This is a great Idea from a Tankless company to use the internal pump to run the fluid through the system.
It's so simple procedure to follow to setup the controller to do the decaling.
Remember you can only do this if your using the middle recirculation port on the unit. It will not work with a cross over valve. Once you get into the descale mode you chose the time you want the pump to run, after the pump will turn off.
With the Navien two filters they do not remove from the housing, so you will have to clean the two filters first reinstall them and proceed to descale the unit.
There is one filter on the cold-water inlet side of the unit (right) and one under the pump, both are exactly the same.
We actually set it for another 20 minutes when the timer went off.
If you have a question, please e mail me at economyplmbg@aolcom
I have started a consulting business because some of your problems are very extensive to Solve, figure out and layout for install. Some people I've spent hours and days helping them.
Please e mail me and I will let you know the cost, it's not very expensive the price is between $100.00 and $150,00

I hope you enjoy the video,
Mike
PLEASE A LICENSED PLUMBER INSTALL, REPAIR AND SERVICE YOUR NAVIEN TANKLESS HEATER. FOLLOW ALL LOCAL AND NATURAL PLUMBING AND GAS CODES AND TO FILE A PERMIT WITH YOU LOCAL BUILDING DEPARTMENT.