Motor Caps...

[SailingHarmonie]

This is one for all you Electrical engineers out there.

In my land based life, I maintained and repaired equipment and as far as I can remember, I never, ever replaced a motor capacitor. Now that I work on boats, I have learned that if an AC motor won't start or won't run the FIRST thing I check is always the capacitor(s). More often than not, that's the issue, the cap is wildly out of label spec.

My question is... is there something about the physical or electrical environment on a boat that causes capacitors to die sooner, then they do in a land-based on-grid system?

I can IMAGINE that that's true, but I am hoping somebody has a more concrete answer. Maybe small gensets have distorted waveforms under high load? Or something?

(Let's exempt non-sine wave inverters from the discussion. I certainly can see the sharp corners of a stepped approximation to a sine wave being tough on a capacitor!)

[Allied39]

Huh, funny. I would have said the opposite. Not negating your experience but I replace plenty of caps. Got to the point that I bought myself a cap tester and actually have spares for some of the more common regular cap fails I have to deal with.

Might be a temp thing, I'm in FL.

I can't imagine marine environment being harder on a cap, shouldn't be exposed to high moisture.....unless poor connections help end a caps life early...but thats not what I have seen.

Early on I used to put electricity alongside voodoo. That was many many years back........but.......?

[Wotname]

FWIW -
I've replaced motor caps on land based motors but never one on a boat based motor. YMMV.

[HeywoodJ]

Every time I replace one on a boat I run down to the local appliance parts place because they have tons in stock at $5 a piece. I’ve replaced plenty in boat generators where they get hot, but same is true on land - furnace blowers, washing machines, lots of small single-phase motors.

[Allied39]

Originally Posted by HeywoodJ

Every time I replace one on a boat I run down to the local appliance parts place because they have tons in stock at $5 a piece. I’ve replaced plenty in boat generators where they get hot, but same is true on land - furnace blowers, washing machines, lots of small single-phase motors.

Ok, I gotta ask, where is it that you are that a $5 cap can be bought?

[SailingHarmonie]

Originally Posted by Allied39

Ok, I gotta ask, where is it that you are that a $5 cap can be bought?

Like... everywhere?

Digikey, Amazon, ebay, every electronic supply house, Grainger, McMaster-Carr.

Yes, there are certainly some that are more expensive, but the typical small motor start cap is dirt cheap. The last one I bought for my AC cooling water pump was $10 for three, so I have two spares.

[HeywoodJ]

I had to go to the expensive place last week because they were the ones that had the 10uF 370V cap in stock, everyplace else had a plethora of 15uF. Could have waited a day and got it for $4.65 at Grainger, but time is money so I paid $10

[Allied39]

Originally Posted by SailingHarmonie

Like... everywhere?

Digikey, Amazon, ebay, every electronic supply house, Grainger, McMaster-Carr.

Yes, there are certainly some that are more expensive, but the typical small motor start cap is dirt cheap. The last one I bought for my AC cooling water pump was $10 for three, so I have two spares.

Huh, like ...uh....we must be using different caps. I can't remember ever buying a $5 cap. Most of mine are dual caps ....60/5 if i remember correctly.

Anyhow, like uh...whatevs.