gas high efficiency water heaters?
I have a gas water heater that is old and I wanted to replace it with a gas high efficiency water heater.
I’ve gotten some conflicting info on efficiency ratings. The guy at sears said they have a Kenmore powermizer 12 that is energy rated at .63 for the first hour. He said the tank insulation is about double what most are. That’s fine but I was interested in one that burned more efficiently also.
The power vented one he had was energy rated at .65
I might be mistaken but it was my understanding the power venting was the way to go.
1.There’s a valve on the vent that keeps heat inside the tank better when it’s not firing.
2. When the burner comes on the fan pulls the heat through the tank further so by the time it comes out the top it can be vented by PVC pipe. The burner breathes well and it keeps more of the heat.
The sears guy’s rating (for the first hour) seemed deceptive.
We have a high efficiency furnace that uses PVC to vent. If I go with a power vented water heater I can eliminate the vent out my roof. So right now the water heater is the only thing venting through it. I can’t think of anything else that would need to vent out of it in the future? Can you?
Edited 12/10/2007 1:42 pm ET by popawheelie
Replies
My Plumber likes the new A.O. Smith unit. I am thinking about putting that in my house. Jay
I had an AO Smith WH in my last house, and had a lot of trouble with it. The flame sensing rod only lasted a year or two. AO Smith would send a free relpacement, but never improved the design of them. My plumber said that once the supply of free replacement flame sensing rods was exhausted that the only option was gonna be to replace the whole water heater. He's apparently dealt with this problem a lot, and has stopped handling that brand.
It ain't braggin' if you done it. [Dizzy Dean]
flame sensing rods on furances can just be cleaned. But I don't know if they use the same technology or not..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The plumber said that the rods could be roughed up with sandpaper and they'd last a while longer. I never tried it - He recommended putting a new one in so it would last longer.
LAWYER: One skilled in circumvention of the law.
You're discovering what I've noticed earlier -- there really are no high efficiency gas water heaters available (short of a full boiler).
No kid'n? It seems like there should be a market for them. This may be wayyy off. But if you have a fan pulling the draft through the tank you could make it wind around more and give up alot more energy. The burning could be hotter. A more complete burn. You could size the tank a bit smaller also because recovery would be increased.
I guess the price of energy is still cheap enough that there isn't a market.
I just called our local plumbing shop and the owner said the same thing. The fan assisted ones arent' that much better. If I wanted a big jump I would have to go to on demand.
I'll just go with a better quality conventional one. The sears Kenmore powermizer12 sounds about right. I'll check around a bit more.
Edited 12/10/2007 5:27 pm ET by popawheelie
I think that it's also the fact that perception is everything, and direct vent water heaters are perceived as being HE, even though they aren't.As it is, the only way to rig up an HE water heater is to use an HE boiler with a heat exchanger tank, and the standby losses begin to eat you up simply because you have about 10x the water heater you need. (Plus it takes 4x the space it should.)
If your view never changes you're following the wrong leader
What you'd do is have about a 20 gallon tank. Flame would loop up through the tank and back down, then go across a heat exchanger for the incoming water. Burner would be modulated, with a low setting for just keeping temp at standby and a high setting for when water's flowing. Having the flame gasses cross the cold incoming heat exchanger last would wring the most energy out, producing exhaust temps below 100F and better efficiency than a HE gas furnace.
If your view never changes you're following the wrong leader
Sounds good to me. Somebody is going to do it as energy prices go up.
Edited 12/10/2007 7:03 pm ET by popawheelie
Check out this modulating burner HW heater; up to 97% efficiency. Same burner/controls as used in Munchkin boilers.
http://www.htproducts.com/phoenix.html
That one seems to assume a recirculating system, so it doesn't optimize the same as you'd want for a non-recirc residential system.
