Adjusting a Rinnai water heater

So I got my first gas bill and was just about bowled over at how much it was. I had been putting off looking into how hot the water was coming out of my faucet (it was scalding hot…), but this was the last motivator I needed…

Here’s what my water heater looks like outside my Leopalace.

There are four screws that hold the front panel on. Two on the top and two on the bottom (as pictured, they’re already removed). After that, the guts of the heat looks like this…

You’ll want to look at the lower right corner for a small circuit board, shielded with plastic.

This plastic shield will flip up. Just below some DIP switches and is a small white and black, cross-slotted dial.

20120525-172125.jpg. This is what you’ll need to adjust to turn the temp down. Be careful! There are a lot of wiring components in here. Think of it as a charged up electric kitten. Fun to play with, but can easily stab you with their pointy claws. Clockwise turning will make the heater hotter! CCW is what we’re looking for here to cool down the water. Keep in mind that this dial is extremely sensitive. I was easily overshooting my goal of 120deg F using quarter turns. Try adjusting it a tiny bit at a time and see how it feels after running for a minute. Once it gets comfortable, then there’s your all set! Make sure you put the access panel back on the heater with the screws properly attached.
If you don’t have a thermometer handy and are testing the temp by hand (literally), then know that your hand can stay under 120deg F water for over minute and should only show light signs of steaming.

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