OT: Water heater question

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That is actually how tankless units are rated. :)
While well water is cold, that is not a unique

Flow Rate.
Tankless units are rated on their temperature rise/flow rate, (gallons per minute). "Temperature rise" being the difference in temperature of the water between input and output. The lower the flow rate, the more the water can be heated.
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On 7/13/2014 8:06 AM, Swingman wrote:

That is how I understand it. Since the precious statement that I was responding to did not indicate flow rate being a factor the broad brush statement of only raising the temp X amount of degrees seemed pretty problematic. I can absolutely understand raising the temp only x degrees at full throttle at the faucet but at a lower flow rate I would find it hard to believe that the temp would not rise.
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On 7/13/2014 9:45 AM, Leon wrote:

One of the problems is that these things sense flow rate internally, so a low flow rate can cause them to either shut down and/or lower the temperature rise.
Counter intuitive as it sounds, one of the cures for that problem that is practiced widely is to turn on a second hot water faucet to keep the sensor from lowering the temperature.
So much for being "green" and "conservation" minded... like many "progressive" concepts which focus on feel good issues, the opposite effect is often the ultimate consequence.
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A common problem with tankless units though, because a "big enogh" tankless unit would require more electrical power than the total service available, and a big enough natural gas one would require a larger meter/regulator, and often even a bigger supply line than the gas co has installed for most residential services. I'd need to put in a new underground electrical supply to install the recommended electric tankless because I only have a 100 amp service, and I cannot install more than 125 amps on the existing infrastructure. My current gas meter would support the water heater with the furnace not running, but would be borderline (at best) for sure if I also had a gas drier or range running
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"Ed Pawlowski" wrote:

------------------------------------------------------- That's going to be marginal.
Water coming out of the ground will be around 50F-54F year around based on a lot of heat exchanger design and development work I did many years ago.
A delta of 65F will give a discharge of 115F at 3.8 gpm.
115F is warm but definitely not hot which is about 130F.
Lew
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It's called a BTU (the energy it takes to raise a pound of water one degree F). ;-) You need 8*gal*degree_rise/min BTU.

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I'll take your word on that, I always understood that they ran full bore when the water was turned on, just like a tank type heater. I understood that any flow rate above "x" ran the heater at full throttle and any below "x" did not turn the heater on at all in the event of a dripping faucet.

Again ill take your word on that but it sounds like a faulty flow meter problem.

Exactly. Take the whole state of California for instance. They are all standing on shaky ground and the more they clean the air the drier it becomes and is ripe for wild fires and preventing rain.
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On 7/14/2014 6:56 AM, Leon wrote:

All units I've dealt with have multiple sensors, and a flow rate restrictor, that use a microprocessor to adjust the heating ability to both the flow rate, and temperature, of incoming water so that that it matches the "set point" temperature (generally a setting that is user controlled).
Also have noted that many user complaints can be traced to the usual reduced water pressure/flow rate on the output side of these units due to the restriction, compared to the input, especially when used in conjunction with modern "pressure" balanced fixtures.
So, yes, there is generally flow rate restriction available/involved internally, and they don't necessarily run "full bore".
Therefore the basis of my original opinion - not for the faint of heart, and certainly more expense to install and _maintain_.
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On 7/14/2014 8:23 AM, Swingman wrote:

I think I was skeptical about them after learning how much the vent pipe cost was on the Ruskin house, now I am certain that the tanks will continue to be in the future for me.
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On 7/10/2014 3:13 PM, Gramps' shop wrote:

The tank could be leaking from anywhere, water is going to show up at the bottom because of that gravity thing. ;~) So check the inlet and outlet pipes first. Gas water heaters tend to fail sooner than electric because of the greater extreme heating conditions that the tank must endure. The bottoms of the tanks are exposed to several hundreds of degrees temperatures. Electrics don't get much hotter than the water temperature at the faucet and the heating elements are in the water vs. outside of the bottom of the tank.
Assuming gas, some units and or building codes require special venting material. Apparently not any old vent will work in all cases. IIRC Swingman had one installed in one of his homes that he built and the vent material IIRC had to be stainless steel. And IIRC that ran about $100 per foot.
So you should for sure look into what exactly the cost will be installed before taking the leap. It may never pay for itself in savings if the unit runs in to the thousands of dollars, installed.
I do not think they offer any advantage other than energy savings and an endless supply of hot water.
Delivery of hot water will be relative to the distance the heated water will have to travel. You are only changing how the water is heated and when, not how quickly the water will be delivered. That is of course assuming your old water heater is not restricting the water flow.
Now with having said that, immediately after install you will get hot water much sooner from a tankless than from a new tank type heater which will have to heat the entire tank first.
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On 7/10/14, 5:37 PM, Leon wrote:

