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matt spinniken
06-24-2008, 07:41 PM
A DIY'er installed a 1.5 hp pump to feed three drip zones, each drip zone is approx. 450ft with a 1gph emitter every 12''. The whole system is run with half inch lines except for a 1.5in intake. The intake is about 80 feet with a check valve and no pressure reducer.

Well, the pump will run a zone for about two minutes and then the thermal shutoff will turn the pump off (so the pump is getting hotter than 120 degrees). I tried hooking a garden house to the top of the pump and the thermal shutoff still turned it off after a couple minutes.

Does anyone have any idea what the problem might be?? Anything I should try/check??

Wet_Boots
06-24-2008, 08:13 PM
Operating pressures? Height of suction lift?

matt spinniken
06-24-2008, 08:27 PM
The suction lift is approx. 3ft. I didnt put a pressure gauge on the pump, I will check that....but for now maybe we could assume around 55psi

Wet_Boots
06-24-2008, 08:43 PM
Seems like a hell of a tiny load for a 1-1/2 HP pump. Since the drip needs nowhere near 55 psi, you could try blowing off some extra flow (noting pressure) and seeing how the pump reacts.

All the drip combined is about 1350 gph, and some 1-1/2HP pumps can push 36,000 gph

matt spinniken
06-24-2008, 08:54 PM
Thanks so much for helping me out with this. One thing that I forgot to mention is that the system is 3 years old and has not had this problem in the past. Also, there was more algae on the lake this year compared to years past.

Wet_Boots
06-24-2008, 09:06 PM
Got strainers clogging up? Algae and drip do not go together.

matt spinniken
06-24-2008, 09:26 PM
yes acutally there was some build up, could this cause the pump to shut off, or overheat?

AI Inc
06-25-2008, 05:01 AM
Definatly want to wire all zones together to come on at once.

Valveman
06-25-2008, 09:20 AM
Low flow won't cause the overload to trip. It is either low voltage, or there is something wrong with the motor. Three year old pump, bought at the DIY store, that maybe all you get.

Wet_Boots
06-25-2008, 09:54 AM
Voltage aside, how little flow could you have before the pumps begin to heat up?

Valveman
06-25-2008, 11:47 AM
A jet pump only needs about 2/10 of a GPM to keep cool. The motor is air cooled and doesn't care about flow but, low flow means low amps and should not be tripping an overload. Only when the flow gets so low that the impeller melts and locks up should flow cause a motor to trip an overload. Basically zero flow to do that.

TPendagast
06-27-2008, 01:00 AM
thats alotta pump for little output, you have alot of back pressure. Im assuming because of the dyi'er you dont have a return hose? Put in a master valve and a return hose, put a ball valve on the return hose. This will help you control the amount of back pressure.
The MV will be open all the time so turn that ball valve until you have enough to run your drip zone but the rest is running back into the pond, if you want to get really crafty you can use the return hose to clean the intake too.

Valveman
06-27-2008, 08:15 AM
Again, back pressure does not hurt a pump. Back pressure makes the pump use less energy. Dumping excess water is a waste of energy.

Wet_Boots
06-27-2008, 08:19 AM
With algae and drip, though, there is a genuine possibility of complete blockage, and having a few gpm running back to the lake does allow for one of those fancy 'self-cleaning' lake strainers.

TPendagast
06-27-2008, 10:04 AM
Valveman, your statement would be true depending on: single phase or three phase, and vfd? Of course with a 1.5 jet pump non of the above is going to exist,so i didnt bother to ask. a 1.5 jet pump has nothing to make it 'smart' so it is going to pump, that's its job. So in this case with too much of a pump, YES that DOES hurt the pump, causes the heat to rise, can cause it to cavatate and ultimately destroy the pump. There are many ways to make the pump work only when it needs to, as drip systems dont deplete system pressure rapidly, however I cant fathom how a DIY'er woud know how to do it or why you would go through the expense for a three zone drip system.

I've done pumps from las vegas to colorado and utah and am now in idaho.
I spent 6 months is Africa working on irrigation pumps.
I know a little something about pumps and have numerous certifications from Monroe pump on the subject.
Check with a pump expert, Monroe pump in Grand junction colorao will tell you the same thing.
The pump is being stressed by pumping against bak pressure, this process is called dead heading and it's bad.

Do what you want with your pump. But don't get snipity and act like an expert when your not.

