Recirculation Pump on Rinnai RU199en

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DoctorPepper

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So I got my external tankless installed and the water heater out of the attic. So far, so good—very pleased with its performance. However, when I bought the unit (RU199en w/ "Circ-Logic"), I also bought a recirculation pump—the GTK03. I couldn't get that to work; I installed it with a crossover valve under the bathroom sink at the other end of the house. I also installed the wireless module and it connected, but the app kept telling me "Recirculation inactive." So, I jumped on the phone with Rinnai only to find out the GTK03 does not work on this unit in a crossover valve application—it only works with a dedicated recirculation line . . . which my house doesn't have. So, my question is, can I add a dedicated recirculation line? If I'm not mistaken, I would just have to tee-off on the hot water line at that farthest sink and bring it back to the tankless, correct? See attached picture. Isn't that the check-valve at the bottom right? What size line would the dedicated recirculation line need to be? And lastly, is that small braided line needed if there's a dedicated recirculation line? (For some reason I was thinking that's only needed on a crossover application.)

Sorry for the long post . . . I'd appreciate any insight!
tankless02a.png
tankless01a.png
 

John Gayewski

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Yes you can add a 3/4" recirc. Yes all you have to do is tee off under the sink.
 

DoctorPepper

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Yeah if you want it to run all the time.
Thanks again! Your thoughts on the braided line? I have a mental block with that? I can't imagine how that line comes into play with all this? The cooled water from the hot line goes back into the cold supply through the check valve and hot water goes back into the hot lines like normal. So what function does the braided line have?
 

John Gayewski

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I don't know what that is. It looks like something that should be valved off and used when servicing.
 

DoctorPepper

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I don't know what that is. It looks like something that should be valved off and used when servicing.
Just saw a video where the installer explains, "It’s a bypass for when the thermal bypass valve closes. The hot water needs to go somewhere so it’s directed into the cold side of the tankless."

Still confused . . .
 

John Gayewski

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Just saw a video where the installer explains, "It’s a bypass for when the thermal bypass valve closes. The hot water needs to go somewhere so it’s directed into the cold side of the tankless."

Still confused . . .
That makes sense but not much. Most of the pump some pump manufacturers claim starving their pump doesn't hurt them, but I don't see how it couldn't. Also the" thermal bypass" seems like a dumb solution to a silly problem caused by putting in an afterthought of a system.
 

Fitter30

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A cartridge pump can't be run dry the ceramic bearings for the impeller are water lubricated. And a pump with a shaft seal the water cools and lubricants the seal.
 
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