Water Heaters - Power Vent Water Heater

Replaced existing Rheem 50 gallon natural gas power vent water heater under large crawl space area. New unit will not operate with heat shield installed at burner door. As soon as it is installed, the burner flame extinguishes. Once removed, the fan powers up and the burner will ignite. This is an open burner. I changed the regulator on the 2psi system at the heater,Thinking a low gas supply. The gas company has changed the outside gas regulator as well. The vent is the existing 3 inch pvc one that was used for original heater. The horizontal run is aproximately 40 feet, with one ninety degree turn. There are notable foundation vents installed. You can stand up under entire crawl space.

Any Help?????????????????????

It almost sounds to me that the heater is starving for air therefore by removing the shield it will then provide the air. Unfortunately that shouldn't have an effect on the power vent blower from starting.

Another possibility is some sort of short or bad ground.

If you can provide the model # of the water heater I might be able to give you a better idea.

It almost sounds to me that the heater is starving for air therefore by removing the shield it will then provide the air. Unfortunately that shouldn't have an effect on the power vent blower from starting.

Another possibility is some sort of short or bad ground.

If you can provide the model # of the water heater I might be able to give you a better idea.
I will obtain that model # tommorro and respond back. Thank you.......