Any thoughts out there about on- demand hot water heaters? We currently have a 40 gallon gas hot water heater and need to replace it.I have seen on demand heaters used in europe but know of no one in the states who uses one.I don’t have a dishwasher, there are only two adults and one teen( on weekends) and two skunk-loving dogs who use the water…any info on favored brands etc. would be helpful….Happy New Year. Hazel8
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Don't know much about them, but while you are waiting for a reply, try using the search function. This, along with almost everything else building related, has been discussed here in the past. I did a quick search and found this one: http://forums.taunton.com/tp-breaktime/messages/?msg=52104.1
Hope your new year is a great one...
Thanks Matt- I will give that a shot- Hazel8
For what it's worth:
I built a 3000+ log home in north Georgia 4 years ago, and installed a gas fired Aquastar on demand water heater. Had zero trouble with it, hot water never runs out, and I'm convinced that it has more than paid for itself in fuel costs. If you're interested, I could give a few more details, but as a quick endoesement, I'd highly recommend the line. Many folks in this area have vacation homes, and a system of this sort is ideal for that application. We live in ours fulltime.
Littledenny
In the mid 80's I tried an on demand heater in my business (where the hot water demand was very low). I believe it was an Aquastar (but my memory could be wrong).
At any rate, it sucked. It could only produce hot water if the flow rate was extremely slow. Then it broke and the needed part was unavailable. I went back to a tank.
I used to post in threads on this subject the importance of the spec...how much water can it raise how many degrees???
But everyone else had so many good things to say that I decided my experience was too long ago to be applicable. But the last thread that I saw on this subject had a post from someone cautioning that if your demand was too great...
So...How many degrees will it raise how many gallons per minute????
If it's enough, great. If it isn't you will know it.
Rich Beckman
Another day, another tool.
I'm going to meet with my plumbing supply rep hopefully next week to discuss one for my house. I moved into my house a year ago with a 50 gal powervent that I do not like. I refuse to go to a larger water heater (3 girls in the house) and I hate to hear the water heater start up in the middle of the night (waste of gas). My brother lives in Germany and that is all they use. All I'm told is that limitations are the amount of flow (6 gpm I think). Brand I'm considering is Bradford White (made by Rinnai). Just wish I had done geothermal in the first place.
John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
http://www.lazarobuilders.com
You could put a timer on your power vent so it doesn't run at night.
I knew you could put a timer on electric water heaters, but you can put one on a gas water heater?
John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
http://www.lazarobuilders.com
If it operates with a standing pilot light and does not use electricity you can't. But if it's a power vent you can put a timer on the 110 volt supply to the water heater (just a plug in appliance timer is enough) and the timer will control the water heater.
Another way to extend the "capacity" of the heater is to make sure you have low flow shower heads. You could give the kids really low flow and yourself a better one.
On demand doesn't work for everyone. But for those with the right conditions and expectaions, it's great.
Conditons
In order to get the water as hot as it needs to be in a short period of time requires a big flame or heater. A big flame is going to require a big and dependable airflow - incoming as well as outgoing. A big heater will require big wire and power.
Don't even think about compromising the venting issue.
I've heard some people complain about their water conditions causing problems with either corroding the inside piping or causing flow restricting deposits.
Expectations
That water flow thru the unit is regulated to provide the desired temperature. This means there is only a certain amount of hot water flow available while the unit is running. It also means that there is a low limit before the unit kicks in.
Running 2 showers off an Aquastar 125 at the same time will cause an undesirable decrease in the available hot for both showers (unless you carefully engineer the plumbing runs). Same with a washing machine and one shower.
Slowing running the hot tap while shaving or rinsing dishes while washing will most likely be below the unit's turn on flowpoint.
Steping up in size of unit to compensate for more hot water need commonly results in a higher low flow limit.
Some people have developed alternative plumbing designs to compensate for some of the limitations.
Some people quibble about whether they really do save energy. They mention that the higher flame or power draw outweighs the smaller conditions found in a tank. It seems to depend upon your demands as well as downtime from travel and such.
Some people fret about replacement parts.
If you're going to do it, plan it well and understand exactly what you're getting into.
