2 hp Franklin pump not drawing enough amps?

[Alan Waterman]

I am always surprised when any VFD or the pump it controls last 10 years.

Franklin agrees with you apparently.

They told me in an email today that the expected life of the MonoDrive XT is 10 to 15 years. I'm beyond that already. Got paranoid and pulled the front cover off to take a look. There are indeed electrolytic capacitors and MOVs. When running the pump, two of the MOVs are running about 15F above ambient which is not super awesome but still well within normal limits. The rest of the 25mm MOVs are all running near ambient.

There are a bunch of 25v 470uF caps that are all running about 20F above ambient which is also considered normal. This winter I'll remove the board and use my ESR meter to check them. No signs of bulging or leaking but unless the ESR reads very low, I'll certainly recap them. I'll for sure be replacing the the slightly warm MOVs.

I'm guessing given the NEMA4 enclosure that it was designed for outside duty but it's been mounted indoors it's entire life which probably contributed to its long life.

 

[Reach4]

No signs of bulging or leaking but unless the ESR reads very low, I'll certainly recap them. I'll for sure be replacing the the slightly warm MOVs.

I had not been aware of the potential need for preventive changing on MOVs. In looking at stuff, it seems to me that the degradation is caused by repeated spikes the MOV deals with. On the other hand, electrolytic degrade with time and temperature.

What is the failure mode for aging MOVs? If open, I guess you could just shunt the old one with the new. You could probably say the same for the caps, but the caps are big, and MOVs are small.

Are the MOVs radial lead devices, or SMD?

 

[Sponsor]

 

[Fitter30]

Must be in a clean environment. The cooling fan and heat sinks get dirty vfd run warm.

 

[Valveman]

Franklin agrees with you apparently.

They told me in an email today that the expected life of the MonoDrive XT is 10 to 15 years. I'm beyond that already. Got paranoid and pulled the front cover off to take a look. There are indeed electrolytic capacitors and MOVs. When running the pump, two of the MOVs are running about 15F above ambient which is not super awesome but still well within normal limits. The rest of the 25mm MOVs are all running near ambient.

There are a bunch of 25v 470uF caps that are all running about 20F above ambient which is also considered normal. This winter I'll remove the board and use my ESR meter to check them. No signs of bulging or leaking but unless the ESR reads very low, I'll certainly recap them. I'll for sure be replacing the the slightly warm MOVs.

I'm guessing given the NEMA4 enclosure that it was designed for outside duty but it's been mounted indoors it's entire life which probably contributed to its long life.

Lol! Not too many people able to change out or even check a capacitor, much less a MOV. If the expected life is 10-15 years, I'll bet the average life is half that. Seven years has always been the average life of submersible pumps as they are designed with planned obsolescence in mind. Of course that means some last 30 years and some only 30 days. Constant pressure from a pump system is a good idea. But VFD's are used to do that mostly as a way to increase cost and be able to better plan obsolescence.

 

[Wellman]

VFD’s are expensive but they’re the best way to regulate flow in ALL pump systems

 

[Valveman]

VFD’s are expensive but they’re the best way to regulate flow in ALL pump systems

Oh boy! You must be new here. Glad to have you but you are in for a ride if you are going to try and prove that one. I have about 30 something years experience solving all the problems with VFD's by replacing them with Cycle Stop Valves or CSV's. There are probably a few hundred threads just on this forum where I have done so. Happy to answer your questions but you might want to research the CSV first.

 

[Wellman]

What lasts the longest and what ls cheapest isn’t always what’s best. In function a VFD operates in all conditions with the most efficiency of any other pump control.Constant pressure valves are great because they’re simple and cheap but if you want precise control under all flow conditions the VFD is the clear winner.
Of course that’s my opinion based after 55 years of being in the well business.

 

[Valveman]

What lasts the longest and what ls cheapest isn’t always what’s best. In function a VFD operates in all conditions with the most efficiency of any other pump control.Constant pressure valves are great because they’re simple and cheap but if you want precise control under all flow conditions the VFD is the clear winner.
Of course that’s my opinion based after 55 years of being in the well business.

You really should call me or at least read the Cycle Stop Valve web page. I hate to highjack someone else's thread, but I appreciate yet another opportunity to explain why the CSV is better than a VFD, the same way I have been doing since 1993.

