Pulsating gas heater

I have a gas heater with a millivolt control that has operated trouble free for years. I noticed that it wasn't putting out much heat so I replaced the regulator at the tank. I dug out one of my surplus old regulators to do this. The heater put out more heat but the main flame was pulsing - big flames, then smaller, then big again, with a fairly rapid cycling (1-2 or so cycles per second) between the two states. So I dug out another surplus regulator - the heater put out less heat and stopped pulsing, but it still wasn't the heater of old that I wanted. So, I bought a new two stage regulator. There is lots of heat now, but the heater is pulsing again. Should I suspect the new regulator, or the millivolt control valve located in the heater? How would I test? Thank you in advance.

 

Hello JRandomLuser. Welcome to the Heating Furnaces forum topic & the Do-It-Yourself Web Site.

I moved your question here, into the gas heating appliances topic, from my gas kitchen appliances topic. The other diy heating professionals can also now provide you with assistance.

Burner fluttering sounds are more often caused by the gas valve. Has to do with the valves built in gas regulator. The diaphram flutters or pulsates causing the gas valve to open and close very rapidly. If that is the case, replacement of the gas valve is the only solution.

Depending upon the severity and frequency of the problem while the unit is running there are the above possibilites. Several others too. Could be a cycling caused by the sensors connection or the module it's connected to, etc.

Gas flow is another possiblity but not likely if other appliances are not having an identical problem. More likely the appliances gas valve. Check to verify that it is in fact fully opened both the one on the supply pipe near the unit and on the heaters gas valve.

Disconnect gasline and allow some gas to freely flow out of the line. Do this only if not source or ignition is in the area and only for a brief time period. Listen for gurgling sounds. Possible water in the gas line which causes gurgling sounds and burner fluctuations. Can also be caused by burner obstructions, burner orifices that are obstructed and/or water or some liquid in the gasline. Water can enter a gasline at any place or location between the heater and the meter.

Happens with buried underground gaslines to outdoor gas appliances like pool and spa heaters. Furnaces located outdoors with underground gaslines. Encountered it many times. The water, in enough volume fills the line, restricts the gas flow throught the pipe and the burner flames flutter.

Another possible cause for burner flames to flutter is a defective gas control valve. Usually but not always, the internal pressure regulator is defective. Either the diaphram is defective (several ways it can become defective). None of which can be fixed or corrected. Valve replacement solves that problem. Remove entire unit as an assembly. Take the entire assembly to your local appliance parts store for testing. Gas valves are not repairable. Replacement is the only option if defective.

The ambient air vent hole in the gas valve is restricted and or plugged. Normal for such to happen. Several causes. None of which should be attempted to fix or correct. Gas valve replacement is the only solution, once again.

Any of and or all the needed parts are available at the local heating parts retail dealers where service techs purchase their parts and or most appliance parts stores. Check the phone book pages for the dealers in your area.

Personal Safety Reminder:
Buckle Up & Drive Safely.
"The Life You Save, May Be Your Own."

 

Have you checked the gas pressure? I assume this is LP? You need to know the pressure needed for your appliance. Gas is nothing to mess with. I would suggest calling a pro.

 

thanks for the very detailed reply. I'll check the gas line for water first, then I'll get the gas valve examined. Your suggestions are a great help.

 

Take a voltage reading, and see what the voltage is. It needs to be steady.

Also, Did you get a gas pressur reading? You can just throw something on it with out takeing a reading!