DVC 500 Fan Speeds and Fire Questions

Has anyone tried turning down or restricting the combustion fan? I really don't think it should be running full tilt all the time. Is there a potentiometer or something that can be put in series with the power supply to the fan that would allow it to be adjusted?

The early DVC's slowed the combustion fan down when the stove wasn't going as hot. I'm not sure why Harman changed this, I think it was to give a more complete burn. All later models and all replacement control boards run the combustion fan full tilt all the time. A motor control could probably be wired in, but here are a couple possible problems. First, as the stove responded to a call for heat, more air would not be introduced and the lack of air through the grates could lead to a poor burn or grate warping. Second, the electric manometer can tell when the negative pressure is incorrect in the firebox, and it will try to adjust for it. I have tried to get slower burns, and so far have been unsuccessful. I did not try to put in a motor control, I am concerned about damaging the control board. I did try restricting the intake, the way the DVC is built this has to be done outside at the intake, you can't get to the fan easily. As soon as I restricted the air flow enough to make any difference, the exhaust fan speed up to full speed, and eventually the stove shut down. This is where we are a slave to our electronics! If I can get my 80hrs using the settings I mentioned earlier, I am doing very well. I can plan on getting 3 days, but more than that is luck. If I leave the distribution fan on high and the stove temp on low, I am down to more in the line of 2.5 days.

Yea, I didn't think it would be worth it to try restricting the intake on the outside of the building. If you look where the ducting hooks to the stove, the air intake is only about 1.5" X 1". The restriction would have to be right there and a very small amount and would most likely be tricky and a pain in the butt taking that ducting off and wrestling with the gaskets.

That's why I mentioned about turning down the combustion fan speed. I was thinking that if the combustion fan was turned down or restricted, the (max) feed would just need to be reduced so that the coal would take longer to burn as it went down the grate. You should be able to still get complete burn but just not the max BTU's out of the stove. I may look into this but for right now, I'm testing to see how long I can get the stove to burn for on a hopper's worth of coal. I have the feed, dial, and blower setting all the way down and it is on room temp. I'll report results when it is empty.

Ok so I tried the stove on room temp with the dial all the way down, and fan all the way down as well as stove temp, both all the way down. In both situations the hopper lasted 3 days until it got to the bottom "ledge". There was still some coal in there but I didn't want to go further. I might have gotten about another 1/2 day or so out of it. Another full day would not be likely so it sounds like I'm in the same territory as BR. I guess it's just how the stove is. I wish I could turn it down more, but I can't. I'm happy with it though.

Glad to hear it's running as it should, even if it's not quite how we would like. Idle fire isn't a problem here right now, -12°F and I'm enjoying the coal heat!