A smokin' hot motor

[Coppersmith]

This is what a breaker does after it has tripped, as opposed to being turned off. There are three positions of a breaker handle, not just two; On, Off and Tripped. The "Tripped" position of a Q0 breaker is a mid-point and in order to reset it, you must push is all the way to the full Off position first and make it latch, only then you can snap it back on.

The breaker was in the on position. It had not tripped. From the on position, I think it should "snap" off even under load.

This thing will cost him like dollar an hour to run it even if you get the motor running within the rated load.

I don't think this is an issue. The main house is the size of a hotel. I can fit my entire house in the lobby area. On the grounds behind the main house are two "guest houses" both over 2000 sq ft each with a pool. Between the main house and the guest houses is an artificial river running between two artificial lakes. The waterfall sits on an artificial mountain at one of the lakes. There is a cave inside the mountain so you can stand behind the waterfall. It looks similar to the "grotto" area at the Playboy mansion (from what I've seen on TV).

The OP did not confirm it is a centrifugal pump. A positive displacement pump such as a piston pump will overload severely with obstruction on the output side.

It's a centrifugal pump. From the pump to the output is about 15 ft in height. I can't remember the pipe size.

 

[kwired]

Were they ever able to run the pump for more then a few minutes?

Any kind of valve on the piping that will allow flow adjustment has probably been opened for more flow - but is now more then the motor can deliver without overloading.

 

[gadfly56]

Pump hp = head (ft) x gpm / (eff x 3957)

look at a pump curve
as head decreases flow increases (as does hp)
so too low head will ol the motor for some pumps

http://cdn.qleapahead.com/zoeller-63/132945.pdf?P185

Your pump curve doesn't say that. Look at the performance curve on the second page of your link. Notice that the HP curve is really pretty flat over the entire operating range. The HP peaks at about 34 feet of head and then decreases (slightly) as you lower the head and increase the flow. Check all the curves in fact; none of them show runaway motor loads as the head drops and flow increases. QED.

 

[Ingenieur]

---

Your pump curve doesn't say that. Look at the performance curve on the second page of your link. Notice that the HP curve is really pretty flat over the entire operating range. The HP peaks at about 34 feet of head and then decreases (slightly) as you lower the head and increase the flow. Check all the curves in fact; none of them show runaway motor loads as the head drops and flow increases. QED.

inaccurate

some show 1.2 HP draw on a 3/4 HP pump

in fact first curve 1/3 HP motor shows 0.5-0.6 HP at low head
the second a 1/2 HP drawing 0.8 HP

 

[GeorgeB]

It does not matter whether you restrict the input or the output, the physics of the moving (or not moving) water is the same.

From a power consumption standpoint, I 100% agree. While I'm in the positive displacement pump side of things, even with impeller pumps, restricting the inlet isn't good as it contributes to cavitation.

 

[gadfly56]

---

inaccurate

some show 1.2 HP draw on a 3/4 HP pump

in fact first curve 1/3 HP motor shows 0.5-0.6 HP at low head
the second a 1/2 HP drawing 0.8 HP

Something is screwy with those curves. Many of them show the motor pulling above it's listed HP over nearly the entire operating range, the second curve being a prime example.

 

[gadfly56]

OK, I checked with the manufacturer, and the motors used on those pumps have service factors from 1.5 to 1.95.

 

[Coppersmith]

Were they ever able to run the pump for more then a few minutes?

Any kind of valve on the piping that will allow flow adjustment has probably been opened for more flow - but is now more then the motor can deliver without overloading.

I don't remember ever seeing it run. I've been there twice before.

I did see a valve with a straight arm. It was on the input side I believe. It was fully open.

 

[Jraef]

...
I did see a valve with a straight arm. It was on the input side I believe. It was fully open.

Bingo. Most likely when it was originally designed, that valve was not supposed to be fully open, It was there to make fine adjustments based on conditions. But someone came along afterward and opened it, now the pump is overloading the motor.

Get an ammeter and watch the motor current as you throttle back that valve. When the motor current equals the motor FLA, you're done. If the end user doesn't like how the waterfall looks, then tell them they need a bigger motor.

Then remove the handle off of that valve and put a sign on it saying that adjusting this valve is punishable by termination of employment.

 

[Coppersmith]

Bingo. Most likely when it was originally designed, that valve was not supposed to be fully open, It was there to make fine adjustments based on conditions. But someone came along afterward and opened it, now the pump is overloading the motor.

Get an ammeter and watch the motor current as you throttle back that valve. When the motor current equals the motor FLA, you're done. If the end user doesn't like how the waterfall looks, then tell them they need a bigger motor.

