AO Smith Pro Max Direct Vent Water Heater

After my previous water heater failed after 31 years, I had a 30-gallon A. O. Smith Promax gas water heater installed on October 30, 2007. On November 17, after 19 days, the pilot light went out. For the next seven months, the pilot light continued to fail and had to be relit.
The pilot failed sometimes every few days, sometimes every day, sometimes four times a day or more.

Eventually, I had to relight the pilot light every time we needed hot water. The plumber who installed the Promax returned five separate times to try and fix it, without success. An A. O. Smith Authorized Technician tried and also failed to fix it. To help find the problem, I installed a camera at the heater viewing window, and videotaped the pilot failing four times. No one looked at the tapes.

I began to think that this water heater must be pretty bad if an experienced plumber couldn’t fix it after five tries, and an A. O. Smith Authorized Technician, who works on nothing but A. O. Smith products, also could not get it to work.

Over seven months, I had to relight the pilot 63 times. At 10-15 minutes per relight (according to A. O. Smith instructions), this comes to a total of between 10-16 hours I spent lighting this heater. I can assure you that having to lay on your stomach at all hours of the day and night, in a cold and dark cellar, is not a pleasant job for an old man.

A. O. Smith, and the Factory Authorized Service Technician (who is paid by A. O. Smith) blame me for the Promax failure and refuse to refund my money. They say (without any tests or proof) that water vapor coming through the dirt floor in my cellar causes excess humidity which clogs the heater’s flame arrestor, disrupts the air flow to the heater, and puts out the pilot flame.

In 2003, the Government got into the water heater business. It required all water heater manufacturers to fit a ’flame arrestor’ into water heaters. A flame arrestor prevents the burner flame inside the heater from igniting flammable vapors outside of the heater. All heater manufacturers were allowed to come up with their own design of flame arrestor.

I learned from some plumbing websites that the real problem with the Promax may not be
my cellar, but the design of its flame arrestor. All incoming air for the heater’s operation must pass through the flame arrestor. The Promax uses a flame arrestor made from a Corderite ceramic disc. This ceramic disc is about the size of a saucer, so limits the air coming into the heater. In addition, the openings in the disc itself are small, further restricting air flow.

Aside from any design problem with the Promax, there are several reasons why A. O. Smith blaming me for the Promax failure is nonsense.

I was given no warning before purchasing the Promax, either from the plumber or A. O. Smith, that humidity was a limiting factor for the operation of this heater. No one told me that this heater needed a certain humidity range in order to work, much less what the humidity range was supposed to be. If I had known beforehand of a potential problem,
I would not have bought the Promax heater.

The excess humidity conclusion is not supported by statements in A. O. Smith’s own Instruction Manual (#184165-003) and Service Handbook (#TC-049RC). In these manuals, the word ‘humid’ is mentioned only once in 93 pages, and then only as an indication of tank leakage, not as a cause of pilot flame failure. These manuals are available on A. O. Smith’s website http://www.hotwater.com/lit.html.

Saying that my cellar is too humid, does not make it so. During December 2008-January 2009, I tested the relative humidity in my cellar using a Honeywell hygrometer. For these two months, the relative humidity was in a range from 51%-65%, staying mostly in the mid-50s.

A 30%-65% range for occupied areas is recommended by The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE thermal comfort standard for Human Occupancy, Standard 62.1-2004). Their chart can be seen at http://www.ccohs.ca/oshanswers/phys_agents/thermal_comfort.html.

This means that even though my family doesn’t actually ‘occupy’ our cellar, the relative humidity there is within ASHRAE standards. This normal reading is more significant in that during January 2009 we had four times as much snow (i.e. more moisture thus more humidity) than during the same period in 2008 when the Promax was installed. In other words, during January 2008, the humidity level in my cellar was probably even lower.

I also tested the wooden beams in my cellar with an Extech moisture meter. All the wood tested normal at 20% or less moisture. My home was built in 1924, so these normal readings are after 85 years of supposedly excess humidity.

These tests show that my cellar is not ‘too humid’ as A. O. Smith maintains and therefore is not likely to be the cause of their product’s failure.

My films of the Promax pilot light failure show that the pilot fails in several ways; it goes out by itself, or when the burner tries to go on, or when the burner is lit and then turns off. A. O. Smith’s lack of air explanation for the pilot failure seems suspect considering that the burner itself, which must require thousands of times the air the pilot does, had no trouble staying lit (once the pilot was lit) during a heating cycle.

The solution for pilot flame outages, A. O. Smith’s Legal Department says, is to clean (vacuum) their ceramic disc flame arrestor top and bottom routinely. To do this the burner must be removed, not a job the average customer can or would want to do.

Some plumbers state (see links below) that it is impossible to properly clean the bottom of this ceramic disc at all, as that part is nearly inaccessible. In any case, calling a plumber ‘routinely’ (every three months? every month?) is expensive and irritating, considering that your old heater may have lasted for decades without any attention at all.

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I believe that most people would consider it intolerable if a brand-new car failed to start 63 times in seven months. After experiencing similar inconvenience, not to mention cold water, I replaced the Promax with a Bradford-White heater (my choice and in spite of the plumber‘s objections) on May 24, 2008.

The Bradford-White has a stainless steel flame arrestor, the full diameter of the heater, and lets in plenty of air. The Bradford-White has now been installed for a much longer time than the Promax, and has worked perfectly in the exact same location, in the exact same ‘humid’ conditions.

I am out almost $1,000 for A. O. Smith’s measly 30-gallon gas water heater.