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Does anyone have experience with tankless water heaters? Shannon and I are about to commence building a new house, and a co-worker mentioned that this was a MUST HAVE for a new house. Do they really save a bundle of $$$?

Here is a website touting their benifits.

http://www.gotankless.com/index.html

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02 Focus SVT
STF 9

No experience with those. I'm very happy with my big-ass propane boiler, though. It's the backup heat for the heat pump (versus electric strip or straight propane) *and* supplies the hot water for the house.

I don't know if you can do this with on-demand systems, but in our system we also did a hot water recirculating loop. See, I *hate* waiting for hot water. So instead of doing traditional piping, we did a loop around the entire first floor and put a very small pump in the loop. Then we tee-ed off the loop to go straight up to any place that needed hot water. Works *great*. Hot water all the time with no waiting.

It's a very good idea to insulate all the hot water pipe, but that's really easy to do and isn't very expensive. The extra pipe, pump, and labor wasn't much extra, either. If you plan to be there a long time, it's something to consider.


--Donnie

Tankless are better in almost every way than other water heating systems.The increased upfront costs are recovered in 3-5 yrs, which is a rediculously short turn around.

You will never run out of hot water, ever. The only short coming they have is multiple users at the same time. There is a flow limit throguh the unit. So if you are a large family that has 2-3 people taking showers at the same time, it won't be able to keep up. But then most conventional systems wouldn't either.

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91 Jetta GLI STS/DSP 111
85 Porsche 944 ASP 11
http://www.blackforestindustries.com

Well, we plan to live here forever and we have two kids, so that's why I went unconventional with the big boiler. 500 gallons of hot water should get us through three showers at the same time.


--Donnie

Donnie, have you done the calculations to see how much it cost to keep 500 gallons of water hot 24/7/365?

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Rob Harvey
919-697-5485
1997 BMW M3
1992 Acura Integra (Simon)

a contractor i know reccomended a tankless after we remodeled. we have two tanks, one for the house and one for the master bath. problem we have is showerhead flow rate is greater than tank capacity and thus cold shower after about 5-8 minutes in the winter for the master bath. if we stay here i plan to look into the tankless for the master bath.

anyway Ryan, when building new you may want to look at two seperate hotwater sources. having a dedicated tank for the master bath is nice.

Rob is right on with regard to the cost of maintaining the hot water in any tank system. I worked for a while for Pacific Gas and Electric in their energy use / conservation department and we typically could show an under 5 year payback for a tankless system, and they were really expensive back then.

The energy cost is also compounded depending on where a tank system is located. Loacted in a crawl space, the winters cause more heat loss through the insulation. Located indoors, some of the summer airconditioning bill is just to remove the heat leaking out of your tank into your dwelling.

When my hotwater heater finally dies I will consider installing an on-demand system.
Charlie Guthrie

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1998 BMW Z3
1987 BMW 325is
2000 BMW
1996 F250 Turbo Diesel

If you anticipate the possibility of exceeding the flow rate, install two, and have each feeding its own zone. although it will cost more you'll never be without hot water somewhere in the house. We had two installed in the kennel. they worked well until we started bathing 200+ dogs, three at a time with the laundry(2 commercial washers) on while trying to wash 250+ dog bowls in the kitchen.

That was fifteen years ago so I'm sure they are even more efficient today.

Along those lines, lets talk about airconditioning. Almost every contractor will under estimate the size of airconditioning. They all try to sell you the smallest unit. I suspect this is to keep their costs down and to make their bids more attractive. In Fact, put the largest unit you can afford in the house.

Case in point our fifteen thousand square foot kennel was supported by 3 three ton units. four years ago we replaced them with five ton units and added a five ton unit to our residence. The total electric bill decreased over a three year peroid by about fifteen percent. All this in spite of two increases in electric cost per KW. We did the same thing at our home in Beaufort, The contractors swore the unit would freeze up because of the light load....BS.... we experienced the same cost reduction in the electric bill. Besides the savings in elec. The units heat and cool the spaces in no time at all. you want it cold "poof its cold". Again Put The Largest Unit You Can Afford In The House. It pays off.

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2004 C5(415whp,390ft/lbs),
1997C5,1997Trans Am, 1986 C4,
1990 Miata, 1976 MGB,1997 Protege, 1989 MR2

All comparisons in the linked web site are for electric hot water heaters, which are very expensive to operate. How does tankless compare to propane? Availability of natural gas in our current house was a big plus, as electric hot weaters and clothes driers are expensive, and the electric hot water heaters take forever to recover. Our next house will have propane, and I need a comparison to that. It looks like all tankless models are electric. Do they have propane ones?

Uh, you're way off base on the oversizing of HVAC from what I understand. The reason contractors sell you the smallest unit possible is one of *comfort*. You can certainly go too small and that's bad, but going too big is also bad. Why? Because you end up with a space that gets really cold when it runs, and then has to warm back up to the temp you asked for. So you end up with this vicious cycle of cold/hot and you can't get the proper temperature.

What's worse than that is that you don't get humidity control like you should. You end up with a very small duty cycle (the unit is off WAY more than it is on) and it can't remove humidity inside well enough. So it feels stuffy. What's worse than that is that studies are starting to show that it becomes much more likely for you to have mold problems in houses where the unit is oversized leading to health concerns.

To me the *real* problem is that units can't vary the amount of cooling they give. If they did, then you could oversize the unit a little but have a controller on it that would maintain a "good" duty cycle...so it still runs 50% of the time (or whatever a good cycle is), but doesn't give you as much cooling when it isn't blazing hot outside. It then ramps up the cooling once it *does* get blazing hot. A good system for doing that would obviously use energy proportional to the amount of cooling that was required, too, thus reducing energy costs.

