Black soot on outside wall above hot air exhaust. Excess flame, incomplete combustion? How to adjust/correct?

You need to get a Plumber or Appliance Tech to come out immediately and check the fuel to air ratio. You are not burning your fuel at the proper mixture. A blue flame is good, yellow-orange is bad.

Normally this is because the burner area is dirty or the pressure regulator may be set too high/low. The black marks are a sure sign that your ratio is too rich and it's just going to build up more soot and become unhealthy and dangerous.

http://inspectapedia.com/plumbing/Gas_Flame_Noise_Defects.htm
Don't wait...

You must get more air to water heater, and check venting .... immediate CO poison danger.
Call qualified plumber immediately.... because deadly carbon monoxide is not being vented properly.
http://waterheatertimer.org/Water-heater-safety-precautions.html#soot

Gene h

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

There is improper combustion taking place . It should be under warranty. Have the ething has failed. i wouldnt use this until it eas fixed. seller take care of this. Obviously som

1) Danger. Sooted smoke indicates incomplete burning of gas, clogged air intake, dirty combustion parts, bad vent, and lazy yellow flame, and absolute danger of fire or explosion of unburned gas in flueway. Call for service immediately.

2) Add comment and include more information about brand, type and model of unit. And include if this is gas fireplace, gas water heater, stove etc. For more possible help.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

here's what Bradford White lists....
Burner Will Not Ignite
REASON REMEDY Excess primary air Adjust air shutter to reduce air supply -- if supplied No gas Check with utility Dirt in main burner orifice Clean orifice -- check for source of dirt and eliminate Dirt in gas lines Notify utility -- install dirt trap in gas line Venturi clogged Clean -- check for source of trouble and correct Pilot line clogged Clean -- check for source of trouble and correct Main burner line clogged Clean -- check for source of trouble and correct Defective thermocouple lead Replace with new thermocouple lead Defective thermostat Replace Defective magnetic valve Replace entire control Thermostat set too low Turn temperature knob to desired temperature Heater installed in confined space Provide ventilation by use of louvers in wall or door time for a service tech.

The difference between an orange flame and blue flame is the amount of air in the combustion process. SO if the flame is orange it is being starved of oxygen. The gas burns dirty and soot is generated.

Sometimes with an older heater the exhaust venturie becomes plugged and carbon monoxide is released into your home- in this case your heater would make a woof or poping sound when starting up or shutting off. This is a dangerous unsafe situation and professional help is needed.

What you can do is try to make adjustment yourself, if your confident the other situation does not exist. Your water heater should have a little deflector shield on the gas line between valve and burner (typically immediatly after the orfice). Sometimes these will have to be slide front or backwards or twisted. The adjustment of deflector shield must be opened more to make the blue hotter flame to mak eyour heater operate at peak efficiency.

Good Luck

EA & EC are telling you that the flame is not covering the flame sensor rod.
Take the front cover off by unscrewing the 2 phillips head screws about 1/2 way down the cover and may be covered by a plastic plate that unsnaps.
Locate the flame inspection glass window near the right side above the control panel. Prepare to observe the flame from start, until the error appears. Visually locate the flame sensor rod: there are 3 rods that pass through the plate below the burner - it is the right most of the 3, angle your head so you can focus on this single rod. Begin water flow by opening a valve or the pressure relief valve that should be outside the cabinet, at the bottom.

Did the flame ignite? it should make several tries before an error.
if it ignited, did the flame cover the flame rod, or did it jump up over it leaving the rod in clear gas below the flames?
In the LCD display, upper right corner, is an indicator in the shape of a flame. It is visably displayed when the flame is covering the flame rod, indicating that the flame is being detected by the electronics. If the flame covered the rod but the indicate is not on, the rod itself may be dirty. Remove it with the other 2 ignitor rods and careful clean the sensor rod with something like steel wool to remove the corrosion. Re-install and test again. If that didn't fix this condition, your control circuit is faulty.

If you find that the flame jumps over the rod and doesn't emerce the rod, check the draft vent pipe for any obstructions, water, bird nest, etc, and any obstruction of the combustion air supply. Check the the gas blower starts up, check for water or white dust in the clear tubing that attaches to the black blower intake from the gas meter.

Otherwise, you will need to follow the procedures to adjust the CO2 and this WILL require a combustion gas analyzer! If you are at an elevation above 2,000 feet, expect to make this adjustment.

Sounds like the burner flame may be too strong (jumping out from burner tube) . Some people think the louder the better, but that is not correct. When burner shuts down like that, it has a tendency to snuff out pilot as well. Adjust your air shutter at burner so that the flame is a nice blue, or with just a hint of orange/yellow at the tip. Whatever setting that keeps the flame solid from burner tube, and not a big gap between tube and flame. Signs of soot (black) up the cover, or side of trailer means it's running too rich, and you've gone too far thus needs more air. Keeping the flame blue but still right out of the burner, actually heats better, is quieter, and should eliminate that pilot getting snuffed out. Pilot should also be a nice blue flame as well. There may be a problem with positioning of the burner tube as well, but doubtful if it has been running well in that position before. Let me know what happens.

Sounds like you're not getting enough combustion air.
If you have a draft motor or blower make sure it is running.

This is also known as a flame rectification sensor. It basically is what the computer board uses to detect if the pilot flame is lit. When it makes an attempt to fire is there any evidence of flame ignition? This error does not mean that the sensor is bad for sure. The error could be caused because the water heater is only making three attempts to fire and then shutting down. These water heaters are very complex and have many sensors,valves, ect that are all controlled by a computer board. Some of the basic things to check for are... Make sure that you have plenty of gas pressure. These units have a built-in pressure switch and will have issues if they are starved of gas. Most of these tankless water heaters are up to 400,000 btus and a half inch gas line or undersized connector won't work well. You can also check and make sure there is no pipe dope are debris stuck in the screen inside the gas line where it enters unit. Inspect the pilot assembly for debris or obstructions and try to blow out with compressed air. Also look for any loose electrical connectors on the board or to the sensors...one may have come loose.