Hot Water Heater Life Span

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by bendhamma, Nov 2, 2004.

  1. bendhamma

    bendhamma New Member

    Messages:
    3
    We are having problems with an A.O. Smith 75 gal Commercial 120K BTU water heater. It has Flue control, that leads to a transformer, which leads to a Johnson Controls G77 control box.
    After three years of use, we are experiencing continuing shut downs, lockouts, whenever we put it under heavy load. (92 gph)
    We've had two factory authorized repairmen visit, but they don't seem to understand the complete system. We may be stuck with having to buy a new system.

    Question: are we better off buying a common Kenmore or equivalent without all the "doodads" and a 6 to 12 yr. warranty. The temperature we require is 140F. Our booster brings the rinse cycle to 185-190F.
  2. e-plumber

    e-plumber DIY Senior Member

    Messages:
    137
    Location:
    New York
    A.O. Smith is an excellent brand, especially for commercial units. It appears that the unit just needs to be serviced by someone that knows what they're doing.
    Call A.O. Smith and complain if you didn't already.
    Any new commercial unit will have "doodads", (ignition module, controls, electric flue damper, etc.) and will only carry a three year warranty. Another point, it sounds like you're operating a food service establishment. Although the dishwasher booster requires 140F to boost the water temp to 180F for the DW's final rinse, it's not a good idea to have 140F feeding restroom faucets :eek: or even sink faucets in the kitchen. A tempering valve may be needed.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Commercial service places an extreme demand on the WH ( nearly continuos operation for several hours or more each day.) This is why the life expectancy is limited. If you are suggesting a standard residential WH as a replacement, it would have a life expectancy of about 6 months, and of course it would carry NO WARRANTY at all, due to use outside the warranted conditions.

    Regarding your present unit, the primary reason to replace it would be if it was leaking. It sounds like your problem is fixable.
  4. bendhamma

    bendhamma New Member

    Messages:
    3
    re: A.O. Smith Commercial

    Thanks guys,

    We are a meditation community that serves 120 people twice a day. So the load on our water heater is at cleanup time... 1.5 hours each. The other time of operation is cleanup after kitchen prep for the next day. Stero corp. estimates the amount of water we draw to be 92gph. Hatco is our booster heater. We bought the hot water heater because we were told we needed 180 degree water for the Stero. This turns out not to be the case as the Stero has a very efficient heater of its own and the Hatco gives us the boost to 190 for the rinse.

    One of our major problems with repair is that we are 40-50 miles from the nearest technicians, and though we pay for their travel time on their initial visit, we tend to get the response not available if we have to give them a call back. So far we've spent close to $400 just trying to get sustainable ignition. That seems to be our only problem (ignition). Our last repair tech said to cut louvres into the door so that the unit would get more air, but if we leave the doors open to emulate this solution, the draft of the exhaust fans to the cooking area seems to cause negative air pressure to the hot water heater.

    If we are patient and persistent, by using the lock-out mechanism, by turning the unit off, waiting a spell, then turning it on, we almost always will get ignition with a 1/2 hour of effort.

    I need to know what the point of no return is financially.
    And thanks, I do need to give A.O. Smith techs another call, they were quite helpful the first time.

    Thanks for your help
    Ben
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Combustion air is a critical element in the installation of any gas appliance. You mentioned doors. If the WH is in an enclosed space, it MUST have a supply of air. You need 1 square inch per 1000 BTU. You must have this area within 14 inches of the floor and the same amount within 14 inches of the ceiling. ( Unless this is a direct vent unit with combustion air ducted in)

    The manufacturer and the National Fuel Gas Code provide the requirements.

    Negative pressure caused by an exhaust fan can cause a DEADLY situatin with regard to carbon monoxide, and also cause improper operation of the burners. I think you need a GOOD technician to look at this installation. Was the present water heater permitted and inspected when it was installed?
  6. e-plumber

    e-plumber DIY Senior Member

    Messages:
    137
    Location:
    New York
    Make Up Air

    "the draft of the exhaust fans to the cooking area seems to cause negative air pressure to the hot water heater."

    We do quite a bit of commercial kitchen work (repair & service); diners, restaurants, schools, etc.
    Most exhaust hoods have a make-up air unit to help prevent the exhaust hoods from creating a negative draft from the water heater or heating equipment flue. A "fan in a can" may help your situation depending on the location of the water heater.

    We have on Mexican Restaurant that we service that has the water heater near the kitchens rear exit door. With the door closed and the exhaust fans operating, the water heater does not work at all, the flames spill out from the bottom, the pilot gets knocked out, the burners shut off, flue spillage, etc. When the door is opened, the water heater works fine. They installed a make up air unit to solve their problem.
  7. bendhamma

    bendhamma New Member

    Messages:
    3
    I don't know how to calculate square inches around the base, we would need 120 sq. in. But I think we're o.k. there with at least 6" clearance all round. The flue chimney extends to the roof through an open ceiling that is at least 6 ft (36 sq. ft.) so we're more than o.k. there.

    The idea of a "fan in a can" seems a simple and hopeful approach to being sure the combustion area has enough air. What I noticed today during a "burn" is that the burners overall burn with a nice blue flame, but that the flame at the front by the ignition and gas/flame sensors burns very yellow and the sensor that I could see was glowing red. Is that significant?

    Thanks for your help,
    Ben
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