How a "Heater" or anything that has a "Load" works, & How to troubleshoot.
A Heater, is a real simple circuit. There are only TWO "Active" wires in any Electrical Circuit, the Phase, Positive, & Neutral, Negative, usually Negative & We also have an Earth, the Earth & Neutral are at the same, "Potential", IE:0 Volts. So imagine it like this, from the left we have a a Power wire, the Phase, this Wire, goes to One terminal on the On/Off Switch, this is called the "Hot" side, of this switch, This switch, when operated, "Breaks" the Phase line, or circuit, From the other terminal,the "Cold" side of the Power Switch, That wire, circuit, then goes from that "Cold" side of that switch, usually, to a "Thermal Fuse", wired in "Series" this "Fuse" is "Normally Closed", when/if, there is an "Overheating Condition", this "Device" will go "Open Circuit". Thus Breaking, the Phase Power, OFF, from the "Element", or "Load". Connection. This wire then goes, from the other terminal of that "Fuse" to the "Hot" side of the "Element". Now the other side or "Cold" side of the "Element" or "Load" then goes to "Neutral", or, return. Thus the circuit is now complete. Now the Earth, the MOST important wire, is bonded to the/any metal case &/or fittings of the unit, thus any "Hot" wire that may break, or touch, the "Earth" will cause a "Short Circuit" to Earth,and "Blow" the Circuit Breaker or Fuse on the Main Power Board. Thus affording protection from shock. Troubleshooting is simply following continuity along the circuit path, and the measuring of the On/Off components for integrity, and the/any "Fuses" and the "Resistance" of the Elements. This can be worked out from OHMS LAW, Volts = Amps multiplied by Resistance. Watts = Amps x Volts. From those two simple calculations we can glean the "Resistance" of the "Load" and what it should be. Then we can measure against that to see if there is any disparity, which would indicate the fault. EG: We have a heater it is 2000 Watts, it is in USA and the Voltage there is 120 Volts. First we must get our Current draw, we then divide the Wattage by the Voltage to get our Current draw. So, 2000 Watts, divided by 120 Volts, this equals, In our case, it is, 16.66 Amps. Now we know our Amps we can workout the Resistance of what our Elements will/should be. Now we Divide the Voltage by the Amperage to get this figure, in our case, 120 divided by 16.66 Amps, which is 7.2 OHMS, if there were 2 elements they would simply be 3.6 OHMS each, or any ratio of that. Now sometimes Heaters have a "Thermostat" this device is Powered from the Line, Phase, & Neutral, and using temperature sensing, it will act like a Switch, that is turned on & off, when a "Condition" Chosen Temperature, is met. It simply Breaks the Phase to the "Load". These "Contacts" are in series, with the Phase, and "Act" just like a/the Power Switch. Now in fault finding, we look for "Open" circuit where it should be "Closed" and "Closed" circuit where there should be "Open", also the "Resistance" of the "Elements" or "Load". So basically we are looking for, "Open" or "Short" circuits, and disparities of Resistance.. We remedy same by "Joining" up the "Break" or "Removing" the "Short" and replacing faulty "Loads" or "Elements".
on Mar 02, 2010 | Heating & Cooling