The physical makeup of the two are so different, it's hard to accurately compare. With the tank heater, there are two relatively small elements or flame to heat, say, 50 gallons of water. With the tankless, there are probably only a couple gallons capacity in the heat exchanger, with the "element" or flame completely surrounding all the water almost by the drop. Think of a car radiator and the air flowing through it. I would guess the heat to volume ration is probably 1000:1.
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On 7/10/2014 7:30 PM, -MIKE- wrote:

OK, we both know what we are talking about, I think. ;~) It was you mentioning that there's not much water running through the heat exchanger. I think what you meant to say was that the heat exchanger does not have much water in it at one time, unlike a tank type water heater.
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On 7/10/14, 7:57 PM, Leon wrote:

Oh, knock it off! Where's the beer?
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On 7/10/2014 8:02 PM, -MIKE- wrote:

Is it Ta-pa-to Or Po-ma-ta? ;~) Beah? Did you say Beah? LOL
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On Thu, 10 Jul 2014 13:13:53 -0700 (PDT), "Gramps' shop"

I'd first check the tank warranty - with a friendly Rheem dealer .. ... 10 years is a very early failure ! Mine - on propane - is ~ 23 years old and going strong ! In the past - I've discovered secret 10 year warranty on my Ford Taurus front springs ... and the SS tub on my clothes washer .. John T.
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On 7/10/2014 8:48 PM, snipped-for-privacy@ccanoemail.com wrote:

It also depends on the water if minerals in the water quickly eat away the anode rod the tank will fail early. You probably have great water.

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Somebody asked this question a few days ago on the Home Shop Machinist forum. In summary, they weren't too fond of the tankless systems: http://bbs.homeshopmachinist.net/threads/63806-OT-Hot-Water-Heater- Replacement
Puckdropper
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On 11 Jul 2014 02:32:54 GMT, Puckdropper

I sure would not get stuck with one if I had any choice in the matter.
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Check out Hybrid: http://tinyurl.com/7o9jn26
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On 7/10/2014 3:13 PM, Gramps' shop wrote:

FWIW: I've have planned, and effected, the installation of "whole house" tankless water heaters in three of the new homes I've built in the past ten years.
Your success depends upon a number of factors: the size of the house and distance of the unit(s) from fixtures; the number and type of hot water fixtures (flow rates must be determined for each fixture); the type of plumbing allowed in your jurisdiction for code purposes; type of unit (gas or electric); the brand; and, most importantly, the design, and accurate implementation of the design at installation.
Biggest issue with any hot water system is the time from the demand to the delivery. Distance is obviously a big factor, as well as any intervening devices in series (point A, through point B, to C, etc.).
Plumbing methods, utilizing a manifold distribution system (PEX makes this much simpler) can make a big difference in the time of delivery as it insures the shortest possible linear 'source to demand point' delivery.
It is my experience that, with whole house units, and without a manifold system in place, and if you have more than one bath, kitchen, and utility room with long runs of in series piping, your best results and satisfaction may require intervening auxiliary tanks and pumps, in some case multiples.
At this stage of the game I would steer away from electric units in the US.
With gas units, which must be vented to the outside, location of the unit is very important as the vent must be double-walled stainless and runs about plus $60/ft, installation not included. This can double the price of the equipment itself, and the labor/material needed to install
Rinnai is a good unit and worth the price. I've also installed one GE unit, at the homeowner's request, with no trouble thus far.
Use a dedicated tankless dealer for design and installation, not a plumbing company that does it as a sideline.
One of the exercises that must be performed is to calculate actual flow requirements of each and every hot water fixture in the house, the expected delivery temperature, AND, very importantly, _the ambient temperature of the water fed to the tankless unit_ coming into the house.
With a good gas unit, proper design of the piping system, and a knowledgeable dealer who provides the design and installation, you can get satisfactory results with on demand 'whole house' units.
My home owner's love them and have had no issues thus far, but it takes a good deal of planning, dedicated supervision of all details, and thus a good deal more expense than a regular hot water heater in order to install, and maintain, a tankless system.
Not for the faint of heart...
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