Jamie
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Posts:1265
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| 01/15/2007 3:45 PM |
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Harvey Juric, a veteran custom home builder in Southern Ontario wrote a piece on tankless water heaters.
Unlike "conventional" tank water heaters, tankless water heaters heat water only as it is used, or “on demand”. Opening a hot water faucet ignites the powerful burners and the computer monitors the water temperature and adjusts the burners according to the need. High demand, high heat. Low demand, low heat.
Because the efficiency rate of tankless water heaters is about 20% higher, averaging around 90% and going up to 96% and there is no stand by losses, savings on your energy bills are evident. |
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bpwrightwv
Registered Users
Posts:29
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| 01/17/2007 12:56 PM |
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Does anyone know if you can use a hot water recirc with a tankless heater? It is nice you save energy with a tankless heater, but, you're still wasting water while you stand there waiting for the hot water to arrive at your destination.
anyone? bueller?
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bpwrightwv
Registered Users
Posts:29
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| 01/24/2007 12:37 PM |
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I got an answer elsewhere, which is yes, you can use a circulator, but you lose some energy savings.
Which I figured, but, if you have a septic system you also don't want the extra water running down the drain, and water isn't free either.
My guess is the cost to keep the water hot at the tap is 'minimal' |
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vhehn
Registered Users
Posts:101
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| 01/26/2007 11:15 AM |
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if you use a circulator you give up most of the benifits of going tankless. the loop of piping will act as a big cooling loop. a better option might be smaller tankless in each bathroom.
one other idea might be to hook up your circulator to engage on a timer or when you turn on the bathroom light switch. |
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Chris Johnson
Registered Users
Posts:296
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| 01/29/2007 9:39 PM |
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| There is a product on the market that you add to the very last plumbing fixture in the line that requires hot water, it is somewhat like a recirc system only it pushes the hot water into the cold side and keeps the hot coming, from what I read if you call for 120f water on the hot side, this device measures the stagnant temp sitting there and when it drops below a certain temp (say 108f) it forces the circulation, kind of a neat product but somewhat pricey (> $ 500.00) eliminates wasting water though |
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Chris Johnson - Pro ICF
Napa, CA
Come for the wine, Stay for the ICF work |
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Bob I
Registered Users
Posts:9
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| 04/16/2007 5:10 PM |
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| Add a recirculating line activated by motion sensors in each bathroom. No pump useage or extra water heating til you need it! |
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David hot
Registered Users
Posts:22
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| 06/04/2007 9:56 AM |
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Posted By Jamie on 01/15/2007 3:45 PM Harvey Juric, a veteran custom home builder in Southern Ontario wrote a piece on tankless water heaters. Unlike "conventional" tank water heaters, tankless water heaters heat water only as it is used, or “on demand”. Opening a hot water faucet ignites the powerful burners and the computer monitors the water temperature and adjusts the burners according to the need. High demand, high heat. Low demand, low heat.
Because the efficiency rate of tankless water heaters is about 20% higher, averaging around 90% and going up to 96% and there is no stand by losses, savings on your energy bills are evident.
I would watch out for claims of 90 percent . I have seem them too . Unless you are condensing water in the flue gas you cannot get this good . I think they are claiming 90 percent but at the higher heating value which ignores all the energy contained in water going up the stack. Can anyone confirm this? |
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bpwrightwv
Registered Users
Posts:29
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| 12/08/2007 9:28 PM |
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Anyone actually have a whole house tankless water heater?
Would like to know how they actually perform.
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Donaldson
Registered Users
Posts:88
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| 01/03/2008 2:32 PM |
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Anyone actually have a whole house tankless water heater?
Yes, I have two electric whole house hot water heaters. I have 4 1/2 baths, Kitchen, and laundry room scattered throughout my house so I went with two units to "BANK" each unit to one side of the house or the other. This is to cut down on the wait time for the hot water to the fixtures. But with out a circulation system this time would be greater with a conventional HW tank in the garage.
Some things to know: At least for electric tankless, if you don't have the option of Gas.
