown through the inside of these pipes & hot air comes out the front of the pipes.
    This is usually done by the room air circulator fan motor.

    MOST PELLET STOVES HAVE 3 MOTORS.
    1. combustion air motor
    2. room air circulation motor
    3.auger drive motorfor pellet feed.
    more info on these motors later.

    SHUTTING DOWN THE PRIMARY AIR DOES NOT SAVE ANY HEAT---- "ON A PELLET STOVE."
    WOOD BURNERS MAY make this bad assumption on a pellet stove, thinking it similar to a wood stove, which it is not.

    HERE IS WHY. The pellet stove will feed the same amount of fuel, depending on the pellet feed setting selected from the control panel, weather the primary air is adjusted for complete, hot, clean combustion or set for partial ,inefficient, sooty, dirty, tarry, colder combustion that only messes up your stove the faster.

    Its not like choking down a wood stove for a overnight burn.
    Some People run their pellet stove with wide open primary air all the time. I run mine about 1/2 open with a clean ash trap & 2/3 or full open if the ash trap is fairly full.
    PRIMARY AIR SHOULD BE ADJUSTED FOR THE CLEANEST BURNING!!!!

    FULLY UNDERSTANDING PELLET STOVE AIR FLOW.

    Many pellet stoves opperate on this air flow pattern, but some will differ. If your differs,find out how from the dealer or manufacturer. MOST Manufacturers HAVE DOWNLOADABLE OWNERS MANUELS ONLINE ON THEIR WEB SITES NOW, AVAILABLE TO ANYONE FOR FREE.

    The 3 inch double walled stainless steel exhaust vent, that goes out through the wall thimble or hooks up into your chimney is connected to the blow side of the pellet stove combustion fan motor's squirell cage fan. This sees air off the fan blades, like water off a steamboat paddlewheel.

    The duct from the back side of the heat exchanger is connected to the suction side of the combustion chamber motor, the center of the squirell cage fan. It should be apparent that the rest of the pellet stove must opperate on suction, at this point in the explination.

    The suction through the outter sides of the pipes of the heat exchanger pulls air across the combustion chamber & through the slots and holes in the fire pot, pulling fresh combustion air from the ash trap under the fire pot. THIS IS THE REASON WHY IT IS SO IMPORTANT TO KEEP A CLEAN ASH TRAP AND CLEAN CLINKERS OUT OF THE FIRE POT.

    tHE ASH TRAP UNDER THE FIRE POT---- Should have a large capacity for ashes to fall down into it from the fire pot. The mfg says it does have a large capacity, but it always fills up, all too soon & HALTS opperation of the stove. the more you burn, the faster it fills.

    AT THE BACK OF THE ASH TRAP is the air duct that leads to the primary combustion air contol & sucks fresh, cold outside air into the stove through the 2 inch diameter air intake pipe at the back of the stove that you or the installer has hooked up to the outside air intake pipe.

    On my stove, the primary air intake control is meerly a round plate of steel, two inch in diameter , pivoted at the bottom of the pipe and attached to a slide rod at the top. I push the rod in and close off primary air. It is stop pinned so that it can not be fully closed & remains 1/8th open. Not unlike the choke of a carburator. I pull the rod out to open the primary air flow.

    Other pellet stoves may have more complex primary air controls.

    AT ANY RATE , ANYTHING THAT BLOCKS OFF , OR PARTIALLY BLOCKS OFF, THIS AIR FLOW SYSTEM WILL STOP YOUR PELLET STOVE FROM RUNNING PROPERLY.

    Pellet stove motors

    combustion chamber motor , variable speed , computer controled. Runs at different speeds.
    For start up cycle mtr runs slow until fuel catches fire well,mtr may get a signal from the heat of the heat exchanger to speed up once Pellets are burning well by way of a heat exchanger thermostatic switch or a computer controled thermo sensor mounted in the heat exchanger.

    run cycle, mtr speed varies depending on heat of heat exchanger,ei, a cooler heat exchanger will call for heat by speeding up the combustion fan mtr to make the Pellets in the fire pot burn faster, combustion fan mtr speed will also vary with pellet feed rate selection.

    Shut down cycle, here, the combustion fan motor runs full speed, wide open, to burn up any clinkers or Pellets stuck in the fire pot or smoldering on the inside floor of the stove.
    It will only shut down after a minimum elapsed time and only after sensing a cold heat exchanger.

    Room air circulator fan motor; My stove selects 6 speeds from the computer control board. Whatever speed i set it at ,it stays there unless iImanually select a different speed. This motor sucks cold air from down near the floor & blows it out hot from the heat exchanger outlet.

    Pellet auger drive motor - this motor runs at constant speed, it is a one speed motor;

    HOWEVER, the computer selects its run time duration as well as the interval of time between activations.

    The auger drive motor may run for six seconds and stay off for 10 seconds on low feed.
    this motor may run 8 sec. & off 10 sec on med low feed.
    auger drive motor may run 12/ 14 sec & off 16 seconds on med setting. Because the motor delevered more Pellets,it needs to wait longer for more Pellets to burn up or risk overflowing the pellet cup.

    The auger drive motor may run 16/18 sec on high feed setting & stay off 20 sec. to give time for the extra Pellets to burn up.

    These numbers are wrong, even for my pellet stove & will definatly be wrong for yours, but I am only giving an example here, so you can catch onto the operating principles & not giving hard tech data.

    That info may not even be in your owners manuel.

    CLEANING UP YOUR NEW PELLET STOVE.

    FIRST, make sure to wait until all the ashes are absolutely dead cold.If in question ,run your hand through all the ashes, & if you don't get burned,its safe.

    Now, instead of buying a ash vac for $400.00, lets use your $39.95 wet dry shop vac sitting out in the garage & I'll tell you how to set up the vac filters so that the soot don't get into the motor bearings and burn up your vac motor.

    Put about 1 or 2 gallons of cold water in the vac tank to act as the first ash filter. You want to keep the water line WELL CLEAR of the paper filter we will be using so that it dont get soggy & disintergrate.
    Your normal vac filter and foam cover should stay in place and buy a paper filter to fit around it. Wal mart,k mart , sears, home depot,lowes,ace & true value hardware all carry them. Bring your vac make & model #,just in case. If you dont have a wet/dry shop vac, the 7,8,9,10 gal size work well, while the 5 &6;gal size--- the water may get too close to the paper filter & sog it out.

    So, here is the secret, the water catches some of the ash,the paper filter catches a lot of the ash,the foam filter catches more of what is left over & your regular filter catches the really fine particles. You end up with a really serviceable ash vac at 1/10th of the price. Works great on wood stoves and oil & gas furnaces, too.

    Remember, water, paper ,foam & corrigated paper filter, you need all 4 filters to properly protect the vac motor.
    The paper filter is the most important of all the filters, but should never be used all by itself for ashes.
    I have seen ashes eat out a vac motor in under 3 minutes without all 4 filters in good shape. They motor wont take it, not even a little, you are relying solely on the 4 filters, so they need to be all there and all in good shape.

    You need a vac for a pellet stove because there just is not room to get your hand or anything much else into the ash trap to clean it out with. The slender crevice pointer vac tool seems to work best. I use a good 9 or 12 LED flashlight, that takes 3 aaa batteries so i can see that ashes & the light is small and handy. Sometimes I use electrical tape to tape a cloths pin onto the LED pocket light to clip it on the sheet metal of the stove for hands free vacuuming.

    That is every thing I know about pellet stoves, although I more that likely forget to tell you some little thing that slip what's left of my mind.