Monthly Archives: December 2012

I didn’t do anything wrong

Ben, a plumber from K&S came by and spent 3 hours going over my install and inspecting the water heater. He found nothing wrong with my install, whew! After talking to technical support we got the unit running by removing the intake and restricting the exhaust. We had hot water, but the install wasn’t going to pass code as it deviated from the installation instructions.

Water heaters go virtually unnoticed, that is until they don’t work!

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!

We need some air in here!

In a previous posting I mentioned running into an issue with our water heater failing to draft when all the exhaust fans and clothes dryer running.  I did some research and through testing I thought the entire issue could be resolved by adding more “make-up air”.   Thus I added a 6″ duct into our mechanical room.  This was in addition to our existing 5″.

You would think that after having ~48″ sq. of open hole to the outside would mitigate any possible negative pressure, but you would be wrong.  The water heater still failed to draft in worst case CAZ testing.

I called a local HVAC contractor to evaluate.  They spent 3 hours trying different things, including adding 3′ to our chimney, but no joy!

The pitfalls of making your home energy efficient

Over Thanksgiving I discovered a torrent of cold air pouring behind our shower in the basement and tracked it to a large opening in our attic. That same day I went and picked up some additional insulation and proceeded to close the opening. Problem solved right? Nope, instead I found out by sealing this rather large hole I made our home too tight. The problem is that in worst case testing (all exhaust fans running and the clothes dryer) a significant enough negative pressure was created which prevented our water heater from drafting correctly.

If you have one or more atmospheric vented gas appliances, make sure to test after home improvements!