Heating with coal usually elicits thoughts of blackened cities with smog, soot, and dust everywhere. Enter the modern era of hi-tech, clean, efficient, and inexpensive heating.
Recommend this product?
Update: as of 11/25/2011 (6 years of warmth), I still love the DVC-500. I have replaced two fans (combustion fan and exhaust fan). I have replaced the burn plates due to a power outage while the stove was running full blast, and the plates warperd. Otherwise, it continues to operate excellently.
What is the Harman DVC-500 Direct Vent Stoker?
In a word, the DVC-500 is a heater. It heats with coal. More specifically, it heats with rice-sized Anthracite coal. The term 'Direct Vent' means that the heater 'pushes' the exhaust air out of the house without the need for a natural draft (or natural air flow). Thus, a direct vent heater does not need a chimney, which is a big plus. The word 'stoker' comes from an old coal industry word that refers to the machinery that feeds coal into a boiler or furnace. In this case, stoker means that the stove is 'automatic'. The coal is automatically fed onto the burning surface as needed. Harman is the the manufacturer of this particular coal stove.
A bit of history first
Many of our grandparents (if you are a baby-boomer like me) probably heated with coal. In those days, before there was even electricity, a person would shovel a pile of coal into a pot-belly stove onto an already lit fire over a grate. The coal would burn well for awhile, until the ash from the coal would begin to smother out the fire. At this point the person would 'shake' the coal. Various stoves had different ways of doing this, but the goal was to shake the ash off the remaining coal so that the ash would fall through the grate. The coal was then able to continue burning and more coal could be added. The ash would be removed from the bottom, either in a bin or with a shovel. Coal has the advantage of burning hotter and longer than other fuel sources such as wood. There are two main types of coal: bituminous and anthracite. Bituminous coal is the softer and (often) dirtier coal and is also more abundant. Our ancestors likely used bituminous coal because it was more readily available and because it was easier to burn (it burns at a slightly lower temperature than anthracite). Anthracite coal is the 'clean' coal and was discovered in the U.S. in 1762. It actually looks like a very shiny rock and is quite beautiful when clean. It glistens in the light. Anthracite has much more heating potential than bituminous and is harder. It also burns much cleaner with very little smoke and ash. This makes it ideal for home heating. Anthracite coal is mainly available in Eastern Pennsylvania in the U.S. Only a handful of countries world-wide have anthracite reserves, China being the largest. Unfortunately, this severely limits the accessibility of Anthracite coal heat for most of the country.
Anthracite coal comes in various sizes depending on the application. Some of the sizes are (in order of largest to smallest): Chestnut, Pea, Buckwheat, Rice, and Barley. Chestnut can be up to 1 1/2 inches, whereas Barley can be as small as 3/32 inches.
What about the DVC-500? How does it work?
Now to the specifics and features of the DVC-500. As you probably guessed by now, the DVC-500 only burns anthracite coal, and it must use the rice-sized coal.
There is a large hopper on the back of the stove that holds about 90 lbs of coal. Once filled, the stove can burn for days with no intervention on the lowest setting. This stove has a built-in thermostat that controls the rate at which the coal is fed onto the burning plate. A piston moves in and out at the bottom of the coal hopper, pushing the coal up a ramp and onto the burning plate. The burning plate has many small holes in it to provide combustion air to the coal. Coal relies on plenty of air to burn efficiently. As the coal is burned and the ash remains, it is pushed off the burning plate and drops into an ash pan at the very bottom of the stove. A small door opens allowing the owner to remove the ash and replace the ash pan. The ash pan will hold the ash from about 180 lbs of ash.
The hi-tech part of this stove is in the control box at the top of the stove. It is located near the back of the stove facing up. There are three control dials.
1) Mode selector: Allows you to choose between Room Temp
Mode, Stove Temp Mode, or OFF. Also
allows you to vary the Distribution
Blower speed by turning the knob to the
"high" or "low" side of each mode.
