I have a programmable Sun Touch themostat model 500670 for a warm wire system. The clock loses the time setting even after a momentary interruption in AC power. I have replaced the unit twice in only two years, once under warranty and most recently by purchasing another one at Home Depot for $139 plus tax. The manufacturer acknowledged a problem with earlier units which was supposedly corrected.
Alas! I discovered that it is not sufficient to only replace the plug-in thermostat, you must also replace the hard-wired receptacle which is furnished with the package. After doing so, the unit worked perfectly and held the time even after a 15 minute power interruption. The model number of the replacement is 500670-SC which presumably replaced the problem plagued 500670-SB.
Post by Christopher on Nov 30, 2011 10:03:29 GMT -6
The SC of the model means it was packaged in a clear clam shell. SB means it was packaged in a box. And you are correct that when replacing the stat, the rear part must be changed, since it is where all the actual functions are. The face plate is just a display.