Reducing Grate Area for Spring Burning

Has anyone ever covered part of the grates on a handfired and achieved a successful burn? I'm thinking of covering about half of the grated in my Vigilant with firebrick. The brick would fill 1/2 of the fire box and reduce the coal volume by about half. Thought is to keep a smaller hot fire going to keep the chimney drafting. If the max stove output is normally 50,000 Btu, this reduced fire should be about half. 25,000 Btu should be enough for the spring temperature cycles of 50-60 daytime temps and 40-50 night time temps. I'm sure I'm not the first to attempt this but I could use the sage advice of those that have more experience with spring coal burning.

Never tried it but sounds like a good idea. How would you mount the firebrick over the shaker grates though?

Devil5052 wrote:How would you mount the firebrick over the shaker grates though?

That is the tricky part, the additional firebrick cannot interfere with the grate shaking. It does work well if you can do it. You need to build the wall out to shrink it, not just cover the grate. It really depends on the firebox design.

coaledsweat wrote:

Devil5052 wrote:How would you mount the firebrick over the shaker grates though?

That is the tricky part, the additional firebrick cannot interfere with the grate shaking. It does work well if you can do it. You need to build the wall out to shrink it, not just cover the grate. It really depends on the firebox design.

On my Harman the entire bottom of the firebox is 2 shaker grates that looks like they have about a 1 inch travel. (+ or -)
I would have to somehow suspend the firebrick over the grates???

Just had another thought......You could put the firebrick right on the shaker grates & just not use the shaker mechanism for these reduced sized burns. You would have to poke the grates from underneath in order to get rid of ash. (Not sure the hastle is worth it )

On many shaker grate designs, there is a perimeter steel box or braket that the firebrick rest on, and enough of this bracket is exposed that a upside down shaped 'U' piece of steel can be made to set on the brackets, wedged tight against the firebrick, leaving a gap between the steel and the shaker grates. This allows the shaker grates to move through their normal motion, and still seal off the section of grates so no draft is lost or can go around the fire... A wall of new addional firebrick are placed on the steel plate to make a new 'back wall' for the shortened firebox.

In my 'Big Bertha' firebox, which originally was 50" long [front to back] I placed a 1/2" steel plate on the bracket on each side of the grate, it was cut to fit tight against the firebrick, so it couldn't slide sideways and rest on the grate. I made a false back wall of stainless steel to support a stack of firebrick, and placed this new 'back wall' at about the 22-24" point in the firebox.. Reducing the firebox by more than half.

Is the grate system on the Vigilant the system that is split in two? requireing shaking one side, then moving the shaker handle to the other grate to shake it?? If so, then just covering one half would be easy, you just ignore the covered grates. ?? I know there is a hand feed that has a split grate-shaker system,, I just can't remember if the Vigilant is the one.

Greg L

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The Vigilant is a top loader with "shaker" grates. There's a series of cast grates, alternating in design so that one is sits high and the next low repeating that pattern from one side of the stove to the other. They sit on notches in the reciprocating back grate rack and the front of the grates sit on a fixed/stationary casting in the front of the box. The back notched piece is attached to an eye bolt that the shaker handle slips into. Moving the handle reciprocates the back notched piece raising and lowering the alternating grate pieces. Works well. I'll just pull the grates pieces that will be covered by the brick and stack more brick on top of them to fill the planned void in the firebox. Might need a piece of flat stock or angle iron to make the brick sit securely.

I'll attempt the modification when warmer weather patterns settle in. I I'll post some pictures too.

I may be all wet, but if you want only 25K BTU output, does it make a differance wheather you burn a small fire hot, or a larger fire at a lower temp to achieve the output? I realize you are looking for higher temps to maintain flue draft, but you just cut your intake draft in two by adding the bricks over the grate. If you have an airtight stove, where are you going to get the advantage of a small hot fire? Won't twice the area of intake air passing through twice the area of medium temp coals come out about the same in chimney draft?

I have read in these forums that a person can establish a draft in a chimney for fire starting by opening the baro damper manually, and room temp. will draft up the chimney. I am new to coal, but have years of wood experience which sometimes is relevent and sometimes leads me in the wrong direction, so I will be interested to hear what some of the more experienced guys have to say.

The problem is the coal can only burn so low before dying out. By reducing the mass, you can push it harder without generating the excessive heat you would get trying to maintain the draft on a fire twice as large. Shrinking the outer edges of the firebox inward reduces the amount of fuel without the problems we are accustomed too when the depth of the coal bed is reduced.

When I started burning coal I was not getting long burns like others. Maybe because I have a large firebox I wasn't putting enuff coal in. I layed an extra row of fire bricks across the back and on both sides. Left the front alone because it seemed the front burned the best because the air comes in the front. From that point on I have had no problems. My shaker was broken and I had poked anyway so that wasn't efected

Quick update ...
Coaledsweat stated it well. What I've done the past years is just bank a fire diagonally up toward one side of my firebox. Trouble with this method is that when I shake, the lean side ends up with exposed grate area. This doesn't happen if I can leave an ash bed across the grates but once it gets near 70, the night fire doesn't thickly cover the full grate area and the lean-side grates open during the morning shakedown. The draft seeks the path of least resistance passing thru this area and starving the coal bed of oxygen on the opposite side - just where it's needed I hate losing a fire bed, only happened once since I started in November last year (trapped at work ) - not a big deal, just a matter of principle. Got close the other day when the lean-side grates got exposed and I couldn't get the recharged bed going good. So out to the stash heap I went and scrounged up some old broken fire brick, pieced together enough to cover about a quarter of the grates and bingo - the recharge took off as planned. So far, this is all I've done to reduce the bed by 25% and it's worked well. House stays ~ 68 at night - even last night when it hit 29.

I use to just let the oil furnace work for the beginning & end of the heating season, but not with $3.54 per gallon for #2, not if there's another simple option. I need to get some more firebrick this week before daytime temps start hanging near 70. I had the stove hovering around 240F last week with the skin temp of the stovepipe 6' above the stove reading 140F. No CO readings from the meter

Maybe a picture says it better. Really simple approach - laid the old brick on top of the underlaying grate's flat spots. I plan to do the same to the other side this week but will add steel plates under each pile of brick asap. KISS works again

VigIIPeaBurner wrote:Maybe a picture says it better. Really simple approach - laid the old brick on top of the underlaying grate's flat spots. I plan to do the same to the other side this week but will add steel plates under each pile of brick asap. KISS works again

Are those bricks laying on the shaker grates?

Yes, they're resting on the end tabs of the last several grates. The grates are "W" shaped with tabs at the ends of "W" that run from the front of the picture to the back. Each tab sits on part of the shaking mechanism: the back reciprocates and the front just slide back and forth. The bottom brick is sitting on top of the "W"'s tabs - the top of the tabs are flat. When I get the steel plates, I plan to set the steel on top of the front of the grates and the lip at the back of the fire box that retains the vertical fire brick. I'll then set the brick on top of the plates. At this stage, it's really KISS.

VigIIPeaBurner wrote:Yes, they're resting on the end tabs of the last several grates. The grates are "W" shaped with tabs at the ends of "W" that run from the front of the picture to the back. Each tab sits on part of the shaking mechanism: the back reciprocates and the front just slide back and forth. The bottom brick is sitting on top of the "W"'s tabs - the top of the tabs are flat. When I get the steel plates, I plan to set the steel on top of the front of the grates and the lip at the back of the fire box that retains the vertical fire brick. I'll then set the brick on top of the plates. At this stage, it's really KISS.

Then my Harman wouldn't work that way since there are no end tabs to rest on. The entire bottom of my stove are movable grates.