A good HVAC person will size a unit for you that can handle the worst of the summer just fine yet still run a good duty cycle. That will also be about the most efficient you can get your system, too. Obviously an overstrained and undersized unit running constantly isn't going to be very efficient, but conversely, an oversized unit won't be very efficient, either.

Don't go asking for a bigger unit just for the sake of having a bigger unit! Get a quality HVAC person and go with what they recommend.


--Donnie

I'm not circulating *through* the tank. Certainly some of that happens, but the loop is completely *above* the tank. Plus the tank is a very well insulated high efficiency tank. I've got no reason to believe it adds a very high cost to the heat bill.

In fact, I know it doesn't, because when we remodeled our mountain house we added a loop and pump to the pipes there, and the electric bill didn't go up any noticeable amount.


--Donnie

Bernie, I wonder if that decrease was because of a better designed system? Were the units that you replaced a lot older then the ones you replaced them with? You might've seen a bigger increase by staying with a new model of the same size you had.

Just curious because we will probably be replacing our equipment in the next two years.

And for Ryan's question. When our hot water tank goes, we are going to replace it with a tankless system.

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In need of car.

Donnie,
With all due respect, you're WRONG..Thats the same line or retoric I've gotten for I don't know how many years now. I've done what I said I've done so the proof of the pudding is in the eating....It works.

First lets address your statement:

"Because you end up with a space that gets really cold when it runs, and then has to warm back up to the temp you asked for. So you end up with this vicious cycle of cold/hot and you can't get the proper temperature."

How cold the room gets is a function of how well your thermostat works. If you demand 72 when the temp drops below 72 the thermo shuts the compressor down. The fan will run for a short time more to decrease the temp in the airbox. This may cause a further drop of one or two degrees.

When the temp rises above the requested 72, the compressor and airbox fan come on again, thus the cycle is repeated. The number of degrees that occur between turn on and shut down is called dead band and is adjustable in the themostat. It is also a function of the thermostat, not the compressor or the airbox...

Your statement
"What's worse than that is that you don't get humidity control like you should. You end up with a very small duty cycle (the unit is off WAY more than it is on) and it can't remove humidity inside well enough. So it feels stuffy. What's worse than that is that studies are starting to show that it becomes much more likely for you to have mold problems in houses where the unit is oversized leading to health concerns."

The humidity is controlled by the fact that cool air holds less moisture that warm air. Most airconitioners dont have driers, its a natural function of cooling the warm air, thus reducing the relative humidity. If the unit is maintaining temperature, its automaticly maintaining humidity. If the air is cooled to the requested temp it doesn't matter how long it takes to get there. The fact that its cool is what decreases the humidity.

Lastly the duty cycle of the unit only equates to how much power its using and how soon it will wear out.

I'm speaking from the exeriences of the past four years with home and small comercial units. I've been there and done this with great decease in electrical cost and with no mold or temperature cycles. Take it for what its worth to you. My comercial bills have dropped more than fifteen percent, residential have dropped more than twenty five percent. I have no mold and and no temp related discomforts in either the kennel or the house. You decide. This is actual, not heresay or theory.

Jason, before we changed to the five ton units we had them install a NEW three ton unit in our apartment. We moved that to our cattery and had a five ton replace it for our apartment. The three ton unit was about a year old, so I don't think new efficiencies are the reason for the decreases.

Lastly, our neighbor's house here in Beaufort was built by the same builder at the same time ours was built, and are very similar in size, insulation, etc. We replaced units at about the same time and he went with the suggested smaller size. After severay months of comparing cost he just didn't want to "play" anymore. His bills were running $150-$175 while ours were right around $100. You can decide.

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2004 C5(415whp,390ft/lbs),
1997C5,1997Trans Am, 1986 C4,
1990 Miata, 1976 MGB,1997 Protege, 1989 MR2

I am not an HVAC specialist but I will play one for the duration of this post…

I tend to agree with Bernie on this. My personal experience with this has been that in our previous house when we had the heat pump replaced with a “high efficiency” unit, the new unit was much larger physically. I think that the trick of high efficiency is not some type of wonder lubricant, etc. that makes everything work better, but is most likely oversized coils, fan and maybe even compressor. I suspect you could just buy a regular unit that is just oversized and then magically you have a high efficiency system. I also don’t want to discount that a true high efficiency system probably has things like variable speed fan internally as well as a decent programmable thermometer.

Regarding Jason’s question about cost savings and a new A/C or Heat Pump. I don’t know how much of the savings that we saw (which was a lot) came about as just having a newer heat pump vs. a high efficiency unit. Regardless the efficiency rating on a A/C or Heat Pump is going to be the first thing I look at the next time I buy one! I am sold on the concept.

Regarding humidity and mold, to take things to an extreme, I “could” see how you would not dump as much of the humidity out of the air if you had a really large unit. If you blasted out frigid air and you didn’t actually circulate enough of the internal air past the internal coils before the thermostat kicked everything off, then I can see where you might have some humidity remain trapped in the house even at a lower temperature. The humidity is removed from the air by the A/C because it has to pass over the coil and condensate on it. If it doesn’t pass through then it has no exit path out of the house.

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Yes tankless "aka instantaneous water heaters" are available in both LP and Natural Gas.

www.noritzamerica.com

We specify their commercial models quite a bit for restaurants, gyms, etc.