Tankless are designed for you to set the temp to the person that likes the hottest shower with out using any cold waterand so that those that like it less hot can add just a little of cold. However they also work on a min. of 2 gpm flow or they can over heat and then cut off giving you hot then cold then hot again. On older homes used as HW replacement this is not a problem because the bath fixtures are of the style that allow you to just turn on the hot or cold water. On new stuff you have to pull out of the fixtures the flow restricters that make each shower unit flow at 1.6 gpm or less. Also, On new construction the new fixtures require a mix of cold and hot as an anti-scolding measures. This means that you have to have cold water coming into the mix at the controller of the shower or bath thus loosing some of your savings as you are always adding some cold even if you put it on hot only. Another thing is to buy a united rated for the coldest water temp coming into the house. I live in central FL and unknown to me the water line follows along the ditch next to my road about three inches below the surface of the dirt. This means that the water temp goes from 78 in the summer to 41 in the winter. If I had know this when I built my house I would have ordered the northern unit rated for incoming temp as low as 45 degrees.
If I were to build again I would find water fixtures for the bath/shower that can be hot and or cold only with out the anti-scolding safety measures. We lived for years with out them. They limit some of the effectiveness of the units especially the electric kind. Even still according to Florida Power my electric tankles units are saving me about 30% on heating a tank of water.
All this said I do love my units for 11 months out of the year but my wife doesn't like warm showers in the winter time and this has forced me to install a solar hot water system. This will replace the need for using the units during the summer for sure and if needed can be a "pre-heat" sustem for the extreme cold and then use the units. I am almost set with the install.
If I had to do it all over again I would have a solar hot water system with a circulation pump to cut down on wasted water coming to the shower. Then have the on demand just in case of extreem cold weather. I have a solar system that can be made for about $600 if you don't mind scrounging for a few things. You need a sirc pump and temp controller and sensors at about $300, I bought two dented electric hot water heaters for $125 a piece for a total of 90 gal of water storage tanks. A sheet of 1/2 inch ply- wood for the back of the panel and a frame made of 2 X 4's all lined with a heavy gauge aluminium foil. One sheet of aluminum backed 2 inch eps foam. Place the foam in the frame box 3' X 8' with the aluminum side up. Make a rack of 1/2 inch copper 7 1/2 feet long of pipe, six rows about 6 inches apart. all connected on the ends, with a water in at bottom one side and a water out top of the other side. Cover the long pipes of the rack with 15 gag aluminum fins so that the fins from each row touch each other. ( you can go to any printing place and get some of their used sheets for printing for free usually). Paint the pipes and aluminum fins flat black and place in the box frame. Cover with one sheet of high temp plexi glass and then use a ferring strip or any 1/2 inch wood all the way around the edge of the plexi glass and then use a sheet of solar glazing also attached with the 1/2 inch strip of anything to attached it. leaving about a 1/2 inch space between the two sheets of glass. Total for the panel about $180 if you use solar glazing at $100 a sheet. You can go cheaper with two sheets of high temp plexi glass, and if you go to any house construction sight you can pick out of thier dumpsters the wood needed ,(you must ask permission). This will be about a 4500 BTU panel. Make sure you attach your sensor to the top fin closest to the water out and run the sensor cable to the controller and set the controller to go on and off at what ever temp you want. Mine are set at 150 pump water, 90 stop. This lets your water heat up pretty good. Warning don't leave the panel in the sun with out water connected to it unless it is covered as it will get up to 450 degrees inside the box.
My whole system costs about $700 and rivals any $2500 system on the market. |
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Jelly
Registered Users
Posts:220
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| 01/04/2008 11:17 AM |
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I have a whole-house tankless gas system. It's made by Junkers and is at least 15 or 20 years old, but I live in Europe at the moment so it's not new technology over here. It also heats the water for my radiators in the winter.
My big complaint is sort of like the minimum gallon per minute flow issue that Donaldson mentioned (and I must say I'm disappointed to hear that because I thought the newer systems would have worked that out!). But the effect it has for us is that it makes it impossible to get a hot shower in the middle of summer. When it's hot outside the water coming from the mains heats up considerably. Since the water heater has to work less to make the water hot, then it doesn't reach the minimum amount and kicks itself off. It won't make hot water for some 10 or 12 minutes after that. It's very frustrating when you're standing in the shower with a head full of shampoo and you get nothing but ice water for 12 minutes straight.
