While troubleshooting an issue with my downdraft range vent external blower unit (Kitchenaid KPED829K. ~20 years old. Motor model: ebm-papst R4E310-AL15-10 ) I noticed that the start and run capacitor wiring seemed unusual. I thought I'd post a question to see if there is an explanation that I have overlooked. I am unable to find an official wiring diagram for this model but I did draw a diagram (below) of the actual wiring, and another of what I had expected to see.
The unit seems to run fine and the only issues that I have had with it is that it is a bit slow to get up to full speed and once it is running the kitchen and living room lights (LED) flicker a little or a lot depending on which speed I select using the variable speed switch. I suspect (hope) the flickering lights may mostly be due to a aging variable speed switch which I will soon replace, but I am really not sure.
I tested both the start capacitor (16uF +/- 5% @ 250V) and the run capacitor (7uF +/- 5% @ 250V) and they are both within tolerance.
This is the current wiring setup:
This is what I had expected to see:
I have no idea whether this was installed this way or changed either intentionally or unintentionally during a repair somewhere along the way.
Are these two methods of using a run capacitor equivalent?
Is the run capacitor actually doing anything for the motor?
Is this unsafe in any way?
Is the run capacitor possibly contributing to my flickering lights (I have no idea why that would be but I figured I'd ask)?
UPDATE 1: Confusingly, I found a similar model (KPED892K) that has those same two capacitors (16uF and 7uF) and a manual disconnect button in its part list but the over simplified wiring diagram (figure 3, page 4 of the installation manual) for that model only shows 1 capacitor and uses different coloured wires coming from the motor which sort of indicates an undocumented wiring harness connected to the wires coming from the motor... based on the diagram provided by @Bryan I'm thinking U1 goes to black, U2 goes to white, Z goes to one side of the capacitor, PE goes to ground). ...but no sign of that second capacitor in that diagram.
