Navien - no dedicated return loop

[Joejsullivan]

Hello!
First post in this forum. I'll be having a Navien NPE-240A installed shortly, I do not have a dedicated hot water return, but was wondering if the cold line could be used as the return. My thought was something like an under sink sensor valve.
Does anyone know if the water heater would support this with its built in pump?

Thanks,
Joe