Domoticz

I'm working on a dzVents script that calculates my energy costs. But I'm running into a problem with negative numbers. Is it correct that a custom sensor can't handle negative numbers?

A custom sensor can handle negative values.
Try it manually with a api call
/json.htm?type=command&param=udevice&idx=IDX&nvalue=0&svalue=VALUE

Already explained to you on github
https://github.com/domoticz/domoticz/issues/5544
Create a COUNTER device for this. They can now handle negative values.
With the edit button they can be configured. Choose CUSTOM and then defined units, label etc.

Thank you. The problem was due to something else indeed.