| 82857.1 | |
| Great article by Scott Gibson, Hot Water Now, Kitchen & Baths Annual Issue. I’m in the process of remodeling my laundry room and want to consolidate two existing 50 gallon water heaters(one in the laundry and one in the garage) to a Tankless for the entire house. My plumber is recommending a larger 75 gallon tank on a recir. system. I want a Tankless (Takagi or Noritz) but he indicates that a recir system won’t do a sufficient job on a Tankless and there will still be wait for hot water. Thoughts or advice? Thanks! |
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Replies
I'm not a plumber, but to me, hot water recirc makes more sense with a tank unit than a tankless.
With a tankless you are going to fire the heater every time the recirc pump runs, which is going to amount to short-cycling an appliance that has a LOT of complex control stuff going on.
With a tank you are simply moving water that is already warm in the tank. The burner will eventually fire absent any other demand, but the cycles will be longer and less frequent. In some situations you can even get convective recirc, depending on fixture and tank locations.
I didn't read the article, and I don't know the state of the art in recirc. We are installing one recirc loop on an upcoming job, where DHW is in an indirect tank fired by an electric boiler. Insulating the loop as well as possible is important.
P.S. 100 gallons is a LOT of hot water--what's the largest bathtub and how many occupants?
Not a plumber either, but I have the Takagi. It can take 20-30 seconds in the morning to get warm water. I had a loop plumbed for a recirc pump but never installed it (the pump) I was told I could put one in with a timer to fire a couple of times a day when I was most likely to need it. I think a better solution might be a point of use pump, where you press a button to start the pump 30 seconds or so before you run the water. But that would only work at one sink, so it may not work for you.
Love my Takagi though.
What about using a 6 gal electric tank heater just enough to keep the water warm enough to circulate? Then feed that with the tankless..
.
Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
To be honest, I need to do alot more research before I can really decide the right thing to do. Our old house was a 980sqft bungalow with a 30 gallon elec. tank. I replaced it with a Bosch tankless gas and had considerable savings and alot more hot water. The Bosch was in a closet in the only bathroom, so there wasn't much lag in recieving hot water.
The new house is 3300 sq. and the tank is alot further away so there is a very noticable lag. But, it is nice to be able to fill the Kids pool with warm water and still take showers right away. The Takagi supplies enough to run the washer, dishwasher and a shower, but if it's been sitting idle for a few hours it takes a while to get hot water. I would have connected the pump by now but it really hasn't bothered me that much. My wife on the other hand.....
I feel tankless water heaters should be the only ones allowed by law. The idea of heating water up 365 days a year is wasteful and ludicrous. There are millions of them through out Europe for many years now, they are finally being used here.
I have used a gas unit for 3 years and then switched to an electric unit about 4 years ago. I switched because I wanted to use the chimney for a large wood stove to further lessen our heating costs. You can not vent a gas HW heater into a chimney while using a wood stove.
Both units worked perfectly in spite of my water being super hard and filled with minerals. I save a ton of money compared to using those obsolete 24/7 water heaters.
I have asked several plumbers their opinion on the tankless heaters, they all said they do not work! Seems plumbers do not like change, they just want to keep putting in the same old units they are used to.
The utilities companies love the old water heaters as they make much more money. They are so small and easy to install, it is a no brainer to me.
woodman54,
What type of tankless do you have? I need to put a tank(less) in my old drafty colonial. I have gas that is vented out the side of the basement. What kind of resources are out there?jross -- FH Editorial
http://www.sipbuilding.wordpress.com
My brother got Stiebel Eitron for 400-450 on line, it measures 14 by 14 by 4 inches and put out about 3 gallons of hot water a minute. This uses electric, the gas heater was made by Bosch for about 350.00 The Bosch put out more, Maybe 3.5 gallons a minute. They both can handle 2 showers going at once.Just Google tankless water heaters and look for the best price.
