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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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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wrote:

AO Smith has the Vertex water heater that gets 90% Weil-McLain has a boiler that does 98% at low temp Bubba
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92-93-94 even 98% water heaters are common even 96% boilers, even a 94% tankless. AO Smith Cyclone tank, Takagi tankless and a Canadian firm makes a 98% commercial hw boiler, 5 years ago I installed at my apt a 92% 1900000 btu AO Smith Cyclone. these are all condensing units,
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On Wed, 19 Mar 2008 04:32:02 -0700 (PDT), ransley wrote:

I think the reason for this is somewhat misleading.
If I understand this correctly, almost all the heat energy put into an electric heater gets put into the water. Basically, the water cools the heater coils down by taking the heat off the heater coil.
In the case of a gas water heater, the water cools down the flame by taking heat off the flame (figuratively speaking) but a LOT of heat goes up the flue.
They baffle the flue to slow down the rising air but they have to let the hot air out. If they cooled the hot air to room temperature, it wouldn't rise and get out of the house and that would be a bad thing from the standpoint of carbon monoxide poisoning.
So, I think the fact that all none of the heat energy that went into the electric coils goes up any flue - it's all absorbed by the water - is what makes the electric water heater 98% efficiency.
But, as someone stated, I suspect the power generation is about 70% efficiency, so, the true efficiency of electric water heating must be vastly lower than 98% taking distribution into account.
But, how can we account for that true efficiency?
Donna
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Electric are all 100% efficent, all energy consumed is used to heat water, and energy factor should be near 100 as well with great insulation. Almost all gas water heaters burners are about 80-83% efficent, but an additional 17-20% goes up the chimney 24 hrs a day, Energy Factor ratings account for loss up the center uninsulated flue part of the tank and reflect overall efficency, which for most gas tank is 50-60 with one I saw of 70. Condensing gas water heaters, Boilers, furnaces, are different, have a second exchanger that lowers flue temp to near room temp and are forced out the flue by a fan. A condensing 93% water heater wont loose 20% in flue loss since the fan stopped some of the heat loss, but even the best condensing tank water heater of 93% may only be 83% Energy Factor [I guess]. Condensing tank water heaters are really commercial units costing thousands. AO Smith has them, I own one a 175000 btu unit, a Cyclone. For most, electrics are and always will be more expensive to run unless you have a cheaper Hydro Dam nearby, since for most oil- gas products generate electricity. Someone stated 70% for electric, that is not true to you for what you consume and pay, he was talking about transmission line loss, for you electric tank is 100% efficient, but here electricity is still 30% more than NG. If nobody in your neighboorhood has an electric furnace then you can bet Ng is still cheaper per Btu. Now in the last 6 months all petroleum products are going up fast, but electric will follow in the long run.
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Correct.
Average power generation isn't anything like 70% efficient. Typical efficiency for a coal fired station is 30-40% with only the latest generation achieving 60%+. Gas fired around 47% and nuclear around 38%. Then another 5-6% is lost in transmission. The average depends on what mix your country has but I can't see it being much above 40-50% overall by the time it reaches your house.
This web site compares the cost of different fuel sources in the UK. It's the only site I've seen that takes into account boiler efficiency. The key figure is the middle one "Pence per kWh after boiler efficiency". The actual boiler efficiency is in brackets...
http://www.nottenergy.com/energy-costs-comparison2
Note that electric heating is indeed 100% efficient but the cost of that electricity makes it expensive to run.
Heat Pumps have efficiencies of over 100% and in the case of a ground source heat pump (GSHP) around 350%. This more than compensates for the loss of efficiency producing the electricity needed to power. Overall a GSHP is the cheapest system to run (ignoring capital costs). It would be interesting to know if anyone makes a small scale gas or oil powered GSHP and how the efficiency of those compare.
In theory it would _just_ be possible to use the heat from a GSHP to power a Stirling engine to power the GSHP. This would not violate COE because there is a heat source (the sun) providing power into the system. However most of the heat produced by the GSHP would go into the stirling engine with very little left over to heat your house. Stirling engines that big would also be rather big physically. Overall such a system would be too big and expensive to be practical - but it would be free to run.
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Actually it's 100% efficient. I mean your reasoning is correct.
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you can get too would up over efficency ratings, nothing is 100% even electric loses a little to the room.
and one must be aware that cost to buy can exceed savings on whatever your trying to be more efficent with
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