Rinnai RU98eN recirc help

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Terry Lawson

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Looking for some help with this heater. Plumber installed it outside my new house (slab) but the recirc feature doesn’t seem to work properly. He ran a dedicated 3/4” return line in conditioned (spray foam) attic I have temp set to 120°. It takes farthest tap over 5 min to to reach 100°. I looked at the dip switches and he did not have sw7 on for dedicated recirc. I turned it on and it shows on the controller that recirc is active but there is no difference in the time it takes water to get hot. I can hear something kick on for a few seconds when I activate recirc but then it’s quiet. Is the flame symbol supposed to display during recirc? It only displays when I open a hot tap. Any suggestions? I had him look at it but he is clueless.
 

OldSalt

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Looking for some help with this heater. Plumber installed it outside my new house (slab) but the recirc feature doesn’t seem to work properly. He ran a dedicated 3/4” return line in conditioned (spray foam) attic I have temp set to 120°. It takes farthest tap over 5 min to to reach 100°. I looked at the dip switches and he did not have sw7 on for dedicated recirc. I turned it on and it shows on the controller that recirc is active but there is no difference in the time it takes water to get hot. I can hear something kick on for a few seconds when I activate recirc but then it’s quiet. Is the flame symbol supposed to display during recirc? It only displays when I open a hot tap. Any suggestions? I had him look at it but he is clueless.

Questions:

  1. What kind of water heater (brand/model)? (Oops, I didn't see your title.) Mine, for example, has an internal recirc pump built into the unit, while many others have a separate external pump. Also, water heaters are rated for indoors and outdoors. Did he install the correct water heater? Natural gas, propane, or electric? (I assume you're not in freeze area. If so, why would he install a water heater outside the house?)

  2. How did he install the system, AS A dedicated line system, or via cross over valve (usually, at the last sink in the line)? My plumber did the latter, even though a dedicated recirc line had been installed, which meant that hot water traveled through a 1/2" choke point, and took ten minutes to heat, versus the 1-2 minutes now for the whole house. (Your mileage will vary, depending on how they ran your hot water line. If it's taking a trip around the world, it'll take longer no matter what, to push the hot water through that pipe.

  3. Compare the manufacturer's diagram with your installation, to see if the installation matches the diagram. (Simple step, I know, even a plumber could do it.) Here's a unit similar to mine your unit. Make sure the flow on your system matches the diagram, including where the varoius components are placed on the line. Note several things, that your guy may not have installed: (a) check valve and cut out valve at the end of the return, and at the beginning of the cold water line. Without the first check valve, or if it's clogged or installed backwards, you'll have cold water entering the back of the line, and have suddenly cold showers (or lukewarm water). Without the second, your hot water may come through your cold water faucets. You also need the expansion tank, because the recirc system creates a closed loop, and water in the line needs "expansion relief" while heating. The valves at the base of the unit are flush valves, came already installed on my Rinnai unit, but can be purchased and installed as a separate item or kit. I also added a 50 mesh 1" strainer on my water main (whole house) and a smaller 3/4" strainer just after the hot water line, to keep hot water tank sediment out of my system. There should also be a manufacturers intake filter (it's below the tank on the cold water line). It's easy to unscrew and check or debris (of course, close water lines first). All of these components should be visible at or near your hot water closet.
RUR98E_install_diagram.JPG

4. There are two banks of dip switches, and they are easy to mix up. Double check your switch positions against the manual, and make sure your reading the numbers correctly (mine were right to left, I believe, e.g. 8 - 7 - 6 -5 etc.), and you're setting switches on the correct bank. (Man, with a digital controller, you'd think these manufacturers could advance past 1960's in their technology, and eliminate pulling the cover off and setting those switches.)

5) The activity with your controller sounds suspicious. If your recirc pump fails, as mine did when the intake filter clogged up, and it couldn't pump sufficient water, it'll set an error code on the controller. Mine would start up, make a funny noise (spinning wildly, pumping air) and then stop with an error. Have you seen any error codes? Second, the Rinnai has a scheduler. Manual override starts the pump for two hours, unless I turn it off. Make sure your scheduler is off, or on the hours you want it scheduled. (Manual, is our mode of operating, i.e. turn it on when we shower, then turn it off to save propane.) Also, the recirc pump will end early, if it senses hot water inbound, i.e. the recirc line is sending hot water back to the unit. I think mine cuts out at 107F, but that's from memory during my reading - not certain.

That'll give you a place to start. If you think something's wrong, it likely is. These units will work, and work well, ** IF *** installed correctly. Water quality, as in my case, will also determine how well (and maybe how long) it works.

That'll give you a running start. I'm not a pro, just a homeowner who studied the "science" a lot more than he ever wanted to. I paid a qualified plumber during my house build so that I didn't have to worry about plumbing. I had to redo plumbing 3 or 4 times on this build, and my water heater, maybe six times. I respect plumbers, and don't want to be one. However, use the manual. It works.
 
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