Woodman54,
I am glad that you feel you have saved a ton of money with your tankless water heaters. The US govt. figures disagree with you. The latest numbers indicate that unless you live where there are very high utility costs, you have not saved more than $10/month. In addition, you have invested substantially in these devices which save you so little money. I recommend you look at the following links:
http://www.askthebuilder.com/451_Tankless_Water_Heaters_-_Some_Surprising_Facts.shtml
Bill
>>I am glad that you feel you have saved a ton of money with your tankless water heaters. The US govt. figures disagree with you.
Uhhh... am I the only one that thinks this sounds snotty? What's the point?
I installed a Takagi that is 80% efficient, choosing against a Bradford White that is almost exactly the same at 79%. These appliances are very close in performance while firing, but the tank models lose heat up the stack while sitting there. The increase in overall efficiency is small, but it's there. The space savings of the much smaller flash unit and the convenience of having continuous hot water when needed made it an obvious choice for me. As a tank unit fills up with sediment the efficiency drops and gains with a tankless improve. I noticed a decrease in propane usage very quickly after switching from the tank we had.
Electric tankless are even more efficient if you have the power available and the space in your panel. A client of mine has a Seisco that using (4) 30A breakers. It cost him $700 and for his small house it works extremely well.
When compared to a new storage water heater, the maximum amount of money that a tankless can save is less than $10/month unless your natural gas prices exceed $1.50/therm (according to the US Dept of Energy calculations). If you use significantly less hot water than the US average, the amount you save will be smaller in absolute dollars. The reason these number are so low is that the average person only spend between $20 and $25 per month to heat their hot water with natural gas. (The numbers are about twice that high for electric water heaters.)
Bill
I beg to differ with your comment about the electric water heaters. Modern storage water heaters have an Energy Factor of greater than 0.92. Since the max. value using conventional technology 1.0, the tankless electric while being better than the storage, they can not be vastly better. The physics of heating water prevents it.
Bill
All I have stated is that there is some energy savings, and that the main advantages are significant space savings and continuous use when needed. I live in crawl space country. If I had a cavernous basement in which to situate a tank, I might do that. Instead, I removed one from my laundry room, where it was taking up much-needed space, and put it in the attic exactly where I want it relative to fixture locations. In my business people are looking to maximize the utility of all of their space, and dedicating a stand-up area to a water tank is not popular, whereas wall hung boilers and flash water heaters are.
Another option in a temperate climate is an exterior mounting with a small dog house. It has the additional advantage is eliminating the nat. gas venting. But it is neccesary to add a solinoid(sp?) which would empty the system in the event of a power outage in freezing conditions.
You can mount a Takagi or Rinnai directly on the exterior wall without anything around (I think maybe Rinnai makes a housing if you want one, but it may only conceal the piping). They will fire briefly to prevent themselves from freezing. I have never heard of using an automatic drain.
This is at my brothers house and he always needs to add something, neccesary or not.
Bill, you may be right that the savings is not all that significant. However, I spent approx. $1000 more to put tankless in my home over a conventional tank install. On my loan that equates to $4.16 a month over the life of the loan. So, if I'm saving $10 a month, and spending 4.16, I'm ahead. Not to mention that the life of these units is longer, and I've never run out of hot water with guests, filling kiddie pools etc. Just a couple of other points to consider.
Let's see, you are paying interest on that $1000 for the entire life of the mortgage...I would not invest in that manner but it works for you. What makes you think the life of a tankless is longer? The claims are that they are designed to last 20 years...their warrantees are usually less than one half of that. The average life of a storage water heater in the US is betwen 11 and 13 years and that is with no maitanence. Some informed individuals expect to get 25 years out of their tank by a yearly draining and checking on the anode health. I have been unable to find any data to support the tankless claim of 20 years in North Americal. If you know of any such data, I would like to get a copy.
Bill
You know, a link to that article gets posted every time tankless WHs come up. I find it a bit flawed, however, due to his calculations of hot water usage.