If your view never changes you're following the wrong leader
what?How would the presence or absence of a recirc system change anything there? I could see if it were not set up for recirc, recirc might cause an issue, but if it's set up for recirc, not having it would not be any kind of problem.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
It changes your standard operating conditions. The water entering in a recirc system is only slightly cooler than desired, while in a non-recirc system it's generally around 50F. The cooler water makes designing a high-efficiency system fairly simple, since you can use the incoming water to extract every last little bit of heat from the combustion gasses.An ideal non-recirc system would be two tanks. Top is hot water, bottom "tempering". Burner is between the two, blows up a loop in the top tank, then down through a zig-zag in the bottom tank, exiting at the bottom for the flue connection (and condensate drain). A sensor at the bottom flue connection would modulate the burner so that flue temp never exceeds some limit (both for safety and efficiency). For a recirc system you'd either bring the recirc water directly into the top tank or into the top of the bottom tank, but if you were just recirculating with no water use then efficiency would suffer.
If your view never changes you're following the wrong leader
Ok, but if the water heater is set up for recirc, you are in no way compromising its effectiveness by not having a recirc system on it....-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
It's just that on a recirc system you can't achieve as high a % efficiency as easily, making the simple high efficiency scheme less worthwhile. But then, of course, with a recirc system you're presumably prepared to eat some efficiency loss.
If your view never changes you're following the wrong leader
Thanks for the heads up pjlacas
I plan on putting in a recirculating system. I have two bathrooms and another kitchen on the other side of the house. I was planning on putting a loop of well insulated 3/4" pex in. I have access in the crawlspace.
I e-mailed the rep for this area. They didn't give prices on the website. I'm not sure if they have to instal it. It does sound like it is expensive.
Edited 12/10/2007 11:10 pm ET by popawheelie
popa,
That .63 = 63% overall efficiency with stand-by heat losses included. Tankless units can achieve .81. Both tank & tankless have an average of 82% operating efficiency - when their burners are running.
There are tank-style and tankless water heaters that can achieve .93 EF, or better. As you'd expect, the cost is higher. OE can hit 99%.
Don't be fooled by seeing a PVC vent. The .63 direct vent models can use PVC by virtue of dillution - room air is drawn in to dillute and reduce the stack temps so that plastic can be used.
The biggest problem with most gas units is the standby losses. Even with a tankless model you lose a lot of heat if the unit is just used in spurts. Problem is that it's hard to effectively insulate the tank when you've got this big-arsed heat exchanger running through the middle of it, connected to an air intake on one end and a flue on the other.
If your view never changes you're following the wrong leader
Many of the commercial hot water heaters we used to put in had a power damper in the flue that closed off the vent to stop that hellish drain of heat up the flue.
roger
>>to stop that hellish drain of heat up the flue.That's what the draft hood is for.
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
">>to stop that hellish drain of heat up the flue.That's what the draft hood is for."How is that?.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
It after the internal flue cools, the chimney draft seems to draw more from under the drafthood (aka bonnet) then through the water heater itself.Generally, the flue cools fairly quickly and the losses of heated room air are a lot less than some folks would have you believe, in my testing.
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
If the WH is in conditioned space then "under the hood" is still going to be drawing conditioned air from the same space..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Rinnai direct vent demand water heater hits 86% eff. Sealed combustion. a few minor caveats but generally a great machine for the money. Tagaki and Ruud close second in my book, possibly a tie depending on price.
Stay away from Bosch, Myson, etc.
m
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"You cannot work hard enough to make up for a sloppy estimate."
Just a note that those power vented water heaters can be kind of loud. The blower really blows if you know what I mean.
I don't want something realy loud. It is in a furnace room with washer and dryer. I suppose the better ones are quieter. Not sure about that though.
The Phoenix gas fired heater is " super quiet".
It sounds like a very nice unit but I think the price is high. Stainless steel tank. Yikes!
You pretty much need SS for the heat exchanger, and getting a good thermal expansion match with the rest of the tank is then important.
