Water Heater Guru (Control Valve Question)

[wolfman00hd]

As usual, my crappy luck reared it's ugly head and on the way home from Home Depot w/my new water heater in the Ram, it blew out and trashed the gas control valve. I priced a new one online and it was almost as much as the water heater was new. I found a new one on ebay and got it for $20. After it finally got here from Canada, I removed the damaged control valve and much to my satisfaction, they look identical. The only difference I can see in the two is this; The damaged one I removed had red knobs and dials and states Main Burner Pressure 4. 0". The one I want to replace it with has blue knobs and dials and states Main Burner Pressure 3. 5". Can anyone tell me what the difference between these two are ? Am I safe swapping them out and installing the water heater in my house? The control valves are Robertshaw Unitrol units. Any help or advice would be greatly appreciated.



Wolfman

 

[ironbutt]

gas valve

The two gas valves are most likely interchangable, The rating of 4" or 3. 5" is the pressure of the gas that goes from the control valve to the burner. This pressure is in (Inches of Water column) for clarification, 1 pound of pressure is = to 27. 7 "inches of water column.

You local gas utility delivers the gas thru the meter at about 6. 5"wc ( could be 5. 5" thru 8. 0" ) and all appliances have control valves that have regulators built in and the delivery pressure to the burner is most often be 3. 5"wc. On a water heater the difference between 3. 5"wc and 4. 0"wc as a delivery pressure is neglegable. ( If for instance the combustion rate is 40,000btu, the difference would be at 4. 0 instead of 3. 5, about 41,000 btu. )

This should be OK. Also about the price of a gas valve, compared to the whole heater. The price of the valve is 3/4 of the cost of the whole thing. :-laf "Ironbutt"

33 years of gas experiance, now retired. Also if it came from Canada, it should have CGA logo instead of AGA . ( AGA stands for American Gas Association, and CGA for Canadian Gas Association. ) That may also be why the blue knobs. If the valve is for LP Gas(Propane) it would be rated for 7. 0"- 11. 0"wc. and it would also have different threads,for the fitting's.