Seems to me that a 2.5GPM fixture, unless it's cranked all the way to the "hot" side, isn't going to actually use 2.5GPM of hot water. The author, however, assumes it will. He also seems to cherry-pick a lower-capacity burner to illustrate his example, when most people in a larger household would install a higher-capacity heater, say a 7.4GPM.
The tankless I'm about to install (Rheem RTG-74 natural gas, 199K BTU) is rated for 4.2GPM at a 77F rise. Even in winter, when cold water comes in at 40F, that would give us more than enough hot water to do laundry and run a shower at the same time.
Seems like either the author's info is dated, or he has an axe to grind, or something...
Jason
That was my take as well. And anyone who thinks they can take longer showers without spending more is a dumbazz.
Your 199K BTU unit will give you plenty of hot water. Our incoming water is very cold in the winter, and it's a complete non-issue.
I hope you enjoy it. If you do the Dept of Energy calculations, you will find that your energy savings will be less than $10/mon. That means it will take many years to pay off your investment.
I am glad that you feel you have saved a ton of money with your tankless water heaters
I read it that he has a tank-type heater, not tankless.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
If tankless are not more efficient, why are there massive tax and energy credits available for them--at least in my state.
Am I missing something.
I will read your link...
I did not say they are not more efficient, I said that they don't save much money because the difference in total energy used is not great. In fact, using the Dept of Energy calculations, a tankless water heater can not save more than $10/month unless your natural gas prices are exceedingly high. At a savings of $10/month, I would have difficulty investing in units with such high hardward and installation costs.
Bill
Mmmn,
I get you.
Probably the easiest investment most of us "Tankers" can make in the short term is a 40$ spa timer--if you have an electric water heater.
I am not going to read the article on your facts.
So lets say he saves 10$ a month. What is the true cost of his hot water use per month. If like my fairly low use house hold it would be a 100% savings. My gas bill in the summer is ? 8.00$ so they be paying me at that rate. After the corporate Icing on the cake bill it's a little higher but the gas chg is low.
And I would like to add a compliment to woodman54 for his efficient use of energy saving goodies.
I would also like to add that ???? the old circle jerk hwheaters will all be performing their best function-rusting away in the junk yard in the very near future.
Tank less is not only the way to go but you'll be getting a kick in the azz to do it.
Why do we continue to do the same stupid thing over and over and over.
I was trying not to put one foot after the other but every time I try flapping my arms I get now where.
Edited 12/18/2006 3:04 pm by ClaysWorld
If you are not interested in facts then I am glad to let you think the way you want to and you can enjoy the consequences of it.
Happy Holidays!
Bill
I think you should do a little more research and not believe everything Ask Tim says about tankless heaters. He brings up figures of 235,000 BTU an hour for some tankless heaters, that is enough energy to heat 3 houses. The whole article seems slanted to me.
The article may be slanted but he has no reason to favor one type over the other. You are right, 235,000 BTU/hr is enough to heat three or four houses but it only enough to heat about 9.5 gpm with a 45 degree temperature range. All tankless water heaters use energy at a very high rate since they store none. Conversely, storage water heaters use energy at a low rate since they store it in the form of hot water.
Tankless water heaters will use less energy in most residential applications. The real question is a financial question...will the energy saved justify the expense of the purchase and installation of the tankless water heaters. In most instances, the financial advantage is not obvious.
Bill
Good summary.
thanks for your kind words. I don't get many when I am trying to get the tankless fans to listen to facts and reason. They seem to have listened too many times to Paul Harvey and believe that he is the expert on water heating and energy efficiency.
Bill
I'm not even sure who that is. Like I said before, I bought mine mostly 'cause it's LITTLE! When we're out of town we probably save a few bucks because I can never remember to set a tank heater on 'Vacation".
