Saturday, January 13, 2007

Rinnai Tankless Water Heater

Above you see pictured my new water heater. I can't remember where I heard this said, but it really isn't a water heater in the traditional sense, the proper description would be a computer that heats water. Please click the photo for a large version if you are interested.

It is made by Rinnai. I sell them at my place of business and I am simply amazed by the performance of this machine.

For those who don't know about these, a little background.

Tankless water heaters are just what their name implies - water heaters without tanks. They heat water as it passes through the unit. I know it is hard to believe but it works like a champ. To understand how, you first have to realize that standard tank water heaters have a 40k btu plate burner on the bottom. This unit modulates from 18k up to 180k btu depending on demand.

There is a rack of burners inside the unit. The computer does many calculations every second measuring incoming water temp, outgoing water temp and flow rate and comes up with how many burners to have on. You can see right off the bat how this saves energy - if you have one sink on, you will more than likely get the minimum burner set. If you have on two showers, the dishwasher and a sink, you will get more burners on. When there is no demand, the unit sits idle. Contrast this to your traditional tank heater. When you go on vacation or are at work, if you don't set your water heater thermostat down (who does this?) you are constantly heating this large container of water to a certain temperature. Then when your water heater ages, and limes up your recovery rate goes way down. More lost energy.

There is no guarantee that a tankless heater won't lime up but the odds are slim. There really isn't much water (any?) stored inside the unit at a high enough temperature for the solids to come out of solution and cake the heater up. If this does happen though, there is a lime sensor inside and it will flash the appropriate error code on the keypad. The simple solution is to valve the unit off with the valves you see below the heater, and run vinegar through it with a pump. Problem solved.

The venting you see on the top is what is called a concentric vent. This means that it is a circle within a circle. Like this:
It takes combustion air from the outer ring and sends to the outside of your house the combustion products through the inside portion. This is great because you aren't using your already heated or air conditioned air inside your house and sending it outside - you are bringing in outside air for combustion.

To boot this thing is very quiet.


As a wholesaler of water heaters, these units are becoming more affordable every day. To the dealer, they are only about $200 more expensive than a single pipe power vented traditional water heater. And the federal government will give the homeowner a $300 tax credit (not a writeoff, a CREDIT) for installing one of these as they are so efficient for the reasons posted above. If it is time for you to replace your water I highly recommend this particular brand as it has many more features than some other brands you will find in home centers.


One problem I had with mine I should share. When it was installed it was discovered that the water pressure entering my house was very high (almost 90 psi) from the city. So when this heater was installed we got a severe case of water hammer. Why? Before, when we turned our faucets off the water had that large tank to slosh back into. With that removed, all of the energy had to be dissipated by the pipes - so they shook and banged. This problem was fixed by installing a water pressure regulator and an expansion tank. You can see the tank in the upper left of the photo.

By the way, please ignore all the cords in the photo, I am re-doing my wireless network setup and have not cleaned up the installation yet. They don't have anything to do with the heater. Also ignore the large pvc pipe you see coming across and down - that is a radon removal unit and also had nothing to do with the heater.

9 comments:

PS Indy From Hobart said...

Dan:

When I was doing research on these, I thought a huge drawback was that even though you got hot water on demand, you are limited to "hot" the water can. Also, another drawback was that if one user in the house was using hot water, the tankless would have problems in supporting hot water if someone else in the house also had to start using hot water.

Do you agree?

Dan from Madison said...

PS I don't understand that first part of the question. As to the second part there used to be a problem with the tankless heaters as far as capacity goes. But now in 99 percent of residences there isn't really an issue, at least with the brand I sell.

mark said...

I just installed a similar tankless, a Bosch Aquastar - with a fair amount of water hammer. It just groans, and is coming from the unit itself (most water hammer comes from metal pipes in the house, I have plastic PEX piping).
Needless to say, I will have to pop in a pressure tank like you mentioned and keep my fingers crossed.
To anyone interested, water hammer and the vibrations in fact do create damage and should be remedied.
Also, as part of your capacity discussion, it is frustrating if you are rinsing your hands, or a spoon, and for such brief events the tankless water heater will not come on. They work best with full flow, and for extended periods. This is because the unit takes a couple of seconds to discover the water is being used, then kicks out the heat, and the result is a delay to the faucet. If the faucet is repeatedly turned on and off, then the hot water is followed by not-hot water (cold) in this sequence.
I have plans to run my hot water through my floors for radiant heat. I plumbed a pump on to a standard electric water heater (tank type) to run with the tankless in a loop.
Each time the tank needs a warm up of water (as in a shower, or running my radiant floor heat) the loop pump starts to pass water thru the tankless heater. This is a very economical use of hot water.
Thanks for the website...
Mark

Anonymous said...

Hello, I am a licensed plumber based in So. California. We install tankless heater on every day basis. Here are my 2 cents....

There are several models of tankless hot water heaters on market these days. The best one is w/o a doubt Rinnai brand. The worst one is Bosh Aqua Star. Ones in between include Noritz, Takagi, Rheem, and Bradford White.

Rinnai tankless water heaters are manufactured in several models and each model differs in hot water output. Yes, you can run 2 or 3 shower heads at the same time with most of the heaters - and get continuous run of hot water at 125 F w/o loosing pressure. Also, Rinnai will activate at smallest water demand, at 0.5 gln per minute. This makes Rinnai the most sensitive to water flow.

Yes, every tankless hot water heater has small delay. But this is something we will have to get used to in order to save energy. Habits are hard to change...

Overall, tankless heaters are great invention and every household should have one.

Best Regards

Anonymous said...

Love my Rinnai in the mountains of Utah. Just a quick post on an error I encountered this weekend, error code was 10 and the vent was clogged as the code suggested. Pulled out a little mouse and all of its home! Might suggest placing wire or mess around the outer ring of the vent!

Anonymous said...

I have had a Rinnai 26 Internal model for 6 years here in Sydney Australia and it has performed brilliantly - easily able to support 2 showers running at the same time and gives the kids great control to choose the temperature they want their showers with a limit of 55C. Efficient, reliable and safe - you won't regret it.

Naoki Dieter said...

Good for you! Purchasing a tankless water heater is the best option. You’ll have an instant and endless supply of hot water. Now, you can save on your energy bills. Just bear in mind: it is best to have an experienced installer do the works for you.

Darryl Iorio said...

I agree with Naoki! With a tankless water heater, you can really enjoy your bath. Before, when I didn’t have my tankless water heater, I always worry about running out of hot water while I’m in the middle of a shower. Well, now, I don’t have to think about that anymore! ;)

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