rinnai vs rheem tankless

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top posting makes the most sense.
120 degree water will burn your hand. But it won't wash dishes. Thanks for the reply. I'll stick with the tank.
steve

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S. Barker wrote:

Post where you want then.
Using a thermometer, the output at my kitchen sink is 142 degrees. At the hall bath, it is 141. At the master bath it is 141. That is as soon as the hot water reaches the fixture. I did not leave it on to let everything get warmed up.
--
Robert Allison
Rimshot, Inc.
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i never have our tank set to more than 120 or so..........
to minimize the chance of a severe burn. i prefer to let the dishwasher heat the water.
i am rewarded my longer water heater life, since the hotter they are the shorter their life.
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snipped-for-privacy@aol.com wrote:

water temps on tankers is that the hotter one stores that water, the more energy will be expended on maintaining that temperature i.e. the greater will be the standby loss expense in $$. I suspect that the increase in expense $$ would rise somewhat with the square of the temperature in degrees, but that is just a guess on my part. Before I converted from tanker to tankless, I generally kept the tanker at about 120F also. The net effect is that whilst taking a hot shower, I am using mostly hot water with a minimum of cold water to temper it. The only rational reason I can think of to keep tanker water much hotter than 120F would be to have more "concentrated" hot water available to "cut" with cold water, so that the available stored hot water could be made to last longer before it runs out. But I am free from such tanker rationale now with my tankless. Free at last!!
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<respectful snip>

I recently bought a Bosch Aquastar 2400E, and I installed it myself. No, I am not in the appliance biz, but I can take care of my own appliances. The Aquastar replaced an old, leaking 50 gallon natural gas tank-type heater.
Now on to your comments: yes, arrival of tankless hot water is slow. It has to be, since the tankless doesn't store any hot water. No, tankless is not necessarily a water waster -- that depends. For short bursts of hot water 1/2 hour apart, like frequent hand washing by family and/or guests, one will use more water & gas to obtain hot water. For longer duration uses, there is not so much wasteage.
In short, tank-type water heaters are good for faster delivery of hot water, but at flow rates above their recovery rate, they *will* run out at some point. Tankless water heaters have a noticeably longer lag time before hot water appears, but once it does, it *never* ends; however, too much demand on a tankless *will* result in cooler hot water.
I have been learning how to plan my domestic time around this new tankless water heater in order to minimize water & gas waste. For example, with the tank type heater, I would always take a shower *before* running the washing machine and/or dishwasher so *I* wouldn't run out of hot water (although something or somebody else might). I would also check with the kids to see if they were planning on showering, and if so, I would wait until they were done & the tank was back up to temperature. Now, I can run washing machine, dishwasher, and take a shower too and not run out. Or do them one right after the other and not run out. Three at once seems to be the maximum limit though -- just like the instruction manual says. My shower heads are 2 gallons/minute flow. I have tested the heater's limit: with the Aquastar thermostat set to 120F, I ran both showers and the kitchen sink all at full flow hot for 5 minutes, and all held steady at 115F. I turned on the washing machine full hot & all temps dropped to 105F in about a minute. Not too shabby. I could probably have bumped the Aquastar up to 130F to compensate if I had wanted to.

Here are some facts comparing cost savings: My ancient tank-type heater still had the yellow "EnergyGuide" sticker on it. The tank-type estimated annual therms were 271. The Aquastar EnergyGuide estimate says 177. At $0.91/therm, that works out to $247/year for the tanker, and $161 for the tankless, yielding a savings of $86/year. As the price of natural gas rises, so will my savings. Also, in my case I have one child about to leave home, and another who may go in a few years... allowing the tankless to remain "off" for ever-increasing lengths of time, which will mean even more savings on the gas bill as time goes on.

You are right, and your point is well taken: it is essential to properly size a tankless unit for demand vs. temperature rise and flow rate. That said, it is also important to size a tank-type hot water heater as well.
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 ;^)
It is interesting to note that tankless water heaters have been in continuous use in Europe (I lived in Belgium 1969 - 1970 and can't recall seeing a tanker), Japan, and I assume many other countries where natural energy resources such as gas, propane, and electricity have always been more expensive commodities than they have been in the U.S. where I currently live. So this "new" tankless concept is not really all that new. And the energy savings are very real.

I agree 100% with that statement. An informed consumer is a wise consumer. In my situation, tankless came out ahead. Your mileage may vary.

I don't feel this way, at least not yet, and I don't think I ever will. I'm not a "tankless evangelist" (say, would that be a "tankless job"? hehe) -- given my situation, I think I did the right thing. That said, if tankless works in my situation, perhaps it would be an appropriate choice for many other homeowners/residential income property owners as well, if only they were aware of the option & did the research.
Thanks for reading me.

