Old Hoval

I am dating myself on this one. Inherited family homestead with a Hoval Duolyte 30 oil/wood/coal combo boiler. Have not burned coal for quite some time and then have always had problem of keeping coal burning. Usually have kept a small "pile" heaped in center of firebox as everytime fire goes out left with big pile of unburned coal. What is correct way to utilize coal. How often should one shake the grate? Can you over shake causing poor perfomance? Because of these problems have always gone back to wood, but this year do not have any and at 3.89/gal oil is a killer!

thanks for help

I assume you are burning anthracite?

It sounds like you have already figured out how to get the fire started - good. Next time fill the entire firebox with coal. Side to side, front to back, it needs to be at least 6" keep. If there are vents for over-fire air, close them almost all the way. Coal needs a deep bed to burn, and the air must not be able to bypass the coal...it must come up through it.

x2 on what Rob said, have flames coming through the fire bed before closing the fire door/overfire air (to avoid big booms!) and don't play with it like you would with wood.

You posted this in the stoker section but I think you'll find more help in the hand-fired area - perhaps a mod will move this?

Mike

Ok being an engineer I am smart enough to get a fire started but not smart enough to keep it going thru the night for a "perk up" next morning. I got fire started yesterday at noon and heaped up the coal got nice warm blue flame and things looked good and no oil burned. Around 9:30 heaped on a load of coal and hit the sack next morning, early, still some coals but much ash and unburnt dead coal. This is problem I had with my old New Yorker when lived in Binghamton, get good fire going blue flame good bed of coals then go to bed and get cold! What am I doing wrong or how do I then perk up the coal that is still burning. Description of what I see when looking at the bed of coals is a small area that is still burning, say size of softball, but rest just ash and unburned coal. Is it possible that heaping coal in mound is not the way to do it but a uniform deep bed instead?

Sounds like you may be burning too hot. Do you know what your air setting is? How do you control the burn? I'm not familiar with your stove but it sounds like you have too much air going to the fire. If your air is controlled with a slider on the ash door try closing it, leave maybe an 1/8" - 1/4" gap. Do you know your stove temp? Draft?

Thanks for the advice. There is a themostatic control with chain to open/close damper on ash door. I had propped open all the way thinking more air and better draft. Just closed it as suggested and added some coal will check in hour or so to see how it is going.

There is no need to prop it open. Set the dial for maybe 4 and leave it. On my DS 4 on the dial is 400° the stove will ramp up to around 500° then then flap will close. When the stove gets to about 400° it'll open again. Just let the stove do the work. You had too much air and burned up all your coal. Fill the stove with coal to the top of the bricks, fill the Hopper if you have one and walk away.

The only time I mess with The dial on the flap is when I want more heat or when I want less heat. I don't know what 4 would be on your stove but it's a good starting point. Remember coal is lazy, so whatever you set the dial for wait an hour or before adjusting it again.

engineer wrote:Is it possible that heaping coal in mound is not the way to do it but a uniform deep bed instead?

Yes.
Don't make a mound,the air will bypass the mound of coal and not burn.

Rob R. wrote:I assume you are burning anthracite?

It sounds like you have already figured out how to get the fire started - good. Next time fill the entire firebox with coal. Side to side, front to back, it needs to be at least 6" keep. If there are vents for over-fire air, close them almost all the way. Coal needs a deep bed to burn, and the air must not be able to bypass the coal...it must come up through it.

Do exactly what rob has said.

engineer wrote:Because of these problems have always gone back to wood

Try to forget everything you do with wood.Once you have blue ladys and flames shut the door and don't touch until 12 hrs. YES, it's harder than you think to not play with the coal fire unlike a wood fire.

To burn anthracite coal you NEED....One: a CO detector (or two). If you do not have one, do not burn coal another night. Two: You need to know your draft. A manometer does this job. Without knowing your exact draft you are guessing. You are either not burning thoroughly, or you are wasting heat up the chimney. Three: You need to control the draft. This is done with a barometric damper. You adjust the damper by using the manometer. (A draft of .04-.06 is great) Four: all air to come from under the coal. Five: a deep bed of coal. Coal likes depth. A shallow bed of coal will lead to it not burning completely or as long. Adding more wood to a wood fire makes more heat. Adding more coal to a coal fire makes more hours of burning. You control how much heat you want by the incoming air. Six: Three screws in each joint of stove pipe.
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Coal has a trick or two.... if you do things just wrong it can make a back-fire of sorts. We call them "booms". What happens is when new coal is introduced it is heated by the fire and it gives off a flammable gas for a period of time. If you allow this gas to build too much it can make a quite explosive boom. The "proper" way is to shake down the ashes until a bit of red is seen coming with the ash. Now with the air intake wide open add a couple inches of coal. Let it burn until "blue ladies" dance...that is...blue flames flicker above the coal. Now add a couple more inches. It takes 5 minutes or so between each load. After the last load has filled the stove and the ladies have danced, you can safely close down the air to the heat level needed. Some people don't want to take the 20 minutes or so to do this, so, they will add more coal at once, but leave one corner of the fire uncovered. This leaves a flame to ignite the gases as they form & hence no boom.
Some stove are more prone to booms, some coal is more prone. Time and experience will teach you. Some are minor, some can be impressive and scary. These booms are the reason that all stove pipe must be secured with three screws each.

Best of luck!

Well it appears the crux of my problem is that there is no barametric damper on the flue pipe! Not sure what my relatives were thinking, or not. The oil burner portion of the system seems to work fine. Cleaned all coal ash, unused coal out of the boiler yesterday. Got good hot wood fire going started to sprinkle coal to get good fire going with damper set 1/4 inch or so. Temps in the high teens and just could not get a good fire to burn, so will stop the experiment and investigate new system.

thanks to all for tips and suggestionos

I think you are giving up too quickly. Your experience seems to me to indicate that air is bypassing the coal grates. If this is so then what you describe will happen. With the grates clean put a light in the ash pan area and look all around the edges for gaps that could allow air to come up outside the grate area. If there are bricks you might have to remove them to see.

A nice picture of the fire box and grates would help.

Attached are pictures of the hoval unit, grates, ash and coal load.

engineer never did say he filled the firebox with coal. This is not the first time people seeking advise have been reluctant to do so. You can lead a horse to water but you can't make him drink.

OK, It appears that the coal burns from front to back instead of bottom to top.

I can't see the air damper but assume it is connected to the temperature control above and is in the side of the ash pit around the corner.

When lighting a fire the air is free to migrate through the front grate and bypass the coal and go out the chimney. To make it draw properly through the coal it is very important to get coal high enough to completely cover that front grate and as high as possible over it.This forces the air through the coal. Start a fire with charcoal and as soon as well lit fill the coal completely as high as you can go. The design should have a much higher fuel bed to operate best.

If it were my boiler I would completely cover that front grate down to the slot on the bottom with a piece of metal and seal the sides of the grate with gasket material. Maybe even thin metal with furnace cement in the slots from the inside. The slot on the bottom of the grate is to insert a flat poker to clear the ash. This would force a more conventional air pattern of bottom to top and make controlling much easier. You also need an ash pan.

The grate system was designed for European fuels such as lignite and would work very well with biobricks or any other compressed wood bricks which you might want to try.

With some simple modifications it should work very well for anthracite. To try the effect of a modification take a square of thick fiberglass and tuck it into the front grate to seal it.

grizzly2 wrote:
engineer never did say he filled the firebox with coal. This is not the first time people seeking advise have been reluctant to do so. You can lead a horse to water but you can't make him drink.

You are right with filling the fire box.