If you have enough electrical service capacity, try an electric on demand heater. SEISCO out of Houston, TX sells them. Suck amps like a whirl pool when they go on - like testing "The Chair" in a Mickey Rooney prison movie. But ours is great. Run a dishwasher, washing machine & shower all at once, and no problems. Water comes out hotter than your bare hand can stand. Teenagers can wash hair, read "War & Peace," whatever else they do in the shower & never run out of hot water. (Waitaminit - if that's the case, get a 10 gal tank explicitly for their shower, & feed it w/ icewater!)
We have been very pleased w/ ours.
Don
Our Aquastar is 4 years old, Best comment "wow, theres still hot water!" Pilot light blew out once (extreamly windy that day) 5 in the house NEVER had a problem, loads better than the old electric 40 gallon!
Glad to hear you're happy with it. My old-fashioned plumber, and friend, said they were unreliable(at least this was four years ago). Now I have a bulky 40g eletric unit, Bradford-White, but the next one is Bosch Aquastar.
Its "new tech" from the last 30 years! God forbid we change with the times. Way cheaper than electric unless you have very cheap electric.
I have a tank less water heater hooked up to my boiler that heats my house. It is a Slant/Fin unit and it SUCKS ! I will get a lot of hot water for the first five minutes and then warm water for the next fifteen minutes. When the house needs heat I will not get hot water until the thermostat shuts off the base board heating system. I usually push down the thermostat before I take a shower. I would like to have a tank water heater so I don't have to listen to my three daughters compline. Unless it a summer vacation home I would stick with a tanked unit.
It sounds like you either have the wrong tankless unit or the wronf setup, b/c tankless heaters shouldn't have those problems. I have a Rinnai unit in my house and it works very well, with a few very minor tradeoffs which I happily accept. For a part time house use with space issues and venting options, tankless can be a great choice.
If you have the space and the circuit capacity, it would make sense to install a small (maybe 30 gallon) electric heater between the current unit and your domestic HW piping. Get a super-insulated model. The electric unit will hardly ever come on, but you'll always have hot water.
I have the Takagi TK1 and it works fine for all our domestic HW as well as our basement slab (radiant heat). Don't believe what others will tell you as to its effectiveness, I had a rental High efficiency gas HW heater before this, and here in Canada, the land of ice and snow and igloos, it works just as good or better than the rental tank did. Plus my gas bill in September was $6.14! Add to this the fact that it is slightly bigger than an average size suitcase and will fit in a closet or under the stairs etc.
My only advice would be buy a good one, don't buy a low-end Bosch from Home Cheapo for example. Up here in Canada, a Takagi professionally installed will set you back about $2800, but you will realize the savings in the long run.
Rick
A gas tankless unit will cost 5X to 10X more to install than a standard tank heater, so any justification based strictly on fuel savings is probably a ways off -- gas just isn't that expensive yet. In my own experience, a natural gas tankless unit uses about 15% less fuel than the old tank unit it replaced. However, if you have special circumstances where a regular gas unit isn't permitted, or if you want to combine a water heater with a boiler, then these units are great.
One way around the flow rate limitations (other than buying a giant 250K BTU unit) is to use a separate storage tank. I know that sounds crazy at first, but it can mean the difference between a marginal system and one that works. The tank can be a standard 30 gallon electric heater where the thermostat controls a small circulator pump. The tankless heater kicks in whenever there is a demand for water at a tap or when the storage tank thermostat calls for hot water. On modern electric tanks, the heat loss through the insulation is only about 1 degree per hour, so the efficiency can remain high compared to the heat lost through the flue of a typical gas fired tank unit.
That is an interesting point, and an opportunity for an inventor. The standard gas heater can't be insulated as well as an electric due to the presence of the heat exchanger (and hence has higher standing heat loss), but if it were turned into an "external combusgion" unit with a pump-fed burner/heat exchanger then heat loss could be reduced dramatically. And the burner/heat exchanger unit could be about 1/4 the size of the typical on-demand unit, greatly reducing its cost.
