I'm getting some unexpected readings when testing a circuit for my wall mounted AC&heat. I'm on standard USA 120V/240V split-phase/three-wire AC power; the specific circuit is 240V.
here's a picture of my wiring terminal:
When comparing black(phase 1) to red(phase 2) I get the expected 240V. When I compare black or red to ground, I get the expected 120V. When I compare red or black to white(neutral) the value jumps around and does not settle within any recognizable/readable range. It also jumps around the same way when comparing neutral to ground. Why is this? I am using a basic digital multimeter(Mastech MS8268).
I want to wire in some extra fans with a fan speed controller, for a filter-box I am building. The controller is only rated to 120V. So I was thinking I would wire it between phase 1 and neutral, although after getting my readings, I am concerned. Is there a problem? Do I need to use a different circuit? I assume the unit was installed correctly, and it has been running fine, although it gets clogged with dust...