| Author |
Message |
RJ Long (67.181.211.253)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 24, 2004 - 6:57 pm: | |
My son has a swimming pool tile cleaning business. He has a portable pump that he uses to drain the pool just below the tile line, and may also use the pump to vacuum any debris that remains after he's finished. The pump is a Pentair WhisperFlo model, using a 3/4 hp A.O. Smith energy efficient motor wired for 120 volts, and is approximately two weeks old. (This motor can be wired for either 120 or 240, and is wired properly for 120, per the lable.) All the plumbing is 1-1/2" ID Sch 40 PVC, and the vac hose used is also a 1-1/2". He uses either a 50' or 100' extension cord from the house to the pump, and these are both 10 gauge wire cords. (And no, he's not running it off a Trace inverter - see, there's the bus tie-in. . . LOL)
The problem he's having is after running the pump while he's vacuuming the pool, he has to shut it down for a few minutes while he cleans the filter element. After 10-15 minutes, when he goes to restart the pump, all it does is "hum" for a few seconds, then it clicks off. Checking the voltage at the house yields 120-124 VAC, the end of the extension cord yields 120-124 VAC, the terminals inside the motor yields 120-124 VAC, the house breaker (15 amp) doesn't trip, yet the motor won't restart - it just hums and clicks off - it doesn't turn over and start running. Feeling the side of the motor housing, it feels hot, yet no hotter than when it was actually running. None of the cooling vents are plugged, and the pump impeller spins freely, so there's no binding of the motor shaft.
It's been over 100 degrees during the late afternoon around here, and this is out in the sun on the pool deck, but the regular pool equipment sits out in this same heat and doesn't suffer the same problem. (I know, the regular equipment's wired for 240, but I'm not sure that's relevant to this situation.)
I'm pretty sure it's ambient-air-temperature related, because in the early morning when it's in the low-middle 70's, the pump works fine.
So, the questions are:
~ What's happening?
~ Why's it happening?
~ Suggestions on getting it running reliably and avoiding the same problem.
TIA
RJ
PD4106-2784
Fresno CA
(I'm also going to post this over on the MAK bbs, just to reach a slightly different audience.) |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 24, 2004 - 7:28 pm: | |
My guess is the 100' extension cord. True the voltage measures 120 at the "pump" end but I'm willing to bet if that measurement is taken while the motor is grunting, stuck, trying to start, that it's an entirely different story.
The way induction motors start is that they have a centrifugal switch inside that adds some nasty hefty windings for startup that get switched off immediately as the motor comes up to speed.
Quick way to tell, if the thing won't start, immediately drag it right over to the wall plug and try, sans extension cord. If it starts, end of puzzle. If it doesn't, something's probably wrong with the motor.
In fact it's totally possible that the centrifugal switch is stuck and takes a long time to set itself up for the next start after the motor has warmed up... if the "start" winding isn't engaged and the motor is being asked to start up, all it will do is hum and not move...
just my guesses.... |
CaptBob (141.149.215.151)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 24, 2004 - 7:52 pm: | |
Having a pool and having been through a few motors over the years, I would guess it's a heat expansion problem. If you think the way other motors act when they get overheated and then stopped, sometimes they seize up. A overheated starter motor for example or a car engine, might run while overheated, but there's expansion and distorion when they are shut down. Motors continue to heat for a short period after they are shut off. Most motors have sometype of integral fins to help cool them while they are running. Also, from experience, my pool pump works harder while vacuuming, than just pumping.
Also, most of the pool pump motors are dual voltage, I'm sure you have it wired right...it would be hard not to if you followed the directions.
Could try a heavier duty extension cord. Low voltage/amps will really put a strain on a motor and can cause it to run hot...
CaptBob |
RJ Long (67.181.211.253)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 24, 2004 - 7:55 pm: | |
Thanks for the suggestions, Gary.
BTW, the last time this happened, he was running the pump on a 25-foot, 10-gauge extension cord.
RJ |
two dogs (63.185.81.93)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 24, 2004 - 8:06 pm: | |
water pressure.......drain the line |
john wood (209.137.231.98)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 24, 2004 - 8:48 pm: | |
Starting capacitor! See post at BNO |
Ed Jewett (Kristinsgrandpa) (4.224.189.119)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 24, 2004 - 8:52 pm: | |
Another thing you might check is the thermal cutout. The long extension cord creates a voltage drop which causes the motor to run hot. As long as the motor runs, the vanes keep air flowing and keep it cool enough to run. When you shut it off the heat migrates from the windings and trips the thermal cut out(if it has one) Check for a little red button on the end of the motor, see if you can reset it. Also try a cold pack of some kind to keep it cooler to determine if that is the problem.
Good luck
Ed |
setzer (204.116.25.24)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 25, 2004 - 11:31 am: | |
I agre with Ed, check to see if it has an internal overload, this might be tripping you off. After a few minutes does it come back on? if so this is probaly the problem |
James Maxwell (Jmaxwell) (66.81.47.86)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 25, 2004 - 1:29 pm: | |
What RJ describes is certainly a motor that is going off on thermal overload. However, that is not the problem. It is going into locked rotor on startup (It hums) and the thermal overload is disconnecting it (then clicks and goes off). Being a new motor, it undoubtedly is defective (for any one of a multitude of reasons). I would return it for an exchange. A 3/4 hp motor is not worth messing with when ure losing time and money because of it, and especially when it is new and under warranty. |
DAveD (142.46.199.30)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 26, 2004 - 11:30 am: | |
The motor may have a problem in the starting winding , starting widing switch or with the starting capacitor is so equipped. Rrunning it on the end of a long exgension cord may have ccontributed to a failure if it has occurred .
Dave D |
Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 04, 2004 - 10:31 pm: | |
RJ, it would be real easy for the starting switch to be changing shape slightly or for it to have been adjusted slightly wrong at the factory. If that were the case, temperature could make a difference when you tried to restart it.
Also, if the armature runs too close to the stator, it can cause the motor to bog down when you wouldn't expect it. Temperature might affect the clearance between these parts.
If you use a clamp-on AC current meter to read the current when you try to start the motor, I would think that it would be real easy to see if the starting circuit was engaging.
If it is not, I would expect a modest current. Otherwise, the current might be pretty high, such as considerably above the rating of the circuit breaker.
You can fool the starting circuit by inserting a piece of paper or plastic between the contacts if you can reach them. If you do this when cold, you should get a couple of numbers that will tell you which is the problem.
The air gap issue crops up regularly on electric starters on engines. When the bearings get too worn, starting current climbs drastically with a drop in cranking speed.
Good luck running down which problem you're struggling with.
Tom Caffrey PD4106-2576
Suncatcher |
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