Capacitor on pump control went bloohey

[techman]

Don:

Capacitor life is affected mostly 3 factors. First is voltage. There is a rated voltage for a cap. Exceeding that voltage can cause a breakdown in the dielectric (basically an insulator). This usually results in a catastrophic failure, as the breakdown allows excessively high current, and therefore heat, which causes the internal paste or liquid to build up pressure. There is a small rubber rupture type pressure relief, but if it is a major breakdown the pressure will be beyond the relief's capacity and the end of the cap typically blows out.

Second failure is due to overtemp. Wrong cap rating or too frequent high current (from frequent starts) will cause an overtemp (higher than rated average current). This results in either a catastrophic failure or a gradual degradation as the internal fluids dry out. Eventually there will be a breakdown, or it may act like it is opened and the cap is useless.

The last common failure is due to aging. As the cap ages, the fluids slowly dry out due to evaporation and a tiny bit of gas leakage (the case isn't perfectly gas tight). The aging is accelerated by thermal stress. Again the failure could be catastrophic or just a loss of function.

Your short life failure is most likely just a defective part.

paul

 

[Junkman]

Don..... you have me confused..... Is the wire to the well the one that is 5 feet from the sub panel and is that wire a #10 and that you were being conservative to save on the cost of that wire, or is it the entire length of wire from the well casing to the pump that you were conserving on? The pump drop wire will will not change when you change over to your own electrical service, but only the wire from the panel to the well casing. Usually, there is a electrical box mounted on the side of the well casing where the connections are made from the electrical panel joining up to the wire from the pump. The reason for this, is that you have to break this connection any time that the pump is removed from the well. If you skimped on the drop wire, that is false economy in my opinion. I would see the pump installation as a permanent event, and the wiring to the well casing as temporary? I don't understand why you would change the pump wiring at a later date.

 

[OkeeDon]

That's OK, I confused meself when I wrote it. Here's the sequence. 30A 240V breaker at the main breaker box, just on the other side of the meter, 100A panel, with only a few circuits in it. #10 wire out of the panel, across the attic and down the side of the garage, and about 125' underground, then up about 6' to the subpanel. Total length, 150' give or take a couple. Underground rated wire, in plastic conduit where exposed, but run 24" under ground without conduit.

Subpanel is outdoor rated, mounted on plywood panel, which in turn is mounted on 2 - 4x4 posts. I forget the actual rating of the subpanel, around 50 or 60A, will handle up to 4 full size breakers. Only one breaker in it, now, a 20A 240V. I bought a pre-assembled whip, #10 wire in a plastic flexble conduit with sealed ends, to go from the breaker to the pressure switch, 6' long. Then, a short piece of flexible plastic conduit and #10 wire from the pressure switch to the control panel which houses the staring capacitor, about 30" long.

I planned to stick at least one 20A, 120V breaker in that subpanel, leading to a duplex outlet mounted on the plywood, so I can plug in a power tool, etc., but haven't done it until I can measure available current when the well pump is running. According to the tables I looked at when I installed it, the #10 wire carrying the 30A from the main breaker to the subpanel should have enough juice at the end of 150' to run the well pump. I don't think it will lose 10A in that distance, but even if it did, there should be 20A left to supply my one breaker at the pump. None of the breakers has tripped, and the wires don't get warm. even if the pump has been running for hours.

All the material that came with the subpanel and the control panel indicate that the #10 wire from the nearby breaker in the subpanel is more than adequate. I wouldn't change that; it is permanent. It's the 150' of #10 wire running from the garage where I would have used #8 if it was permanent; that definitely would have given me enough juice at the end of the run to operate a couple of outlets in addition to the pump. As it is, it's marginal, I believe. I'll probably still install the outlets and only use them when the pump isn't running. The most they will be used is for a circular saw of for chargers for battery operated tools -- I always keep spare batteries plugged in.

The failure I had was the paste leaking out of the capacitor; it didn't totally rupture or blow out the end. It's mounted to the cover of the control box panel, and I've placed my hand on the outside of the metal cover when it has been running for at least 30 minutes straight; the capacitor is only 1/8" away on the other side of the cover, and the cover has not been warm.

Excessive starts are unlikely; when the pond level drops, the float in the Hudson float valve drops, and the pump runs continuously until the water level rises enough to push the float closed. The pressure switch is set at 30-50 psi, and when the pond float valve is open, it runs steady at a continuous 35 psi, meaning it never builds up enough pressure to turn the pump off. The pump is supposed to be capable of 25 gpm; the well had a tested capacity of over 60 gpm. The pump feeds a 1-1/2" pvc pipe which runs about 650' to the pond, where it chokes down to a 1" pvc pipe and shutoff valve, because the Hudson float valve has a 1" inlet. The float valve is rated at 65 gpm and 130 psi, so at my theoretical max of 25 gpm, I'm not pushing it. 25 gpm is 1500 gph, or 36,000 gals per day, and according to my rough calculations of area, that's just about exactly what it has been feeding, before the pond reached the level I established for it.

After that, as best as we can tell it runs a couple of hours per day, max, to maintain the level. Florida ponds are water table ponds, without liners or clay sealers, and I expect to lose water every day through seepage back into the ground, unless it rains enough for the water table to reach the pond level naturally. Due to the heat and breeze, I also lose water to evaporation, but I haven't bothered to calculate how much.

I've been doing some other digging around, and I tend to agree with those who said I just got a weak capacitor in the first place. It failed after only about 3 weeks of use.

The proof will be in the pudding -- I didn't change anything after I installed the new capacitor. If it fails again in a relatively short time, I'll start digging around for the cause. If not, then it's pretty likely it was a bad capacitor.

Attached is a picture of the pump and wiring setup, in the background is the garage (the blue building on the right) where the main breaker panel is located, on my daughter's property. The pressure switch is located on the backside of the "tree" that contains the inlet/outlet from the pressure tank; the control box that holds the capacitor is mounted to the top of the well casing.

 

[Junkman]

Most of the amperage draw is only when the pump starts, so I have been told by the pump installers. I have never checked the actual draw of my pump, but I know that it isn't very much. My pump is approximately 300 feet down and the wire from the control box to the well casing is about 100'. If my memory serves me correctly, it is a 12 gauge wire to the well casing and it has been that way for 20+ years with no problems. I believe that it runs on a 20 amp two pole breaker.