I have a home built in 1900 which has its original coal fireplace insert. The insert firebox is about 2' deep, 2' across at the front and 1.5' across at the back and from the bottom of the basket to the bottom of the back damper (fill line), it is about 1.25'. It is mostly cast iron pieces. It has stamped "UP TO DATE" on the inside back, which may be the stove or who knows what. It has two dampers. One is in the back and opens straight up the chimney. The other is in the front and draws air against the front cast iron insert plate and back over the top of the firebox then up the chimney. The coal basket is freestanding and is about 2 inches off the base of the fireplace and is about 4 inches deep. In front of the coal basket there is a decorate floorplate that allows are through and starting about 5 inches from the base of the fireplace is a cast iron front piece with allows air to pass through its decorative design and holds in coal piled up in the firebox. Above that is the opening which is closed by a large iron plate which rests on that front piece and seals the firebox.
I have been burning soft coal of nut size (from Clearfield County PA) for about a month with a five gallon bucket's worth lasting about 10 hours depending on how cold it is, but with tending needed about every 6 hours. I have pretty much no control over the draft. It was running OK, but I really would like to have it run with less need to tend. I brought home some anthracite nut and added it to the fire and it was OK for a few hours, but seemed to burn more quickly. Then I added more before going to bed and it went out.
I know I'm not providing the best information, but I really don't know how better to describe the insert. My biggest problem with the soft coal was bridging and then going out if not broken up and new coal added. The anthracite doesn't seem to want to stay burning as easily and I have little control over conditions. So, I'm thinking I may have to stick mainly with soft coal. But it still leaves some questions:
1. Should I be using nut or some other size? Pea probably would fall through the coal basket, but maybe using stove would be better?
2. Should I perhaps mix hard and soft coal or is that a bad idea?
Due to the decorate nature of the insert and the fact that it remains with the original fireplace in this home which we are restoring, I don't want to replace it. But, I would like to continue to use it because it alone provides about 30 degrees of heat to 2800 sq ft of high ceiling living space.
I've attached a couple pictures to show the insert so you know what the heck I'm babbling on about.