Most efficient water heater?

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I'd like to switch to a direct vent water heater. Looking at the A.O. Smith site I get confused with all the models. Efficiency information is hidden. There is no convenient chart to distinguish the models. It would seem that these are my choice:
ProMax Closed Combustion Power Direct-Vent ProMax Power Vent (C3 FVIR) Power House Sealed Shot Power Direct-Vent Power House Power Shot Power-Vent
But I can't figure out what is different. Plus each of the above has variants.
So, what is the most efficient 50 gallon tank water heater with the longest tank warranty? The run would be about 40 feet and will have a bunch of 90 degree bends.
Don <www.donwiss.com> (e-mail link at home page bottom).
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wrote:

You forgot the Vertex Power Vent water heater at 90% efficiency The Promax Closed Combustion Power Direct vent means you have 2 pvc pipes. One brings air in for combustion. The other pipe vents the flue gasses out. The Promax Power vent C3 FVIR is just a single pipe water heater with the technology to stop gasoline tank vapors from exploding due to those retarded people that like to store paint and gas cans next to their water heater. Goverment required. The Power House sealed vents further and has two pipes. The Power House Power Shot is a single pipe that vents further. All those have 6 year tanks and parts The vertex is going to be the most efficient and the most expensive to purchase. Bubba
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Most efficent is tankless since efficency is misleading, the Energy Factor is what has the most meaning in water heaters , gas tanks of regular vent and 80+% efficency are around 50-60 energy factor, i dont know about direct vent though, tankless start around 80 energy factor.
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tankless have lots of downsides, from delay when you fiorst draw water till heated water arrives, to poor operation at low flow levels.
standard tanks actually have very low standby losses, just got touch your tank hot hot is it?
current hoigh efficency condensing tanks are over 90% efficent. that should be enough for anyone
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That's not really true, a standard 80% combustion efficient tank heater has an energy factor of around 0.60, so of the theoretical heating value of the fuel burned, 20% goes up the flue, and the other 20% is roughly standby losses from the tank. Even an electric tank water heater, which has a 100% "combustion" efficiency has an energy factor of 0.91-0.93, so 7%-9% of the energy is lost as standby.
Also, a conventional tank water heater has most of its standby losses up the flue, which travels through the middle of the tank. This is why the standby losses are much higher than an electric tank. You wouldn't notice this by touching the outside of the tank.

Combustion efficiency is not the same as energy factor. AO Smith doesn't have an energy factor rating for the Vertex, they say that anything about 65,000 BTUs/hr input doesn't need to get rated. One can guess that the standby losses are less than a conventional water heater (due to the helical flue in the Vertex), but still more than an electric. So the energy factor is maybe 0.75-0.80.
For a tankess gas water heater, the standby losses are zero, so the energy factor is equal to the combustion efficiency. So an 80% combustion efficient tankless has an energy factor of 0.80.
Yours, Wayne
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Hallerb , have you used a tankless, no I will bet not, you put them down because you cant afford one and have never used one. The delay in hot water arriving might be 5 seconds longer than a tank since it fires in seconds. 90 % efficent , yea the burner is, so how can you explain 50-60% Energy Factor on tanks and 83-90 on Tankless. As I said thats more of a true efficency rating, so what if the tank isnt hot, what do you think goes up the middle of the tank and out the chimney, heat!
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I'll put them down. AND I CAN afford them. All i have to do is ask you what is the maximum temperature of your hot water in the winter, when the incoming water is about 39 degrees? There, the argument is over. There's NO WAY you can get 140 degree water from 39 degree input with a tankless. And you can't wash dishes properly with 98 degree water. Hell, I'll bet with 39 degree input, you can't even take a decent hot shower with all hot and no cold on.
steve
Hallerb , have you used a tankless, no I will bet not, you put them down because you cant afford one and have never used one. The delay in hot water arriving might be 5 seconds longer than a tank since it fires in seconds. 90 % efficent , yea the burner is, so how can you explain 50-60% Energy Factor on tanks and 83-90 on Tankless. As I said thats more of a true efficency rating, so what if the tank isnt hot, what do you think goes up the middle of the tank and out the chimney, heat!
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That's simply false. The burner's firing rate is modulated based on the flow rate and the needed temperature rise to provide the set temperature.
Admittedly, a tankless water heater will be somewhat taxed by cold incoming water. For example, the Noritz N-0631 has a maximum input rate of 180,000 BTUs/hr and can achieve a 3.0 gpm flow rate at 100 degree F temperature rise. So that's just enough for two 2.0 gpm showers simultaneously (since in a shower you will mix it down to 110 degree water).
Cheers, Wayne
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I can afford one but wouldnt buy one. its not just a matter of the up front cost. our incoming water is near 40 degrees after zero weather. for tankless we would need 2 high btu tankless in series. and a new gas line to the other side of the street, the entire incoming line and meter are too small for the flow.
but even if it were all upgraded at a cost of 5 grand i wouldnt want waiting for hot water, or wasting water every time we turn it on, or in a power failure having no hot water, let alone in this day and age the tank water might no be tasty, but drinkable if terrorists somehow took out the water system.....
geez my 50 gallon 75K BTU tank serves us very well, and frankly the projected savings isnt worth the draw backs
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In article

