High efficiency, high recovery water heaters

[Rick-Meister]

{{{{That makes no sense to me. It fires up and instantly starts heating the water. All the heat goes into the water and into the dishwasher, except for the heat in the water left in the pipes at the end when the use stops. The latter happens exactly the same with a tank type unit. Nor do some of the other comments here make sense:}}}}

They make a lot of sense if you look at how a demand WH works.

Take a pot, fill it with cold water and put it on the stove. Turn the burners on high. Then dump out the warm water and refill with cold water. Repeat that scenario over and over again. That's exactly what's happening when you use a demand WH for to fill a dishwasher. It takes a fair amount of heat to bring the heater exchanger tubes up to proper temp. You basically keep reheating the pan. You never get to take full advantage of the "warm up" energy. In addition, the burners in many demand WHs are rated for a 2.5gallon/minute flow rate. But most dishwashers don't fill at the rate of 2.5 gallons/minute. If the dishwasher fills at the rate of 1 gallon per minute, all those extra btu's go right up the flu. You can do the math on this yourself. The worst part is that the dishwasher refills several times in a cleaning cycle. A shower, on the other hand, provides maximum efficiency because it's using the proper flow rate for the BTU input. The downside, of course, is that if your demand heater is rated at 2.5 gallon/minute and a second person tries to take a shower, the demand heater can't provide enough hot water. If you size the demand heater to 5 gallons/minute, then you're wasting even more fuel in low volume operations.

I wasn't saying that demand heaters aren't efficient. I was just pointing out that they're not efficient across the board. If you use them at the rated flow rate, they're far more efficient than most tank models.

[ransley]

That is bs, if it was true then how do I get a 9$ gas bill, with gas dryer and stove, all my usage is quick a few gallons,, but of course you cant get proof of your bs statement, Now im at a location with NG tank and now I pay 45$ a month, My Ng tankless has gotten me a 4 year payback, Again out of the woods come people that dont use them and post unsubstantiated bs crappola, I hate these tankless threads, to many morons posting. Tank Salesman.

[ransley]

Then how do explain a TH1 which is Condensing, that has a 95% efficency and 95% EF factor on propane, because the heat exchanger is extremely efficent

[Wayne Whitney]

That's not true--the demand gas water heater has a modulating burner and adjusts to the flow rate.

Wayne

[hallerb]

so your comparing the savings of a regular electric tank against a natural gas tankless......???????

guess what nearly anywhere in the country a natural gas heater will save money over electric water heating. sure electric is 100% efficent, but per BTU electric is super expensive to operate.

If I were the OP I would investigate moving the tank to a new larger location, and going with a condensing 98% efficent condensing tank heater. outside air is drawn in, so interior air isnt burned for combustion, and the exhaust just like a condensing furnace exhausts thru a PVC pipe. Install a drip pan in case a leak would cause damage. most condensing tanks have copper coils inside the stainless tank. this leads to extremely long life.

previously ransley has talked about servicing his tankless. and his claim of 30 year life is pure bogus. tankless use sophiscated parts, which one day may be no longer availble, poof gone, no parts no hot water.......

Here we just replaced our 1965 furnace with a condensing one, next up will likely be a new condnsing water heater. our existing tank is 8 years old, it had a 6 year warranty.

with the rising cost of energy we should all do what we can to save $$ $.

also looking at gutting part of our house, and adding spray in place foam, along with wiring and new kitchen......

[Rick-Meister]

Some demand heaters have a modulating gas valve......some. Not all. And certainly not the low end units.

I'll say it again. I'm not saying that demand heaters aren't efficient....they are. But there are a few issues with them regarding efficiency across the board and low flow.

Geez guys, settle down a bit and read the whole post before you flame. All I told the guy was to evaluate his usage and be aware that there are some circumstances where the demand heaters, well, I'm repeating myself.

End of discussion--at least for me.

[trader4]

Before it ends, I'd like an explanation and reference for a couple of your statements:

"The higher the water pressure, the larger the BTU's required to handle the same usage. "

This makes absolutely no sense. If the tankless is heating 5 gallons of water, what possible difference in efficiency could it make if the water pressure is 30 PSI or 60PSI? I have never seen anyone claim that pressure factors in at all to sizing a tankless.

I also don't buy the analogy of comparing a tankless to constantly refilling a pan heating water on the stove. You state that you are constantly reheating the pan, as if the pan itself somehow takes and holds heat. In reality, the heat is going into the water. Some is escaping as loss around the pan, to the surroundings, but that happens regardless of whether the pan is being refilled every minute or left alone for 10 mins. In fact, MORE heat will be transferred to the pan in the case of it being refilled with cold water, as the cold water will absorb more of the heat without it being lost to the surroundings.

If you refill the pan 10 times in 10 minutes, you wind up with 10 pans of barely warm water. If you leave one pan sit for 10 minutes, you wind up with one pot of hot water. If you think some energy inefficiency is at play here, explain exactly where this lost energy is going?

