Check valve at the well's pit,?

[Rreeuuvveenn]

Dear Forum,

our 520 feet well pump, blew a fuse, and went from 6 amp current, to 40 amp!!!!

Grundfos pump, 1.5 hp, 1.25 secdu. 120 pipe,ss fittings,

Motor's resistance checks good,

20 years old check valve at the well head pit( can not upload a 138k picture),

Could the check valve be a blocker for the pump,????????

I do hope,

thanks in advance,

reuven

 

[Reach4]

It could be a failed control box.

I don't think this problem could be that check valve.

 

[Sponsor]

 

[Boycedrilling]

A Grundfos MS402 1 1/2 hp motor pulls 10.7 amps at full load, service factor amps are 11.6. Locked rotor amps are 58.0. Your resistance between black and yellow wires should be 1.9 - 2.3. Red to yellow 7.8 - 9.6.

A pump running at dead head (blocked check valve) will draw less amps not more.

As a first step you could replace the control box. But you’d better plan on replacing the pump.

 

[Rreeuuvveenn]

A Grundfos MS402 1 1/2 hp motor pulls 10.7 amps at full load, service factor amps are 11.6. Locked rotor amps are 58.0. Your resistance between black and yellow wires should be 1.9 - 2.3. Red to yellow 7.8 - 9.6.

A pump running at dead head (blocked check valve) will draw less amps not more.

As a first step you could replace the control box. But you’d better plan on replacing the pump.

thanks for your kind replies,
I did messier motor resistance, all look fine,( three phase 208 volt)

control box, matches clamp on amp. meter,

Do not understand,

Block output of the pump, will cause the pump to work less???!!!

Or to build up more pressure, to over come a blocked pipe,(stuck check valve),

 

[Reach4]

thanks for your kind replies,
I did messier motor resistance, all look fine,( three phase 208 volt)

control box, matches clamp on amp. meter,

You could have mentioned 3-phase earlier.

Same current in each phase (before the breaker trips)?

Block output of the pump, will cause the pump to work less???!!!

Sounds incredible when you first hear that, doesn't it.

 

[Rreeuuvveenn]

hi
normal amprage was 6-7 amp, cut off the pump, at 4.5 amp.

clamp on amp showed 40 amp, on one phase, when we shut it off,

might try in two days again, ( till we get the budget to rig the pump out),

might try to bypass the upper check valve,

control box is motor saver 777-LR,

thanks

 

[Boycedrilling]

Yes 3 phase 208 volts makes a big difference. Kind of important to know that. Now your full load amps are 6.6. Because current is being carried evenly by the 3 current carrying conductors. Locked rotor amps is 40.5. Dead head amps would be around 60% of full load amps, so 3.5-4 amps.

Why does the pump draw less amps with no flow or at deadhead? To understand this you need to learn about pump affinity laws (Google is your friend). Simply put it takes more power (amps) for flow than it does for pressure.

An example would be a pump running at 30 psi and putting out less just say 15 gpm (I’m just picking numbers out of the air for this example). And let’s say it’s using 10 amps at this flow and pressure. Now if we open the valve so that the pressure drops to 10 psi. The flow is now 22 gpm. Did the amps go up or down? The amps went up to 13 amps. Because we increased the flow. Now we partially close the valve so we have 60 psi. The flow has now reduced to around, lets say 10 gpm. The amps are now 8.5 amps.

The pump manufacturers don’t typically publish the horsepower curves for the smaller submersible pumps. They do on larger sub pumps and line shaft turbines. A few years ago I sold a farmer a 300 hp Peerless line shaft pump. It was designed for 1,000 gpm. Don’t remember the head it was designed for. I do remember that the pump performance report showed that at dead head, it only required 150 hp, 50% of total horsepower.

With a 3 phase pump you do not have a start box with capacitors and relays. You have a box, but it contains overloads and a contactor. 40 amps is locked rotor amps.

Unfortunately this means Time to pull the pump and replace it. Now there may be other factors that caused the motor and or pump to fail. But your pump is dead.

