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Tankless Water Heater Gas Valves

A water heater gas valve or a control gas valve is a device located inside of your tankless water heater, and is designed to open or close the gas supply to the pilot or the main burner. Every gas-powered appliance has one of these valves. Whether you have a standard water heater, one for an RV trailer, camper, boat…the procedure remains almost identical. Tank-type models may have two valves–one at each end of the tank that controls both hot and cold feed lines. Tankless, on/off cycle systems are equipped with one point of delivery (POD) single phase heaters which they only have one end where the gas and water enter the heater. Tankless systems with a storage tank to maintain temperature must have two PODs, one for incoming hot and cold.

What About Safety?

The gas control valve is made with a built-in safety shut-off that shuts off the gas supply to the burner and pilot light if the pilot light goes out for any unknown reason. The electrode or a thermocouple is the device that sends the signal. In most cases this is done automatically after 30 seconds of no activity from flame, but it can also be closed manually very easily by turning a knob. This knob will be located directly on top of the tank’s cover or near/below it in case of a wall mounted heater (that has its own dedicated space). Tankless heaters usually have their gas valves located somewhere on the front of the unit. Tank-type models are installed at the topmost part of the tank, near the opening where you pour water or install a pipe for hot water. Tankless heaters do not hold any standing water, therefore they don’t need one.

How Does The Gas Controller Work?

The controller works only if electricity is supplied to it; in case it does not get power (no power source), it will remain closed and your device won’t operate even with the main switch turned on. If this is your problem, check both incoming lines–the black wire that feeds electricity from your home’s circuit breaker box must be connected to its designated terminal; otherwise changing the fuse or resetting breakers won’t help.

This valve is opened by the thermostat to allow water flow through it. In case of an electric heater, a fan or blower sends air over the heating element to create the warm air that goes into your rooms. Tank-type heaters operate in two stages: ignition and main burner operation. Upon turning on a hot water tap, a small amount of gas is released from the valve via a pipe called a ‘thermocouple’. This signal causes the controller’s spark generator to make its own flame which heats up and ignites any gas still passing through. As soon as both flames meet at one point, they merge into one big fireball that starts burning brighter and stronger according to how much gas you have put in by opening the valve. Tankless heaters are very similar in operation, yet they are equipped with a powerful burner that is used to ignite the gas that comes from their PODs when they need it. If your tank runs out of hot water during use, you simply open the valve knob located on its cover and then another one (usually lower) at the bottom of the tank if needed. Tankless systems may also have two valves depending on how many PODs they have; this will be determined by their manufacturer though.

Also known as: Gas control valve, Gas stop valve, Gas control shut-off device, Burner shut-off device

How To Test For a Faulty Gas Control Valve?

To test for or to replace a faulty gas control: Turn off the power supply and turn off the gas supply into the heater that supplies it. This may require turning off your home’s main gas line if that unit is in a basement or utility room, for example–do not attempt to do this yourself if you are unsure of what needs to be done.

Once you’re sure you have no power or gas feeding into it, remove any screws or bolts holding the cover on the top of the device with a screwdriver. Some tanks don’t use bolts but rather clips–in which case you need to pull up on these using both hands until they disengage from their locked position over whatever holds them in place (the edge of a metal piece). Once open, look for and locate the gas valve near/on top of the burner with a flashlight. It may have two knobs–one big at the top and another, smaller one on the side of the first one; in this case you need to turn both in order to close it. When doing so, pay attention not to push the knob inside the water heater because this will cause problems that are not easy to fix.

Once done, simply put everything back together in reverse order by following these steps backwards. If you have trouble reattaching your device’s cover or if there are no bolts or screws holding it in place, use extreme caution when pushing clips back into their locked position or trying to wedge any other part of it together again. Tankless heaters are designed to be used outdoors for this reason, but if you must use yours indoors, it is best to leave the installation of its components to a qualified technician.

PRO TIP: If your heater has no manual and/or you don’t feel confident enough to do this job yourself, call a certified heating technician for assistance. Tankless heaters usually come with a warranty so always keep the receipt about where and when it was purchased as well as its serial number somewhere safe, just in case anything goes wrong or if parts need replacing (PODS can last up to 10 years).

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