Replies to post #47365 on Wanderport Corp (WDRP)

[BeerIsGood]

More KW. For example the Rheem RTE7 uses 240V and is 7KW. It has max flow rate of 2.5 gallons with 20³ temp rise. NOT enough for a shower.

The RTE 18 is 18KW, operates on 240v, requires (2) 40 amp breakers and can support 50³ temp rise at 2.46 gallons per minute.

WDRP MCMHU is only 4 mags totaling 6K watts. If this unit is only for under a bathroom sink it might work fine for washing your hands but for showering the unit would be need to be a MCMCMCMCMCMHU.

[Hockmir]

what wattage does the electric tankless hot water tanks use?

and how many BTU/HR does the gas tankless hot water produce...

if these other forms are producing hot water without tanks with more than 50 delta t at 2.4 gallons /minute.... why can ours not do the same?

Let me answer your questions with actual data from the Home Depot website entry for one of the lines of tankless electric water heaters they sell. The PowerStar series lists 4 models available through this popular outlet. The manufacturer claims a 99% efficiency, which means virtually all of the heat produced by the electricity consumed is transfered to the water.

Their AE3.2 model lists as a 120 Volt powered unit which consumes 29 amperes, which means it is a 3.5KW unit. This heater can deliver 1 gallon per minute with a 20 degree F rise or a 41 degree F rise at a flow rate of 1/2 gallon per minute.

The largest electric unit shown is a 12 kilowatt unit which requires 220 Volts at 208 amps. (Note that this is greater power than is usually available in a residential electric service hookup).

Now, with a 12 kilowatt system, you can get a 70 degree rise at a flow rate of 3/4 gallons per minute, or a 55 degree temperature rise at 1-1/2 gallon per minute flow rate. At this rate, you might just almost nearly get a sort of warm shower kinda, if you don't turn the flow rate up too high.

Now, as for gas on-demand heaters, if we look at a brand like State Industries, their line of tankless domestic heaters consume 11,000 at minimum and 199,000 BTU/Hr at maximum using natural gas or propane. They claim an 83% efficiency for their heaters, which can deliver about 4 gallons per minute with an 80 degree F temperature rise, which is plenty enough to provide a nice comfy shower for as long as you care to pay for the gas and the water.

so, these are real-world systems which live within the laws of thermodynamics which illustrate how much hot water you can get from specific amounts of energy.

No miracle, magic, smoke and mirrors or chicanery can alter the amount of energy that can be transfered into water given a fixed input energy flow. Arm waving about multiple passes is just plain horse-hockey. Pulsed, not pulsed , multiple chambers, single chambers, a zillion chambers, the output volume of water and its temperature are controlled by the amount of energy which has been input to the system.

Try this experiment. Deposit $100 dollars into the bank. Then drive through the teller window and withdraw it all. That's 100 percent efficient money transfer. Now drive through the window again and withdraw the rest of the money you deposited. Sorry. All gone. No matter how many passes you make through the teller window, there is no additional money that will end up in your pocket. Same thing with heat into water. Multiple passes or chambers makes no difference. You get what you get, and no tricks will change that.

Got it straight now?