 

[Rreeuuvveenn]

Yes 3 phase 208 volts makes a big difference. Kind of important to know that. Now your full load amps are 6.6. Because current is being carried evenly by the 3 current carrying conductors. Locked rotor amps is 40.5. Dead head amps would be around 60% of full load amps, so 3.5-4 amps.

Why does the pump draw less amps with no flow or at deadhead? To understand this you need to learn about pump affinity laws (Google is your friend). Simply put it takes more power (amps) for flow than it does for pressure.

An example would be a pump running at 30 psi and putting out less just say 15 gpm (I’m just picking numbers out of the air for this example). And let’s say it’s using 10 amps at this flow and pressure. Now if we open the valve so that the pressure drops to 10 psi. The flow is now 22 gpm. Did the amps go up or down? The amps went up to 13 amps. Because we increased the flow. Now we partially close the valve so we have 60 psi. The flow has now reduced to around, lets say 10 gpm. The amps are now 8.5 amps.

The pump manufacturers don’t typically publish the horsepower curves for the smaller submersible pumps. They do on larger sub pumps and line shaft turbines. A few years ago I sold a farmer a 300 hp Peerless line shaft pump. It was designed for 1,000 gpm. Don’t remember the head it was designed for. I do remember that the pump performance report showed that at dead head, it only required 150 hp, 50% of total horsepower.

With a 3 phase pump you do not have a start box with capacitors and relays. You have a box, but it contains overloads and a contactor. 40 amps is locked rotor amps.

Unfortunately this means Time to pull the pump and replace it. Now there may be other factors that caused the motor and or pump to fail. But your pump is dead.

thank you very much for your time, experience, lesson,and kindly sharing it,

 

[Boycedrilling]

the motor saver 777 is an excellent electronic overload detection device. It is usually a retrofit to replace thermal overloads. You still have a contactor that the motor saver and pressure switch control to energize and de energize the pump. Additionally you will have fuses or a circuit breaker as part of the pump panel or they could be in the main electrical panel.

 

[Boycedrilling]

Your original post says you blew a fuse. Did you try replacing it and re energizing the pump? Can’t hurt anything to try that at this point.

 

[Rreeuuvveenn]

the motor saver 777 is an excellent electronic overload detection device. It is usually a retrofit to replace thermal overloads. You still have a contactor that the motor saver and pressure switch control to energize and de energize the pump. Additionally you will have fuses or a circuit breaker as part of the pump panel or they could be in the main electrical panel.

you are right boyedrilling,

still have contactor, and 30 amp fuse, middle fuse blew out,

 

[Reach4]

If one fuse of 3 blows, I wonder why a second fuse does not blow. Could you have an open phase?

 

[Rreeuuvveenn]

If one fuse of 3 blows, I wonder why a second fuse does not blow. Could you have an open phase?

maybe the middle fuse was the weakest link,

when i tried the system after , i did shut it down when amperage start climbing to 30 + amp,

rest of the house worked fine,no reports of failure, we have other three phase pumps, no problem,

we have a backup generator,

on Tuesday i will give anther check of the well pump

 

[Boycedrilling]

On a 3 phase fused disconnect. It is very rare that all three fuse will blow at the same time. Usually only one fuse will blow. The pump saver 777 will detect the loss of phase and open the contactor to shut the pump off.

 

[Valveman]

A fuse blowing or an overload tripping is mainly to protect the electric grid from your shorted motor. By the time a fuse blows or an overload trips it is usually too late to save the pump. The pump can be saved by catching low amps, which happen when the pump is deadheaded or running dry, and was very well explained by Boyce. The pump can also be saved by not letting it cycle on/off too rapidly. Having something that stops or catches these conditions will protect the pump.

 

[shane21]

As Boyce stated you are pretty much stuck pulling the pump at this point and hoping to find a shorted wire down the well during the process. It happens, but unfortunately it doesn't happen very often.

Block output of the pump, will cause the pump to work less???!!!

