ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
sparky 5
Recent Posts
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 04/30/17 02:30 PM
201 volt equipment?
by bigpapa. 04/29/17 12:15 AM
Schneider LC1D09
by jraef. 04/28/17 11:05 PM
Electrode boilers question
by annemarie1. 04/27/17 01:40 PM
Why cables look like they do
by LongRunner. 04/26/17 09:36 AM
New in the Gallery:
SE cable question
Popular Topics(Views)
235,042 Are you busy
169,884 Re: Forum
163,072 Need opinion
Who's Online Now
0 registered members (), 66 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#205889 - 04/20/12 01:14 AM Flygt slurry pump  
Merlin  Offline
Joined: Jan 2004
Posts: 170
NW Indiana
I got a call from a good customer of mine today regarding a slurry pump issue. This is a 16 hp 230V single phase submersible pump. It has a control panel with capacitors, circuit breaker, contactor, and a relay. The pump wouldn't start, and tripped the breaker upon trying to start.

I found that the coil on the start capacitor contactor was bad. So, I robbed the contactor from his spare control panel. When I engage the switch to start, the capacitors snap. Why???? When I left it running for about 3 seconds, one start capacitor started boiling.

So, I decided to install spare panel. Now the pump just hums and sometimes snaps at the run capacitors. Why??? It acts like a bad start circuit but all capacitors check out o.k. It is driving me crazy that I can't seem to figure out why this won't work.

Work Gear for Electricians and the Trades

#205890 - 04/20/12 01:38 AM Re: Flygt slurry pump [Re: Merlin]  
LarryC  Offline
Joined: Jul 2004
Posts: 783
Winchester, NH, US
Couple of thoughts.

Overheating start cap sounds like excessive current. Excessive current could be due to fried winding, shorted wiring, or jammed pump.

Have you ohmed out or meggered the motor leads to check for shorts to ground?

Can the pump be pulled to check for mechanical binding?

#205893 - 04/20/12 09:04 AM Re: Flygt slurry pump [Re: Merlin]  
Merlin  Offline
Joined: Jan 2004
Posts: 170
NW Indiana
Yes, the pump was pulled and checked. It was free with no mechanical binding. I did ohm all the leads with no short to ground and phase to phase resistance. The strange thing is that it ran once until the caps started boiling. That is when I decided to switch to the spare identical panel.

#205898 - 04/21/12 10:29 PM Re: Flygt slurry pump [Re: Merlin]  
LarryC  Offline
Joined: Jul 2004
Posts: 783
Winchester, NH, US
Electrolytic caps do not like AC current. When the dielectric fails, they become resistors and the electrolyte usually boils and vents. I suspect that the start cap is failing because the starting circuit is remaining energized. That points to a centrifigal switch not opening up or an insulation failure between the start cap and motor frame or earth.

#205900 - 04/22/12 03:09 AM Re: Flygt slurry pump [Re: Merlin]  
Tesla  Offline
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Requires megging...

Off hand it sure smells like the motor windings are shorted/ fused.


Upon replacement have a 3-phase motor installed with a soft-starting VFD sized to the load -- and then some.

VFDs take line power and rectify it into DC... which is then used as a 'tank' of EM potential to synthesize AC -- with all kinds of solid state physics tricks.

This approach is THE current best practice...

Your conductors can be compromised every step down the hole. Blown capacitors in the starting winding circuit can roast it before the OCPD kicks in.

WRT cap failure: my experience has been that they fail in a fused and shorted state -- for what it's worth.

BTW, I have two 10 hp single phase motors... and they ALWAYS fail at the capacitors first. Fortunately, they are ONLY operated while attended.

You're not so lucky.


#206040 - 05/13/12 09:44 PM Re: Flygt slurry pump [Re: Merlin]  
Merlin  Offline
Joined: Jan 2004
Posts: 170
NW Indiana
The owner took the pump in for repair. As it turns out, the pump had a seal blown and got oil into the windings. $3500 later, the pump is back in operation.

Member Spotlight
Posts: 421
Joined: September 2005
Show All Member Profiles 

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.013s Queries: 15 (0.003s) Memory: 0.7764 MB (Peak: 0.9226 MB) Zlib enabled. Server Time: 2017-05-01 02:28:13 UTC