I'm going to put a Takagi TK1s in our house as soon as I can get around to it. More for space reasons than efficiency or unlimited hot water. We've got an utterly simple place to put ours on an exterior wall and the install will be simple with no additional venting to run. I've put a Rinnai on one job and a Takagi on another and both owners were satisfied. Neighbor has an Aquastar and is satisfied with that. On the Takagi install we did the venting detail was complex and VERY expensive. Anyone installing a gas tankless should figure out the vent path and price the parts out before jumping in. There's a couple of eBay sellers who sell Takagi at the lowest prices.
You're right about the vent cost. A couple of pieces of 'c' vent can set you back a 100 dollars easy! We mounted our TK1 in the 1st floor mudroom adjacent to the side door above the mudroom closet in its own little cupboard. Using that arrangement I was able to get away with 1 x 90 degree and 1 x 1' straight piece to the exterior termination box, but if the unit was in the basement it could easily cost 6 to 8 hundred bucks for pipe.It's kind of similar in price to insulated chimney piping.Rick
Hazel8:
We have had a Renai for about two years now. It replaced an 80 gallon electric which was on it's last legs. It was expensive but I will say that it's been worth it.
Renai has a great warranty and when I had problems with the first one after a few months they sent a factory rep out and he spent half a day working on it. When he couldn't find out why the intermittent problem was happening they sent a brand new unit (actually a better model than I had purchased originally) and paid my plumber for all his work without a question.
It produces 6.2 GPM at 140 degree water using a 1" gas line and a 120volt outlet. The output water temp is adjustable via a wall mounted control(s). I have found that we only use the 140 degree setting when washing dishes, we shower at about 110 with no cold water added in at the faucet. Because we don't need any cold mixed in when showering we don't get that cold blast when the toilet is flushed in the other bathroom, I've never been unhappy with the water temp or flow and I've even used it to fill our hot-tub. It's really great to have multiple showers, one after the other and not have to worry about whos's going to get the cold "pay off". Venting was pretty straight forward, we decided what the easiest route to take was, and ordered the kit with the water heater.
I would say that because of the expense, it would probably not make sense if your only reason was to save money, but if you have to replace your unit anyway and want a unit that makes a little more sense environmentally, go for it.
BILL
Check this out, has a few interesting points.
I have had a Bosch Aquastar installed in my home as the sole source of DHW for a few years. It works well in steady-state situations. However, the response to transients is a little slow. I guess the main problem is that the performance is marginal. I will never own one again, and soon this one will be used to heat my garage slab. I am gong to replace it with a 50 gallon tank GWH with a recirc system.
They do save gas, but a basic 40 gallon GWH costs about $250. I paid about $650, 5 years ago, (LP, power vent, spark ign), I think.
I just priced a 50 gal gas water heater $383+ tax! 6 year tank warranty. Bradford white. they tell me its all due to the price of steel and the new controls required.
I'm also looking at a tankless unit. mainly because I cannot fill up my hot tub without running out of hot water.I've got a 40 gallon Bradford white NG hot water heater. it CLAIMS the First hour is 71 gallons.So the heating place I called said that the cheapest install of a Rinnai Tankless unit they've ever done was $2100! (I can buy an Aquastar from HD for $600). I did not realize that the installation costs were 4x the price of the unit.Anyway, they're gonna come out and see if I can even have it in (this 4' from any window requirement may negate that. All I've got are windows around the house).Otherwise he suggests a "good" 50 gallon HW. But even the "best" one I've seen only has a First hour rating of like 83 gallons or or something.Not sure if the $850 or whatever they quoted for the 50 gal unit is worth it either. I doubt the extra 10 gallons would allow me to fill the tub up (it usually runs out of hot water halfway through). And a puny 71 to 83 galons for the first hour doesn't really speed up the recovery time.
how old is the water heater you have? You might be able to add a second unit to give you 80+ gallons. Much cheaper than running all new stuff, faster fill of the tub too. Its like having a pre-heat for the water coming in works well too.
Unfortunately I do not have room for a second hot water heater, unless I block access to the existing one. Which would really mess things up if the first hot water heater died (having to remove BOTH units to replace the one? eeesh)It's a Bradford White and it's only 3 years old. I got it "new" as part of that dip tube class action lawsuit (they went to replace the dip tube and the guy had a problem for some reason so they gave me a new one).I suppose I could always install a bigger hot water heater myself and safe $500 or so on the installation.Providing that there's nothing funky about the venting on a 50 gallon power vent unit.Of course, Whirlpool doesn't list diddley on their website about their hot water heaters (they don't even acknowledge that they make them) and GE doesn't list any specs on their website (flow rate, efficiency, etc.) on their units either.
