How Thermocouples Work on Ones Nashville Water Heater

Posted by on Dec 9, 2013 in Water Heater Repair Nashville

Ok, not to get too technical with you today, but Water Heater Repair Nashville wants to share some information on a water heater’s thermocouple.

The Family Handyman correctly concluded that “when thermocouples wear out, the pilot light goes out, the burner won’t light, and you don’t get any hot water.”

Standard design
Likewise called universal water heater thermocouple. It screws into below the gas valve and a probe on the other end slides into a holding bracket near the pilot light. It appears like a piece of copper wire.

Universal thermocouples are available in lengths from 15 to 36 inches. An 18 or 24 inch will be sufficient for all domestic water heaters utilizing universal kits. Nearly all older waters heaters and numerous of the newer design units with a covered burner compartment and a seeing window will use this thermocouple.
If you wish to utilize a specific replacement length simply eliminate your old one and determine it.

TCO style

Thermal Cut Off style has a re-settable thermal shut off switch indispensable into the thermocouple. In case of a flash fire or blow back from the burner the TOC will close down gas flow to the burner and pilot. In case of a shut down the TOC should reset itself after it cools down and permit you to relight the pilot. The TOC switch looks like a watch battery. You will just find the TOC on more recent style water heaters with seal burner compartments.

TOC non-resettable design

These thermocouples have a tiny TOC build inside television. They look much like a basic one other than the diameter is bigger about midways of television. When these TOC’s switch off they will not reset and must be changed.

Exactly how Thermocouples Work

A pilot thermocouple sends out a small electrical current to the gas valve when the probe is heated to a certain temperature level. This electrical current informs the gas valve that the pilot is lit and its ok to send gas to the burner if the thermostat requires it.  There are some great images to illustrate how this works here.

To test a water heater thermocouple push the pilot button down on the water heater gas control valve. Then light the pilot. If after holding the pilot button down 30 to 60 seconds the pilot light doesn’t stay on when you let go of the button, the thermocouple is most likely the reason on older devices. The TOC or air flow can be the issue on newer units with a pilot light viewing window.

If the pilot does not light at all the issue is gas flow, gas control valve, TOC tripped.

Usual Thermocouple Problems

The most usual problem is the idea on the thermocouple probe weakens. It can quickly be replaced.

Thermocouple Repair

If the probe appears white in color this is carbon build up. It may keep the probe from getting hot enough to send a signal to the gas valve. Try sanding it with emery fabric and relight the pilot. It ought to work for a while however keep a new thermocouple useful.

  • The thermocouple probe have to be in the pilot light flame.
  • The thermocouple must be screwed into the gas valve snugly.
  • Check the pilot thermocouple tube for kinks.

Water Heater Repair Nashville hopes this has actually been a great intro to a water heater’s thermocouple for you!