I'm all with you on loyalty to a TANK water heater but would you please check the tag on your heater. I would LOVE to have that sort of input (ultra-high recovery!) on a "mere" 50-gallon tank. Looking around, anything with that high of BTU requires a larger tank.
I replaced my heater a couple years ago with a new State Select 50-gal with 40k BTU input. It works FINE. The only time I consider the waste heat as truly wasted is when the air conditioning is running. I have a bi-metal flue damper that addresses much, if not all, of the issue of heat wasted up the flue.
As for the issue of waiting for hot water to arrive at the tap: There is a wait interval for BOTH technologies, isn't there?
--
:)
JR

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my tank is a 50 gallon 75,000 BTU model they are made but arent as common as lower BTU models its first hour is 108 gallons and energy guide 171 bucks a year.
my old 40 gallon 34,000 BTU wasnt enough for us, and we didnt have the physical space for any larger than 50 gallons, originally i wanted 75 gallons.
our current tank was installed in november 2000.
the wait time for tankless is longer, in both cases you have to use up the cooled water in the lines but the tankless needs time to realize water is on and trn on burner.
I have thought about getting a tankless to feed a regular tank. operating costs would be the same, andthe tankless act as a pre heater.
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home depot carries 75K 50 gallon tanks but they arent always stocked in the store.
life is full of standby losses, cars idiling at stop lights, car warming up, etc etc.
most arent worth the cost to fix
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If you used the old tank as a pre tempering tank, stripped the casing and insulation and let the house air to preheat it you would save alot more, if you used the tankless before the tank you would have to run 2 units, you would loose this way. I use my old electric to temper the water but I left the insulation on so savings are not much if anything in everyday use.
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I should not have said you cant afford one, that was wrong. But you can get a 460$ Bosch as I did and leave in your old tank to temper water. Even so 90f rise gets me a fine hot water shower with 34f incomming. Did you ever actualy measure the shower water as it exits the shower head, I need only maybe 106f, thats a 66f rise for you, even if you need more its the units capicity if you use a standard not full flow head. I use mine without the unit on high but maybe 80-90% on. My gas supply was fine as is, I switched from electric to gas tankless and just ran 3/4". Only with a manometer test will you know supply is inadequate. A power failure, mine uses battery ignition, 2 C cells which last so far 1 year. Wait for hot water, I wait maybe 5 seconds more, you still with your tank have to push out cold water in the line. 5000$, mine installed cost me maybe $900 and my payback is 4-5 years.
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Here we go again, sombody who does not have a clue to the facts, has not used one, but can give false information putting them down. I have a water main incomming on a hill which is too close to the surface since dirt is going away, when its -10f out my incomming has gotten to 34f. I dont even have my small 117000 btu Bosch on high and the shower is great. Look at specs, 90f rise is what you can get, 130f water is to hot and a waste of money. 98f with 39f incomming is only 59f rise, far short of 90f rise which my unit does, and I have measured it. Consider something else, Tanks loose 1-3% efficency every year due to scale buildup at the bottom of the tank, I recently removed a maybe 25 yr old tank with 13" of rock scale in it, I bet it was only 50% efficent, Tankless dont hold scale, Tankless you just pur in Lime Away through a valve you add, a simple 30 minute procedure to keep it 100% efficent 25 years down the road, you cant clean out most tank units. Tanks loose efficency every year and you cant stop it by flushing it.
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Here we go again, sombody who does not have a clue to the facts, has not used one, but can give false information putting them down. I have a water main incomming on a hill which is too close to the surface since dirt is going away, when its -10f out my incomming has gotten to 34f. I dont even have my small 117000 btu Bosch on high and the shower is great. Look at specs, 90f rise is what you can get, 130f water is to hot and a waste of money. 98f with 39f incomming is only 59f rise, far short of 90f rise which my unit does, and I have measured it. Consider something else, Tanks loose 1-3% efficency every year due to scale buildup at the bottom of the tank, I recently removed a maybe 25 yr old tank with 13" of rock scale in it, I bet it was only 50% efficent, Tankless dont hold scale, Tankless you just pur in Lime Away through a valve you add, a simple 30 minute procedure to keep it 100% efficent 25 years down the road, you cant clean out most tank units. Tanks loose efficency every year and you cant stop it by flushing it.
YOu stupid fuck in the perfect whirl heat is either gained or lost at the toilet depends on how warm your turd was and incoming water temp.
--