Then remove the handle off of that valve and put a sign on it saying that adjusting this valve is punishable by termination of employment.

And based on what I read here, we could start with the valve fully closed and there would be no danger of damaging the motor, correct?

 

[JFletcher]

And based on what I read here, we could start with the valve fully closed and there would be no danger of damaging the motor, correct?

Starting a centrifugal pump with the discharge valve closed wont damage it or the motor immediately, no. The motor could still be overloaded at zero flow, but that is the lowest current it will draw.

 

[GoldDigger]

Starting a centrifugal pump with the discharge valve closed wont damage it or the motor immediately, no. The motor could still be overloaded at zero flow, but that is the lowest current it will draw.

But watch out for some pumps (including the classic submersible pump at the bottom of a well) that rely on water flow for cooling and will burn out if run dry OR possibly even without any water flow for any length of time.

 

[JFletcher]

But watch out for some pumps (including the classic submersible pump at the bottom of a well) that rely on water flow for cooling and will burn out if run dry OR possibly even without any water flow for any length of time.

Yep. Seen a few sump pumps with stuck floats blow up from running dry. Also saw a grit tank pump seize up from running with a shut discharge valve. It had been running 16+ hours, the energy put into the water in the volute had caused it to boil.

Positive displacement pumps blow piping apart pretty quickly with a shut discharge valve. and at a WWTP, that's always a huge, nasty mess.

 

[kwired]

And based on what I read here, we could start with the valve fully closed and there would be no danger of damaging the motor, correct?

Motor no. Pump only if you leave it fully closed. All the energy delivered to water in the pump doesn't have much of anywhere to go, things start to heat up. No water at all may take out pump seals pretty quickly.

 

[Sahib]

With pump suction opening above water level and discharge pipe about 15 feet high, I do not think pump motor over load due to excessive water flow. Meggar the motor. Check input voltage to motor.

 

[Sahib]

Or there is a motor and pump mismatch: smaller motor driving a bigger pump. Check it also.

 

[kwired]

With pump suction opening above water level and discharge pipe about 15 feet high, I do not think pump motor over load due to excessive water flow. Meggar the motor. Check input voltage to motor.

Input voltage is a possibility - but I'm thinking that would have the most impact on it only running a short time before tripping breaker would be if it were supplied with 120 instead of 240. If it were rather severe voltage drop like 240 dropping to around 200 volts, I doubt it draws enough to trip breaker, especially the 70 amp breaker.

Many 240 volt motors will run on 120, but just won't have enough torque to drive a full load, in a single phase motor that may result in low enough RPM the start capacitors are never taken out of the circuit, which will increase current, and can take out start winding in pretty short time as well.

 

[wbwill]

smokin hot motor wheres the original

smokin hot motor wheres the original

Megger is good, never trust even a new motor, What is the voltage at the motor open circuit? How long a run of wire? Dual element fuses are generally better protection for an Electric Motor, than only a circuit breaker. Once up to code if allowable a fuseable disconnect could be added. Id find out the voltage at the motor, clamp it, recheck the motor connections.

Its a JP frame motor, designed to have impeller on the motor shaft, close coupled with with normally some sort of standard mechanical seal. Often flange mounts, this one useable on 208 volts.

Wheres the first motor, likely the same [because of frame size ] but ID check why did the first motor fail? Repaired rewound motors for too many decades, motor comes in, we try to provide our best root cause of failure, half the time especially single phase, first motor burns up, due to WHATEVER, WHATEVER IS NEVER CORRECTED, repair or replace motor, second motor burns up like the first motor, warranty evaluation, half the time either both start and run windings are burned out, or the start winding is burned out, mechanical seal could be bound up, when everything is wired correctly, sized correctly may have to go to volcano mfg to find out the scoop, if it needs a 10 HP [unlikely not a lot of 10 HP single phase out there, 7.5 at standard eff costs $30 a minute to run ] but if it does need more go then maybe the 6 wire will be too small, depending on how far, etc,

When and if you can find out what the thing needs, a much better way to go at that HP is a single to three phase VFD and a three phase jp frame motor, the VFD has a starter, has overload protection, and speed can be adjusted, a VFD and three phase motor can be bought for the price or real close of one single phase motor,

 

[Ingenieur]

Need
measuremens
running voltage
amps
we have pf and eff
calc hp

then plot on the pump curve

 

[kwired]

[unlikely not a lot of 10 HP single phase out there, 7.5 at standard eff costs $30 a minute to run ]

You must have outrageous utility bills, I figured 7.5 hp even if only 80% efficiency would only cost me maybe around 70 cents an hour to run.