Steam Timer Question

TeachMeSteam

I am hoping someone can help me. I have an American Steam Timer. The model is a Steam Miser.



In order to calibrate the outdoor sensor, the temperature needs to be set to 55 degrees. And, then the calibration screw needs to be turned clockwise and counterclockwise until the boiler turns on and off.



This doesn't make sense to me. If the temperature is set to 55 but the outdoor temp is 70 degrees, wouldn't the outdoor sensor now think it's 55 when it's really 70 degrees? Wouldn't it make more sense to set the temperature to what's the outdoor temperature is? And, then, adjust the calibration screw?

Mike Kusiak_2

Calibration

I am not familiar with that specific model, but the older Heat-Timers use a similar procedure for calibration. While performing the adjustment, you hold down a calibrate switch, which substitutes a fixed known resistance for the outdoor sensor. This substitute resistor has a Ohm value identical to that of the outdoor sensor at a temperature of 55F. So in this way, you can calibrate the electronics of the timer regardless of the outdoor temperature.



Of course, this assumes that the outdoor sensor is exactly calibrated to the correct resistance at 55F. A more accurate procedure is to wait until you have a day with a constant outdoor temperature of around 55F. It is best to calibrate at the temperature you want the heat to actually go on at, as the setting dial is usually only accurate at the temperature at which it is calibrated. If for example, you want the heat to activate at 56F, slowly turn up the setting dial to 56F, at which point the heat should activate, If not, adjust the calibration screw so that it does so at the desired setting corresponding to the measured outdoor temperature. This procedure is slightly more accurate, as it takes into account and compensates for both the errors in the timer unit and the sensor itself.

TeachMeSteam

Thanks

Mike,



My timer is the exact one you are describing.



I've been using the method that you described second. It seems the better way but it totally contradictory to the instructions....

Mike Kusiak_2

Setting

Keep in mind that if you use the second method, you do not press the calibration switch when making the adjustment. The calibration switch is really there to allow a fairly accurate setting when the outdoor temperature is nowhere near 55F. It allows the contractor to set up the timer at any time of the year as it is being installed or serviced.