The Bosch AQ1 side wall power vent kit has now been discontinued for several years. It is now completely unavailable. The AQ1 vent kit was used for Bosch AquaStar 125B tankless water heaters that were vented horizontally out the side wall.
The current replacement for the Bosch AquaStar 125B is the Bosch Therm 520PN. The 520 PN uses the AQ4 side wall power vent kit for all horizontal venting installations. No power vent kit is required when venting the 520 series tankless water heaters vertically up through the roof.
The AQ4 cannot be used as a substitute side wall vent kit for any Aqua Star125 tankless water heaters. The Bosch AQ4 can only be used for the Bosch Therm 520 series and the older Bosch 1600 series tankless water heaters.
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