Dimensions are based upon Peter van den Berg's 5” base dimensions. Used a P-channel dropping down to just below the opening of the port, fabricated from two 1” square tubes coming in from the sides feeding a 1” X 2” (inside is 7/8 x 1 7/8”) rectangular tube with a cut back facing the riser, just below the top of the port. Slight modification of the port, keeping the same dimensions, but raising it up one inch off floor, creating a small threshold before the heat riser.
This attempt being made with used firebrick (mostly pieces), some new firebrick full size, and a few half high for the combustion chamber and lower part of the riser. Red clay brick (mods, so they are slightly smaller than the firebrick, necessitating some finagling) for the riser. Using a broken kiln shelf as a door. Floor of combustion chamber is flat for now, but will cut bricks or mold refractory mix for floor that angles from sides towards the center, once design is set.
I am at the testing stage of dry stack bricks. It will smoke a bit when first lit, but a draft is established fairly easily with the door open. Restart from coals is very quick. Keeping wood not too densely packed and not too close to the door or blocking the port. Once the wood is fully involved and the bricks heat up, closing the door down to about 4-5 sq in primary air, coming in below the door, I'm getting heat without smoke & a very mild roar, flames a short way into the riser. But only got up to max 530 deg F checking the inside temp of the top brick of the riser. I was hoping to get to a higher temp!
Taking the lid off the combustion chamber to inspect, the bricks forming the port and the combustion chamber are clean except in the top corners. There is also some soot on the inside top 1/3 of the door and part of the first brick of the roof. There is no soot inside the bottom about 1/4 of the heat riser, but some soot inside the rest of the heat riser. Remainder of the fire is mostly ash.
The port had been raised in an earlier trial and error of a floor channel/pre port tube that didn't seem to make a difference, and I wanted to lower it in the port without cutting, so I raised the port, without effect. Removed the floor channel, went to the earlier style P-channel. Do I need to pull the stove apart and bring the port back down to the floor?
There are lots of cracks between bricks I have not yet sealed with clay slip. I intend to cover it with a clay/perlite mix for insulation. Will that bring the temperature up to expected range? Is the riser sucking air between the bricks and cooling the air?
I don't have testers, just the temp gun, so I'm going by exhaust color, sound, flame, and color of bricks inside the stove after the burn.
Just found my pyrometer, what placement would give me usable info?
Intending this for use outside, to heat a water heater tank within a surround of an insulated 50 gallon drum, exhaust running between the tanks. Water heater tank will be topless or vented to atmosphere, so no boom squish. Water will be run continuously via circulating pump to second larger mixing tank and back. (thermosiphoning from tank to tank impractical due to height of the riser) This mixing tank will be insulated and also open to atmosphere. (Using mixing tank vs mixing valve, as it acted weird in the prior iteration of the system, when we had the old style wood boiler.) The tank serves water to a manifold in the house supplying hot water to a radiant floor with two zones of PEX tubing (max 140 degrees F) via another circulating pump. This water only goes to the hydronic system, so no Legionella concern. The intention is to fill the batch box a few times a day, depending on the temperature outside (central Kentucky), to keep the water warm. The water heating system replaces an old Kentucky wood gobbler type outdoor wood boiler that is too corroded now to repair. We also run a Fisher stove, retrofit with a heat riser in a bell that serves as a primary heat source, but need heat going to the radiant floor of the kitchen and downstairs in the main part of the house/shop.
Am I way off base in application?
Suggestions for optimization? Or is it doing ok, but my expectations are too high?