Wet_Boots
06-27-2008, 10:14 AM
I always thought deadheading was a term of zero flow, but you can get uncomfortably close to it (hence my minimum-flow question)

Maybe a better question for the OP is if there is a way to eliminate (most of) the algae, and if not, whether another means of irrigation, other than drip, could be considered.

Valveman
06-27-2008, 11:07 AM
I know your pump experts at Monroe Pumps. They sell mostly VFD controlled pump systems. So they don't want you to know that choking back a pump with a valve will reduce the energy consumption as much or more than any VFD, even though it is the truth.

Dead heading is 0 flow, and yes that will overheat and destroy a pump. However, a small jet pump can be choked back to about 2/10 of a GPM flow and remain cool, and it will last a very long time doing this. AND, it will use considerably less energy when restricted with a valve, similar or better than when controlled by a VFD. Pumps are already "smart", they don't need smart controllers (VFD's) to save energy, just smart installers who understand how pumps really work.

I have about 40 years experience with pumps. I teach classes in this country and others about pump controls, including many classes for pump installers and manufacturers for the National Ground Water Association and others. Your guys at Monroe Pump and yourself could use a class or two. I hear the kinds of mis-statements like the ones you made all the time. Centrifugal pumps are "counter intuitive", and even most pump and pump system manufacturers don't really understand how they work.

Your statement;
"The pump is being stressed by pumping against back pressure."

This statement is absolutely FALSE, and is one of the key indicators I use to determine how much or how little a person really understands about pumps. You can easily prove this to yourself if you know how to read Brake Horse Power on a pump curve.

I have been doing this to about 30,000 pumps a year, for the last 15 years. So I think I know what I am talking about but, I don't mean to be snipity, I am stating facts.

Wet_Boots
06-27-2008, 11:32 AM
Here's a related question, connected to using a submersible pump in a river or lake. Can enough heat be conducted through the pump casing to prevent heat damage, in the event of deadheading? I mean, you do expect a pressure relief valve to do its job, but in the event it didn't....

Valveman
06-27-2008, 12:37 PM
No, the only thing that can dissipate heat is flowing water. During a complete dead head condition, steel casing around the submersible motor will just get hot and the motor will be destroyed. Plastic casing will melt, and form a tight outer cover over the motor. I have had to cut the plastic casing or motor shroud off of pumps from this, many times.

Even a submersible in an open body of water will get hot if there is a no flow condition. The water around the motor can actually boil, while the entire thing is submerged in cool water. It has to have a flow past the motor to stay cool. This is why a motor shroud is even more important for a submersible in a lake or pond, than it is when the pump is in well casing.

As I was explaining earlier, when you use a valve to choke back the output of a pump, the amps drop the same as if you slowed it down with a VFD. Choking back the flow of a pump can make a 10 HP motor be "derated" to only pull a 5 HP load. A derated motor can actually pump "hot water" and maintain enough cooling. So a derated motor needs very little cool water to maintain proper cooling. Choking the output with a valve, the motor will stay cool with much less than .5 feet per second of flow past the motor.

A VFD actually "creates" a smaller motor from a larger motor. It is not "derated" as when choking with a valve. When using a VFD to slow down a 10 HP motor until it is only pulling a 5 HP load, you have "created" a 5 HP motor from the 10 HP. This motor still needs enough cooling flow to properly cool a fully loaded 5 HP motor. So you must still maintain at least .5 feet per second flow past the motor to maintain proper cooling.

All this really means is that a submersible motor can safely deliver a much smaller flow rate when it is simply choked back with a valve, than when slowed down with a VFD.

Dirty Water
06-27-2008, 06:57 PM
Is the pump on a relay, or a 60/40 switch?

It may be completely dead heading and boiling the water. I don't care what Valveman says, I've replaced enough melted pump fittings to know it happens.

Or it could just cycling because its a 1.5 HP pump and its going to max out the flow of that drip zone very quickly.

TPendagast
06-27-2008, 07:28 PM
If you read my previous statement I mentioned choking it back with a ball valve and also mentioned that small of a pump wouldnt warrant VFDs.

40 years of expereince huh? curious that pre dates this industry by quite a bit.

Ive run into guys claiming to have 40 years experience in stuff that hasnt existed that long.

They all just seem to be old an talk alot and hope that intimidates people.