So... I was hoping that was just some strange antiquated method used by Junkers that wouldn't be an issue in new systems. I was planning on using tankless when I build in Louisiana, but I won't if all the units behave like that! My wife will have my head. Are the smaller tankless systems that are mounted for use in one bathroom for example any better?
There must be some flawless systems out there. If they're going to catch on they need to work the bugs out. Donaldson, do you think the issues you have with yours are specific to that manufacturer, or is it tankless systems in general? |
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irnivek
Registered Users
Posts:260
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| 01/09/2008 10:06 PM |
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We have and enjoy our tankless.
However, it wasn't until a couple years ago that I learned that many electric co operatives have to purchase power during peak use times throughout the day. Peak use times are generally in the morning and when people return home from work, in any given time zone. "Normal" power is relatively inexpensiveto produce, but when the local power provider has to purchase power on the open market to meet demand, rates overall increase exponentially. Tankless water heaters contribute to "peak demand" shortfalls far more than conventional water heaters. Those who have them should be conscientous about being a burden on the power grid by using hot water during non peak hours when/if possible.
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canadiyank
Registered Users
Posts:6
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| 01/11/2008 9:21 PM |
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Interesting issues brought up.
Does anyone have experience with the smaller, individual ones in each bathroom? |
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Meghan
check out my green-building blog: dreaminggreen.wordpress.com |
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Richard A
Registered Users
Posts:4
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| 01/13/2008 6:02 AM |
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I can't vouch for this product from experience but I'm going to try it in my new sip house.
LINK
I'm going to use a gas fired tankless heater. This recirc unit starts with a push button or remote and stops when it senses a preset temp at a sensor that you presumably place downstream of the last hot water outlet.
I haven't ordered it yet. Anyone see a glaring reason why I shouldn't.
Dick |
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Donaldson
Registered Users
Posts:88
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| 01/13/2008 11:32 AM |
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?Donaldson, do you think the issues you have with yours are specific to that manufacturer, or is it tankless systems in general?
Hi again, and the problems that I experienced would have been easily avoided if I would have known what my incoming water temp would be at the coldest part of the year and then asked around which new shower controls allow the greatest amount of hot water through or just used old style individual hot and cold water handles. At the sinks the water never stops and comes out 120 all the time its great. I too was introduced to on demand over seas living in Venezuela for 6 years. There the heaters were located at the shower head, you only had cold water plumbing and then chose to turn on the heater as desired. But this close to to 220 current always gave me a shiver and once in a while you get a little tingle if you steped on the grounded drain pipe.
Fortunately that is not the case in the new systems in the US. The problems mentioned had simple solutions. And when I get my Solar pre-heater connected it will eliminate the biggest problem of cold incoming water. If I would have gotten the unit that was rated for up north I don't think I would have had any problem other than having to take out the flow restricters in the shower heads. |
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David hot
Registered Users
Posts:22
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| 01/13/2008 12:45 PM |
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Posted By bpwrightwv on 01/17/2007 12:56 PM
Does anyone know if you can use a hot water recirc with a tankless heater? It is nice you save energy with a tankless heater, but, you're still wasting water while you stand there waiting for the hot water to arrive at your destination.
anyone? bueller?
Seems to me you can. I would create a piping loop with the circulator fed from the hot side of the heater with a second loop delvering from the piping return to the cold side of the heater. A restrictor would limit the return flow to the cold side of the heater to just enough flow to kick the unit on when temperature drops. The heater would kick on briefly to make up for heat losses around the main loop every once in a while. The best unit for this would have a low minimum heat capacity & a low initating flow. When a serious flow off the loop occurs , new water will come in & the heater will bump it up to required temperature . A second restricting valve on the main loop after the "bleed" would be required to force flow of the bleed to the cold side of the heater. Insulate the loop to minimize waste unless your house needs the heat anyway
Anyone see a flaw in this concept? |
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bpwrightwv
Registered Users
Posts:29
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| 01/14/2008 8:53 AM |
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I've had the chilipepper (with regular hot water tank, not tankless) for a couple of months now. It works alright (not as good as a unit my father in law had pre-installed with new construction) but it does the job. It's not whisper quiet, but it's not that big of an issue.
