as the BTUs to heat multiple faucets at the same time can easily be
200 amps.
once a potential users checks the cost of a main service upgrade, to
200 amps for heating water and 200 amps for all other uses, they will be in fiancial shock and likely need a new service drop from their power company.
tankless are a nice concerpt if sized and installed properly.
but do remember the stanby losses help heat your home in the winter, so they really arent lost.
i hope more tankless owners users report in with their experiences
When we did a major remodel/addition in 2004, we replaced one of the two 50 gallon tank water heaters in the house with a Bosch 125 gas tankless. This one feeds the laundry, kitchen, and a half bath (no shower). We are very pleased. It takes much less space than a tank, which was a major factor in buying it.
Because of our relatively light hot water use in the area, almost all the gas use of that tank heater was standby loss. We put it in the summer and our gas use dropped in half, from $20 to $10 per month. I figure this is about a four year return on investment. Since this is Texas, water heaters tend to be in unconditioned space, so lost heat is truly lost. Also the input water never gets all that cold.
We get lots of hot water fast. Since there are no standby losses, we can set it high enough that the dishwasher does not have to preheat. When the other tank heater starts to go, I plan to replace it with a Bosch 250 (two simultaneous use) or equivalent. We've got a big tub that my wife loves to fill. The current tank heater doesn't quite do the job.
You're right, they must be installed correctly. But when they are, they are nice.
If your water heater location only gets a little bit below freezing, some makes of tankless heater have freeze protection built in. (It's a heat exchanger, after all -- just run the heater a bit when ambient temperatures drop below freezing.)
My Takagi also has a remote sensor available for the ambient temperature circuit -- that's used when the heater is installed indoors, but with a short flue to sub-freezing weather, so that the freeze protection will keep the exchanger warm despite subzero backflow in the flue.
Completely draining the heater is typically quick and easy for a tankless setup, they're normally plumbed with draining and backflushing in mind. For a summer cabin, I'd say completely draining the plumbing off-season would be a good idea no matter what type of water heater you have. A friend's summer home even has an air-compressor port on the highest line in the house, so you can open one fixture at a time to blow out any water trapped in low spots.
ONE MOMENT PLEASE!!! The owner's manual for my Bosch 2400E states that "The 2400 E is not approved or designed for solar/preheat backup or high temperature booster use". Why this is so, I know not -- and no explanation is given in the manual. This is too bad because if I decide to install solar collectors at a later date, I won't be able to feed solar pre-heated water to the Bosch unit I just shelled out $998 for. Also, I did not know about this until after buying the unit & reading the manual.
Once upon a time, I worked for a company doing solar hot water system installations. At the time, a popular setup was to run stored solar heated water through a Paloma tankless. If the inlet temperature was greater than the Paloma's thermostat setting, the heater remained off. Same thing if a swimming pool was involved.
Perhaps someone will comment here as to why the Bosch 2400E is not approved or designed to be fed pre-heated water.
[also, I'm going to start a new thread on a technical question I have about my particular heater -- look for "Bosch 2400 E" in the subject line]
Nit pick point well taken. I don't think I'd ever recommend electric, other than to say it is an option and the product is available that way. If you were *really* off the beaten path -- no natural gas lines nearby, no propane available -- then electric might be the only option. Especially if it were only for occasional use, as in a summer cabin in the middle of nowhere. Most people I know who are heating *anything* with electricity tend to spend more to heat it than they would have with natural gas.
That said, tank-type electric water heaters get by with less standby loss than gas units, since they have no flue to allow heat to escape.
That sounds logical. OTOH, could also be a corporate "CYA" defense against potential lawsuits and nothing more.
I don't think it's an impeller-driven device that enables the burner, I think it's a pressure switch -- but you may be right. Somewhere in the manual I recall reading that when the outlet pressure drops 0.8 psi with respect to inlet pressure, a sensor sends a signal to the processor to activate the burner. So, it could be a pressure differential sensor, or a flow rate impeller wheel as you suggested. Whatever it is, I would like to increase its sensitivity in order to achieve lower flows of hot water. Or, I suppose I could install a pressure regulator on the heater's inlet side, which would serve to amplify the pressure drop if I regulated it down far enough.
I'm in the process of writing a new topic for this newsgroup about that, in the hopes that a Bosch 2400E techie will read it & respond.
I personally think this is great! I think that any practical attempts at recovering otherwise wasted energy are generally a good idea. I also realize that with some recovery schemes, a mathematical point of diminishing returns may be a reality. It occurs to me that with "Power-Pipe", that point of diminishing return may materialize sooner in a small-scale application than with a larger scale application, such as a factory, school, large office building, etc. due to installation costs. Higher volumes of warm-to-hot drain water into a Power-Pipe system would yield greater rates of energy recovery out. So Power-Pipe would do well to market their product among large industrial/commercial customers, I would think.
all recovery ideas are wonderful, unfortunately many cost too much, add to much complexity, or gain so little back its not worth it.
homes could be built in a thermos bottle, but its unlikely anyone would want to pay the upfront cost, and then ventilation comes along and ruins it anyway
Almost all "whole-house" tankless units have modulated burners or heating elements, and raise the water temperature only to the pre-set output temperature.