If you have all this expereince, why cant you figure out this pump problem by yourself?
I would it done without posting about it.

Kiril
06-28-2008, 12:51 AM
So they don't want you to know that choking back a pump with a valve will reduce the energy consumption

You might want to check your math.

matt spinniken
06-28-2008, 09:51 AM
There is a pump start. I am considering selling the homeowner a half horse pump, I still have not been able to stop the thermal shutoff.

Wet_Boots
06-28-2008, 10:20 AM
What kind of strainer(s) and filtration is there on the drip system?

Wet_Boots
06-28-2008, 10:24 AM
You might want to check your math.There is a change in current draw, although it isn't proportional to the reduction in flow. There are low-water shutoff devices for submersible pumps that work on current change.

Kiril
06-28-2008, 11:02 AM
OMG, did you just agree with me?

Wet_Boots
06-28-2008, 11:09 AM
OMG, did you just agree with me?The living dead don't have to agree :)

Kiril
06-28-2008, 11:19 AM
The living dead don't have to agree :)

Right, they only accede the point. :waving:

Wet_Boots
06-28-2008, 11:24 AM
Right, they only accede the point. :waving:what point
http://tbn0.google.com/images?q=tbn:vnhu562Z0_yv-M:http://www.clsp.jhu.edu/~chelba/pics/ona.gif

Kiril
06-28-2008, 11:29 AM
WTF is that, your business logo?

Wet_Boots
06-28-2008, 11:33 AM
Never heard of "Me and My Arrow" ?? ~ you deprived infant.

Kiril
06-28-2008, 11:38 AM
Yes, I was a deprived infant....no TV most of my childhood.

Mike Leary
06-28-2008, 11:45 AM
Never heard of "Me and My Arrow" ?? ~ you deprived infant.

Deprived is right, lotsa smart stuff in that film, including my engineering.

Kiril
06-28-2008, 11:49 AM
Deprived is right, lotsa smart stuff in that film, including my engineering.

?? Harry Nilsson

Mike Leary
06-28-2008, 12:04 PM
?? Harry Nilsson

Yep, did Nilsson Sings Neuman with him, too. Miss him, not the party that
never ended, though.

Wet_Boots
06-28-2008, 12:19 PM
Talented guy. College radio stations without cart machines couldn't figure out how to deal with Son of Schmilsson

Valveman
06-28-2008, 02:45 PM
It may be completely dead heading and boiling the water. I don't care what Valveman says, I've replaced enough melted pump fittings to know it happens.

"Complete Dead head or a loss of prime will melt the fittings in a very short time. A little less than 1/2 GPM of fairly cool water flowing through the pump, and the pump will never get the fittings hot.

Valveman
06-28-2008, 02:55 PM
40 years of expereince huh? curious that pre dates this industry by quite a bit.

If you have all this expereince, why cant you figure out this pump problem by yourself?

I am afraid I predate a lot of things. However, I have a certificate from a pump school at TRW Reda Pumps in Bartillesville, OK dated 1975. I had been working on pumps for several years before that, and have been through numerous pump and related schools since then.

And I have figured out the pump problem. Either there is less than 1/2 GPM flow, suction leak, or there is something wrong with the thermal switch.

Valveman
06-28-2008, 03:05 PM
You might want to check your math.


Flow X Head diveded by 3960 X eff always equals less power consumption when you restrict the discharge flow of a pump. More back pressure means less flow and less power consumed. It is counter intuitive, and that is why it is so hard for many people to understand.

Valveman
06-28-2008, 03:10 PM
OMG, did you just agree with me?

NO, Boots said "there is a change in current draw". At least there are a few people like Boots who do understand.*trucewhiteflag*

Kiril
06-29-2008, 02:12 AM
Some reading for valveman (and I guess boots) so he (they) can understand.

http://www1.eere.energy.gov/femp/procurement/eep_centrifugal_pump.html

http://www.engineeringtoolbox.com/pumps-discharge-regulation-d_310.html

http://www.energy.wsu.edu/documents/engineering/motors/MotorDrvs.pdf

If you believe these sources to be in error, please provide a mathematical proof of why.

Wet_Boots
06-29-2008, 07:18 AM
Some reading for valveman (and I guess boots) so he (they) can understand.

http://www1.eere.energy.gov/femp/procurement/eep_centrifugal_pump.html

http://www.engineeringtoolbox.com/pumps-discharge-regulation-d_310.html

http://www.energy.wsu.edu/documents/engineering/motors/MotorDrvs.pdf

If you believe these sources to be in error, please provide a mathematical proof of why.You want to tell Franklin Electric (who manufactures pump motors) that their Pump-Tec device is a fraud?