The biggest problem with the instant hots is the exhaust system. Not a tough job to do but it is 5" double wall on the bosch. There is a powervent system for them if you have the logistics for it. With the bosh you will have enought hot water but it will take longer to fill than with tank style heaters. If you flush out the water tanks to remove sediment often then the heater should last 20+ years.
My Bosch vents with 3" single wall stainless steel sealed pipe. 1" clearance to combustibles, but it has a max flue temp of 450 degrees. Yikes!
It also produces hot water at any temperature I want with the bath valve wide open. I can fill the tub for the kids just as fast as I could before.
MERC.
Interesting, when I installed mine I had to use 5" pipe double walled. But it works great! Comment on the first day of using it "there's still hot water" (bear in mind the first user was the teanage son who would empty the electric 40 gallon in a single shower)
Well, it apears that while I can buy a Bosch Aquastar 125 for about $600 from the HD, by the time I get the powervent, etc. I still won't be able to install it and meet the 4' minimum distance from any window/gas vent (dryer and furnace vent out the side of the house).Sigh.Plus the local installers wanted about $2,000 to install a unit.On the other hand, they want $1600 to install a 50-gallon super efficiency Bradford White (I think) hot water heater with "power vent".I think that's a little pricey to install a hot water heater. It's not that hard.I could probably install the sucker myself (I can do basic plumbing and electrical and it's not hard to cut a hole in the wall to stick the 3" PVC pipe through).
Yeah, I looked at installing an on-demand gas unit a few years back, mainly to free up the space. The 4-foot rule made it impossible, at least without running the flue across the middle of our family room.
Difference between installs is $200 in unit cost, and some in pipe size for the flue. the rest is the same. Check the size of your bath tub to see if 50 gallon is enought when cooled with cold water to get it warm enought to use. Replaced a few tubs with smaller because of the "small" water heater. And your right not a tough job if careful and you know what to do.
Wow, thanks for all the input on hot water heaters- I think that we are just going to replace the one we have with another one just like it (a cop out)but I am seriously considering putting an on-demand heater in our cottage on cape cod- where the venting is not very extensive and space is more of an issue....Thanks all Hazel8
Yeah, I think the units make a lot more sense in that situation, where the place may be unoccupied for a good % of the time, and you're probably willing to put up with a few of the unit's limitations.
52104.24 in reply to 52104.22
I just priced a 50 gal gas water heater $383+ tax!
Im reading this thread and thinking , "whats the deal? "
Im hearing about kids and running out of water during normal demands.
Im hearing tankless units are 5 times your price or so they said.
Story;
I had a daughter at home that would drain a 40 gallon hot water heater. I have no idea what the deal was , but shes been on her own now with a baby and husband. I asked her if she still drained the hot water heater ? She said no way , its too expensive. Well, telling her all those times didnt registrar I guess.
Anyway, while she was home I did some rough calcs. [1.8 heads on showers per minute] I figgured the hot water usage at some where close to 1 gallon per minute! I installed the heads on three showers.
I figgured 30 minutes in the shower was plenty of water , so I replaced the 40 gallon with a 30! Ill mention here that its natural gas. Well, the thing is they sell 30 gallon heaters but cheap as cost leaders in sales. 139.99 each. I called around and found a dented one for a 100 bucks. I have rentals and do that sort of thing all the time. I installed it .
No one noticed any difference or at least didnt mention it . DW and I had enough common sense to wait on our showers after the girl. We however could take two in a row. We actually scheduled ours at different times all together anyway.
We got a hot tub and I decided to fill it up from the hot water at the washing machine. I ran the water out till "cold", and went to the hot water heater to time its shut off so I would know when to re-empty the water heater. A fact here blew me away. It recovered in 15 minutes!
So, Im wondering unless youve got a whirl pool, whats the deal? A 30 gallon gas has an exellent recovery and seems to be plenty, all for a 100 bucks. . Not five times the cost of a 40.
Tim Mooney
Tim,
You and your wife could save even more money if you shower together - and it's good for your heart.
