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I have a thermostatically controlled water heater. The controller is a simple on/off controller which has an adjustable set point between 10 and 36'C. Its use is to simply keep a water volume warm at around 26'C using an Electric Pad Heater. The controller has two lights one indicating that power (240V) is present and the second to indicate when the heater is powered up via the thermostatic controller the heat sensor to which is a simple thermocouple.
Now the weird problem. I wanted to reduce the set point to 22'C, the heating light went out as expected. The temperature of the water vessel which is not particularly well insulated stayed at about 25'C for several days. This suggested that the power was still getting to the heater and was being controlled at a temperature which was not the set point . If the heater was permanently powered I know the water would have risen to around 34'C. I checked the water temperature and conformed it to be 25'C and as such controlled powed must be getting to the heater. So I then reduced the set point to about 14'C but still the water remained at 25'C This confirmed to me that some controlled power is getting to the heater.
But throughout the period when I have the set point at 14'C the heating light does not illuminate. My Next observation was to turn up the set point to see when the heater light illuminates. It did at 25'c as expected.
SO the set point of the controller seems to be fixed at 25'c but if I set the set point to above 25'C then the heater switches on.
What appear to be happening is that the set point of the controller cannot be turned down below 25'C but the controller seems to work perfectly correctly above 25'C.
I have no circuit diagram of the controller but the control function seems to be illogical.
Sorry about the drawn out description, but I am stumped to understand what is going on.
Is it possible that the heater light is operating just to indicate that the water temperature is above or below the set point and it is not as I expect and that is the light indicates power switched on to the heater element, and that the set point for the actual heater is stuck at 25'C and the set point dial is not actually changing the set point at all.
Not knowing the circuit diagram of the control unit I cannot determine if this could be likely
Any bright ideas anyone.
Now the weird problem. I wanted to reduce the set point to 22'C, the heating light went out as expected. The temperature of the water vessel which is not particularly well insulated stayed at about 25'C for several days. This suggested that the power was still getting to the heater and was being controlled at a temperature which was not the set point . If the heater was permanently powered I know the water would have risen to around 34'C. I checked the water temperature and conformed it to be 25'C and as such controlled powed must be getting to the heater. So I then reduced the set point to about 14'C but still the water remained at 25'C This confirmed to me that some controlled power is getting to the heater.
But throughout the period when I have the set point at 14'C the heating light does not illuminate. My Next observation was to turn up the set point to see when the heater light illuminates. It did at 25'c as expected.
SO the set point of the controller seems to be fixed at 25'c but if I set the set point to above 25'C then the heater switches on.
What appear to be happening is that the set point of the controller cannot be turned down below 25'C but the controller seems to work perfectly correctly above 25'C.
I have no circuit diagram of the controller but the control function seems to be illogical.
Sorry about the drawn out description, but I am stumped to understand what is going on.
Is it possible that the heater light is operating just to indicate that the water temperature is above or below the set point and it is not as I expect and that is the light indicates power switched on to the heater element, and that the set point for the actual heater is stuck at 25'C and the set point dial is not actually changing the set point at all.
Not knowing the circuit diagram of the control unit I cannot determine if this could be likely
Any bright ideas anyone.
