stoker-man wrote:He's using the Bacarac draft meter. The scale is exactly the same as Wood n' Coal's meter, except, the positive side of the scale is on the left.
I don't understand why there is such an emphasis on the positive side of the Dwyer scale when stoves require negative drafts.
Only because the Dwyer meter is intended to be connected in a different application, for example on a forced air system to monitor the air flow through a filter. The high side tube is connected to a point before the filter, the low side after. If the filter is after the blower it will read positive pressure. As the filter becomes clogged the reading on the meter will begin to climb.
Since the negative side of the scale is so short we just use the positive side, in effect using the gauge backwards, since it's not positive pressure, but negative pressure (vacuum). The same would be true in a forced air system with the blower after the filter, since it would be all negative pressure.