You shall not heat!

As I was unable to correct the negative pressure causing my atmospherically vented natural gas water to back draft at start, I decided to replace it. The 15 year old AO Smith 40 gallon, 40K BTU water heater had absolutely no issues, except that it left our house hold yearning for more hot water.

Obviously a new atmospheric vented water heater was out as it would exhibit the same problem as the old one. What other options are there?

  • Atmospheric (what we had)

These are the old type that have existed since the beginning of water heating. Burner on the bottom with a flue up the center which has a draft hood and vents out a chimney. Exhaust is very hot because of low efficiency and it naturally rises and vents out the chimney.

  • Direct vent

Sealed combustion, used outside air for combustion. Non-powered (no electricity), horizontal and vertical venting with special pipe within a pipe with very stringent requirements. Not used very often as the water heater basically needs to be right against the wall. This is basically an atmospheric water heater with sealed venting and are typically not very energy efficient.

  • Powered direct vent

Sealed combustion, requires electricity, horizontal and vertical venting using plastic pipe. These have a wide range of efficiency ratings.

  • Power vent

Open combustion which uses inside air, requires electricity, horizontal and vertical venting using plastic pipe. These have a wide range of efficiency ratings.

Since 2003 water heaters have Flammable Vapor Ignition Resistant (FVIR) technology. This prevents home owners from blowing up their houses due to heaver than air explosive vapors. This has caused water heaters to rise dramatically in complexity and price. It has also been the cause of class action law suites.

As I was trying to mitigate a negative air pressure issue, I went with a powered direct vent. I purchased and installed a 50Gal 60K BTU Powerflex Direct (PDVG62-50T60-NV) from Lowe’s (ref.) . My dad and son helped with the install and after about 6 hours it was ready to go. I filled it up, went over the check list and then plugged it in. The gas was lit by the hot surface igniter and then it sounded like a rapid sequence of explosions and then the unit would turn off. This was repeated twice more and the unit got stuck in lock out. I called technical support and after talking for a while we decided to have a plumber come out and take a look, but that would be the next day!