Navien NPE-240A - Temperature Fluctuations

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Manlius, NY
Just chiming in that I have this same issue at exactly 1 GPM but only after it comes down from a higher flow (like the tub spout is going at 4 GPM before pulling the shower diverter). I keep my set point at 140F and have thermostatic valves at each point of use, but get to have very hot water for dishes and laundry. This makes my shower blend about 50/50 hot to cold.

I watched it tonight and the unit ends up in a loop where the temp is too high (from the flow decreasing after high throttle), so it throttles down. But then before it gets back to the set point the throttle comes back up too fast to meet it so the temp starts going up and it starts the internal recirc pump to avoid scalding. Rinse and repeat, so to say.

It does NOT do this if going directly to 1 GPM from off, and it does NOT do this at other low flow rates coming down from high (like to 0.8 or 1.2). I’m pretty sure this is a control system error, and unless they start shipping firmware updates, best to set your temp to avoid 1 GPM during your shower.
Hey, wait a minute.

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