Well, Ive always wondered if showering together leads to "more" hot water . I dunno , but thats a thought . <G>
Tim Mooney
That technique usually ends up using more hot water because you end up taking your time.
I keep meaning to make the switch myself, but in each residence where I have considered installing one, there has always been a venting problem - i.e., heater was nowhere near a chimney and I didn't want a huge through-wall flue sticking out into my yard. Electric units drew too much power for my old houses, so they wouldn't work either
Keep in mind the gas units consume beaucoup btus when they are fired up, and thus require special venting provisions. High capacity electrical units require 80+ amps. Add that to your air conditioning, electric range, toaster, hair dryers, computers, and it sounds like a typical residential 200 amp service is getting overloaded.
Someday I'll build a house DESIGNED with tankless heaters in mind, but til then I've yet to live in one where a retrofit is a feasible solution.
I put in a Bosch Aquastar 250SX recently. This is a sealed combustion unit, runs about 180k BTU max. I live in NC with ground water at about 60 degrees, so it has no problem producing hot water for two showers.
I agree with the other posters on the cost of the vent. My WH was $1k, the venting was just short of $500. Couple of elbows, 18' horizontal run, wall termination, it all added up.
In use, it does require some getting used to. When washing dishes at the sink, if you shut the water off, the heater shuts off. Then when the water comes on, there is a delay before ignition (about 3-5 seconds). So you get a shot of cold water somewhere along the line. Same would go if you like to shut the water off in the shower. Sometimes you can get any with priming the run of copper from the unit to the sink and then use that water as your "tank" and hope you finish before the cold water comes.
Other than that, I think it's good. The bosch has a WIRELESS remote, so you can dial up the temp for any application. I shower at 108 or 110. It was the only unit I could find that had wireless, all the other remotes are hard wired.
MERC.
I went through this debate last year. We have a large house with 3 full, 1 half bath plus the usual kitchen stuff. When I searced around, there was basically just one brand that had anything for this size of house- Bosch/Aquastar. There have been mergers over the years. Basically, you should start with what temperature your cold water comes into the house at its coldest, consider what peak demand for hot water MIGHT POSSIBLY be in gallons and degrees, and then figure out how many degrees you need to raise your coldest water and how many gallons you need.
BTW, I went with a 75 gallon gas water heater.
I installed an on-demand hot water heater (Controlled Energy Corporation http://www.houseneeds.com/shop/atop/subprod_cec.asp) for my house that I installed a whirlpool tub. Not wanting to pay for heating 150 gallons of water all the time for a tub i would use once a month. Bottom line, this was the best decision I ever made. There is an endless supply of hot water and it reduced my gas bills significantly since it was only on when I needed it. Caveats: it was more expensive to install and the unit was more expensive, but I counted the savings in gas right away.
Hey you guys I was under the impression that an indirect water heater connected to a boiler was the most energy efficent,at least thats what I have read about.What say you all to that.
Greg
Lead,Follow,or Get the Hell Out of the Way!
Efficient in the winter, but not necessarily in the summer.
I thought the low stand-by loss(1/4 degree an hour )was the kicker?Lead,Follow,or Get the Hell Out of the Way!
It depends on how well insulated/contained the boiler is, and how much (if any) storage there is for domestic HW. Many boilers aren't that well insulated on the assumption that they are used for heat ("so what difference does it make if a little heat escapes"). This costs you double in summer if you're running the AC. Plus the boiler will likely have much more capacity than you need for hot water, meaning it will cycle rapidly if there's no storage, or the storage is insufficient -- not an efficient mode of operation.Having a decent-sized storage tank improves things significantly, of course, but won't necessarily even the balance.Like I said, "not necessarily".
Interesting I must say.
I have heard that the on demand units are not really that efficent and that the indirect tanks are the way to go.There was a poster here a while back that had recomended a web site (ask the builder)and this guy crunched the rate of rise numbers among other things and came to the conclusion that the on demand units were not as good as the manufactures claim.I like the real life comments myself though they are the ones that count for me.I installed a Buderus Boiler with a 79 indirect tank with the logomatic control and some day when the house is finished I might even be able to tell you about it.
GregLead,Follow,or Get the Hell Out of the Way!