Valveman
06-29-2008, 09:54 AM
http://www.powerqualityanddrives.com/payback_analysis_vfd/

http://www.powerqualityanddrives.com/energy_savings_pump_vfd_part_1/


OK, here is a little light reading for you. I can certainly understand WHY you think a VFD would save energy. There is enough of the kind of propaganda you linked to out there, to make anyone think it is true. However, the government wants you to think that they are here to help you, so they fall head first into the false information being spewed out by all the VFD manufacturers. And the VFD manufacturers want you to buy VFD's, so they make horse power calculators and articles that deceive you into thinking that a VFD always saves energy by the cube of the speed. The bigger the lie, the easier it is to get you to believe it.

The ONLY time a VFD can save energy, is when the pressure can be lowered while low flow rates are being used. In other words, your sprinkler systems would need to be able to operate at 70 PSI for a large zone, then be able to work at say 30 PSI when there is a small zone. Of course we know that when only running one sprinkler, you need the same amount of pressure as when you are running 6 sprinklers. So a VFD can save energy for people who are not smart enough to figure friction loss in pipe lines. If the pipe line is so small that you have tremendous friction loss to overcome when running max flow, then a VFD can reduce the pressure at low flow when there is less or no friction loss in the pipe line. This means that a correctly sized pipe line would save energy, and a VFD is actually burning excess energy because you have to up-size the pump to make up for the friction loss from the badly designed pipe system.

The first link you gave said that throtting does not reduce power consumption but, the curve they provide shows it does. Also the curve they supply doesn't maintain a constant pressure. It lets the head fall much lower than would actually work in the field. This is how they deceive everyone.

This is the stuff I teach at classes all over the country. I can't tell you how many engineers, pump installers, irrigation specialist, and even pump manufacturers have told me that they never realized that because head is reduced by the square of the speed, a VFD cannot slow down a pump enough to save any energy. VFD people make a big deal about reducing power consumption by the cube of the speed but, they hope you don't realize that reducing head by the square of the speed, extremely limits any possible speed reduction.

I am working on a new horse power calculator that will take limited speed reduction into consideration. It will also add in the "parasitic losses", efficiency losses due to harmonic content, and other things that VFD manufacturers conveniently neglect to figure in. Of course this is only for people who cannot read and understand a regular pump curve. All of this information is easy to see on any standard pump curve, you just have know how to figure the minimum possible speed that will deliver the head required, and how to add in the normal losses from the VFD itself.

Of course all this only matters if the VFD last long enough to give a comparison. In my 20+ years experience with them, the average life of a VFD has been less than 4 years. This means that even IF a VFD could save energy, it would never save enough energy to pay for itself before the unit fails.

Mike Leary
06-29-2008, 09:57 AM
Have we not beat this one to death and beyond?

Wet_Boots
06-29-2008, 10:01 AM
Still, if you had a known flow and pressure target, you'd go for the pump that has your target on the sweet spot of their efficiency charts, everything else being equal.

Of course, it's usually a moving target, so it isn't so easy as pointing at one graph.

Kiril
06-29-2008, 10:07 AM
There is enough of the kind of propaganda you linked to out there, to make anyone think it is true.

The laws of physics is "propaganda"? BTW, I could care less about pumps, VFD or otherwise. This is merely a question of the forces and energy involved when throttling output from a pump.

If you believe these sources to be in error, please provide a mathematical proof of why.

Valveman
06-29-2008, 10:45 AM
The laws of physics is "propaganda"? BTW, I could care less about pumps, VFD or otherwise. This is merely a question of the forces and energy involved when throttling output from a pump.


The laws of physics is what you don't understand. All the math is there if you know how to follow it. What happens when you throttle a pump is "counter intuitive" but, it still follows the laws of physics. Don't feel bad though, I have been beating this to death for years, and you are certainly not the only person who doesn't understand how pumps really work. Start with learning how to read a pump curve.

