A.O. Smith, Intellivent, White Rogers, Rheem.... error code 6

[Alex Lipowich]

I've got the dreaded Error Code 6.

I have a pair of hot water heaters next to each other, different models. Older one working for 10+ years, the twin sister one died, and was replaced about 7 years ago with this now out of warranty and problematic heater. It has worked flawlessly since installed.

Suddenly Error 6: I drained 1/2 a gallon in case there was sludge, I purged it a bit to clear that out. I went outside to confirm no blockage of the vent, and on start up with it running and burner on, it seemed to blow outside just as hard as the one next to it with its own vent.

Reading up, error six could be low gas supply. I doubt it. On reset, the burner lights up immediately, and seems just fine. Neighboring HWH works great. Same for voltage and polarity of supply. No change over the years. All indications so far from reading would be possibly the flame sensor. I did shut off gas, unlug, and remove the burner unit. I lightly sanded flame detector with a 600 grade sandpaper, it appeared lined up according to the specs I can find online. I re-installed all this, and still, although it fires right up, when I come back in 30 minutes, it has cycled off, and has this code.

I hate to "throw parts" at a problem, any ideas what to do next?

 

[Master Plumber Mark]

Start throwing parts....if sanding the flame sensor did not work, its probably the thermostat

 

[Sponsor]

 

[Alex Lipowich]

Thanks.
I took it apart a second time, and sanded it really well, using a fine file, and then two grades of steel wool.

On restart, it fired right up beautifully. It stayed lit for at least 5-7 minutes. Then, suddenly died. On the first automatic restart attempt, I could see the igniter glowing REALLY well, but no gas seemed to come out?

Same on second automatic attempt,

Can the gas valve fail in such a fashion that it works at first, but then closes as if weak spring or bad solenoid or something and won't restart automatically..... But after a "rest" or hard restart it seems fine for a few minutes, but then fades again?

 

[Master Plumber Mark]

there is also that pesky pressure switch that can be trouble too and suction lines
that can come loose... when they start to do this it can be like "hell on earth" to figure out
what specifically is going with the unit... feel grateful that it is at least giving you an error code

these things are and have never been anything but a pain in the ass and typically I pass on
working on them because of the time it takes and the frustration involved.... it is probably
something internal in the valve that has gone bad

I see a new intellevent control valve in your future

 

[Alex Lipowich]

Thanks again. I didn't check the pressure valve directly, but that hose I did examine, it's in place. (I may be wrong, but I thought there was a specific code for pressure valve failure)

It's a Richmond from Menards.
I see they sell replacement thermostats, and at first glance the price seems reasonable.

I also saw a kit with both burner and new thermostat at Menards. Guess some people just throw both parts at the problem....

I can order a replacement thermostat with some degree of patience as last time I had a failure, I put cutoff valves in the supply and output from each heater, so I can take a bad one offline while the other serves the house.

I'm going to search the forum to see if you've discussed series vs parallel HWH, and just how critical the pipe lengths are after a split to draw off parallel ones so both HWH are utilized equally.

Thanks for prompt responses!

 

[Master Plumber Mark]

the heaters should be in series if they are different brands ...
they never work properly in parrallel

 

[Alex Lipowich]

So... good news, and feedback for others that might follow in my footsteps.

First of all, as always, no substitute for experience. I learn this over and over in life.

I found an affordable open box replacement thermostat locally for $90, it came today in AM. This evening, shut off gas, unplugged, and drained the tank. Disconnected the gas line, and undid all the connections to the thermostat, and removed the unit from the heater. To be honest, I did not examine it closely, I just reversed the process, and re-installed the new unit, adding some yellow tape where needed, and carefully cleaning off the old tape during the reassembly. Used some white tape for the thermostat. Filled up the tank, turned it all back on, adjusted the heat, and was immediately impressed by one thing. The full on flame was DRAMATICALLY larger and stronger than the prior thermostat and valve EVER showed me when I started the investigation. To me this spoke to low gas flow through the valve. But on closer examination, looking NOW at the old thermostat valve, there was a fair amount of debris accumulated up against the screen AT the thermostat inlet for gas.

Hmmmm in retrospect, I wish I had taken the inlet pipes apart and carefully examined that screen. It did not occur to me that during my installation several years ago, I may not have cleaned all the pipes well enough, and some tape or debris accumulated up against the screen over time.

Or, maybe, having unscrewed the thermostat/valve and turning in over and over to unscrew it released debris from the inlet threads. Who knows at this point. But, I'll save the thermostat just in case it IS actually ok, and was just junked up at the inlet screen.

Either way, the unit is working beautifully now, and I'm back in business. Had I more experience with this, I would have recognized the poor overall flame that I did see as way, way deficient and immediately known to either check that screen, or swap in the thermostat. It is a huge difference.

Thanks for all the help, and good luck if you're reading this.

 

[Master Plumber Mark]

do you have a drip leg on the heater , or it is called a sand and debris trap???

 

[Alex Lipowich]

Yes, there is a debris tap on it. Of course, until you question its presence, I didn't know what it was, or what purpose it had.

Again, no substitute for experience.

Had I really understood its function, I would probably have approached the R&R of the HTW differently the first time years ago. For all I know now, I may have spun the whole assembly of pipes around and around to remove it from the thermostat/valve. This would surely have spread the debris around a bit, and may have actually led to the problem.

Come to think of it, I should probably take apart and clean out the work I just did now to make sure I didn't replicate that mistake.

Thanks for asking and pointing out the function of that trap.

On the subject of dissimilar HTW with the draw on both in parallel. I measured one leg of the "T" at 10 inches to the one, and 10 1/4 to the other. Not exactly the same. Is that quarter inch making a difference, and preferentially drawing off one heater, and not the other? If so, the longer or shorter run? (or) is the preference to drawing hot water from one or the other based on a differential of temperature?

If you don't mind, why or how does it "not work" as you say in parallel?

 

[Master Plumber Mark]

it is supposed to draw evenly if everything is close to exactly the same....the problem begins
when time passes and one of the unions on top of the heater becomes corroded shut then it begins
to draw more off one unit over the other...... if you have 2 different brands of heaters they will never
work properly and its best to plumb them in series.......