Navien 240A compatible with NR-21DU?

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John DC

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Kansas City

I have an NR240A which was installed in 2020. I was able to add external recirc and an external pump without a problem using the Parameter list and the dip switches. I purchased an NR-21DU to add a timer to my recircluation.

I cannot get it to communicate properly with the 240A. It allows me to change the temperature, but is 20 degrees high (120 on the 240A shows 140 on the NR-21). I can't get recirc to work at all. I have tried connecting it while the heater is on, while it's off, and even while power is disconnected.

Any parameter settings I am missing?
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