2) Temp Dial: Allows you to adjust the room temperature in
Room Temp Mode using the outer scale marked in degrees Fahrenheit. It also allows you to adjust the stove temperature while in Stove Temp Mode using the inner scale
marked from 1 to 7.
3) Feed Adjuster: Sets the maximum feed
rate, 1 to 5. An additional position called "Test" runs all motors at full speed for two minutes to check operation. After two minutes the stove will go to minimum burn
and the blowers will alternate from high to low every two minutes to remind you that you are still in "Test Mode".
There are also 6 different status lights giving you information about each of the blowers (2) and motors (2), plus a power light and a 'status' light. The Status Light
will be lit in either Stove or Room Temp Mode when pointer is not within "off" position band except after normal shut down. It blinks to indicate errors.
The DVC-500 has numerous safety features.
The ESP (Exhaust Sensing Probe) is a temperature sensing probe located in the exhaust outlet. The ESP works with the Control to perform all burn rate functions as well as high and low limit control.
The Room Sensor is a small temperature sensor placed where you would normally put a thermostat. The Room Sensor is extended to the stove with normal thermostat wire. The Room Sensor works with the ESP and the Control to provide
the right size fire.
The FSS (Firebox Static Switch) is an electronic pressure switch that senses firebox pressure. The FSS works with the ESP Control to adjust the draft blower speed to compensate for wind and changing house pressures.
The TCP (Temperature Control Probe) is located on the left side of the feeder. The TCP works with the Control to reduce the feeder temperature if the temperature begins to rise.
I installed the DVC-500 myself, although the dealer offered to do it for an additional $200. I made my own floor protector using plywood underlayment and tile. The vent needs only a small square hole through the wall behind the stove. The DVC vent is a special system designed just for this stove. It is double-walled steel, is square, and the sections bolt together. A special wall thimble gives the proper clearances and protection from the heat. The vent pipe is special in that the inner lining takes the exhaust gases to the outside, while the outer lining brings fresh air from outside to feed the stove. There are two advantages to this system. 1) the pipe is always warm to the touch, but not hot. This reduces the likely-hood of fire or injury. 2) by using outside air to burn, your house is not deprived of oxygen and there is not the 'vacuum' created in your house that many wood-burning stoves produce when they burn the oxygen in the air, and thus pull in cold air through the cracks of your house.
I also painted the stove a custom color to match our living room. I used standard stove paint in spray cans to do the job. Setting the stove on the floor covering, cutting the hole, and installing the vent pipe took several hours. This stove is HEAVY at 455 lbs, so having a hand dolly helped in the moving process.
The DVC-500 is a true direct vent coal stove, the first of its kind, and does not require a chimney for installation or operation. It is extremely safe and airtight, obtaining 100 percent of the air needed for the fire from outside your home and returning 100 percent of the exhaust air back outside.
Harman’s air wash system keeps glass cleaner, longer.
Optional battery backup system is available. It consists of a special charger/sensor device and a Marine grade 12 Volt batter. This can run the stove for up to 8 hours during a power outage, or longer with additional batteries.
Optional 24 carat gold trim and decorative air grill adds classic touch to view of fire.
New DVC-500's carry a very nice warranty:
6 years material & workmanship (mine, purchased 3 years ago has a 5 year warranty) - covers the body of the stove and components made by the Harman Stove Company.
3 years parts & labor for mechanical & electrical components - covers circuit boards, wiring, motors and igniters.
100% Transferable to new owner.
So, what is my "EPINION" of the DVC-500?