[hallerb]

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one issue with tankless is the delay between draw water to hot water arrives.

the tankless must detect water flow, and turn on water, .........

as a tankless owner told me, we save energy on heating water, but waste water and sewer....

now admittedly its not a killer cost but it is there.

another tankless troubling issue..........

if you have temperature control shower valves the fast changing temperature from tankless can cause valve hunting, where the shower temperature doesnt remain stable......

here we have AOSMITH vertex tank type water heaters. 96% efficent without the downsides of the tankless.

one last tankless issue.

most require power line voltage to operate. no power no hot water at all.

unlike tank type heaters that have at least a couple quick showers onboard at all times...........

so one morning the power is out:( Your choice before work:(

No shower at all or a cold one...... which do you preferr:)

tankless are fine, just like the original vW BUG was....

it will take you to the same place as a more comfy larger vehicle, but has limitations. saves energy though.

if your willing to live with the many limitations more power to you. myself I prefer the comfort of a regular tank, espically when Vertex can supply both the comfort of a tank with the efficency of a tankless.....

hey ransley, you can get one when your tankless craps out in a few more years:)

[ransley]

Where I installed tankless yes, I took out an electric tank, and electric dropped 35$ NG went up about 5$ and NG included stove and Ng dryer, Im at a tank location now and 45$ was my last Ng bill, my savings only a blind person cant see, do you qualify?

I have not serviced my tankless yet except for new D batteries, where you make up this shit is beyond me, I am ready to pour lime away through but havnt yet.

30 yr life is in the design, do your research, its stated. There is no tank to rust out, its copper pipe. How long does copper piping last, alot longer than 30 years. Do research before you post false statements. And bs on your parts theory, these designs are not "going away"

Get your facts straight, there are no 98% efficent ng tanks made, and overall efficency or EF is no higher with a tank than the 70- low

80s. Tankless EF ratings start at 82 and go to 94. Thats 15-20% better than any tank made....

[ransley]

The low end 460$ Bosch does, any quality tankless has modulating valve. Maybe 10 years ago it was different.

[ransley]

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Here we go again, Hallerb you are 1 can short of a 6 pack. I think I should just call you, yo, 5pak.

Delay might be 15 - 30 seconds

Waste, my water bill has not changed, and once pipes are hot you dont realy notice anything, but of course you never used one, but think you know

What total bs, tankless dont change alot or hunt on temp , again your lack of use is lack of knowledge

A vertex is NOT 96% efficent, its near 80 EF, the burner is 96% but not overall efficency which is what you need to learn about. And notice AO Smith wont tell you EF of a Vertex or cyclone. I have a 93% AO Smith Cyclone a 80 gal 190000 btu unit. Ive had it for 6 years and its EF is near 80. Yes its saved me alot over my old tank of near 45 EF. But dont kid yourself, Tank are 15-20% less in overall efficency to tankless. Read EF ratings, not burner ratings

My 117000 Bosch needs No AC, it used 2 D batteries for ignition. Your condensing tank, needs AC

Here again I have a AO smith 93% Cyclone, give me one valid reason my tankless should "Crap out" soon you cant.

Hey 5 pak. The Vertex is not as efficent as even a Non Condensing Tankless. Learn EF rating and quit postin crap

[hallerb]

e =EF=BF=BDtankless.-

[Wayne Whitney]

The added delay from the tankless is more like 5 seconds. So there is a little extra water wasted per shower, it is true.

Cheers, Wayne

[Wayne Whitney]

Thermal efficiency is a red herring when it comes to tank type water heaters. They are just saying that 96% of the possible heat from the gas burned makes its way into the water. There are still standby losses from storing the hot water, so the overall energy factor is likely 0.80-0.85. That's still quite good, comparable to a tankless.

Cheers, Wayne

[Oren]

Will 20 years or more years be close enough?

...."Most tankless water heaters have a life expectancy of more than

20 years. They also have easily replaceable parts that extend their life by many more years. In contrast, storage water heaters last 10?15 years. Periodic water heater maintenance can significantly extend your water heater's life and minimize loss of efficiency. Read your owner's manual for specific maintenance recommendations."

[hallerb]

And no the vertex is near 80% in

I said a standard tank is a simple appliance that rarely requires any service, I am 51 and in my entire life perhaps one needed a thermocouple.

heres a paste from AO SMITH

Vertex offers up to 96% thermal efficiency with performance that rivals much larger water heaters

[Wayne Whitney]

And again, thermal efficiency isn't overall efficiency, due to standby losses. Thermal efficiency just measures how good it is at burning gas.

Wayne

[ransley]

You are pushing Vertex, a complex condensing unit, more complex than tankless of higher EF, Vertex is near 80 or less EF. 96% rating is for suckers that dont know what EF is. EF is akin to AFUE.