Opinions on AO Smith Vertex 100 96% Water Heater
I have decided 100% to forget about going to a tankless water heater - some people love them, some hate them. In any event I am seriously considering the AO Smith Vertex 100 50 Gallon 96% Efficient 100,000 BTU Hot Water Heater. It claims to never truly run out of hot water. I need one that can be vented out the side of my house. I am planning to eliminate my chimney all together.
While it carries a fairly good price tag, I would be getting 50% off of the cost going through the NJ clean energy program. And that is before any other rebates/promotions.
So cost aside, is this the Mercedes of water heaters?
Unless you need a whole lot of hot water on a recurring basis, you will probably find that unit will short cycle under normal usage. Short cycling will affect fuel usage and equipment life negatively.
Originally Posted by tomwk
Another make with a similar design is the Polaris by American Water Heater. They have a unit with a smaller 34 gallon tank (32% smaller). Even with a smaller tank it would be best to set a somewhat wide temp band so that when the unit does fire it has to raise the water temp a meaningful amount (on at 115* and off at 135* or something similar). This will help mitigate short cycling. Make sure you have a mixing valve on the output side of the unit to set the delivered water temp to avoid scalding.
Unless your going to use some of this hot water for radiant heat it would be too large a unit and as been mentioned will short cycle just like a over sized furnace would that is sized too large for a home, no difference. These type of HWH are designed for use with a radiant floor system in mind as it will delivery plenty of domestic and radiant heat for a family of 8-10 person. Have you watched the video on there website, or on HGTV they review this product as well.
I will have to review the links on the model. I assumed since I already have a 50 gallon ao smith water heater, that I would just upgrade to this much more efficient and advanced 50 gallon model. My contractor never mentioned anything about short cycling.
It will not be used for radiant heat, and there will eventually be 4 people in my household.
Won't ba any worse then a 155,000BTU mod/con connected to a 40 gallon indirect.
Originally Posted by tomwk
Your current water heater is probably about 40,000 BTU and at a much lower efficiency. With this new unit having 100,000 BTU burner and more of those BTUs being put into heating the water (much higher efficiency) then the unit has much higher capacity.
The Vertex and Polaris both are using a somewhat smallish tank with a large high efficiency burner to provide you with all the hot water you could ever need as a tankless unit does, but since they do have a tank they resolve the cold water sandwich and other issues that people have with tankless units.
But it is real easy to go over board with these. One thing to compare is the first hour draw. Assuming your current water heater is providing all (or nearly all) that you need, compare the first hour draw of it to the Vertex. You will see the substantial additional capacity of the Vertex.
Sounds like your contractor is selling efficiency. As always there is more to it than that.
I would assume the typical household with family of four would find that set up over sized for their needs too. They would probably have all the hot water they need with a small 22-25 gallon indirect with a burner that size firing it (assuming the indirect had priority and maybe even without it).
Originally Posted by beenthere
Originally Posted by mchild
Use more fuel because of it, or short cycle, nope. Its not like an oversized furnace running 3 times an hour. The water heater won't fire more then a couple times a day to maintain temp.
Small tanks on mod/cons tend to short cycle while hot water is being used.
I just watched the video for the vertex on the ao smith site. It was installed in a house for a family of 5. It has the ability to use an additional hot water out for radiant heat, but you don't have to use it. Obviously the video raved about it, and never mentioned short cycling.
So why would this unit be considered oversized? My current 50 gallon ao smith water heater is 4 years old and has never run out of hot water since I installed all new low flow shower heads, but it used to before I switched them all. Plus I have kid #1 now which is starting to take a lot of baths. And kid #2 is on the way which will eventually mean more baths. And baths take up a lot of hot water.
If everyone still thinks it is oversized, then should I just consider a smaller vertex model? I still want the high efficiency and performance.
Had you mentioned having alot of baths I would have then said go for it, Thats the other thing these type of heaters are good for, is to provide endless hot water and in your situation with possibly 2,3, 0r more baths per day plus a couple of showers, along with laundry, you would be able to do most all of these activities simultaneously daily.
You're quite right about the tankless issue. Love them or hate them, there seems to be 2 distinct fields of thought. A good rule of thumb for a house that does not have a large soaker tub is about 10-gallons for each person in the home. When speaking of oversized, there's a big difference between the tank size and burner size. So if you draw a 10-minute shower at 2.5 gpm that's 1/2 of the tank capacity, right? But in both your existing unit and the new unit, the burner fires when the tank temperature drops with the influx of cold water. Now how fast that cold water gets heated is in direct proportion to the number of Btus being added every minute. A 40,000 Btu burner is putting 666.67 Btu's of heat into the tank every minute it's on. You're taking 20.8 pounds of water out of the tank every minute and if the incoming water temperature is 50 and you need to raise it to 120, that's a 70-degree temperature rise x 20.8-lbs. = a need for 1,456 Btu's per minute. Anything less and the tank is constantly cooling. Now replace that 40K burner with a 100,000 Btu burner and you're upped the Btu input per minute to 1,666.67. So you now have MORE Btu's available to supply that 1,456 Btu's needed. So you could, when using 2.5-gpm or less, actually have the burner fire, raise the tank temp and shut off during the 10-minute shower. Then refire, heat the tank up and shut off. That's short cycling, even with the same 50-gallons of storage. However, if you have 2-showers running simultaneiously, or the shower and diswasher or clothes washer or all 3, then the larger, 1,666.67 Btu burner will keep on burning andn keeping the tank much hotter than the smaller burner, again, with the same size tank.
Those are the facts, now do what makes the most sense for you. I'd be happy to sell you either tank as long as you know the facts and are making the decision that works best for you and your lifestyle. My opinion matters not a snitch if I can't make a solid case to NOT put in the larger burner.
If YOU want change, YOU have to first change.
If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!
Originally Posted by tomwk
Tom it would seem to me you are wanting to spend money for the sake of spending it. If you want true efficiency replace your hot water heater at the end of its life not at the beginning.
Kids really don't use that much hot water. Trust me I know kids, I have 6 of them. If the water doesn't get cold they don't know the shower is over.
Clearly you have noticed the technology is reaching the hot water arena. Are you going to need to jump into the next great new thing in another 4 years?
It would be an output of 1600BTU's at 96% efficiency.
You're taking 20.8 pounds of water out of the tank every minute and if the incoming water temperature is 50 and you need to raise it to 120, that's a 70-degree temperature rise x 20.8-lbs. = a need for 1,456 Btu's per minute. Anything less and the tank is constantly cooling. Now replace that 40K burner with a 100,000 Btu burner and you're upped the Btu input per minute to 1,666.67. So you now have MORE Btu's available to supply that 1,456 Btu's needed. So you could, when using 2.5-gpm or less, actually have the burner fire, raise the tank temp and shut off during the 10-minute shower. Then refire, heat the tank up and shut off. That's short cycling, even with the same 50-gallons of storage.
It would take just over 9 minutes( 9 minutes and 6.6 seconds) for the burner to heat that 20.85 pounds of water from 50 to 120°. I don't see the burner refiring again in the next 50 or so seconds.
The water heater isn't just heating up the water that has replaced what was/is used.
It is also heating up the water higher in the tank.