Yeah, try asking for evidence of justification for foam inslation. They say it costs four times as much, "but you make it up in volume". Then after not offering any numbers they insist that there are other reasons to use foam. Stiffer structure? Well, if your house is wabbly then I think you have other problems rather than foam vs FG. LOL.
Acording to the numbers provided it would = 125% savings.
I did not see any government figures in that article, only one guys opinion. Here in western Mass, we have some of the highest gas and electric prices in the country. 13 cents a KW I believe. We changed out two 20 year old heaters, 1 80 gallon ele and 1 40 gallon gas for one tiny tankless electric HW heater.We were heating 120 gallons of water for almost 9000 hours a year in a 45 degree basement. Now we heat just enough water for dishes and an occasional shower. Who cares if you smell as long as you are saving money right?My SIL pays the bills but I am sure we are saving a lot more than 10 bucks a month.We only spent at most $500 to buy and install the heater, since the other heaters were so old it was necessary anyway.
If you had 1 80 gal elect and 1 40 gal gas for the DW and occasional shower then you clearly had the wrong setup.And they where almost 20 years old and would have had much less insulation than modern units.So way to compare that setup with ANYTHING that was appropriate to the application..
.
Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The two heaters were for a 16 room two family house. We put in one tankless unit to heat water for both houses, it has worked out great so far. The 80 gallon heater had about 1/2 inch of fiber glass on the outside of the tank. It had nothing inside for insulation, I know because I cut it in half to get rid of it. 1/2 inch of insulation is what? 2R at most.
The $10/month was for gas water heaters. If you compare electric tankless to modern electric storage at 15 cents a KW-hr, the maximum annual savings according to the DOE is about $75/year. The reason for such low savings is that electric storage water heaters just as efficient at heating water as the tankless electrics are so the only difference is standby loss. On a well insulated tank, that standby loss is quite low. In fact, if the buy the best electric storage water heater with an EF=.95, then your savings at 15 cents a KW-hr according to the DOE is closer to $5/year.
Bill
Electric tankless on a small house works better, but until prices come down, I'd sit it out and wait. As an affordable homebuilder, I'll be installing one on a special project as a test, but to date the energy ofset has not paid back the capital investment fast enough to justify. But the theory is right on; there's no good reason to heat water 24/7 when you only use it on occasion. In my native Argentina, people have tankless at each bathroom and light the pilot right beofre taking a bath or shower, and then turn it off when done. Ditto at the kitchen sink.
The day of the tankless will come, but it's not today. ;-)
Just to throw another question into the mix.... where does the lost heat from the tank heater go?
Perhaps up the stack in a gas unit, but no stack on an electric.
My tank heater sits in an otherwise unheated laundry room, the heat "lost " heats the room. I don't consider that a loss.
If your tank heater is within the building envelope you aren't losing heat , you are paying to heat your house using a differant heat source than you usually think of. (heating season only of course)
I looked at the new totally foam enclosed tank heaters , cost a bunch so I passed, but next time.
Clearly the world heats it's water with tankless water heaters but in the US the low cost of energy and the high demand for hot water makes them a lot less attractive. You may be right that they will take over the market, I doubt it because I think well-designed, high efficiency storage water heaters are a better investment. When truely high efficiency storage water heaters are introduced to the residential market (as they are in the commerical market today), any energy savings advantage that the tankless have will be eliminated.
Bill
$10/mo X 12mos/yr X 7 yrs = $840. Takagi is paid up. Enjoy the savings thereafter. Return on investment is 7 years.
Ever been to Europe? There in lies half the answer tothe question.
My partial answer is whatever Europe has I don't want. And that includes their bathrooms. And your left side of teh aisle in Congress has for years thougt it a good idea to give you 50 cents, one Dollar, or two dollar per gallon gas taxes. And they say "what is good for Europe is good for America and we are pieces of crp if we disagree". Naturally these politicans have gone mum now. I wonder why?