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wrote:

Where are you located? I'm considering tankless for if/when we ever build a house, but we have long cold winters up by Lake Ontario, and the heat dissipation of the water heater tank in the basement isn't a bad thing, per se, during winters, and the tank technology seems to have simpler problems to solve compared with the tankless (plus, some areas where we live don't have natural gas supply).
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KLS wrote:

[thanx for the compliment, I spent some time wanting my post to be accurate]

I am located approximately 40 miles northwest of Los Angeles, California. I'm familiar with your climate; my father lives in Buffalo, NY and keeps his sailboat at a marina in Toronto. I lived for 15 years in the Eastern Sierra region of California where the temperature can drop to below zero F overnight. I am aware of the complications that cold weather can bring. And I really enjoy the Mediterranean climate down here in Southen California! ;^)
I'm convinced that tankless is the way to go, with a few exceptions. Lack of natural gas is not an issue as tankless heaters can run on propane or electricity. If saving $$ in the long haul and/or enviromental concerns are priorities, tankless is the solution IMHO.
Regarding the Lake Ontario region, one exception to the above statement that comes to mind is the possibility of any standing water inside a tankless heater freezing and damaging the heat exchanger. If your basement never freezes, then that would be a good tankless location. However, damage would certainly happen if the heater were mounted outside the house -- and Bosch (and others) make externally-mountable units. Tankless would not a good choice for a summer cabin, for instance, unless any standing water could be completely drained in preparation for winter. I suppose one could aim a 150 watt heat lamp at a tankless heater to prevent it from freezing, but that might negate some or all of the tankless' energy savings. Ideally, you'd want a drainback valve as used on solar hot water collectors in cold country, but I don't think the tankless heaters are available with such a valve.
Before installing my Bosch heater, I removed its steel cover just to have a "look under the hood [bonnet]". There is a lot of stuff in there, but I can't remember whether or not I saw a drain plug. I would not want to take a chance on a $1,000 heater that might have some trapped water that could freeze and do something expensive...
Let's see if anyone reads this & has some experience with tankless hot water heaters installed in places where freezing temperatures are a concern.
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wrote:

Well, environmental concerns are my top priority along with saving $$ while conserving energy, so I suspect I'll be installing one of these babies if/when we build, along with passive solar heating panels on the south side of the eventual house to heat the indoor space. I would not install an exterior unit, only one in the basement, which I would probably build with insulated cement block. I also am reading up on how to heat the water with solar (Mother Earth News has some good references).
I do have a colleague who installed a tankless recently in his city house, so I should email him and ask for a report. And Buffalo is a wonderful city; hope they can straighten out their budgetary messes.
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just a nit pick point.
tankless electric are nearly never a good choice.
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
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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.
-- Doug
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You advice will seem less useless when you learn the difference between power (watts or Btu/h) and current (amps) and energy (watt-hours or Btus.)
Ignorance is curable...
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

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the bosch range of temp rise is likely not wide enough to accept pre heated water, and scalding could result.
say water in 50 degrees out 130 degrees
pre heated water in 100 degrees, out 180 degrees.....
!!!OUCH !!!!
i suppose one could install a tempering valve to prevent too hot out.
but the too hot in may damage some delicate bosch input parts, perhaps the impeller that trips the burners on.
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snipped-for-privacy@aol.com wrote:

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.
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Almost all "whole-house" tankless units have modulated burners or heating elements, and raise the water temperature only to the pre-set output temperature.
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Well, I asked the friend who I thought had bought tankless to replace his water heater, and here's what he said:
==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.
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KLS wrote:

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 ;^)
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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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snipped-for-privacy@aol.com wrote:

Please refer to the details in my previous post. If you find errors, you won't bruise my ego if you let me know what those mistakes are. There is only one variable, and that is the price of gas, which in my case is $0.915 per therm at the moment. My apologies for stating "at the current price of natural gas"; I should have given the actual cost. However, the price of gas this week or next month is irrelevant for the purposes of *comparing* tank vs. tankless heaters (the thread subject & my current ambition), as are weather, incoming water temp, etc. I am comparing one type of gas water heater, a storage tank type, to another type of gas water heater, a tankless type.
As to my estimated payback time of 8.1 years, that is based on the current 91.5 cent per therm price. And my estimate is probably off by 10% one way or the other. As the price of natural gas goes up, which it probably will, the payback time will shrink accordingly because the tankless will consume fewer therms over a given time period than a tank-type heater.
Regarding your comment on the downside of endless hot water, you raise a valid point. Another poster previously did as well. So far, that does not appear to be an issue in this household, which consists of two teenage sons and me. In my case, sewer charges are flat-rated i.e. are not tied to water usage. So the only lurking "hidden costs" for this endless hot water -- and the gas to heat it -- would be minimal to unmeasureable, I think.
After this morning's flurry of hot shower-takings, my older son took off to spend new year's eve day with friends. Only two of us remain. The current time is 3:30 PM PST, and no hot water has been used since all those showers. I wonder how many times the old tanker would have cycled on and off during that time? Wait! A lady friend is coming over later this afternoon, perhaps she'll take an "endless" shower. Perhaps I'll even encourage her ;^)

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as to heat loss my old tank sprung a leak just after I showered, hearing water running I investigated and found water spraying out of the flue.
so I turned gas and water off and went shopping for a tank. the next day I got a quick shower, the new tank would be in first thing in the AM, i tended to shower after work.
I was happily surprised turned water on, ran and took shower the water was still hot. near 24 hours after its gas shut off for the very last time ever.
tanks reheat very infrequently, and the losses do heat your home. just like other energy uses.
........................................................................................................................ I am very interested in your stated savings and cost comparison. are you basing this totally on the energy guides label?
because water heating cost depends on many factors, temperature of incoming water, temp the tank or tankless is set at, cost of gas varies each year.
do you have a meter on your tankless to find out how many MCFs it uses in a year? and a meter on your old regular tank unit?
way too many variables, please list exactly how you found your dollar savings per year.......
thanks i really want to understand
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