Results 1 to 8 of 8
Thread: New Water
08-13-2007, 10:04 PM #1
Well the water is not new but the design of the appliance is.
Today was the first time I ran across this product. Anyone else?
Howard Harris Builders Home
08-14-2007, 06:37 AM #2
08-14-2007, 07:16 AM #3
Re: New Water
They are working against the laws of thermal dynamics and energy loss, implying that energy can be transfered at 100% transfer.
Step 1: Fill tank with water.
Step 2: Heat water in tank. (The tank is open to atmosphere and is non-pressurized, meaning it has no explosive capabilities and does not require a T&P relief valve.)
Step 3: The water in the coil within the heated water takes heat from the heated water. (That's rather obvious.)
Step 4: As water is used and drawn through the water heating coil, the incoming water is heated by the heated water in the tank. (They are, it seems, implying that this does not lower the temperature of the heated water in the tank, that the heated water in the tank 'just stays hot'. At least that's how I read their claim.)
Step 5: Huh? When you take heat from the heated water, that heat must be replenished.
A regular electric water heater directly heats the water, at whatever that efficiency is.
This thing heat the water, at whatever efficiency that is, and then *INdirectly* heats the water in the coil by thermal conductance of heat through the coil, whatever that efficiency is.
Thus, just to play with numbers, *assume* that a regular water heater is 80% efficient (using electricity to directly heat the water).
Let's further *assume* that the thermal conductance efficiency is 90%.
That water heater is not 90% efficient, it is 72% efficient. The 80%efficiency of heating the water directly is further reduced to 72% by the loss in heating the water within the coil by thermal conductance through the coil.
Forget my *assumed* % numbers, just think of the process of heating something directly, versus, heating something to heat something else. There is a loss each time.
Plus, what happens when the fins on that coil become contaminated and mineral deposits build up, causing a further loss of thermal conductivity.
Plus, they say 'fill the tank once at time of installation' ... then say to check the water regularly to keep it full????
OF COURSE! You will lose water due to evaporation by heating when you have an open container. You must "manually" fill that tank with water.
Why not install a water level control valve like is in a toilet? That will keep the tank full. Of course, though, that adds maintenance due to those valves not always working properly, and you would need a drain line in case of a malfunction ...
Good or bad?
Don't know, but *I* am going to stick with my regular old fashioned water heater ... at least for now.
08-14-2007, 07:55 AM #4
Re: New Water
It sounds like they are trying to have a hybrid system of sorts.
The heater "element" like a tankless electric which is inside a tempering tank. I don't see the savings. Electric water heaters are very efficient, close to 100% since there is no loss of input energy up a flue with the products of combustion as with a gas unit. The losses of an electric heater are primarily "standby" losses through pipes and insulation. The only benefit I can see is the faster recovery due to tempering the potable water in the closed lines with the water in the open tank; which as Jerry said has to be heated from somewhere. Sounds like snake oil to me.
08-14-2007, 12:12 PM #5
Re: New Water
They are gaining some thermal efficiency over a standard electric water heater by heating a smaller quantity of tempering medium within a more thermally efficient vessel. As you know, plastics do not transfer heat as efficiently as metal does nor does it have all of the additional mass of a metal tank.
In a standard electrical water heater, the mass of the metal tank must also be heated and its ability to efficiently transfer that heat out of the system must be fought. These inefficiencies are much easier to deal with in a system that utilizes a plastic tank in a more compact profile where heat losing surface areas can be better managed.
If the heat exchanger immersed within the heating medium is an efficient one (as it appears to be in this case) then I see no practical reasons why the system would not work and work well. I did get a sense of marketing ‘hype’ over just how well it works when reading their web site though. But then I supposed that is to be expected when dealing with someone who has something to sell.
Ultimately though, if you can get the hot water delivery performance of a 50 gallon electric water heater by only having to heat 33 gallons of tempering medium in a more thermally efficient design then there should be some legitimate savings there from the cost of operation standpoint.
I actually do like the idea of not having a pressurized vessel but I do not like the idea of having to depend on the user to monitor the level of the tempering medium in the vessel. I would feel better though if I knew there was a safety shut off of the heating element when the heating medium level gets low.
08-14-2007, 03:46 PM #6
Re: New Water
That's one of the problems, they are not.
Their test was based on a draw of only 3 gpm. Take two showers at the same time and I seriously doubt that will keep up.
Our house has standard 50 gallon electric water heater and it keeps up with two showers at the same time, with excellent pressure and flow at each, and does not run out of hot water, and, in fact, we have even followed those two showers with a third shower at times, and still have not run out of hot water.
I doubt that setup could keep up with that usage.
For less usage, closer to the tested 3 gpm rate, yeah, it might work.
I actually do like the idea of not having a pressurized vessel
Same here, much safer.
but I do not like the idea of having to depend on the user to monitor the level of the tempering medium in the vessel. I would feel better though if I knew there was a safety shut off of the heating element when the heating medium level gets low.
Nothing I saw discussed the frequency of evaporation and refilling, just "The water level in tank must be checked and maintained periodically to obtain maximum efficiency.", so ... How often does it need to be checked? How often does it need to be 'topped off'? Where does all that evaporated water go? (I know, into the room this is installed in.)
08-14-2007, 04:02 PM #7
Re: New Water
The builder had a pair of tanks in series. Mo legtricity use! The manufacturer recommended a pair if a hydrotherapy tub is used.
Funny thing thou, no manufacturer's literature on site. Had to go to the web for what I did get. And as all can see, not a lot of info there.
08-14-2007, 09:59 PM #8
Re: New Water
IF there were a low water cut off switch (like on a steam boiler system) then it would be triggered when some small percentage of the overall heating medium content had been depleted via evaporation when open to atmospheric pressure.
The product web site I believe said 4.5 to 5 inches from the top of the un-pressurized vessel is the required fill level. I (personally) would put the absolute shut down point at 6 inches below the top of the "open to atmosphere" vessel given the height/width dimensions of the unit for peek efficiency. Others would likely put it at the critical operational limit for the top mounted heating element.
How quickly the vessel would get to any low level cut-off point between user top-offs would depend on the temperature setting of the system's thermostat and the temperature/RH of the space the system was venting to. (The user top-off requirement at that point would be a few gallons and would not necessitate a full refill of the system.)
Personally, I liked your suggestion of having an automatic fill valve on the system though it does complicate functionality a bit.
Expanding more, I would also say that it would be best to have this system's open heating medium vented to the exterior of the structure rather than have it vented to interior spaces (where the system is required to be installed).
We certainly do not need the additional moisture into the interior spaces here along the gulf coast. But! If you happen to live in a climate where a humidifier is a good ideal then there may be an added benefit to venting such a system to the interior space.
We could even go deeper still and look into the pros and cons of other more efficient indirect heating mediums such as glycol solutions. At this point though we are getting too complicated for the residential consumer's pocketbook.