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Water heaters

professor
professor Member Posts: 1
in THE MAIN WALL
If water heater efficiency rating is based on 50 degree incoming water, what is that rating when water temp is 80 degrees

Comments

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    It depends...

    If you are talking about a conventional tank style heater, it MIGHT make a few points difference in output efficiency. No biggy.



    If it is a tankless, then its really not going to affect the efficiency of the appliance all that much, but it will make a difference in the GPH capacity of the appliance, based on the manufacturers published data.



    This is one area that really sticks in my craw, and I know we've beat it to death around here, but there is no "Gold Standard" if you will, as it pertains to water heater (specifically tankless) capacities. So tankless manufacturers are allowed to make some rediculous statements as to the capacity of their appliance. "Our unit produces 200 gallons per hour of hot water" Then, when you read the small print, you find that those numbers are based on a 50 degree differential, not the 100 degree differential that conventional tank style heaters are tested against.



    Buyer beware. A BTU is a BTU is a BTU. The only thing that changes that is conversion efficiency in converting from a fuel to hot water. So, if it is a non condensing appliance, it is probably 80% efficient (give or take a few points) and the math can be used to compare the output of one to another based on the same parameters as it pertains to delta T and GPH capacity.



    One of thee days, our governing agencies MIGHT get smart and put everyone on an even playing field, but in the mean time, as I stated, buyer beware... Don't hold your breath :-)



    HTH



    ME

    There was an error rendering this rich post.

  • bob eck
    bob eck Member Posts: 930
    water heaters

    on the Noritz tankless gas water heater web site it shows GPM for 30*F to 100*F temp rise. The noritz NR83 180,000 BTU input unit at 100*F temp rise delivers 3 GPM or 180 GPH. I believe tankless gas water heaters have there place in the market. If you have a large family where they run two three or four loads of laundry  and then run the dishwasher and then there are one or two shower taken and finally you want to hit a long hot shower the tankless unit is a great way to go. It all depends on the home owners life style and how they use hot water. This is where the professional contractor can sit down with the home owner and ask a few questions and then direct them to the right type of water heater either a tank type or tankless type. A O Smith makes a great tank type gas fired water heater called the Vertex one model is 50 gallon with 76,000 BTU input and it delivers 127 GPH and recovers at 92 GPH vents with PVC pipe. this unit delivers more hot water than their 75 gallon power vented tank type water heater. If the home owner want to go tankless most of the time the gas line will need to be made large but if they go to the Vertex with only 76,000 BTU input the gas line might already be large enough. Another way to make your hot water last longer is to use Alsons - Delta 1.6 GPM shower heads and replace the 2.5 GPM shower heads the home owner is now using. I have the 1.6 GPM shower heads and they work great. Two daughters with very long hair and they never told me that they do not get enough water from this shower head. Not all reduced flow shower heads are equal some work fine and others no so much.  
  • icesailor
    icesailor Member Posts: 7,265
    Water Heaters, a better way:

    An even better way to help tank type water heater is to use a quality thermostatic mixer on the outlet. If you run the water out at 120 degrees, but store the water at 140 degrees, you (theoretically) increase the size of the stored water tank.

    Two tanks of 50 gallons, one with 75,000 BTU input and the other with 95,000 BTU input, will deliver the same amount of hot water over the same period as long as the demand doesn't go over what is available. The smaller 50 with the mixer will out perform the 50 with the bigger input, every time under most conditions.

    Honeywell/Sparco AMX-101 direct connect thermostatic hot water heater mixers ROCK on water heaters. They have internal checks and a re-circulation port.

    For a lot less money than the indirect in total out of pocket install expenses in a direct replacement situation.  
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