Efficient gas water heater

You say 30 gallon, which implies storage. The only way storage is efficient is when the energy source is free or very inexpensive, as indicated by Del...

Any time you are storing anything hot, you are losing energy to the surroundings. You can reduce the losses to a minimum by excellent insulation, but a better way is to wait until the heat is needed, then heat very quickly. I presume that the makers of what I know as 'flash' water heaters have gotten the efficiencies pretty close to the peak. I doubt seriously if an individual or even a small company can do much to improve them - they have been around for a long time. I had one in South America well over 40 years ago, and I suspect that they had been available at least in Europe for at least 10 years before that...

Go to any good plumbers supply store and buy one Trying to build one yourself is NOT a good idea it would be very easy to burn you home down or blow yourself up. Rinnai Rheem or any of the other good brands are very efficient and safe. These companiesw have spent millions on R+D its silly to blow yourself trying to reinvent the wheel.

Design a water heater? Again? Why?

Now that we know and see the effects of global warming -do to fuels burning- It has non sence to keep using a gas water heater, neither to desing a new one any more.

You better design a solar water heater -to help nature to restore its temperature-.

No more fuel burning please.

I'd have to agree with the other posters. Buy one from an existing water heater company it'll be cheaper, more efficient and safer.

Contrary it what many think, market forces usually compel the larger manufacturers to produce an efficient, high quality product. ffeJ

All the the above comments are duty cycle dependent and usually not correct in many cases.

The DOE evaluation of "electric" water heaters that heat on the spot and do not store any hot water actually take MORE energy and co2 (from a coal power plant) than do typical water heaters, depending on duty cycle and size. Read the side by side comparisons...you will be amazed. Then realize that heat from electricity takes around 2-2.4 times as much fuel burn (co2) for a given heat addition. (A gas driven heater does not, however).

A heater that has no insulation will heat a finite quantity of water and then when it is done, it will release all that energy. If you want a short blast of hot water to wash your hands, make a hot drink (180 F) every 10-15 minutes the water will cycle all the way down without the insulation.

The dirty little secret is that to heat water at 55F (ground temp) to 105 (50F) to take a shower at 2.5 gallons/minute (standard low flow shower head), you need around 18.75 KW (gpm x del T x .15...or 2.5x50x.15=18.75), which is a LOT of power.(!)

Can you imagine what the grid would do if every household took a shower all at the same time (6:30 am say)? At 240 volts that is 78 amps. Long and short of it is, the market for electric instant water heater at the Home Depot and Lowes is dead. Why?

Because it takes a lot to heat water. Most real people like 5 GPM showers, so you can double the 78 amps to around 150 amps or so, but what if Mom and Dad, kids are all taking a shower? Woops! Most house electric boxes are 100 or 200 amps. The lights will flicker when the elements come on and off for Dad, and you will fry the bank for 2-3 showers.

Remember, all electricity is only 30% efficient from the grid.

Electric water heaters that heat on instantly do however have a place in a system, but not as they are now marketed and designed.

How do I know? I am going into the business...with a new way to do it that the "big boys" have not seen as yet...

There is a place for a 30 gallon tank, but not how it has been done.

Actually, all water needs to be over 131F to avoid certain bacteria. Such high temperatures will hurt children.

As for directly answering your question, to make an efficient water heater you need to have the air out the stack be near as possible to ambient (70F) as possible. Hint: you need at least three tanks thermally isolated in reverse to the incoming flow.

I like your ideas are you talking of near perfect waste heat recovery from boiler flue gasses?

Will,

Yes, recovery from flue gasses and from roof heat, and mostly from a systems point of view. I am coming from a systems point of view with a motor I am developing that will integrate the pieces.

My curiosity is escalated at the statement "all electricity is only 30% efficient from the grid". I do not doubt this is true. I am simply curious what the basis is for this statistic.

As for designing efficient hot water heaters, I advocate insulate, insulate, insulate. A little trick to consider is to turn off your water heater when you are away for several days (vacation, etc). To this end, and to give you an idea of how efficient water heater insulation already is, I have noticed that the burner does not turn on (after switching my gas water heater on) returning from a summer vacation. I suspect that only the pilot lights maintains enough heat to keep it at the thermostats temperature.

T

Since seaplaneguy hansn't responded - Commercial powerplants that burn a fuel to generate electricity convert only about a third of the heat energy of the fuel consumed into electric energy, the other 2/3 going up the stack or through the cooling system into the air and/or water. The electric energy then has to be carried over the distribution system to reach your home, and of course energy is lost to heat in the process, leaving less than a third actually reaching your home.

Generating the electricity locally can eliminate most of the distribution losses, but unfortunately smaller generators are generally less efficient, so nothing is gained...

So if heat is required, it should be created by burning a fuel as close as possible to the point where the heat is needed. Whenever possible electricity should be used only to produce light and motion, not heat. Of course electricity is incredibly clean and convenient at the point of use - I'd really hate to give up my microwave oven!

Dick

dk,

I think you can just google DOE and grid efficiency and firgures of 1/3 efficient on average are typical and, like you say, lines loose some, ending up with about 30-32%. GE has some new turbines with multicycles that can get 60%, so many of the older steam/coal generators are less than 1/3 on average, one would reason.

If you can get to 60%, like what GE does and what I am working on, then you have an electricity 2/3, waste 1/3 ratio where the waste can be used for process (dishes, showers, etc) water heating and 2/3 goes to electric. At that point central power generation is like a mainframe computer...

Go to "Lowes" buy a new low energy water heater and a water heater insulating blanket. Then insulate the hot water pipes.

COPY AN AO SMITH CYCLONE 93% EFFICENCY