The founder of Blue Rhino propane-tank refill stations has a new product.
"Callahan has invented a football-sized electric water heater with patented
technology he believes could save everyone lots of water, energy and money.
No more running the water for a minute before its hot enough to use, no
more plating parts, no more scalding, he promises."
Good from the first drop.
On 4/10/2012 8:54 AM, firstname.lastname@example.org wrote:
I read the patent app and some stuff about it at the company's
website. Apparently, the lack of heating electrodes means less surface
area for scale to accumulate upon. That might also be a factor in its
comparatively small size, even for a tankless heater.
There's such a glut of nat gas that unless producers drastically cut
back storage capacity will be exhausted come October.
The only way I've ever heard of seeing a lower propain price is to
Regarding gasoline, for example, "rocket up, feather down" is justified by
When a gas station refills his tanks and the refill costs him ten cents a
gallon more, he has to increase his retail price accordingly, not only to
recover this price increase, but to lay in a surplus in anticipation of the
If the delivery truck charges him ten cents a gallon less, he still has to
recover the cost of the gas in his storage tanks. That is, if his storage
tanks are half full when the tanker truck pulls up, he can only drop his
price by five cents. Then with the next fill-up, he can drop his retail
price by 2.5 cents, and so on.
In engineering and science it's known as hysteresis. In any kind of
control system, hysteresis prevents wild swings and oscillations. The
thermostat for your home relies on it as does the power steering in
your vehicle. I'm no economist but I'll guess there is a term used in
that field that means the same thing if not the same term. ^_^
I'm a bit suspicious of a tankless (near as I can tell, it's tankless)
electric water heater from a guy who sells about $16 worth of propane
for $23 to $35.
If it's truly a tankless electric and it has a better electrical
energy input to water heated ratio.....then it might be more efficient
as he claims.
But I'd have to see the numbers......electric energy input and water
flow (gpm) & temperature rise.
If he's waiting a minute for hot water then he's got ~80' of 1/2
copper tube or ~40' of 3/4 copper tube.
(that's the length of tube that holds a gallon of water) . Hot water
flow assumed to be 1 gpm.
His comment "no more running the water for a minute before its hot
enough to use" seems more than a bit unrealistic.
Resistance heaters are only 100% efficient
(electrical energy input = mass of water x temperaure rise)
in a tank water heater situation AND where the water has sufficient
Resistance heaters are 100% efficient regardless of
where they are or what the residence time of the water is.
100% of the electric energy is converted to heat. Longer
residence time for the water only means it gets hotter.
Flow the water through at rocket speed and the water
might go up only .01 degree, but 100% of the electric energy is
converted to heat. Some amount of the heat from the
water is then lost through the heater to the ambient,
but 100% is always converted to heat. And increasing
the residence time, ie decreasing the flow rate, would
only make that lost heat greater, because the temp of
the heater would be higher.
Good point, my thinking was faulty.....
Because there is no "exhaust or flue", there is no way for energy to
leave the electric water heater except through the water.
A very small amount (insignificant I would imagine) could leave
through the body of a poorly insulated tankless unit but that's
btw on gas fired units 100% of the gas energy is turned to heat but
some goes up the flue.
Additionally, 100% efficiency means that 100% of the input energy goes
into the heated water.
Electric units are very, very close to that. Only the energy lost to
the surrounding environment does not go into the water.
There is no way an uninsulated electric water heater could be
considered "100% efficient".
Merely turning 100% of the electrical energy into heat is meaningless
if only 50% finds its way into the hot water.
Gas fired units are different animals. The flue gases can contain a
fair amount of energy in a convention gas water heater.
Hence the desirability of condensing combustion.
You are paying for convenience. You have noticed that prices in
"convenience" stores are higher than the prices at much larger retailers
at longer distances from your neighborhood? Could you
imagine what gasoline for your car would cost if you had to swap
tanks every time you needed fuel and the fuel tanks were in locked cages
at the corner store? O_o
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