NeutralAxis

AO Smith and State water heater companies make identical 96% efficient gas-fired water heaters.  But they have what I consider to be a design flaw that can render them unsuitable at best, or useless at worst, in certain settings.

There are commercial and residential versions of each.  AO Smith calls their commercial line Cyclone and the residential line Vertex.  State uses Force 90+ and Premier.  They’re identical units except for badging.  I recently specified two of the AO Smith models (BTX-100) for a restaurant project and learned that these super high efficiency models are finicky beasts.  The controls and venting require a 120V circuit and draw only a few amps, so the electrical was designed such that the two water heaters, sitting side by side, would share a duplex GFCI outlet on a 20A circuit.  During startup, the heaters balked and wouldn’t work reliably.  Eventually the AO Smith sales reps told us the problem was that they are susceptible to electrical interference if something else is on the same circuit.  In this case each water heater was interfering with the other.

But that’s not the end of the problem.  AO Smith also warns that a GFCI outlet can cause electrical interference that can hinder the water heater’s operation.  Commercial kitchens are required to have GFCI protected outlets in all locations.  For residential uses, a water heater located in a garage or unfinished basement area will have to be on a GFCI circuit as well.

For the kind of money these things cost, $2,700 each, I’m surprised they’re not better shielded against electrical interference.  And what happens to the residential versions (Vertex and Premier) where they inevitably will share a circuit with other things?  I’ll keep these water heaters in mind for future projects, but I’m going to have to be very careful where I use them until until the manufacturer figures out how to better protect them against this problem.

AO Smith Cyclone Water Heaters
State Premier Water Heaters