I am new to this forum. I am switching from electric appliances to gas, and I am wondering if the tankless water heaters from Rinnai really work well? Thanks.
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Welcome. You are in luck, this is a frequent topic in Breaktime. If you search the archives there you'll find lots to read already.
Tankless heaters tend to be quirky (they need a minimum flow to operate, so you have to turn faucets on full to get them to kick on). They never run out of hot water, but are limited in the number of outlets they can service simultaneously. Their energy savings is modest, and given their high purchase cost they can take well over ten years to pay back. Depending on your circumstances they may not pay back before they wear out.
Tankless heaters tend to be quirky (they need a minimum flow to operate, so you have to turn faucets on full to get them to kick on). They never run out of hot water, but are limited in the number of outlets they can service simultaneously. Their energy savings is modest, and given their high purchase cost they can take well over ten years to pay back. Depending on your circumstances they may not pay back before they wear out.
One of the points of the tankless heaters is that they really don't wear out. The warrenty on the heat exchanger on my Aquastar is 20 years. Will I go thru two regular water heaters in that time?? Probably. And if the heat exchanger were to run out it is a replacable part and I would not have to buy a whole new heater.
Daniel Neuman
Oakland CA
Crazy Home Owner
I only owned one tankless heater, so my experience is limited, but the claim that they never really wear out is weak.
I purchased a heater new, installed by the dealer. Within a year or so it failed. It took 12 days (during which I had no hot water) to get a new control valve. A month afterwards it failed again. This time the cost of replacing the part (a thermocouple if I remember correctly) was more than the cost of a new water heater, so I scrapped the whole thing.
In my opinion as an engineer, a common way the heat exchanger could fail is a build up of hardness minerals (calcium and magnesium carbonates) on the walls of the tubes. This occurs because these minerals are inversely soluble with temperature. Such a buildup would reduce the heat transfer from the flame to the water, causing the metal temperature to rise and the efficiency to drop. Over time this could cause failure of the heat exchanger or high operating cost. I would not surprise me if the warranty, which may not even cover the moving parts of the control system likely to wear out, may exclude coverage for the heat exchanger due to mineral buildup.
Since my unit was not reliable and wasn't saving me money after I tracked actual gas usage, I would not use one again in my home. I know from real use that the claimed savings are overblown.
Wow sounds like maybe you got a lemon? I have a Bosch Aquastar 125S model. We have had one now for 3+ years and we have never had a problem with it.
With the heat exchangers there is a recommendation to back flush it every once in a while with some sort of deposit dissolving material. I just checked the warranty and its 15yrs on the heat exchanger and only 2 years on everything else. Anything goes wrong in those time frames and they will replace it free of charge.
Though if you are saying that they are not as common as regular water heaters and thus replacement parts are not as easy to find then yes I would agree with that.
Daniel Neuman
Oakland CA
Crazy Home Owner
I am about to take out my old Junkers (same as Aquastar in the US) heater, and will take a look in the heat exchanger to see if there is any build up of crud. Since I have extremely hard water, if there is a build up issue, I will have it.
However, I do not think that that is the main failure mechanism. The heater exchange pipe is fairly narrow resulting in a high speed water flow precisely to combat the build up of calcium deposits.
The previous owners of my house did replace the heat exchanger, for what I think is most likely a more common failure mode. They had it hooked up in series with a solar heater (simple circulation type with a big tank on the roof) When that failed, it sent large quantities of sediment into the heat exchanger which totally blocked the water passages. (I added a filter! very cheap insurance!)
I have no idea why the safety switch didn't shut the system down.
I am replacing it now because the gas regulator has become flaky, and every so often the unit starts up with a big bang. Since the cost of the regulator is near 1/4 the cost of a new system, and the heater is 18 years old, and I am in the middle of a small construction project in that part of the house... I just picked up a nice new Ferroli heater.
Incidentally, my heater has separate circuits for hot (domestic) water and radiators. Not sure if they sell these in the US. Yisrael
Prof.
We recently installed one in our home. (Rinnai model 2532) The system works fine with one exception. The hot water arrives to the location of the demand at what appears to be a longer time than with our old electric unit. Once you get accustomed to that there are no negative issues. We like it.
Tom
Working for nothing is not getting any cheaper.
Professor - Make sure that your gas/fuel supply system is adequate for the flow demands. When I checked into installing a similar Takagi water heater for my 2 bathroom house, I was told that the natural gas supply piping to the heater had to be at least 1". You're putting in a gas system in for the first time I assume, so I expect that whoever designs it will specify a correctly sized meter and gas supply lines.
Tejonista in Orange County, California
Aloha Prof,
I don't know about the Rinnai brand, but we have a Paloma that works great.
They are also called "on demand" water heaters so if you don't demand any hot water, you don't get any. We took out any water limiting devices on the shower head and turn the hot water all the way on and then add in cold water to get the temperature we want. We also have a huge tub to fill so having the "tankless" water heater is great. We can fill the tub and shower at the same time and never run out of hot water. It is a larger sized Paloma, though, so that would be another factor into how much hot water we can get at the same time.
We have a gas water heater because we live on solar power so an electric water heater isn't a consideration for us. We also don't have a gas line and the Paloma is running from 5 gallon propane tanks. We didn't want to keep a tank of hot water heated all the time, so that's why we chose the "tankless" water heater. Everyone's situation is different so not everyone will want the same water heaters. Get whatever works best for you.
A hui hou,
Cathy
Aloha, sounds like you are in Hawaii -- I'm very interested in talking to you. I have to decide within the next week to install at Takaki or regular gass heater to fuel three showers. There are just two of us but we have frequent visitors - we are looking at the Takaki junior but can switch out to a traditional water heater if it doesn't work. Can you tell what type you purchased and from where? Also do you have problems with the temp fluctuating during your showerer (a frequent complaint according to our plumber.)
Aka hele,
I'm sure there are different variations to the many brand names and models of tankless water heaters. I installed an Aquqstar in our remodel 5 years ago. I swear buy it. It didn't seem to work that well at first but signifigantly improved over just a few months. I've had no problems with it at all. I'm useing propane. I also located it near the bath, kitchen,and laundry and it doesn't seem to take very long to get hot water. Best of luck with your choice!!
I purchased a Bosch Aquastar 125B tankless heater a year and a half ago and I'm very happy with it, although if I had to do it over again I'd buy a bigger model. This model heats one application at a time, which I thought would be adequate for a one-person home. It didn't occur to me that I might want to do laundry while I washed the dishes or took a shower! While it's true that the cost savings for fuel (gas) may be negligible, the main reason I got a tankless was the fact that there's no chance of a major leak. Anyone who's lived through a tank "blowout" knows how miserable that is. I had a tank heater leak in the middle of the night years ago and it soaked the carpet in two nearby rooms. The tankless gives me peace of mind, as well as more space in my laundry room.