Power vent water heater is similar to direct vent models but it uses electrically operated powered vent. Blower is used for the assistance to mechanically exhaust the combustion gases to the outside while forcing the fresh air to get in. Blower assembly is factory installed, so accept installing venting pipes there is no other work needed.
Use power venting when replacing an old electric water heater where there is no access to the chimney.
When installing the water heater near the exterior wall.
When electrical power is provided for the gas unit.
Venting system must be able to run from the water heater to the termination with a minimal length and number of elbows.
Note: When selecting location for your hot water heater, consider the inlet and exhaust vent system piping and combustion air supply requirements. Venting system must comply with local codes and per manufacturer specification.
The vent pipe of the power vent water heater can terminate horizontally through the exterior wall or vertically through the roof, where pipe runs must be adequately supported along its length.
There are two venting options you should consider for your water heater:
Single pipe system; either as concentric system (two pipes in one) or one-pipe system that uses a discharge pipe while internal air is used for gas combustion. When the internal air is used, designated room has to be provided with an access to sufficient air supply.
Water heaters with two separate venting pipes are using one pipe to supply the air from the outside and the other to discharge products of combustion. They can run either horizontally or vertically.
When you run pipes vertically, keep in mind to install elbows at the end of the pipes to prevent the rain or snow to enter. For horizontal termination provide the slope downward to prevent potential condensate to affect the blower.
If the water heater is installed in an unconfined space within building, infiltration air is usually adequate for proper gas combustion. If it is installed in confined space provisions for ventilation air must be provided.
Note: If the power vent water heater is being installed as replacement for the existing power vented unit in pre-existing venting, the proper inspection has to be performed to ensure that requirements are met.
Buying venting kit from manufacturer is worry-free purchase as they meet standards and safety requirements, but in some cases they can be purchased from plumber suppliers also. Use manufacturer guide and specifications to determine the BTU rating, model, venting lengths and other requirements so you can properly dimension the system.
For example; plastic pipes cannot be used on tankless water heaters, only stainless steel, due to acidic nature of products of combustion.
On storage tanks water heaters, PVC, ABS or CPVC pipes are recommended and the most common sizes are 2", 3" and 4" in diameter, Schedule 40. Very flexible for installation, power vented gas heaters can be installed as far as 60' from the exterior wall and side by side with other furnaces or boilers.
When assembling the air inlet and vent outlet both pipe diameters must be the same size. This requirement applies for both 2" and 3" diameter pipes.
Based on the venting length there is a number of elbows allowed. Use manufacturers guide to determine the right length and number of bends. Venting should be as direct as possible and with a minimum number of bends (pipe fittings), with no reduction in vent diameter, unless otherwise stated.Some manufacturer manual guides explain that reduction in diameter at any point is allowed as long as the maximum and minimum length requirements are met.
Power vent water heaters, when installed in the building, cannot be connected to the chimney and share venting with other appliances as the significant building depressurization will occur affecting the performance of all gas combustion appliances.
All venting materials and components must be joined with the approved primer-cleaner and solvent cement, but do not cement the vent pipe to the heater. Rubber coupling and gear clamps are supplied with the water heater to connect the vent to the blower. These connections must be properly sealed to prevent leakage of the products of combustion into the living area.
Conclusion: Correct installation of the vent pipe system is mandatory for the safe and efficient operation. With the unobstructed flow of combustion and ventilation air, power vent water heater will work properly for many years.