After giving you all of these details and explanations, you're probably wondering how I LIKE our DVC-500. To put it simply, I am truly amazed at how it has performed the last three years. My original intent for this stove was to supplement our natural gas boiler in our old 4,000 sq. ft. home. The first winter I kept the DVC on a lower setting and kept the boiler running, assuming that the DVC would keep the furnace from running so often. At the end of the winter I had burned less than 1 ton of coal (which cost about $200 in 40 lb. bags) and my heat bill was somewhat lower. The second winter I purchased 5 tons of coal in bulk. Total price was $700. I also turned the DVC up to about 75 degrees on the thermostat. To my amazement, I was able to turn my boiler completely off for most of the winter. My previous heating bill was over $2,000. Now I was paying only $700, and I had some coal left at the end of the season. There were some extremely cold days (below zero) that I turned my boiler on just to keep pipes from freezing and to heat the outer rooms of the house a little better. We have the DVC situated on the first floor in the center of the house. The heat flows very well upstairs and all of the bedrooms stay at a nice 65 to 67 degrees. We have two rooms on the first floor that don't get much heat from the stove. I added a couple of small 'door' fans to move the hot air to one of the rooms. This helped raise the temp a few degrees to around 62, but I do sometimes add heat to that room.
The main work of the stove is filling it. In January and February, the coldest months of the year, we fill up the hopper about once per day. This is two five-gallon buckets of coal. Every other day we empty the ash pan. My kids (ages 9 to 14) are able to handle the coal and ash OK, as is my wife, but mostly my 14 yr old and I keep the stove running. As the outside temperature reaches 32 degrees and above, the coal can last for over two days.
The main downside of this stove (besides the manual work of filling it and emptying it), is lighting the stove. It takes about 20 minutes, and you have be watchful during the startup process to insure that the fire does not go out. Anthracite coal has a high burn temperature, and thus it is harder to light. Unlike pellet stoves, which can self-ignite, a coal stove must be lit by had. Interestingly, the recommended way to light a coal stove is by using wood pellets. Once the wood pellets are lit by using either starting gel or a propane torch (my preferred method), then the coal will ignite from the heat of the pellets burning. Gently dropping pieces of coal onto the pellets as they get red-hot seems to help the coal ignite more quickly. Fortunately, starting the stove is only necessary at the beginning of the season, during occasional maintenance during the heating season, and after the occasional "oops, we forgot to fill the coal hopper". Once lit, the stove runs itself if you feed it regularly.
The other downside of the stove is the annual cleaning. Coal does not produce creosote like wood does, so cleaning the vent pipe is a breeze. The fly ash that is produced by anthracite is light brown in color and is easily sucked up by a vacuum. There is a small tray inside the stove that catches any coal dust that settles to the bottom of the hopper. This is easy to pull out and dump. The other maintenance is the occasional cleaning of the glass, although again, this is much easier that with a wood stove, which can get black with ash and creosote in a matter of days.
All of the functioning parts have held up well these three years. I had to replace the glass ($80) after it broke due to the door being slammed very hard. I also replaced the burn plates ($30) because they became weakened due to some extreme heating times. One such time was when the stove was turned way up, and then the electricity turned off - leaving the plates very vulnerable. The manual warns against unplugging the stove because the high temperatures on the plate increase when the airflow is turned off. In this case we could do nothing because we had no electricity for awhile and did not have the battery backup system. I was able to pull my car up to the house and use a standard power inverter to run the stove until the electricity came back on, but one of the plates had already cracked at that point.
Weight 455 Pounds
BTU Output Range 7000 to 75,000
Heating Capacity 2200 Square Feet
Fuel Anthracite Rice Coal
Hopper Capacity 93 Pounds
Distribution Blower Size 135 cfm
Flue 4" Harman DVC Vent
Wattage 295 Watts
Control ESP with Micro-processor
Width 25 3/4"
Height 40 3/4"
This stove has already paid for itself in heat savings after three years. We enjoy the ambiance of the blue-ish/orange flames. It is fairly quiet when in operation, with only the mellow rumble of the blower fans. Most winter mornings you can find one or more of our family members standing in front of the DVC-500 to soak up the rich, delightful heat.
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