Bison,, you just are not getting what I am saying...
The robert shaw gas valve has been around for decades
and decades,,, on occastion they have had bad ones,
but very rarely....
The WHIRLPOOL heater does not have the same air intake
as the RHEEM AND GE... we agree on that....
The WHIRLPOOL DOG overheats and constanty kicks off the thermostat when their high limit thermal fuse on the side of the heater thinks their is a fire..
this is constantly shutting down the unit...
So between over heating and starveing for air while it is burning and constantly shutting down every few hours or days, the HIGH LIMIT circuit in the ROBERT SHAW gas valves wear out quicker on the whirlpool ,
becasue it is being taxed to its maximun limit
The SMITH DOG, also is giveing me fits lately too...
we are going out on smith heaters and installing new T-stats and
burner assemblies ...about once a week, becasue they are in
laundry rooms and are sucking up lint...
that same valve is interchangeable with any older pre 03 unit
but when you put it on a FVIR heater, the LINT kills it off quicker///.
Mark,
That is a plausible scenario and the sort of explanation I was looking for. How is the overheat detected by the owner/plumber after it occurs? Is there something visible on the thermal switch to indicate it has activated?
I've never seen evidence of mine overheating during a run or shutting down early. Instead all I've observed is the pilot is out. I've also not seen any evidence of lint on the flame arrestor (and I was expecting it and checked both sides.) I don't have a lint problem in the utility room since I've fixed the original poor/leaky HVAC duct installation by the professionals. I tracked down the Whirlpool Flamelock thread here early enough that I had been diligent about keeping the water heater screen clean months before this happened.
Instead, much like many others have reported: the pilot went out, it could be reignited and stay lit a handful of times...until the burner cycle ended with a fully heated tank. Then the pilot stopped. A fully heated tank (as in: to setpoint) doesn't indicate a thermal switch cut out. I could even hear with the dial where the temp. was at in the tank when this occurred when I swept back and forth around set point. The water temp was right in the shower without readjusting valve positions. After a few times (two in my case) the pilot could not be made to stay lit.
I still don't have any direct indication that the system is restricted enough to overheat. But if it is a draft issue, that can be easily and safely fixed...actually it would be safer than the original design and could still fulfill the FVIR role.
If I have thermal shut down problems I expect a combination of things to occur: 1. The pilot will go out, requiring a manual relight. 2. And either the tank will short cycle and not get hot (~120F setpoint for me.) 3. Or the tank will get too hot--but that requires the thermostat portion to have already failed. I'm not seeing evidence of either of the last two and #1 is very short.
If the Robert Shaw valve were to fail after only three shutdowns, then there is a problem with the design or execution of the Robert Shaw valve. That is not a robust design. In that case while the U.S. Craftmaster/American Water Heater/Whirlpool/A.O. Smith ventilation design appears to be marginal, it is
also revealing a serious flaw in the Robert Shaw valve which then masks the flame arrestor problem. This is not an uncommon troubleshooting scenario. Often it takes the presence of several weak design aspects to produce a serious problem. Looking at the flipside: a better ventilation design may be masking a weakness in the Robert Shaw valve in other equipment.
Looking now I see the same Unitrol Robert Shaw valve on the conventionally ventilated Bradford Whites (or at least in the Defender information for them.)