Irrigation Pump Problem - Need Help

[jobondur]

This is for a well pump that runs my sprinklers and a couple of outside faucets but I figured why not ask this forum since the responses are always fast and thorough and for the most part a pump is a pump - right??

I have a Grundfos JP-7 pump hooked to a AO Smith 3/4 hp single phase motor wired for 220 (model C48K2DB11A16). When I went to start it up this spring it just hummed so I replaced the capacitor but that didn't fix it. I then pulled the motor from the pump and turned the impeller a couple of times by hand to break it free. That seemed to work as it then started but after a month or so it started making a sound like it had bad bearings. So I disassembled the motor and the front bearing was shot. I replaced both bearings with Timken bearings and replaced the pump seal with one from Amazon. I reinstalled everything and it just hummed, didn't run. I pulled it off the pump housing and checked everything and then bench tested the motor. The motor runs fine not connected to the impeller but when I put the impeller back on it seems to tighten down so much that it compresses the pump seal and ruins the seal. The order of assembly for this on the pump end is as follows:

1. Motor with pump mounting plate installed
2. Sling ring
3. Seal plate
4. Shaft seal (white part)
5. Shaft seal (carbon ring - with carbon ring mating with white part)
6. Large washer
7. Impeller (no screw or nut securing back of impeller)
8. Pump housing gasket
9. Main body of pump housing and connector ring

I haven't messed with the pump housing at all and I have primed the pump as required. I pulled everything back apart and ran it with the impeller installed without tightening it much and ran it not connected to the pump housing so I could observe it, knowing that I would likely ruin the seal due to lack of water/cooling. When I did that, I could see the impeller tighten down on the shaft and then the seal started smoking and cracked from too much friction. I checked for shaft runout and got at max 0.001" of deviation when turning it by hand and measuring with a dial indicator. The only thing I know of that is wrong with the motor is I did break off a small section of one of the fins of the fan. That being said, the motor runs very smooth when not connected to the impeller. The only part I'm not 100% sure of is the placement of the large washer (#6) but I'm about 95% sure of that because its the only place it really fits and it had wear marks that line up with putting it where I have it, so pretty sure it's correct. The motor turns easily by hand with the impeller not cranked down on the shaft. Once it runs for a bit, the shaft will not turn easily by hand as the impeller tightens down to the point it compresses the shaft seal too much and binds against the shaft (at least that's my theory).

I've tried 3 different capacitors and 2 different shaft seals (same specs, just different mfrs) with no luck. What's going on? Any advice/troubleshooting tips are appreciated.

 

[Texas Splash]

Good morning. Not sure how much we can do for you, but we'll try. We have a lot of experience on the forum. Since you posted this last Weds, did you get it resolved?