So I’ve never taken @Raymond’s Bad Caps class. But I think I have one! Although I’m a bit confused because I can not find anything that remotely seems like it could hold charge and create an electric field. Instead it just looks like a hornets nest.
This starter motor cap is from my garage door opener.
In other news, do folks have any favorite places around town to get replacements? Looks like Amazon has purchasing options.
So, unless there is another cap in there serving as a run cap, I suspect they are pressing a start cap that is designed to be in circuit for a second or so into running the whole time the door is opening or closing. Usually a run rated cap will be physically larger, but if you have space, it might be a smart idea to move up from a start cap to a run cap. Tanner electronic usually has a good selection of run caps, and a smaller selection of start caps.
Thanks, Kevin. Unfortunately I don’t have the exact make/model for my machine (don’t even ask how this is possible), but on-line I found a model (and schematic) that “looked” like mine. I don’t remember seeing a runtime capacitor in the schematic, but I’ll check the physical unit tomorrow.
I do, however, know that the starter capacitor “died” while the unit was running. In fact, it happened at the very end of the garage door closing cycle - not during the motor start-up. So I’m thinking you have it right.
Thanks for the Tanner’s suggestion - didn’t even cross my mind to check there.
The run capacitor would likely be just as large (or larger) as this one. Induction motors won’t run (including start) on single phase without some way to fake a third phase. So run caps are designed to pass the required current (out of phase) for as long as the motor is likely to run. In applications that need more starting torque, they parallel in a starting cap on a timer that increases the third phase current for the first half second or so. Often these are much larger value capacitors, but to keep space requirements down, they don’t build them to be able to dissipate the heat they would generate by being used more than a second or so at a time.
But the bottom line is that if there is a separate run cap, it should be fairly obvious, by being similar in size, and hard wired to the motor, where the start cap should have a timer and relay to disconnect it once the motor spins up. I, strongly suspecting that they just used a start rated cap where they should have used a run cap.
General rule of thumb, plastic black case caps above 50 mfd are usually considered start caps. I have seen 85 mfd run caps, infact I have 1 or two of those. The run caps are usually steel cased.
Start caps stink when they have the smoke let out.
I would suggest local HVAC supply houses for said cap
OK. I can then safely say without looking inside the unit again that there is NOT a runtime cap.
This was the first blown starter cap / hornets nests I’ve seen. Literally my first thoughts when I opened the unit was “Crap, there was a hornets nest in here” followed immediately by “why is there a lightbulb fixture in here? There’s already two on the other side.” (I can laugh at this now, but at the time it was definitely a WTH is going on moment)
I don’t recall any bad smells, but I didn’t actually open the unit up for a few hour later.
At the time, I was just thrilled to learn the garage door spring still works and that it wouldn’t take a herculean effort on my part to open the garage door.