Um, the only person who has mentioned Europe here is you. Non-stop.
jack, you might try learning to read. I clearly was not the one to first mention Europe.
Is Jack a short version of your name or nature?
Want a shower that dribs out on top of your head? Go to Europe. Want a shower where your front side is covered in warm water and your back is left out in the cold air? Go to Europe. Or I suppose you can get a tankless water heater and stay home.
Half tongue in check here. Not teh part about Europe that is all true. I will withhold judgement on the tankless heaters, and actually love the idea as you and several others do as well. But do they work? Can I run a loud of laundry and take a shower at the same time? Can I get enough water to cover my body? I just no the answer is no in Europe. So if Europe is the comparison. If Europe your basis for tankless waterheaters, FORGET THEM in my book.
Sounds like you don't have any experience with a good tankless. You can get as much hot water out of the shower as you want until the gas runs out. With mine you can adjust the temperature the heater produces using a remote control. Not sure what your complaint would be.
Some one here mentioned Europe. You, know, the answer to everything! And Europes tankless heaters suck, not to mention the bankrupcy of everything socialist.
I dunno, man... just the other day I was looking at some really wicked nice boilers from Germany, unequalled anywhere as as far I as can tell. Don't worry, no one's going to make you move there.
do ya think they are going to drop gas prices?electric can be made without fossil fuels..but can it handle the draw?im in the same dilema but with a vacation rental(bogus) it would be worth it ..
An electrician can do a load calc for you and tell you whether or not you have enough power available. The electric units I have seen definitely work. We pay ~$2/gal for propane and .07 for electric, so it's very competitive.
And the price of peas in China is ?
"The utilities companies love the old water heaters as they make much more money."
You are applying logic not facts here! Check it out. Utilities across the board are paying people to use less power! They pay for new energy efficeint appliances. They pay to insulate houses. They pay for water heater blankets. THEY want people to use less power, not more! Why? Because it is cheaper for them to pay you, have you use less power, than it is to build a new power plant.
Just thought I'd chime in with my experience.
I have a trinity tankless boiler that co-heats the radiant flooring and the domestic hot.
No furnace, no tank. Lower utility bills and living in comfort. Three members of the family can shower at the same time no problem.
In fairness, my old furnace was an ancient floor model. Mike
Trust in God, but row away from the rocks.
I have asked several plumbers their opinion on the tankless heaters, they all said they do not work! Seems plumbers do not like change, they just want to keep putting in the same old units they are used to.
Exactly what my plumber told me. But my next remodel will have one, either gas or electric depending on the situation.
Heating water is a pretty simple thing to do all you need is water, a vessel to contain it and a source of heat. Where it gets complicated is how convienent is it and how much do you want to spend for the convienence of hot water. Much has been written regarding tankless units and their required maintenance, slugs of cold water, etc. I have a couple of points to make. First is that I recieved a letter just this week from my electric coop utility. The jist is that they do not want tankless electric water heaters installed on their system due to high peak loads that they impose. They also said that they may impose an additional peak demand charge for those customers that do install an electric tankless water heater. (The utilly recently installed an automated metering system that records everything and sends the info back to the central office) The second point I want to make is that the energy costs to heat water are roughly the same for either tankless or tank storage type units. The difference is that the tankless folks claim there are no storage losses vs the tank type heaters. I like simple systems so I went with a well insulated storage tank that my propane fired boiler heats as required. The boiler is rated around 90% efficency, I live in a northern climate that generally requires some sort of de-humidifcation during the summer months. The small amount of heat radiating off of the boiler seems to keep the finished basement dryer resulting is less run time for the dehumidfier. For me the change has resulted in a slight decrease in the amout of propane I use by going to a more efficent single heat source vs seperate gas fired water heater. I have 75 gallons of hot water available with a recirc pump on a timer. I spent less money by my estimates for this setup than the purchase and installation of a tankless water heater would have cost. I very pleased with the outcome. Roger
I heat my home(infloor radiant) and all domestic hot water with Takgai propane.
