Venting requirement for Bosch AQ4 Powervent kit

The Bosch AQ4 Powervent Kit with built-in freeze protection is designed for the Bosch Therm 520HN (Hydro Ignition) and 520PN (Pilot) tankless water heaters. This accessory allows the Bosch 520HN and 520PN tankless heaters to vent horizontally out the sidewall of the home.  The AQ4 does require power to operate and operates on 120V and comes with a 3' cord to plug into the outlet.  

  The AQ4 is a power vent kit and will allow a horizontal vent run of up to 25 feet with one elbow (subtract 5 feet for every elbow). This kit includes the power vent motor.  There is also a vent hood with damper that gets mounted on the outside of the home and this built in flapper prevents the cold air from coming in when the heater is not in use.  Please make sure to refer to the installation manual and that the hood is properly installed so that the flapper stays closed all the way when not in use.  

The AQ4 powervent kit comes with a 5" to 4" reducer. This reducer fits right on top of the heater and then you would use 4" type B, C or stainless steel AL29-4C venting (not included) to go to the powervent motor.  There is a minimum of 2 feet of straight pipe required between the reducer and the blower motor.  Any venting (if needed) "after" the powervent motor must be 4" sealed stainless steel AL29-4C.  The Blower motor should be placed right at the opening where the termination hood with damper is to be installed on the sidewall of the home.

The AQ4 powervent kit is activated by a flow switch and gets attached to the cold water pipe on the right side of the unit just before it goes into the heat exchanger. 

The blower motor for the AQ4 has a new design and includes a delay setting that goes from #1 - #5 and this lets the installer set the blower motor so that when it senses flow it can be delayed for 1 - 5 seconds before the blower comes on.  This will help to ensure the pilot and burners light without getting sucked out by the blower motor. 

There is also a built in safety spill switch that gets attached to the tankless water heater and this will detect high temperatures from any flue gases in the case the blower motor does not activate and will shut the unit completely down.