How to Detect a Faulty Hot Water Thermostat System

Blog | January 29th, 2019

There are parts of a hot water system that simply must function. There are safety valves, of course. Then there’s the thermostat, the control subsystem that delivers temperature-controlled warmth to your skin. With the importance of thermostat control now firmly in mind, how are these important controllers watched over? Is there a troubleshooting strategy you need to be aware of here?

How Do Hot Water Thermostats Operate?

In electrical systems, things are just that little bit easier to troubleshoot. A copper rod contains the thermostat, and there’s a thermistor inside the hollow tube. When the current travelling through the temperature-sensitive resistor varies, it exerts control over the system element. Gas-fueled equipment adopts the same mechanism, at least they do when they include an electrical control subsystem. For purely mechanical setups, gas valves use other temperature sensing solutions, including bi-metal strips and thermocouples. For those latter equipment types, temperature changes force corresponding alterations in the metal components.

Troubleshooting Faulty Hot Water Thermostat

Okay, so there’s not enough water to keep everyone warm. According to the system specs, that shortfall shouldn’t be happening. There’s a fault in the hot water heater. Two system sections pop into the mind of a repair technician. The element is possibly damaged, or the hot water thermostat is defective. Initial tests, as carried out on an electrically powered unit, yield results. The elements are not damaged. The tech knows this because he’s run a continuity test on the element terminals. A multimeter was used to measure the resistivity of the wires contained inside the elements. And this is the next obstacle, the fact that there could be two elements in the system. To control both of them, two thermostats are fitted, although they’ll most likely be contained inside a single housing. Here’s what the repair procedure advises next:

  • Continuity tests on the upper and lower element thermostats
  • Carry out a powered test with a suitably equipped multimeter
  • Determine which thermostat is faulty

Contained on a single terminal block, the troubleshooting procedure electrically examines the circuitry as the device controller is adjusted. If the thermostat doesn’t “call for hot water,” then the equipment part is broken. It should be replaced immediately.

For gas-fueled systems, the procedure is harder to master. A trained heating engineer is needed here, someone who can safely navigate the burner compartment, pilot light controller, and electrically charged components. Likewise, inside an electrical thermostat, there are dangerous currents flowing. If a fault is suspected, and if a resistivity test doesn’t yield satisfactory results, call out your heating engineer to continue the detective work.

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