One of the first things a CSV is better at than a VFD is range of flow. Although we have multiple articles, customer data, studies from people like at the USDA, and many other things discussing this subject on our web page from as far back as 1994, this is a link to a fairly recent article from the Florida Driller.

https://cdn.shopify.com/s/files/1/0147/4392/files/FGWA_2023_2nd_Quarter.pdf?v=1688654199

However, reading back, I notice that among all the things listed in that article, a pump working at lower flow rate when using a CSV as compared to a VFD was not brought up. Can only put so many words in an article I guess. So, I will give you a couple of examples that you can verify if you want to do the research.

Working on a 100HP line shaft turbine pump in Florida at the moment. Currently it is controlled with a VFD. However, the irrigation system varies from 2000 GPM to as little as 200 GPM. With the VFD control they are unable to make the pump work safely below 800 GPM. Equipped as explained in the article I linked, a CSV will be used to maintain a constant 50 PSI, while the set point of the VFD is at 60 PSI. With the pump running at full speed and the CSV controlling the pressure, the pump can safely operate at a flow rate of as little as 10 GPM. So, the smaller 200 GPM irrigation zones will not cause the VFD to trip off the pump/motor. We know this will work because we have done this on 50 or more irrigation wells for other universities over many years.

Another example would be a 10HP or 20 HP, 200 GPM, 6" submersible in a 7" flow inducer or casing. With a VFD that motor would require 25 GPM minimum to stay cool. With a CSV it will work safely and not cycle when using as little as 5 GPM.

The same thing applies with a 2HP, 25 GPM pump. While a CSV would let it work safely down to as little as 1 GPM, a VFD controlled motor is still going to require the same feet per second velocity as needed to cool a fully loaded motor.

I have lots of articles comparing efficiency between CSV's and VFD's as well. But many of those are 20-30 years old and I would have to look back to get you the links.

This is a subject where there is proof from pump curves, studies, and testimonials from many who have systems working in the field. Based on my 57 years in the well business, I believe people should here the facts instead of relying on opinions.

 

[RetiredInGueydan]

You really should call me or at least read the Cycle Stop Valve web page. I hate to highjack someone else's thread, but I appreciate yet another opportunity to explain why the CSV is better than a VFD, the same way I have been doing since 1993.

One of the first things a CSV is better at than a VFD is range of flow. Although we have multiple articles, customer data, studies from people like at the USDA, and many other things discussing this subject on our web page from as far back as 1994, this is a link to a fairly recent article from the Florida Driller.

https://cdn.shopify.com/s/files/1/0147/4392/files/FGWA_2023_2nd_Quarter.pdf?v=1688654199

However, reading back, I notice that among all the things listed in that article, a pump working at lower flow rate when using a CSV as compared to a VFD was not brought up. Can only put so many words in an article I guess. So, I will give you a couple of examples that you can verify if you want to do the research.

Working on a 100HP line shaft turbine pump in Florida at the moment. Currently it is controlled with a VFD. However, the irrigation system varies from 2000 GPM to as little as 200 GPM. With the VFD control they are unable to make the pump work safely below 800 GPM. Equipped as explained in the article I linked, a CSV will be used to maintain a constant 50 PSI, while the set point of the VFD is at 60 PSI. With the pump running at full speed and the CSV controlling the pressure, the pump can safely operate at a flow rate of as little as 10 GPM. So, the smaller 200 GPM irrigation zones will not cause the VFD to trip off the pump/motor. We know this will work because we have done this on 50 or more irrigation wells for other universities over many years.

Another example would be a 10HP or 20 HP, 200 GPM, 6" submersible in a 7" flow inducer or casing. With a VFD that motor would require 25 GPM minimum to stay cool. With a CSV it will work safely and not cycle when using as little as 5 GPM.

The same thing applies with a 2HP, 25 GPM pump. While a CSV would let it work safely down to as little as 1 GPM, a VFD controlled motor is still going to require the same feet per second velocity as needed to cool a fully loaded motor.

I have lots of articles comparing efficiency between CSV's and VFD's as well. But many of those are 20-30 years old and I would have to look back to get you the links.

This is a subject where there is proof from pump curves, studies, and testimonials from many who have systems working in the field. Based on my 57 years in the well business, I believe people should here the facts instead of relying on opinions.

You are being played.