Rinnai Tankless REU-V2520-EFU. Water isn't as warm as it used to be.

Rinnai Tankless REU-V2520-EFU. (4-6 years old) Water isn't as warm as it used to be. Any ideas what might be causing this? Any suggestions on how to remedy it?

I did notice that the installer used a bathroom controller to control the unit, which limits the temperature to 120 degrees (instead of a master controller that allows temps up to 140 degrees.

Thanks in advance,

Jim

you probably need to have it de-scaled if it is not too late....

have you ever had it done???

it is supposed to be de-scaled at least once a year or it voids your warranty....