=== We ended up with a bit larger traditional hot water heater, with some energy saving features. It's been working out well, as has our new high-efficiency furnace and AC unit. A tankless hot water system was not recommended for our home. Two independent assessments confirmed it. One concern was that the water from the street is too cold. Also, tankless systems are so expensive that to buy, install and maintain, that any savings and convenience evaporate quickly. ===
And on top of the recent post from maxodyne alerting us to Bosch's warning not to use solar-heated water with their tankless, I'm leaning toward staying with the tanker and using the solar water heating, but time and experience will tell.
Not sure if you caught the original thread (which I wrote) from which snipped-for-privacy@aol.com is quoting ... the question was why Bosch states in the installation instructions that "The 2400 E is not approved or designed for solar/preheat backup or high temperature booster use". I hadn't planned on using it as such, but I was disappointed that a) the heater cannot be used in a Solar hot water system e.g. be fed solar pre-heated water, and b) I didn't learn this until after the purchase was made and the box opened.
My thoughts were that it really *cannot* be used this way because something will break, or else it is a corporate disclaimer to relieve them of any liability if their heater is used in a solar heating system. The latter I understand, but I can remember once upon a time installing Paloma tankless heaters as part of a fresh-water solar hot water system. The Paloma would get its water from a large storage tank of solar heated water; if the water temperature was greater than the heater's thermostat setting, the water would pass on through and the heater would remain off.
Do you know why this heater cannot be used in a solar preheat system?
KLS -- don't give up yet! The tankless water heaters go so well with a solar hot water system -- assuming you'll be storing solar heated water in a large, insulated tank, which is a common method. From there, the pre-heated water gets circulated to your tankless which will remain off if the water is pre-heated enough. No need for standby tanker loss when you have oodles of already hot water stored elsewhere.
Just because the Bosch heater that I ended up with was not designed for solar doesn't necessarily mean that they are all that way. I think we have some expert appliance people in on this tankless vs. tanker thread; perhaps one of them can tell us which tankless heaters will work in a solar pre-heat situation.
I'd like to address two issues in your friend's statement:
"One concern was that the water from the street is too cold"
Then that water will be cold regardless of how it is heated. I can't say about other tankless water heaters, but Bosch makes higher-BTU models for very cold inlet water applications. I would think that Takagi also does, as it can get quite cold over there in Japan ;^)
"... tankless systems are so expensive that to buy, install and maintain, that any savings and convenience evaporate quickly."
Hmm, I wonder why anyone would buy such an appliance then? Certainly, they are expensive. And certainly, people are buying them anyway. I'll testify as to the expense -- OUCH! I *could* have just slipped in a replcement tanker and have been done with it, for around $500. For those who may have missed my "tank-type vs. tankless cost analysis" in a previous post, I have included it below.
Preamble: I was not motivated to go tankless on cost alone (initially high until payback time (8 years), then cheaper). I was willing to pay more money up front in order to consume less natural gas in the long term.
Here are some facts about my heater replacement cost: A new Whirlpool
50-gallon tanker was $430 at Lowe's, and my Bosch was $998 at the same Lowe's (a popular U.S. homeowner's supply store). The Bosch also qualifies for a $300 federal income tax credit (expires 31-DEC-2007). Doing the math, I am now losing $268 for choosing to go tankless vs. tanker.
Add to that loss about $75 for 3/4 copper pipe & fittings, $35 for a new
3/4" gas flex line (gotta have a large one for high BTU tankless installations; fortunately for me the steel line is 3/4" all the way out to the meter), and 8 feet of new stainless 3-inch flue (can't use the original tanker's galvanized due to the tankless' almost continuous condensation in the flue) which came to $325; all of which were needed to do this one-time tank-to-tankless conversion and I'm in the hole about $700 (Next time, if there is a next time, the cost will
*theoretically* be just for the tankless heater alone). At the current price of natural gas, payback time for choosing tankless vs. tanker will take approximately ($700 tankless vs. tanker added expense divided by $86/year savings) 8.1 years. I'm OK with that.
But IMHO there is more than just money involved here. I chose to go tankless because it uses less energy in the long run -- a responsible thing to do in this day and age, I believe -- and I have no regrets in that regard. I am learning to adjust my lifestyle to compensate for my new tankless heater's idiosyncracies, as previously mentioned. Plus, there is the endless hot water advantage -- upon which someone else in this thread sagely commented can also lead to "endless hot shower advantage" in some circumstances ;^)
Tankless have been in use in Europe and Asia for many years, where they are generally considered to be low-end appliances. They're used because they're easier to install in apartments than a central tank, and because they have little or no footprint in space-limited apartments. (many apartments may only be 600-700 sq ft, so even the tank's footprint is significant.) In Asia where I've lived, one of the marks of a higher-end apartment is that it uses tanks instead of tankless.
I've used them in several apartments and always found them somewhat finicky and less satisfactory than tanked units.
Therefore, when we upgraded our present house we installed a second hot water tank that services only the master bedroom, with the other tank serving only the kitchen and other bathrooms. The MBR has about 650 sq ft, and we put the hot water tank in a small closet in the adjacent guest bedroom. We get almost instant hot water, the temperature and water volume never vary, and the unit is out of sight.
After experiencing tankless units of several different types, I wouldn't consider one for my home. Regards --
How EXACTLY did you calculate your water heater cost savings?
gas varys in price constantly, incoming water temp variations depending on how cold weather is, amount of hot water used, presumably with endless hot water more water sewer and gas will be used to heat that water.
with so many variables how did you arrive at a exact figure?
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