I've been doing HP assessments for 12 years, but find myself a little limited in my knowledge of this issue.

Here's the scenario: I do an initial assessment where I find a 7-year old NG water heater with 1500 ppm undiluted CO. The homeowner brings in his plumber to "fix" it. The plumber, who doesn't own a CO monitor, cleans the burner and air intake grill, and proclaims it good. After work is done on the home, I re-test and find the CO to be even higher this time, and the draft weak.

What typically can be done to a fairly new water heater to fix the CO problem? The gas/air ratio must be out of wack, I'm thinking. Is it usually corrected by replacing the gas control valve?

The homeowner is left hanging, the plumber is without a clue and me telling him it needs to be corrected. I would recommend a different plumber, but I want to find out what a knowledgeable individual would typically do to correct this, short of replacing it. One thing I know is I need to align with a knowledgeable person to address this in the future.

John Shillito

Tags: CO, heater, plumber, water

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I'll let a pro (which I am not) jump in on the correct adjustment, but you said:

"One thing I know is I need to align with a knowledgeable person to address this in the future."

That is a mouth full and one of the major steps needed to be a successful energy auditor.  There are many things we run into that we are not certified to fully advise on, nor should we be.  But that list of who to call to give you and the home owner the advice you can trust is a must.

You say the draft is weak, do you see a reason?

Bud

Bud, the weak draft was likely due to sharing a clay lined flue with a furnace. It was at an acceptable level.

Wrong orifice for gas type? Bumped the burner knocking it out of alignment?

Poor draft due to it cant pull as well due to air-sealing, etc... was a fresh air intake pipe added?

Sorry but the only true & correct answer / fix which should have been given to the homeowner up front is that the unit has no business being in the house & should be replaced with a direct vent system

9 ways to get high CO.  High presser low presser  impingement ( rust on burner- mis alined burner) to high flue presser lack of flue,  low temp very high temp. Flue to small or to cold   I find most plumber do not tune up hot water heaters or can test flue gas.  I had a 350 lb dud pick me up my neck spiting on me about lack of venting I did not pass.   

Surprise, John! The homeowner is the expert! Assuming your CO meter is properly calibrated, the flue vent is not blocked, and the gas control valve is a-ok, it is strictly up to the homeowner to read the equipment manual, and go in and adjust the air shutter for a true "blue flame" without yellow tips, in the case of NG. The homeowner must check for proper flame size, and check to see that not too much black soot from lack of combustion is forming on the bottom of the tank. It is the responsibility of the homeowner to have new CO detectors on each floor, in case of spillover from the flue. Even though 1500ppm CO is much greater than the BPI limit of 35ppm CO, the effect on combustion is minimal, and not unsafe unless the flue is blocked.

help on regulators: http://inspectapedia.com/plumbing/Gas_Regulators.htm

help on black soot: http://www.waterheaterrescue.com/pages/WHRpages/English/Troubleshoo...

As declared above the home owner has the complete legal and practical responsibility to correct the condition, or must replace the equipment. There is no expert in this field, not even at the water heater company. I am not an expert on your problem. 

The problem with a high CO in the flue is that if conditions such as floor movement, new fans installed in the house, insulation/air sealing issues may allow a system that already has high CO escape.  High CO will multiply when in a confined space at a high rate and create unsafe conditions..  

Hello:  If it's an FVIR heater, there can be restriction in the air intake caused by nearly invisible dust.  Washing off (or blowing off, or vacuuming) the intake screen and flame arrestor might not be a bad thing to do.  I'd also check the flue design (according to the National Fuel Gas Code)  to see if it is likely to provide good draft.

Yours,  Larry Weingarten

when we do cleaning for air conditioning or furnace work we also clean the air filter on the FVIR hot water heater.  look at my web sight under "peak"  HVAC  www.ericsenergy.com   I have seen 100's of full hot water heater screens then will not get the air to run.  When do a flue gas test the O2 JUST GOES DOWN to under 2% and then CO go up -  I have seen 1560PPM CO off the hot water heater

Eric & Larry are both right , recorded here: http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html  this site is super great!

A common cause that I have seen is undersized gas supply piping, especially when a combustion appliance is added to the line. Undersized gas supply pipe = lower gas pressure => high CO

Thanks to everyone for the great replies. I contacted the manufacturer, and the reply I was given by way of their technical department was that 2000 ppm CO is not a problem as long as it is venting properly out of the home. Testing for CO in the first place is not part of the installation or servicing of their water heaters!

Tom Delconte said: "As declared above the home owner has the complete legal and practical responsibility to correct the condition, or must replace the equipment. There is no expert in this field, not even at the water heater company."

How right you are! Not even at the company.

I found a local installer, who at least took the time to speak to me on the phone, but could seemingly only wrap his brain around CO readings in the house, not in the vent. When I told him what I meant, he told me to test in the vent connector, after any elbows, and with the dillution air the reading would surely drop to below 100 ppm!  Oh Brother................

hey thanks for the links. Very informative on FVIR units

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