Variable Frequency Drive 101
As director of education with Gicon Pumps and Equipment, Calvin Hale is in charge of technically training employees, vendors and customers on the pump products the company develops. His groundwater industry experience goes back more than three decades, but he says education on pumps and related equipment has grown especially important within the last 10 years. While the actual pumps haven’t changed much, he says the control equipment has become more technically advanced due to increased demand for real-time updates and mobile device connectivity.
One pump product that is being affected by this trend is the variable frequency drive (VFD), which controls water pressure. Hale spoke about this at the Texas Ground Water Association’s (TGWA) 2017 conference in a presentation titled “VFD for Water Systems.” The course covered how a VFD works, the logic behind it, benefits of using it and installation best practices. National Driller recently conducted a follow-up interview with Hale on what groundwater professionals should know about VFDs.
The interview has been edited for space and clarity.
Q. You’re director of education for a groundwater industry product manufacturer. If you could, please talk about the importance of education in this realm and the approach you take.
A. It has become important in just the last five to 10 years because of the equipment becoming more technically advanced. It’s not that the pumps have become more technically advanced, because they haven’t really changed that much. But the control equipment for the pumps has become more technically advanced. And, this is something that’s fairly new, is the demand for more technically advanced equipment has come up in the last few years, meaning that the public is used to smartphones and things like that; they want their equipment to be up to date. Normally, the groundwater industry was a very conservative, technically, industry. It’s now moving into the highly technical side of it because there’s demand for it.
Q. Why did you decide to cover VFDs for water systems? What significance does the topic hold?
A. First off, the real answer to that is I was asked to, but the reason I was asked to is because that’s where the biggest need is. I have taught that class I’m going to say 30 or 40 times in the last three or four years in four different states and I still get requests for it because there are not a lot of people teaching that class, and it’s probably one of the biggest needs there is, for people to be trained on variable frequency drives.
Q. Do you have a sense of why that need is so strong?
A. It’s changing at a rapid pace. The groundwater industry was the same for 50 or 60 years, and then, all of a sudden, we started getting these variable frequency drives and every manufacturer of pumps makes their own, or at least puts their label on one. So it’s getting to the point where they have to know about them. In the early days, they could have said, “Well no, we don’t do variable frequency drives,” and got away with it. Now, if they go out on a job to do service, they still have to know about them to help somebody with equipment somebody else put in. So the need is there and it’s growing rapidly, and the technology is advancing quickly. That’s the biggest reason.
Q. What is a variable frequency drive and what relevance does it hold to the groundwater industry?
A. Basically, it is a device that allows you to change the speed of the pump, thereby varying the flow or the pressure. It allows you to run a pump slower if you don’t need as much water and faster if you need more. So it really becomes an integral part of a water system, so that it makes it very smooth and makes it easier for someone to use. I stress this in my class, that basically, the variable frequency drive is for the comfort of the end user. So a person living in a home that has a water well that has a variable frequency drive on it — instead of having a big drop in their pressure and then the pump coming on, getting high and then going low again while they’re in the shower — they cannot even sense the difference in the pressure while the pump is running because a variable frequency drive is modulating that pump so that it always maintains the single amount of pressure. So it’s really for the comfort of the end user, and that’s the relevance it holds. As far as the equipment is concerned, there is energy conservation, protection for the equipment, and then there are great diagnostic tools that help the installer and driller know what’s happening with the equipment.
Q. How long have VFDs been around and how have they changed over time?
A. This is the big thing because I was surprised at this too. One of my suppliers, I asked him the question. He said, “Well, they’ve been around since the late ’60s.” I’ve been in the water well industry since the early ’80s and I really didn’t come across them until about 10 years ago. I was in a different industry before this, making reverse osmosis units, and we had them there, but they were very basic. What’s happened now is they’ve become more industry-specific, so they have application software in them so that if I sell a VFD to someone, it’s made for groundwater applications. All of the stuff on it is pump-specific, so it makes it a lot easier for them and there’s a lot less programming involved. In the last 10 years, they’ve become very prevalent.
Q. You mentioned the top three reasons to use a VFD during your presentation. What are they?
A. They are energy savings, equipment savings and protection of the equipment. You save energy using one, but you also save on equipment because the VFD converts the power from single-phase to three-phase. You can use smaller wire and since you’re varying the flow, you can use smaller pressure tanks. So there can be a lot of equipment savings also. Then, your pump is digitally protected, so you can … be very specific about the type of protection. Also, it protects against underload, not just overload, so there is a lot more protection for the pump.
