incomplete combustion

The Tank incomplete combustion

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  • #15498
    MikeP
    Participant

    I recently had the gas valve and tcouple go out on my 10yr old, 9yr warranty, Maytag gas heater – it does have a mag rod but I can’t get it off to check it.

    After replacing the gas valve, I noticed a terrible build up of odor in the house the next day, smelled like combustion fumes. Never had this before. I pulled the burner and orifice and baffle. Cleaned the burner with a wire brush, and used a pipe cleaner to get down into the ports as well as the orifice (which looked fine). I wiped down the baffle, reinstalled it, and vacuumed all the debris out of the bottom of the unit.

    I fired the heater back up and although the major smell is gone, there is some. I can tell when the heater has been running hard that there is some slight smell, my wife can’t detect it. I didn’t have this before replacing the gas valve.

    The old valve was a WR, the plumbing supply store sold me an “equivalent” Robersthsaw. However either I had a problem before and didn’t know it, or I have a new problem with the new valve. A CO monitor near the heater doesn’t detect a thing, and it’s less than one year old.

    I did look at the flame, and notice that it’s fairl tall. But not sure how tall is correct and what is too tall – I have emailed State for advice on my particular heater. I do see some yellow dancing on the tips, and the flame does appear to be about 3″ tall, and when I put the inner metal door back on it turns a LOT yellow as the air flow changes.

    If anyone has any ideas on what I need to troubleshoot, or if it’s time to replace the burner, or worst the heater.

    NOTE: I have been encouraged by this website providing great info on how to make heaters last a LONG time. However, if the other parts (burner, valve, etc) don’t last I’m wondering how long you really can go on them. This thing is starting to get expensive on parts, enough to almost buy a new heater.

    #15499
    energyexpert
    Participant

    A yellow flame indicates gas/air ratio is too high. Are you propane or natural gas?

    David

    #15502
    MikeP
    Participant

    I have natural gas.

    #15506
    Ej
    Participant

    Try this test. With the heater on hold a lighted match or lighter just on the outside of the vent cap. Slowly move your match to just under the edge of the cap. The flame should be pulling in and upwards toward the flue. If the match blows out before you get the match drafting upwards then you have a faulty draft and this is the reason for the smell. Several steps can be suggested if this is your problem.

    #15507
    Ej
    Participant

    Also if your flue tees into another appliance such as a furnace then make sure your furnace is on also at the time of the test.

    #15508
    Ej
    Participant

    The older valves had a 4.5″ WC and the newer valves have a rating of 5.5 WC. Make sure you bought the correct valve.

    #15509
    MikeP
    Participant

    Thanks EJ – Hmmmm – now I had to look. The old valve was rated for 4.0″, and the new one is 3.5″. I took the old one with me to the plumbing supply store. What will the pressure difference do, if the new one is rated for a lower pressure? I do notice that I had to put the heater on the lowest setting to get just under 140F; on the second setting it was close to 160F.

    It seems the dealer just handed me what would fit connection wise without looking further.

    What’s my fix: go back and exchange the valve, or get a new burner that matches the regulator pressure?

    Still need to check on the flue. I do have a furnace that ties in below the heater.

    #15510
    Ej
    Participant

    Your new valve at 3.5″ WC shouldn’t make any noticeable difference. Do check the flue with your furnace on. I took a call just the other day with the same problem as you described. The heater drafted fine until the furnace was turned on then the force of the fan blew the heater emissions back out from the vent cap and into the room.

    #15513
    MikeP
    Participant

    I tried the match thing, and could not see a noticeable difference in the manner in which the flame wafted, it pretty much didn’t move as far as I can tell. And the smoke when I blew it out pretty much went straight up into the room, wasn’t sucked into the flue.

    I also realized that it’s been above 32F since I have been smelling the vapors, which means my dual source furnace has been in heat pump mode the entire time. So the only source of the vapors is the water heater.

    I’ll see what the local plumbing supply dealer says about the gas valve.

    Would replacing the burner, or buying a new unit possibly fix this? I say that because I wasn’t smelling vapors before I swapped the gas valve.

    I was able to pull the mag rod, and it’s totally gone. Not sure about the combo rod that came with it on the outlet. BUT, if they both are gone then it’s not long for the heater and I might just replace it and see if that fixes the problem. Otherwise, I could try getting a burner that is matched to that gas valve and then buy a powered anode from WHR – but only if the heater still has a lot of life in it – at this point it’s already going on 10yrs old.

    #15514
    energyexpert
    Participant

    Mike,
    I wanted to respond just to the gas issue.

    The unvented gas logs in my fireplace are rated at 40,000 BTUs. At that rate it is not long before you have to either shut them down or roast. The flames also had more yellow than I wanted (which looked more natural) because yellow flame indicates incomplete combustion and the possibility of CO.

    I tried throttling down on the logs’ cutoff valve. When the solenoid opened the gas pressure after the cutoff valve was low enough that the thermocouple flame did not reach the thermocouple and everything shut off. I repositioned the thermocouple so the small flame still impinged the thermocouple when the solenoid was open. Now I have small blue flames in the logs at about 15,000 BTUs. I don’t have to cycle the logs but they don’t look much like real logs burning.

    You should be able to throttle your WH cutoff valve and observe color and size of the flame. If throttling down gives you the right color flame then you have too high of gas pressure. But if the thermocouple flame then does not reach the thermocouple you will either have to reposition the thermocouple or if you can’t, a new valve is in order.

    David

    #15558
    MikeP
    Participant

    Eneryg Expert – Although I like the concept of reducing the gas flow as it’s a novel idea, it’s a bandaide for my heater.

    State technical support suggested I call their parts department to check on compatability of the new valve with the burner. However I have yet to make contact with them.

    Based on the current state of my anode, GONE, and combustion chamber, CORRODED and or undersized, I think it’s best to call this one quits. The local plumbing store I think will give me my money back since I’ve called and been in there numerous times to follow up on this thing – not to mention they are the Polaris rep if I choose to buy one.

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