jpadie Posted April 30 Share Posted April 30 morning all, my sewage pump is no longer pumping. the motor hums then the protection box conks out. rotor spins freely. no evident short to earth. The pump is a horizontal discharge Semison 450L is this likely to be the cap or if not are there are tests I can do before stripping the pump or more likely buying a new one? thanks justin Link to comment Share on other sites More sharing options...
dpmiller Posted April 30 Share Posted April 30 likely capacitor, yes. 1 Link to comment Share on other sites More sharing options...
ProDave Posted April 30 Share Posted April 30 Yes almost certainly the capacitor, the question is how easy is it to access. Is it a submirsible pump? 1 Link to comment Share on other sites More sharing options...
jpadie Posted April 30 Author Share Posted April 30 thanks both! 5 minutes ago, ProDave said: Yes almost certainly the capacitor, the question is how easy is it to access. Is it a submirsible pump? the pump is submerged in a 7m sewage pit. pumps out to town waste. however the control box is in the basement about 50m away. easily serviceable. which is annoying as I spent yesterday afternoon pumping out the sewage pit and lifting out the pump! the pumps mates with a concreted-in union and getting it to drop back precisely onto the mating pins is not something to do when the household has a swear-box policy. an irony is that this sewage pump went at the same time as a rain water evacuation pump. I serviced that yesterday too - working now but I discovered. that the cistern into which the rain water is pumped has magically sprung a hole into the sump. so the pump is pumping happily but the water is going straight back in the bottom (pic below). quikcrete it is, I think. at least that explains the higher than normal leccy bills. Link to comment Share on other sites More sharing options...
jpadie Posted April 30 Author Share Posted April 30 I measured the cap and it was reading 17uF. The rating was 20uF +/-5%. Which is a bit silly since that's the tolerance of the average meter... I've got a new cap and will keep my fingers crossed that this resolves the issue. Link to comment Share on other sites More sharing options...
jpadie Posted April 30 Author Share Posted April 30 new cap measures good but the issue remains. i've bypassed the thermal cut out switch and recorded that the current maxes out at 19.8A. voltage is ok so far as I can tell (it's hard to measure 50m away from where I'm running the tests!). any advice? feels like a wiring issue rather than a dead pump but i'm open to suggestions! Link to comment Share on other sites More sharing options...
ProDave Posted April 30 Share Posted April 30 If the cap is located remotely, then both windings will be connected back to the control box. I would expect a 3 core cable in that case (but could be 4 core) With the mains disconnected, what is the ohm reading between the two pump wires connected directly from L to N? And what is the ohm reading from N to the pump wire that connects to the capacitor? Link to comment Share on other sites More sharing options...
jpadie Posted April 30 Author Share Posted April 30 I've lifted the pump and brought it in to the basement where the control is. Control is now bypassed with the pump working on just the breaker. It's four cores with the cap bridging black to brown. Sadly no change. Still possible that it's a wiring issue but the cable doesn't have any obvious issues. Despite my previous optimism it now feels more likely that the motor is unhappy. I'm out trying and failing to buy a replacement but will measure the resistance when I get back. Link to comment Share on other sites More sharing options...
ProDave Posted April 30 Share Posted April 30 Can you sketch a wiring diagram and I will give you some ohm readings to take Also post a picture of the pump. Link to comment Share on other sites More sharing options...
jpadie Posted April 30 Author Share Posted April 30 Blue to black = 3.5ohm Blue to brown = 750MOhm Dead windings. Oops. Link to comment Share on other sites More sharing options...
ProDave Posted April 30 Share Posted April 30 Looks like it, less likely to be a cable fault. Could just, if you are licky be a connection inside the pump. Soak it in a bucket of water / bleach for 24 hours then have a go at opening it up? Link to comment Share on other sites More sharing options...
jpadie Posted May 1 Author Share Posted May 1 The pump came to bits surprisingly easily. Difficult to manhandle a 25kg pump whilst being delicate about disassembly. Even with the "foot" removed it's 18kg. In all the many times I've tried to chase faults in motor coils I've never been successful. This time I found the break close to the neutral and was able to create a good solder joint. The wire around the area is blackened and I don't know how compromised it is. The coil resistance is 7Ohms which is twice the other one. I've not tested black to brown (resistance across both coils) but that would be an interesting measurement to have. I will test the pump tomorrow. Fingers crossed it's resurrected. Link to comment Share on other sites More sharing options...
ProDave Posted May 1 Share Posted May 1 Keep us posted. 1 Link to comment Share on other sites More sharing options...
jpadie Posted May 2 Author Share Posted May 2 22 hours ago, ProDave said: Keep us posted. Amazingly it all worked! The rotor was in perfect condition and the oil still clear and non viscous. Not bad for 15 years under water. Hopefully a new lease of life for a few more years 2 Link to comment Share on other sites More sharing options...
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