Q. How do VFDs and energy efficiency relate?
A. I’m going to make it as simple as I can. First, there’s something called the affinity law, so when you vary the flow of the pump so that it only runs as fast as it needs to, there’s savings involved. The deal is, it’s not just simply a percentage savings; it’s exponential savings. If I slow down my pump from 60 Hz to 50 Hz, I save the speed divided by the cube of the rpm. So basically what I’m doing is I’m exponentially saving. So I’ve saved about 21 percent of the electricity by going down only 12 to 14 percent in rpm. So that’s the big savings. If you have a variable flow and the pump can slow down to meet that, then you save on electricity there.
The other, which is important, is what we call inrush current, meaning, if we start across the line, and as soon as I turn the pump on, it has to run at full speed, there is a giant usage of energy right in the first second and it spikes. So when I use a VFD, instead of having that big spike, I just ramp up. So there’s another big savings there. So it saves in two ways.
Q. When it comes to installing a VFD, what best practices should groundwater professionals implement?
A. I think the very first thing is electrical safety. This is electrical equipment, so you’re hooking up high power to it. I think safety is the big thing. I see people power these things up standing in front of them, and you should never do that because you could always make a mistake wiring and have a flash fire or something like that. So I think electrical safety is paramount. I always tell people at my pump school, “If you don’t feel qualified to wire this up, don’t do it. Hire an electrician to do it.” Other than electrical safety, the environment in which you put the VFD matters a lot. If you’re going to put it outside, you need to make sure it’s in an enclosure that can withstand rain and snow, or being squirted at by a sprinkler. So environment of installation is another thing that’s paramount. Then, the last thing, and this is the thing that as a supplier we really have to look out for, is sizing it properly. If you don’t size them properly, on one end they simply don’t work, and on the other end they don’t give you enough protection.
Q. You covered water systems logic. What does that involve and what should water well drillers and pump installers know about it?
A. In the presentation, I kind of likened it to how the old system worked. The old system worked with a pressure switch, so it would build up the pressure and shut off, and then when you began to use water, the pressure would go down, the switch would close and the pump would go back on again. So I likened the logic in the VFD to be like that. So, when do I come on, how long do I run, how fast do I run, when do I shut off and when do I know to come back on again? That’s the logic that has to be in the VFD so it can work with the pump on a pressurized system. Now that is very common for it to already be as an application. So you just choose it and you tell it what pressure you want and you’re done.
Q. Are there any VFD limitations that have yet to be addressed?
A. I answer that yes, but they’re specific to each one. What’s happened in the last few years is that a lot of variable frequency drives have become application specific, not just industry specific. So a pump company will make one that is strictly for submersible pumps of a certain size. They’re trying to do that to make it inexpensive and to make it where there’s not very much programming, so it’s a plug-and-play deal. The problem with those is they are plug-and-play, but when they quit working, there are no diagnostic tools. So it becomes a throwaway item and it’s a very expensive throwaway item even though they’re trying to make it less expensive. So the limitations are basically put in there to make them less expensive, and I prefer having one with all the bells and whistles so I can see what’s going on.
Q. What are some of the most common questions you get about VFDs, and what are their answers?
A. As I drive around, I also get a lot of questions about troubleshooting, but I won’t go there on this. I want to go with this, and I got asked this at that very presentation. After the class, some people came up to me, and basically their question was, “Can I make it do this?” So they want to do something extra. Maybe they want to turn a light on at the barn if the tank’s out of water or they want to flush a sand separator after five minutes, after it kicks the pump on; they want to do something extracurricular with the drive and they want to know if they can do it. In a lot of cases, if it’s a full-service drive, the answer is yes. That’s the question I get the most: Can I make it do this?
Q. If nothing else, what do you hope audience members take away from your presentation on VFDs?
A. This is the easy answer: confidence. I think this has been the factor that has kept people, especially contractors, from using variable frequency drives, is that they just don’t feel comfortable with them because of the highly technical aspect. They also don’t feel comfortable that they can’t explain it to their customer. That’s why I explain the logic in the form of the old logic, because I want them to feel confident that this really isn’t that difficult, and if I’m training my guys who are selling it to them, so that they can help them so that they’re not going to be stuck out on a limb. … We’ve got their back so they can have confidence.
Q. Is there anything I didn’t ask you about that you think it is important to mention about VFDs?
A. The future is integration with home automation so that people who have water wells will be able to know the condition of their water well without even having to go out to it. They’ll be able to check it on their home computer or their cell phone. A lot of the manufacturers of these water well specific variable frequency drives now have Wi-Fi and Bluetooth hookup, so, in the next few years, you’ll see this become very popular. If their water well fails, they’ll get a text or email and it’ll pop up on their cell phone, and they won’t have to wait until they’re completely out of water to have to call a service technician. Monitoring will just be another part of their household. That’s the future, and I think that is a great future.