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The Rinnai 2520, a few years later

Permalink 03/31/08 10:36, by Ryan, Categories: Geekery , Tags: , , , , ,

This is an update to a page I wrote a few years back about our then-new water heater, the Rinnai Continuum 2520 instantaneous tank-less gas-fired water heater. All of the cool stuff is on that page, but to summarize:

  • Nearly-infinite supply of hot water
  • Efficient as all heck
  • Compact
Anyway, I've received a number of e-mails over the last few whiles and have always been too much of a lazy-ass to reply. So, here's an omnibus update to answer everyone's questions:

What is the coolest thing about the water heater?

Never having to worry about the supply of hot water. Being able to start the washing machine and the dishwasher before a long, hot shower saves a bunch of time.

What is the most annoying thing about the water heater?

This is a tie:

  1. When you're using short bursts of hot water (e.g. brushing your teeth), you end up with a somewhat variable water temperature out of the tap. This is due to the lag time between the water flow starting and the gas jets firing. It could be mitigated with an external holding tank, but it's not that big of a deal.
  2. If it is particularly cold outside, a sudden "full throttle" hot water demand (e.g. filling the washing machine) will cause a brief but loud vibration sound, not unlike a dying cyborg cow. This seems to be harmless and is most likely caused by thermal expansion of the heat exchanger. That part has a substantial warranty, so I'm not going to worry.

How much did it cost?

A little under $1900, from soup to nuts.

Holy crap! That's a lot.

Yes, it is. However, consider:

  • Almost half of that is labor and miscellaneous parts. It took two plumbers a day to install this, including a new exhaust vent, new gas piping almost all the way to the meter (conveniently located almost as far as possible from the water heater), some amount of new water line, and a wee bit of electrical work. Moving from a floor-mount tank unit to a wall-mount tankless unit is a lot more work than just replacing an old water heater.
  • There was a tax credit which helped out a lot.
  • The unit should last at least 20 years, so this will probably be the last water heater I have to buy before we're all living in space colonies and using centralized hot water robots.
  • Over that 20 year lifespan, there should actually be a savings -- I whipped up a crazy spreadsheet back when I was trying to justify this, and the best I came up with was $392/year to own and operate the best tank heater I could find, vs. $321/year for the Rinnai.

Really, was it worth it?


Where can I get the unit, cheap? I've got my own plumber.

Alas, I don't know where these things come from. My wife is an electrician and I'm a telephone guy, but the plumbers are a completely different union and they won't tell us where they get their stuff. So much for trying to be nice by telling them about Graybar! Just kidding.

Actually, our installer handled everything for us. Sure, I probably could have saved a little bit by buying it online and all that, but I just wanted to write one check and have it all taken care of. Lazy? Sure.

That said, Rinnai's website has a way to find an authorized dealer or distributor near you who might be able to work something out...

How can I get rid of that loud noise when my washing machine starts to fill up?

As mentioned above, the noise sounds like the heat exchanger (or some other parts) rapidly expanding. In my experimentation, I've found that making things less "abrupt" helps with that. For instance, try turning back the valves on your washing machine a ways to decrease the flow rate. (This also helps with ensuring that you don't freeze your spouse if you happen to start a load of laundry while they're in the shower!) Or, run the hot water in the laundry sink a little bit before starting up the washing machine.

I don't believe the noise is harmful, so I've stopped actively trying to avoid it, but it is still a bit annoying.

Is 5.3 gallons per minute enough?

For our application, yes. We have one bathroom, a kitchen w/ dishwasher, and a washing machine, and usually the washing machine, dishwasher, and shower can run at the same time without causing doom. (The valves feeding the washing machine are eased back quite a bit, though... I don't care how long it takes to fill the washing machine, as long as the shower works! :-) Two showers shouldn't be a problem either, I figure.

The 8.5 gpm unit is somewhere around $200-$300 more, and might be a good idea if you have three or more bathrooms. The install shouldn't be any more expensive, although it could be if the plumbing needs to be beefed up to go from 5.3 to 8.5 gpm.

What is your water temperature set at?

110 degrees. I find this results in a solid shower where you just need to modulate the cold water valve a little bit to meet your temperature preferences. The dishwasher takes quite a bit longer to pre-heat at this temperature, but screw it, we use biomass for electricity. Plus, if someone/something does use a lot of hot water suddenly and the showering person adjusts the cold water to compensate, they won't get roasted when things return to normal.

On Chore Day (typically Saturday), I bump it up to 120 degrees after the showers are done to cut down on dishwasher time and to give the bedsheets a nice hot wash to neutralize the cat dander.

What if I use electricity instead of natural gas?

Well, then, I suppose this isn't the unit for you :-) I've always been partial to those little under-sink units which might be just enough to run a shower, but that are small and inexpensive enough that you can just put them where you need them. This would let you run just cold water to your fixtures, cutting down on copper/PEX runs and heat loss. It would also ensure more work for your electrician. But that's just theory.


Anyway, if you have any other questions, let me know and I'll wait another year before answering them!


Comment from: ron [Visitor]
ronYou said that the 2520 was $250.00in 2008.Where did you find it for that price. Can`t find it for anywhere near that price. Even with inflation plus the newer models. A ton more $.
I was told by retailers and wholesalers. Impossible. Looking for a better price .thanks Ron
10/14/10 @ 14:29
Comment from: Ryan [Member] Email
RyanThe $250 price was for a plain old electric water heater... I don't recall the exact price on the Rinnai, since it was about five years ago, but it was somewhere around $1000.
10/17/10 @ 00:33

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