If your view never changes you're following the wrong leader
I called Heat transfer that makes the Pheonix and they wanted me to call contractors. They have a contractor map locater page so I just went down the list and e-mailed about 8 of them. Cut and pasted them.
I still don't have any idea how much the installed unit will be. I said in the e-mail that i had a circulation system in place. I can do that with a little help.
If the Pheonix is to much I'll just put in a water heater. That 97% efficientcy does sound go though. That unit should last a LOONNGG time too.
My friend just put one of these in: http://www.radiantec.com/systems-sources/polaris.phpIt does his domestic and his infloor. Super efficient. Not cheap though. He has had it for only two months though.
popawheelie,
I switched from gas to electric for efficency reasons as well as the lack of a vent reduces the stack effect.. another words 24/7/365 you have a hole in your roof/wall drawing heated inside air out. It's like leaving a window slightly open all winter long..
The cost of electricity in Minnesota is under considerable pressure. We have two well run nuclear power plants & several large coal fired plants (and we're the closest metropolitan center to the western coal fields) in addition southern Minnesota is covered with those large windmills which should be shortly hooked up to the power grid further reducing demand for power.
In addition there is a plant in northern Minnesota all set to come on line waiting only permits..
Thus there is little chance electric costs will get out of line..
I noted a decent sized drop in my energy costs when I switched from a gas water heater to this electric one. It's hard to compare exact costs since this is a totally new house and I have yet to see the worst months bills (December and January) I do know my gas bill has plummeted from $500 a month (worst months) to $127 a month. That's due to many things though not just eliminating the water heater.
I don't know what your electric costs are and what sort of power generating situation you have but if it's affordable you might consider electric..
Did the same thing, with a nod of agreement from the HVAC company that just ran in the NG line and converted our furnace from propane.
I had a 50G direct vent propane WH and replaced it with a 60G electric. Price quoted to install a NG HW heater was $1400-$1600. I came in at under $600 to buy the electric tank and install it. Add a $35 insulation blanket and I have the same efficiency as the higher priced electric units for less money.
In addition to the stack effect that's 24/7 as you say, there is the large volume of conditioned air that is sucked out of the house for combustion each time the gas HW fires up.
Add that all together and I imagine that all the costs issues even out. Maybe electric even comes out ahead.
Varoom,
Yes, I don't know for sure that the electric is that much cheaper to operate than gas. although just looking at raw numbers seems to indicate that. However I have done exact comparisons between gas and electric units.. the electric units make the claim and the raw numbers seem to be superior to gas.
I am counting on them to work to an astonishing degree.. I have a pair of them, one the 80 gallon unit is for household hot water and the smaller one is for in floor radiant heat..
I've plumbed them so one will back up the other and can be switched with a simple turn of a valve.. thus I have twice as much BTU production as I calculate I need.. in addition to that I have a back up forced air furnace (my old high efficiency furnace which is what heats the huse currantly) and finally there are two gas fireplaces and ultimately a masonary wood fireplace. So worst case I should be able to withstand minus 150 degree temps ;-)
Last winter I looked at as many water heater specs as i could find on the web
I found very little difference.
Just because furnaces with higher efficiencies use draft fans doesn't mean that a draft fan on a water heater makes it more efficient burning.
The fan mixes a lot of air into the flue gases, cooling them and diluting them so they can be vented out the side of the house.
>>The burner breathes well and it keeps more of the heat.
??
Based on my training as a combustion analyst, that makes no sense.
A key measure of efficiency for water heaters is the flue gas temp at the top of the flue.
It is basically the same in atmospheric drafts and induced drafts.
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
RJW
Hey, I'm interested.. You say you've actually tested how much air goes out a typical water heater gas flue? I'd really like to know. I just assumed it would be the same as any 4 inch flue would flow I know a round flue will flow more air than a square hole or a rectangular hole and when I did the math it turns out it was the same as leaving a window open 3/4 of an inch all year around..
If you have differant numbers I'd be facinated to hear them..