Electric On Demand Water Heater

[Mark P]

I'm considering installing an electric on demand water heater in my house. I was looking at a "Tempra 29" manufactured by Stiebel. http://www.stiebel-eltron-usa.com/tempra.html

Does anyone have any experience or opinions on a good manufacturer or model?

[John Kogel]

The Tempra 29 requires 3 50 amp double breakers. I think there are 3 heaters then, like 3 high powered kettles, and the unit draws 28.8 kilowatts.

If you have the space in your panel for those breakers, I'd say go for it. German engineering is usually a good thing.

[kurt]

Why would you want a tankless? Are you going to install a circulator system?

[David Meiland]

I've had a few of those installed, various sizes and brands, they seem to work fine but you need a LOT of big wire to hook them up. Last one was (4) 60-amp breakers.

[Mark P]

Why would you want a tankless? Are you going to install a circulator system?

Good question... We have hard water, so much so it destroyed our dishwaher a few years back. I'm getting ready to completely gut and replace our kitchen to include a new dishwasher. I want to install a good quality whole house warter softener, but I have no place to put it. The house is on a crawl. So I came up with the idea that if I remove the 40 gl water heater and install a tankless then I can put the water softner where the old water heater was.

I know I may need counseling.

[Greg Booth]

.........I would just mention to check your incoming water temperature. I recall an installation where water was supplied by a well with an incoming water temp. in the low 40 degree(f) range. Had trouble achieving a satisfactory rise in temp. The solution in that instance was to install a large "tempering" tank in the basement..........Greg

[kurt]

I don't know all the design parameters and restrictions, but I'd be looking at water quality systems first, water heater type second.

I am biased, though. I don't like tankless water heaters unless they're set up as point of service operation.

[Marc]

I'm with Greg. I tested one on a new construction years ago by turning on the sink faucet and a tub faucet at the same time. The electric tankless never got beyond 90 degrees and this was the summer season.

Don't mess with electric tankless unless you do the math and keep the sum of connected fixture GPM's within the capability of the heater. Not much need to do the math for gas.

The gas tankless units I've seen are mostly 199K btu/hr. That translates into 243 amps at 240 volts!

Marc

[John Kogel]

Hey Marc, thanks for doing the math.

Not too many people have 150 amps to spare for the Tempra 29. But an average household would not be happy with less than that, IMO, if that is about 120k BTU/hr.

[davidlord]

I have a Rinnai RL94 (propane) that supplies my entire home (3 full baths). Slickest thing since sliced bread. Going on 2 years and not a hint of a problem. Never run out of hot water. No issues whatsoever. I wouldn't buy anything else.

[kurt]

They work fine, and one definitely doesn't run out of hot water. That's not my gripe.

It's the tripled water bill and doubled gas bill from family members taking endless hot showers, and the aggravating cold water sandwich effect at the kitchen sink. I didn't anticipate paying triple the price for a water heater that increased my utility bills and made me wait for hot water at the kitchen sink.

If there's not a circulating system, and one has a larger house with far flung baths and fixtures, one gets to wait inordinate amounts of time for that hot water.

If folks dig 'em, fine with me. I just don't know anyone that has found them to save money or provide the *on demand* experience they advertise.

[David Meiland]

Agree with Kurt. We had a Takagi for ~7 years, I sold it and put in a standard tank. I do miss the remote control, because it would make the water 165 degrees for cooking pasta sooner, but that's it.

[fyrmnk]

Just hit 4 years since I installed our gas tankless and will never go back to a tank again. Guess I'm in the minority. Our gas bills have stayed about 30-40% less since installing (grant it our old tank heater was not as efficient as a new one). Even with longer showers, gas is significantly less. Have had a slight increase in water bills, but our water is cheap here. We love it, can run three showers at once as well as whatever else we need. Love the remote thermostat where the boy can adjust temp down for his showers and wife can kick it up to 140 if she wants for dishes, etc. Extra storage space in the utility room is a plus too.

[kurt]

I think satisfaction with tankless has something to do with particular houses and distance to the water heater. I may be wrong.

Do the folks that like them have the heater fairly close to a wet wall, or are baths and kitchen close to each other? Do the proponents have "stretched out" floor plans, or are things compact?

[fyrmnk]

We live in a split level and our bathroom is at the uppermost level opposite end of the house from the water heater, which is in the basement. It does take a bit for the hot water to reach it at first but then it stays constant temp as set with no problems. Kitchen and one other bath on same level as ours.

[Mark P]

With my 40 GL water heater it takes time for the hot water to reach the faucets, so I don't see any difference in that concern. For me it is really a matter of space. I (my wife) want a water softner and I have no other place to put it.

With the model I'm considering there is supposed to be no temp fluctions. From their website "ensures a constant temperature output no matter how great the hot water demand is. Tempra Advanced Flow Control? technology works by automatically adjusting the flow of water to eliminate unpleasant temperature fluctuation."

[LeePlace]

An Item that you can use for both tanked & tankless water heaters is a Chili Pepper pump. http://www.chilipepperapp.com/howit.htm .

