Proper piping for multiple Navien tankless heaters, First in Last out

I get a lot of questions about this, and I see a lot of improper installations on social media on what a great installation and the hot and cold-water piping is done the wrong way. When you are piping multiple tankless heaters together it is very important to pipe them in as first in last out, if not the unit with the cold water going into it first will do the lion's share of the work.
It is also important to consider the header size of the piping, two unites should have a 1" header size and so on. See Naviens piping diagrams for further installation instructions.
If you follow this video and properly size the water piping, you will have no problem with the unites.
remember to also use the Cascade cables to make the unites talk to each other.
If you have any questions, please E-Mail me at,
[e-mail]
If you're interested in my training class, you can also E-mail me at the above address.
I hope you enjoy the video,
Mike
PLEASE USE A LICENSED PLUMBER TRAINED IN NAVIEN LEVEL THREE TRAINING AND TO FOLLOW ALL LOCAL AND NATIONAL PLUMBING AND GAS CODES. FILE A PERMIT AND OBTAIN AN INSPECTION WITH YOU LOCAL BUILDING DEPARTMENT.

[@PokeBuNz]

I was under the impression that by cascading the systems via the communication cable the units were able to balance hours used by way of the water adjustment valve. Last year I attended the Navien class in New Jersey and I thought we went over this. This may only be for Naviens, and I may be remembering incorrectly, but I just thought I’d ask why you would need to do FILO in that scenario.

[@ThatTanklessGuy]

Without the correct piping the cascade cables won't work correctly. Only the hours will operate.