Bituminous burning air

My boiler has a small grated "inspection" window in the door, should this stay opened (air to burn gasses) or closed (better draw through bottom). Also, for draft control in the chimney, is it better to use an adjustable internal damper (to save room heat) , or an adjustable draft control door. I have both. I'm quite comfortable with all operations, I just wonder what is more efficient/recommended.

Welcome to the forum!

The "inspection window" would be for controlling secondary (above the coal bed) air, not really a peep hole for viewing the fire. Allowing some secondary air will help burn the coal more cleanly, help extract more heat from the fuel and limit soot build-up.

As far as controlling air flow through and above the coal bed, you want just enough air to efficiently burn the fuel with the least amount of smoke without losing too much heat up the chimney. You should be able to acheive this by trying different air settings over a period of time.

Jimbitmen wrote:for draft control in the chimney, is it better to use an adjustable internal damper (to save room heat) , or an adjustable draft control door. I have both.

When you say "adjustable draft control door" are you talking about the primary draft control in the ash pit door or is this a "check damper" at the flue outlet of the boiler?

An "adjustable internal damper" or smoke pipe damper is commonly used but I don't like to use them with bituminous coal because soot can quickly build up on them adversly affecting the draft.

The best thing to do would be to get a manometer (draft gauge) to see how strong the chimney draft is so you can choose the type of damper you need to best control the draft to this boiler.

If you're not familiar with a manometer or how to use one, do a search on this forum and you'll find all the information you need

Thanks for some great info. Yes, it is a check damper, which I can vary from fully open to fully closed. My thoughts are that this is also removing my basement heat since I usually need to leave it fully open, so I'm leaning toward the internal damper (I have a "T" in my stove pipe so I can access the damper and keep it clean). Have not measured the draft, but I know it is quite good (Eastern Canada is cold and windy in winter). Are there any other "issues" with the internal damper?

Hello JimBitman. welcome.

First, please tell us what type or model of stove you are burning in. how tall and the location of the chimney? [inside the house or on the outside of a wall].

What type of coal are you burning? if you are from eastern Canada? Where are you getting your coal from? Is it Bit, Sub-bit, ever burn Antracite,? They all have different burning characteristics.

The type and location of the secondary air vent can be very important. On some antique stoves, that were designed to burn high volitile bituminous coal, the secondary are was allowed to enter at the back, lower level of the stove, where it was preheated by the firepot, then the air was distributed just above the coal bed, in a ring around the top of the firepot, this preheated air added at the right location burnt off the volitiles and greatly reduced the smoke from the bituminous coal.

If you can, post a photo showing your stove so we will know what and where the air dampers are located.

An in pipe damper is often a soot trap with bit coal.. if the chimney draft is extreemely strong, and your bit coal is not one that creates a lot of soot, then a pipe damper [MPD=Manual Pipe Damper] may be a good item for your install, but if the draft gets restricted, the MPD can be dangerous. The best way to know is to install a manometer.

Hope this helps..
Greg L

Very old Dominion #1, five section. Secondary air is small adjustable grill in the loading door. Check draft is in the cast elbow on rear of furnace. Bituminous coal. Lots of soot at times but shop-vac it out regularly. The damper is in stove pipe about 12" after check draft. Internal brick chimney, about 10" x 10" ISD. Have been running it since I was a kid (30 years). Works great, good heat with almost anything I do, I just notice more heat and better burn with different setups and am curious to what the experts suggest. This site is the holy grail for coal burning, so here I am. Thanks for the help, I already have a better burn with the info in the previous post (and I consider myself quite experienced with the furnace).

sounds like you are an expert with your device. Glad you can get some pointers from this most excellent site! welcome to the forum and you will be giving pointers most likely for similar stoves and coal.

Kevin