Space saving, endless hot water (Think lots of people) are major advantages to a tankless heater along with energy savings of not having to maintain a tank full of hot water. But the cost of the heater, Branch circuit / Panel upgrade or gas piping up sizing, flue venting change and water treatment for water with a total hardness greater than 12 grains can be very high and should be included in a comparison of Price Vs. Value.

Some other things to take into consideration would be, No Power No Hot Water, No Power No Freeze Protection and no Emergency Water Storage.

Lee

[davidlord]

In my particular situation I had a conventional gas water heater with a dedicated hot circulation loop powered by a Grundfos pump that I had installed at the time of construction. This provided hot water at every location immediately.

Not long after moving in I noticed we were using a lot of propane (very little metered natural gas in these parts). Dual fuel range in the kitchen, gas dryer, gas water heater, and gas at the summer kitchen. I thought for sure there must be a leak somewhere.

After confirming no leaks I started paying attention to the water heater run time. It was practically running all the time due to the temp drop created by the circulation loop. Also the circulation loop added additional pressure (even though the Grundfos pump is low pressure) to the system resulting in two ruptured water heaters in a span of 3 years.

It takes 2 minutes for the hot water to reach the master bathroom with the tankless but I'll take that over the other issues I was having. Using the hot water loop with a tankless is convoluted so I don't use it.

When I feel that my 14 year old has lingered to long in the shower I just go out in the garage and hit the off button.

[kurt]

Makes sense. I did the turn off thing for a while too, but it just pissed people off.

Circulators don't increase pressure; they're not a pump. Well, maybe they do, but only a teeny fraction of psi. How could they cause a water heater to fail?

Also, we've found that insulating water lines is critically important when using a circulator. If they aren't insulated, you end up with what you described; a continuously firing water heater and a lot of expense.

[MPdesign]

The PROOF: First off - goto Amazon and find the nicest most highly rated top 5. Now look further into the ratings and you will see, even on the best rated, that 30-40% of the people HATE them (leave 1-2 ratings).

I do have one and I like it.

Todo:

Make sure that the load does not overload the panel with spikes. I have seen many complaints that they dim the lights if the panel is not large enough and you are talking about 150A of draw. That is substantial.

I did install one in my house and I am happy with it; but there are issues. I could set my old tank at 130 degrees because it was undersized and I knew that I needed to do that in order to be able to take showers. I could not do that, if needed, with the tankless. That is not because it won't let me, it can be set that high; but it it is not a perfect system. It is close to putting out the right temp, but sometimes it gets wonky for a few seconds. That is ok if I have it set on 109 degrees and it goes to 115 for a few seconds; but if it was set way higher - and the temp varied for a few seconds, it could really hurt you. So - if you undersize it, don't plan on turning up the temp to compensate...

I have a small 1400 SF house with 2 showers with low flow heads. Just my wife and I and ours is fine. No more waiting 30 minutes between showers.

I bought a Stiebel Eltron Tempra 20 Plus Electric Tankless Whole House Water Heater, 240 V, 19.2 kW

[Jim Katen]

I'm reviving this discussion because I just finished inspecting 30 units that were all equipped with Stiebel Eltron Tempra 36 water heaters. (36kw fed with three 50-amp breakers.) We were going through the units with 3 inspectors so we had the kitchen sink, dishwasher, washing machine (set on a hot cycle), showers, and sinks all running at once at times. I was amazed at how steady the hot water temperature was. It hardly fluctuated at all. However, it did this with their "Advanced Flow Control" technology. As we piled on fixtures, the water heater simply cut the water flow to maintain an even temperature. So when everything was running, only a trickle of water was coming from each one. I imagine that the residents will quickly learn how far they can push it and still get the shampoo out of their hair. (Any two fixtures at once were fine, but after that, the flow started to choke down.) 

[Les]

how did you write it.  not looking for verbatim, rather how was it reported?  This info is what i learned today; january 18th, 2020.

 

[Marc]

That's about 123,000 btu/hr.  The largest resid gas-fueled tankless heater you'll find here is 199,000 btu/hr, so 123K isn't too bad off.  The service entrances must be large and the electrical grid possessed of abundant capacity for the utility to allow such a thirsty water heater.

Edited January 18, 2020 by Marc

[Mark P]

As the person that started this thread way back in 2014, I can report that we are happy with the water heater and have no regrets in the purchase.  

[Jim Katen]

On 1/18/2020 at 4:38 AM, Les said:

how did you write it.  not looking for verbatim, rather how was it reported?  This info is what i learned today; january 18th, 2020.

 

I didn't write it. Our inspection was on Thursday & Friday and I left for IW first thing Saturday. One of my partners will be writing it this weekend. If I were to write the report, I'd include it as an FYI note: 

These water heaters have an “Advanced Flow Control” feature. It ensures that the hot water temperature doesn’t fluctuate very much (a common problem with many other on-demand water heaters), but it does this by reducing the flow of water when too many fixtures run at once. For instance, if a resident runs the dishwasher and the washing machine (on hot setting) while taking a shower, the shower flow will be much lower than it would be if the other fixtures weren’t running. Consider telling the residents about this at their orientation to avoid complaints after they move in.