I have had good luck over the years explaining it to people like this:
Water is heavy and a motor has to work hard to spin the pump that moves it. Once the pump no longer has to move that heavy water, like when a check valve is broken and opens so far as to stop water flow through a pipe, the motor doesn't need to work as hard. Once people realize that moving the water is what makes a submersible motor work so hard it often times just "clicks" and makes sense to them.

 

[Valveman]

I have had good luck over the years explaining it to people like this:
Water is heavy and a motor has to work hard to spin the pump that moves it. Once the pump no longer has to move that heavy water, like when a check valve is broken and opens so far as to stop water flow through a pipe, the motor doesn't need to work as hard. Once people realize that moving the water is what makes a submersible motor work so hard it often times just "clicks" and makes sense to them.

Excellent explanation! You understand the amps are reduced and the motor is not working as hard. That means the motor is de-rated and could even safely pump hot water. So, it no longer needs a half foot per second of cool water to stay happy.

 

[shane21]

Generally speaking, when the motor is de-rated it can certainly pump warmer water and stay cool but most residential submersible de-rated motors will only use 15-20% less amperage at no load so to say de-rating the motor eliminates the need for cooling is just incorrect. Amperage of the running motor is what creates the heat, so even if the pump is de-rated it is still drawing ~85% of full load amps and still needs similar water flow around it facilitate proper cooling.

I always side with a manufacturer's published cooling specs for the motors they produce because they have little reason to misrepresent the cooling needs of their product. Arguing against those published cooling specs is a fruitless venture, mostly because the specified cooling can easily be provided in any situation for a small fraction of the total project cost - in essence why not provide the recommended cooling when it can be done cheap and easy.

A proper analogy would be changing oil in your vehicle. If the manufacturer of your vehicle says to change the oil every 5,000 miles but you think to yourself "I drive my car in a less demanding way than most people so I am going to disregard that 5,000 mile interval and change it less frequently because I am sure the manufacturer is incorrect" it is possible you are right, but why would you risk an issue when changing your oil is so simple and inexpensive?

 

[Valveman]

Yep I am one of those guys. I only change my oil every 10K or so, because I know the manufacturers are lying to increase repeat business. Pump/motor companies are even worse. I am the Amsoil salesman of the pump industry. I am not going to get 95% of the business, because 95% of people are sheeple and will just blindly follow the "guidelines" handing over more of their hard earned money than they should. The only customers I get are the smart ones. Ones that do their research and see that a motor de-rated by as little as 11% can safely pump 131F water. A small percentage of people are smart enough to deduce that if a motor can pump any flow rate of 131F water, it would take very little 60F water to keep it cool and happy. Once they understand this, they no longer trust installers who keep telling them a CSV doesn't allow enough flow to keep the motor cool. Then when they get one and realize all the other benefits from a CSV, they really no longer trust the installers. That is why they are on this DIY forum to start with, and you are just proving their point.

 

[shane21]

Okay, but if you are using an oil additive or a synthetic oil in your car you are no longer comparing apples to apples with manufacturer's specs for oil. You are now muddying the waters by introducing additional variables that the manufacturer didn't address. Try to stick with an apples to apples comparison, it will make it easier for you to understand all this.

Back to submersible well motors, I am not saying the motor cannot handle pumping higher temperature water, even when it isn't de-rated, I am merely saying that anytime you use an electric device in any environment that is warmer than it was intended for, you are likely reducing the life of that electrical device. That fact isn't even debatable. Maybe you are arguing that submersible motor manufacturers purposely lie about the capabilities of their respective motors to remain properly cooled in warmer water, but if that were so what would be the motive? If you were designing, engineering and manufacturing a single motor to withstand a multitude of liquid environments, including warm water pumping conditions, you would be costing yourself business by not promoting it to handle the environments you designed it to handle. Your argument is devolving more into conspiracy theory than rational thought at this point.

I, as stated previously multiple times, sell and use your CSV product. I just always make sure to account for the motor manufacturer's minimum cooling specs when I install any system, including those that use a CSV. It is just patently irresponsible not to adhere to the cooling specs of a manufacturer, especially when those cooling issues aren't even an issue for majority of installations and require zero additional work or money to satisfy.