Ok, this might be a dumb question, but why would you want or need a barometric damper on a power vent setup? I think I've read here that some users have a baro with their PV and I can't figure out why.
The way wind blows around a building can create pressure changes in the structure. So a Pv is adjusted to pull a minimum draft and the baro is there to prevent that draft from exceeding what the PV is set at.. Pretty much the same reason a baro is used on a chimney..