You need to edit that file. As you are in the Americas, I suggest you change
const byte Vrms_USA = 110;
to whatever value you want to use for your apparent power calculation, and you need to set
boolean USA = TRUE;
(it is false by default).
Provided you do not have the a.c. adapter connected when you power up your emonPi, that should calculate apparent power at the voltage you set.
DO NOT now do the automatic update of your emonCMS saying it is an “emonPi” - if you do, the change you have made will be overwritten by the new release of the ATMega sketch. You can update it if you say it is an “emonBase” - the update of the ATMega will fail and your sketch will not be overwritten.
The emonPi sketch should detect if the AC:AC adapter is present at start up, once that test is done once at start up it will not change by unplugging the AC:AC or pulling it to ground.
Are you restarting/reseting the ATmega328 after disconnecting the AC:AC?
If that isn’t working then maybe your emonpi board has an issue that is causing the sketch to detect an AC:AC signal even when one is not connected.
This should cause a fixed Vrms value to be used. 110v if use=true and 230v otherwise. The USA=true can be set via the serial connection by sending 2p
You can of course set the USA value to 115v in the sketch as Robert says and you can also set it to default to USA too, alternatively if you are using the emonSD and want to keep everything stock(ish) so you can use the update routine, you could make the adjustments from 110v to 115v externally to the sketch eg in emonhub, adjust the scales for Vrms, power1, power2 and power1pluspower2 by multiplying them by 1.045 _115/110) or in emoncms if you are not using emonhub.