We love it. I had the same system on an electric tank the first year. We did save money the next year.
I did not buy it for that reason. I bought it because I can do many loads of laundry, dishes etc. and still take a long shower or fill the tub without running out of hot water. I can set the temp of the water with my remote so I shower at the temp I want without adding cold water to the water I just heated.
Yes I wait a few seconds for hot water. I don't have to have a mixer valve for my radiant heat as the ingoing water is set at what I want it to be and does not have to be cooled down.
I plumbed and wired it myself. No big installation costs.
Jill
I reffered some of the coments to a mechanical engineer, James Lyons with Newport Partners, in Maryland. Unlike most enginers, James specializes in residential. He replied in his typicaly thorough fashion. Where he mentions the "CH" he's reffering to the PATH Concept House, a demonstration home my company is building. If you want the complete scoop on tankless, opinions and hunches aside, here it is:
That is a fun little lightning rod article. Comparing hot water systems is really complex b/c of various unit types and efficiencies, differing utility costs, and especially due to a different usage pattern in every single home. All these weigh into how well a system performs. Up-front cost is a justified knock on these systems, but the consensus (including HUD’s ToolBase) typically concedes operational energy savings in the 10-20% range. DOE states:
For homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters. They can be 8%–14% more energy efficient for homes that use a lot of hot water—around 86 gallons per day. You can achieve even greater energy savings of 27%–50% if you install a demand water heater at each hot water outlet.
Using a tankless with home runs and low flow fixtures in a centralized location is also a nice system for water conservation – which doesn’t have the payback in most areas but is increasingly seen as an important feature in the world of green building and LEED.
A few general comments on the article:
We have low flow (1.8 gpm fixtures) – which will require less flow. So the “running out of hot water” scenario is less likely to occur in this design. Seisco continually cites an NAHBRC field evaluation which concluded that The single SEISCO residential unit has been sufficient for all the homes evaluated with less than 2% of the total hot water usage time that exceeded its capacity when the inlet water temperature was as low as 40 degrees. (NAHB "Performance Comparison of Residential Hot Water Systems" done for the NREL in 2003.)
The entire piece discusses gas units, whereas the electric unit we have in the CH has an energy factor of 99.3%. Gas units would be lower.
“A typical tankless heater with a 165,000 Btu burner can raise the water temperature to 110F and deliver 3.8 gallons per minute of this heated water indefinitely.”
THE RA-32 HAS A 32 KW INPUT (122,800 BTUH INPUT). CONSIDERING THIS AND THE TEMP RISE DATA CITED BELOW – THE UNIT IN THE CH WILL PROVIDE ABOUT THE SAME FLOW AS THE AUTHOR MENTIONED (DEPENDING ON INLET TEMP) AT A LOWER ENERGY INPUT TO THE UNIT.
TEMPERATURE RISE
MODEL
RA-32
RA-28
RA-22
RA-18
65 F@ 3.4 gpm
60F @ 3.6 GPM
55F @ 3.9 GPM
95 °F @ 2.0 GPM
76 °F @ 2.5 GPM
64 °F @ 3.0 GPM
48 °F @ 4.0 GPM
75 °F @ 2.0 GPM
60 °F @ 2.5 GPM
50 °F @ 3.0 GPM
37 °F @ 4.0 GPM
61 °F @ 2.0 GPM
49 °F @ 2.5 GPM
40 °F @ 3.0 GPM
30 °F @ 4.0 GPM
“Your cost of gas compared to mine means nothing! In other words, if I pay more or less it does not matter. You are simply concerned with how much gas will you use with a tankless heater vs. a traditional tank heater. “ THIS IS NOT TRUE IF YOU ARE EVALUATING PAYBACK. THE AUTHOR BELIEVES THERE IS NO PAYBACK, WHICH MIGHT BE WHY HE MADE THE STATEMENT.