Wet_Boots
06-29-2008, 11:07 AM
You can look at pump curves, and I'll look at other curves
http://tbn0.google.com/images?q=tbn:VtxssuuTuqJqXM:http://images.tribe.net/tribe/upload/photo/8e0/0bc/8e00bc9b-2322-401b-8101-b6994475e626

Valveman
06-29-2008, 11:13 AM
I like those curves better but, I will bet they are also "counter intuitive".

Wet_Boots
06-29-2008, 11:18 AM
She has a counter you can do Shakespeare from...

TPendagast
06-29-2008, 12:43 PM
I dont understand why would the government want (or care to get involved) with something trivial like VFDs?
Areyou trying to say the manufacturers of these types of systems have enough lobby in washington to get the government involved with promoting them, or that the government is "misled" in beleiveing they work.

In most cases where I see the VFD used its on a system like this one:

Subdivision origially with 44 homes and 3 valves per home.
4" mainline,looped.
all zones vave 8-12 1800 series pop ups with various halfs fulls or quarters.
I don't recall the original pumps that were on this skid.

However they added to the subdivsion but used the SAME Irrigation system, they now have a phase 2 so there are 90 homes with about the same system set up, exceptsome monkey only did TWO zones on many homes (
you know to savemoney on those hugely expensive commercial valves, ha)

Then another monkey decided to solve flow and pressure issues just ADD bigger PUMPS (never mind the 4" pipe couldnt handle more)

anyway long story short, we had put different pumps on the ksi and the VFD is used to manage the different requirements through out the day,there is so much irrigation water demand comming form one source and about 1/3 of the homes in this subdivision have their own clocks (originally designed to run off central clocks, indivisual home owners hired their own landscapers who disconnected them from the main system and set up their own clocks.)
So there can be ALOT of demand say at 4am and little demand at say 12 noon.
This is a constant pressure system. Not a them pump is on f a zone is open kind of system. Pumps only run as much as they need to to bring pressure up.
This is a three pump system on the skid Two 7.5s and a 3hp, the three is a pony/prime pump that also runs the self cleaning strainer.
Usually only oe of the 7.5s will run at 70% but the VFD decides if it need to kick on the other pump.
USed to be that both 7.5s ran at 100% but I took alot of those pop ups and put mp rotators on them. So that made a big difference too. Especially on zones where there are 15 heads running off a 1.5" valve.
The system was a mess from the beginning, and then they added to it trying to use the existing pipes, pumps etc.
I think the VFD works well here.

Kiril
06-29-2008, 06:38 PM
Start with learning how to read a pump curve.

I can, can you?

Wet_Boots
06-29-2008, 06:52 PM
I can, can you?I don't think you guys are having the same argument. Aside from everything else, the fact the Franklin Electric developed the Pumptec device is proof enough that there are changes in motor current as the load changes. That it doesn't equate with the energy savings of a multi-pump VFD station feeding a subdivision achieves can also be taken as a given.

Kiril
06-29-2008, 07:27 PM
I don't think you guys are having the same argument.

Perhaps not. My point is, head and flow are not 1:1 (which is clearly seen in system and pump curves). I'm not saying here that there aren't cases where a throttle output might conserve more energy over bypassing flow, or running a pump wide open, but to say it will ALWAYS conserve energy is wrong, and there are plenty of case studies done to support that conclusion.

Perhaps a review of The Bernoulli Equation (http://faculty.poly.edu/~rlevicky/Handout12633.pdf) is in order here.

Wet_Boots
06-30-2008, 11:29 AM
I'm still going to place some faith in the sheer investment that creates multi-pump systems, as something of a proof that they are more than sheer whimsy, despite the comfort factor of a good old plain-vanilla pump of known reliability, being throttled down by a specialty valve. Future technology isn't welded to the shortcomings of the past, even if those shortcomings inform our decisions of the moment.

Strictly from a consumer standpoint, any "They don't want you to know." pitch will sound the alarms and raise my suspicions to the max.

Mike Leary
06-30-2008, 02:15 PM
Strictly from a consumer standpoint, any "They don't want you to know." pitch will sound the alarms and raise my suspicions to the max.

Ditto that; hope that puts this thread to rest, I'm sick of it. How about some
pics to torment Kiril?

Valveman
06-30-2008, 05:53 PM
Your suspicions are misguided. You should be watching the VFD crocodile that is giving you a ride across the river, not the bird shrieking the alarm that is "over your head".

Wet_Boots
06-30-2008, 05:58 PM
Just a friendly aside about promotion. Me for the soft sell.