Pump start-up problem

My pump (2.5HP Hayward) has a problem - when it kicks on for the first time each day,
it makes a horribly loud buzzing noise, which goes on for about 5 seconds,
then it shuts itself off (the water does not flow while it is buzzing). Maybe
30 seconds later, it tries again, buzzes loudly, then shuts itself off again.
The pump basket is still full of water when this happens (as it's supposed to be).
If I open the pump basket and let some air in, then close it again and
start the pump, it will start up and re-prime, and work fine (though it does make
the loud buzzing sound for a second when it starts). But then the
next day, it does the same thing. You'd think it'd have an easier time when
the pump is primed, but the opposite seems to be the case.

(The pump is <1 year old.)

Any ideas?

Thanks.

My first guess would be that the wiring is too small. Allowing air in lets the motor get up to speed without a load, then it can handle the load. Motor startup currents can be huge, and to do it under load may be dropping the voltage so much that the motor can't start.

Sharkey,
Welcome to the forum.
This is puzzling. The loud buzzing and shutoff is an indication of a shorted starting capacitor. Some education....there are two windings in these motors. A running winding (RW) and a starting winding (SW). I hate typing. The SW has a capacitor in series with it, and also a centrifugal switch. Once up to speed the switch cuts out the starting winding. The SW is a low resistance winding compared to the RW. The capacitor is used to create a phase difference to start and determine the direction of rotation. If the capacitor or switch are open then the motor won't start and you'll hear a low humming sound. Eventually the thermal cutout will kick in. If the capacitor is shorted then you'll hear the loud hum/buzz and the thermal cutout will kick in quicker...like the 5 seconds you mention. Capacitors are cheap and do fail. What is puzzling is you stated it starts when you dump the water by opening the basket.
Some questions:
--I assume this is a new problem since you said the pump is < 1 year old?
--Did it start happening after the Winter? Maybe the cold caused a problem.
--Is the pump still under warranty?

I'm wondering about a series of coincidences here. Try opening the basket first time each day and see if it starts, before letting it try on its own normally. Quite possibly the thing heats up, trips the thermal cutout, then after a couple tries when you open the basket it starts. Who knows. I doubt the wiring is an issue because you said it does run eventually, the thermal cutout trips, and if the wiring gauge was too small it would at least start and run and maybe cycle between the start and run cycles.
Best I can do for now.
Al


Edit: Thinking more about this...a 2.5 HP motor is pretty big. You could be hearing just the hum of the running winding. Capacitors fail open or shorted, not intermittantly. Best guess at this time is crummy centrifugal switch contacts. Starter winding isn't in the circuit and you get no rotation. Something else to try is when it doesn't start, give the back end of the motor a couple sharp whacks with a short 2x4 (instead of a hammer) with power on....not enough to dent anything. Switch is located in the back end. Sometimes the shock will be enough to jar the contacts and start the thing. If that's the case, fix is simple. Clean the contacts. Tell you how if we get that far.
Got a model number of the pump and motor?
Al

(ajs-1)

Thanks for the reply.

Yes, this is a new problem. I started noticing the loud buzz at start-up a couple
weeks ago, but I don't know when it started this on-off procedure (I'm not
usually home when it comes on). More than likely, it's been doing that for
a while, and it just eventually gets started after a few tries.

I believe the wiring is fine, since everything worked fine for the first 9 months.

Yes, it seemed to start after Winter ('though it is Texas, so it doesn't get that cold!).

Yes, it's under warranty - I've already called it in.

I thought of the starting cap, too, but like you, I'm having a hard time understanding
its failure mode, since it will start if it's unprimed. The only thing I can think
of that makes sense is if the cap has partially failed, like it's a multi-layer cap
and some of the internal layers have opened, reducing its capacitance. I doubt
the cap is multi-layer, though - if it's electrolytic, though, maybe it's somehow
dried out. I don't know, I guess we could speculate forever.

I like the contact idea, though - it definitely seems like nothing is rotating
when the buzzing is going on. I'll try whacking it next time, if I get a chance
before the techs come out. What would cause bad contacts in less than a
year, though?

I hope you don't feel like I've wasted your time, since it's under warranty. I
just like to understand what's going on, so that when it's NOT under warranty,
I can fix it myself. (Plus, I'm an engineer, and you know how they are.)

Thanks again,

Steve

Steve,
No wasted time at all. I like these challenges too. It's a non-polarized electrolytic and when they fail it's either open or shorted. The only ones I've ever found failing intermittantly are low current ones. Like in amplifiers etc. As for the contacts, they are usually silver and all it takes is one bad lump of pitted stuff to make a bad connection. Have to admit though, one year isn't that long but as I said, only takes one lump of goop on the contact. Back to the cap...not sure but I'm betting on the high current ones used for motor start, the layers are basically in parallel. That is the conductive material is wound but is connected along the long edge rather than at the short edge. Not sure I said that right but you know what I mean. Haven't taken one apart for a long long time...advertising my age.
Keep us posted on the progress.
Al

"Plus, I'm an engineer and you know how they are."

YEP!!!

Watermom

Well, they finally made it out two days ago, and when I came home,
I had a new motor. Unfortunately, they didn't try and diagnose the
problem, they just replaced it. Oh well - just an infant failure, I guess.

Interesting thing, though - the new motor is a two-speed. Right now,
it's not wired up for two-speed operation, but after surfing around a bit,
I've found out how to do it, so I think I'll just have to try it out. I do
have a question about two-speed motors, though, but I'll start a new
thread for that...

Thanks again,

Steve

Wow, nice they gave you a 2 speed. Significant cost difference between single and two. Whoever did this I'd write them a note of thanks....if you don't get a bill. Good to hear a story with a happy ending. And yes, infant mortality is a well known engineering term.
Al