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Whatever you have now, keep it.
Just had to replace a direct vent and estimates were all around $1400 with just a 6 year tank warranty. Electric would be less than 1/3. I decided to go with an on demand system to replace the direct vent. It cost around $3k but at least had a 12 year warranty and normally lasts 20 years.
If you go with a on demand system, consider having the gas company doing it. Tons of things had to be done including replacing the gas meter. Get a unit that has a low flow start rate. Stay away from Bosch.
The downside is that the hot water tank was apparently keeping my basement warm and warming the cold water. So now that cold water in my house is much colder and so is my basement. An advantage during the summer, disadvantage during the winter. That is why people think it takes longer for hot water to show up.... cold water is much colder with an on demand system.
Also if system isn't installed right or you buy wrong one you will get inadequate flow rate. It gives you unlimited hot water but not immediate or unlimited flowrate. There are compromises. I like the idea of no tank though.

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On Sun, 16 Mar 2008 20:27:22 -0400, Don Wiss wrote:

Yes there is.
The whole reason I wrote up my water heater saga was so that others benefit from all the help people here gave me. One of the references in the thread was the recent DECEMBER 12, 2007. CONSUMERS' DIRECTORY OF CERTIFIED EFFICIENCY RATINGS for Residential gas, oil, and electric water heating equipment.
http://groups.google.com/group/alt.home.repair/browse_thread/thread/8e5a55b7ffa87831/42ae7352780031d7?q=donna+ohl&lnk=ol & Mon, 11 Feb 2008 10:54:32 EST
In that reference PDF are the efficiency ratings for the hundreds of residential hot water heaters sold in the USA (under a handful of manufacturers but scores of brands).
I challenge you to find a water heater efficiency rating NOT in this 36-page listing for a water heater currently sold in the USA. http://tinyurl.com/38eh4d (long url) http://www.gamanet.org/gama/inforesources.nsf/vAttachmentLau nch/C2AAFB8D41D003F485256E9000607F66/$FILE/12-07-gas-rwh.pdf
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http://www.gamanet.org/gama/inforesources.nsf/vAttachmentLaunch/C2AAFB8D41D003F485256E9000607F66 /$FILE/12-07-gas-rwh.pdf Where's the A.O. Smith Vertex model GPHE-50 that Bubba recommended?
Don <www.donwiss.com> (e-mail link at home page bottom).
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I saw one unit near the bottom with an Energy Factor of 70, only a few in the 60s and most in the 50-60 range. Vertex, I have a several year old similar AO condensing ccommercial unit but I only know its 92% efficent or so
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