I'm not standing there watching water go down the shower drain any longer waiting for hot water, and it also helps ensure I'm getting hot water in my front load energy star machine.
I also had a couple of install questions, and their 'support' went AWOL--wouldn't answer my emails. I had to special order the 3/8 to 1/2 couplings b/c I couldn't find them at Lowes or a local hardware store.
It's the least expensive of the retrofit models, I could install it myself and it does the job I wanted it to do.
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paredown
Registered Users
Posts:2
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| 01/19/2008 11:24 AM |
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We've been using a Bosch (250sx; now 2400E) whole-house gas tankless system we installed during a major remodel:
Advantages:
-Space saving, fits in a reconfigured laundry room with stacking washer/dryer and folding table, all in a quite small space
-no tank to leak in the center of a ranch style house to destroy floor coverings, etc.
-no hotwater tank sitting hot while we travel (critical for us right now.)
Considerations:
-hard to find a knowledgeable/experieced installer--we worked with a very good plumber and figured it out together.
-need to vent exhaust to outside for gas, since wall mount is not always practical-requires special stainless steel pipe
-on the longest run (new powder room added on the front of the house), we installed an electric under counter as sole heater, because of the long time before hot water would have arrived.
-If we did it again, we might add something similar with a cut out for the most used sinks--kitchen and main bathroom to cut down on waste water flow...showers are less of a problem, since the volume is much higher.
Price is more than a standard heater, even before install, but you also have a longer service life for the unit.
The heater has worked like clockwork, & you can actually have 2 "loads" at once, ie dishwasher and shower or two showers (I tried this to confirm the advertising...) |
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hedgehog
Registered Users
Posts:37
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| 01/20/2008 12:29 AM |
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| just adding to what donaldson said, i have a whole house tankless electric water heater, i believe it is a 29KW, i had the temp setting on it cranked to 52C to try and get enough hot water for our jacuzzi tub. with it set here, i get in the shower, crank the lever all the way to hot, once it is hot slowly turn the lever towards the cold, but not to far or the unit turns off, then ice cold shower!! i dont know why they dont put a lower set point on the activation. i am going to have to monkey around with the temp to get it right, since it doesnt have the capacity for my roman faucet anyways. i am using this heater as backup, as soon as my geothermal's desuperheater gets plumbed in i hope it wont be an issue anymore. as for having a circulation 'circuit' to have hot water on tap, it is unlikely that the low flow would activate the unit anyways. |
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2r3d
Registered Users
Posts:10
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| 01/23/2008 3:28 AM |
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| I had 2 tankless water heaters and Wish I never bought 1. The first one was a headache because of all the safty shut off's on it. Between those and the polit light going out once every 2-3 weeks. Nothing worse than getting wet from cold water and not hearing the woof of the burners kicking in. Is it the polit light or a safty shut off gone bad this time.... Pushing in 1 button while while hitting the polit starter with a towl wrapped around your waste...After 150.bucks in parts the darn thing freezes up on me right before Christmas eve. I had to buy a special heating pad to prevent that, I live in centeral Wisconsin. So now it's shot. Go out and buy a different brand, I mount that one on a inside wall in the basement.... 3 weeks into running it. It freezes...... I didn't buy the $100.00 plus anti draft protector. After you spend a $1,000 dollars on a product, you just hate the idea of $100.00 more. Plus with it being 6 ft. away from the outside wall you think it shouldn't freez here. That was it! went to Menards and went electric......I still have the 2 tankless heates and maybe some day I'LL get them fixed and use them for heating 3,000 gal. fish tanks. |
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RickM
Registered Users
Posts:2
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| 01/25/2008 10:27 AM |
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| THere is an excellent article in this months "Fine Home Building" addressing this issue with recirc and or small stand by water heater that acts as a reservoir |
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