MES's AIRGO Well Pump Soft Starter - Problem Solved!

MES Group is posting this guest blog from installer Mike Bishop who originally published it as his "Slow Power" blog. Mike works in northern California. Everything below this introduction is Mike's original text.

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Disclosure:

This blog post features a specific "soft starter" brand. They gave me two free soft-starter units and in-person support (see details below). While I feel compelled to reciprocate by sharing this blog post... I genuinely recommend this soft starter, and don't anticipate getting more free stuff from them (or cold hard cash).

Over the summer, I installed an off-grid power system for a small organic farm in Stockton (system photo here). The farm's main load is a 5.1 kW submersible pump. While its normal operating current is around 26 amps (at 240 volts)... its in-rush current was 86.7. I didn't know whether two Victron MultiPlus-II 5-kva inverters (in split-phase configuration) would be able to handle this in-rush. It'd be right at the edge of spec... at best, I'd expect noticeable voltage sags and nuisance trips (and an annoyed farmer).

So my first field work was to install a pump "soft starter".

A conventional "hard starter"... is like giving a baby on a resting swing ONE BIG PUSH. The baby immediately gets to the target high point. She's also crying and a bit... degraded. A soft starter is like pushing the baby gently until she's at the target high point. ...Giggling without whiplash and future talk therapy. In other words, the soft starter ramps up the voltage slowly until the pump gets to its normal operating state.

Better soft starters will "learn" the characteristics of a particular pump over time. ...They learn the optimal voltage ramp, that will keep the baby giggling while getting her up there asap (because the baby has photo-op work to do).

I went with MES's AIRGO NC soft starter. I'm very happy that I did.

On my first visit to the farm, I opened the pump control box and then stared. And stared. And then sheepishly passed control-box photos to ChatGPT when the farmer wasn't looking. Oh man, I didn't know what was going on in there. (I wish this occurred to me then: Continuity tests (thru a multi-meter) are a great way to learn what's electrically connected to what.)

I've since learned... The black device on the left is the contactor. When "closed", power flows from the source (connected at the top) to the pump (connected at the bottom). Those beer cans above it... those are capacitors. The two little ones are the run capacitors (operating in parallel... effectively one capacitor split in two). The big one is the start capacitor.

Why the capacitors? Single-phase AC power is "back and forth" power. Three-phase power inherently supports rotation of a motor's rotor. But single-phase power doesn't. A capacitor makes a "phase shift" between a "start winding" and a "run winding" (by getting the current waveform out in front of the voltage waveform). ...Which sort-of simulates the rotational effect of three-phase power.

An analogy: A greyhound-dog race. They're motivated to run by a fake rabbit. Let's say it's a 400-yard race on an oval track. For the purpose of the analogy... a fake rabbit is attached to a wheel 100 yards down the track (at the end of the first straightaway) (instead of being on a rail). There's another wheel-attached fake rabbit at the finish line.

When the race starts, the 100-yard wheel rotates one time. The dogs go "OMG THAT'S A MOTHER FUCKING RABBIT!", and sprint. By the time they get to the rabbit, the wheel has brought it below where they can see it. Their momentum keeps them going, and then — as they're coming around the curve — they see the finish-line rabbit at its climax. They run hard thru the finish line.

To beat this analogy to death (like a drunk dog racer might beat his loser dog to death)... If one or two rabbits were at one spot, the dogs would just jump around that spot and salivate. If the two rabbits appeared at the two spots at the same time... the dogs would be confused and wouldn't go all the way around the track. Back to a motor: The separate start winding and run winding give spatial separation. The capacitor gives temporal separation.

The more wheel rabbits there are along the track, the smoother the dogs run (i.e. three-phase power with three windings is more efficient than single-phase power with two windings).

The start capacitor is some extra muscle to get the rotor going. The run capacitors stay in operation the whole time.

Back to the control-box photo. The little white box in the middle is the relay. When the pump is started, it's closed (i.e. it allows power to flow thru it to the start capacitor). When the pump's induced voltage (EMF) gets to a certain level, the relay opens and the start capacitor is removed (I must admit: pretty cool that this happens without electronics).

Back to the AIRGO NC soft starter...

This is a relatively new product from MES. Rep Jason Demicoli offered to fly over to the farm from the Midwest, to help me install a complimentary NC unit (like friggin Mary Poppins). One of his motivations was to write a related white paper (forthcoming). I took him up on this. BTW: Jason's technical support is arguably the best I've ever experienced. He really cares... very refreshing and inspiring.

Shout out also to MES's Bob Cramer, who answered my panicked after-hours phone call on his way to a grocery store (and talked me thru it).

Here's Jason on site (with the messy background blurred by ChatGPT):

Jason introduced me to the PicoScope oscilloscope software. ...I got to see the gentler voltage ramp with the soft starter. ...I saw how the ramp improved each time, as the HDMS unit got more familiar with the pump's characteristics.

With the soft starter installed, the pump's new in-rush current was 38 amps (from 86.7). A lovingly-pushed giggling baby.

Jason and I learned the hard way that the HVAC-dude hack of shorting a capacitor with an insulated-handle screwdriver... is not good (instead always use a bleed resistor). ...This caused the relay to fail closed, which caused the NC unit to fail a few days later. It was my job to install the replacement unit, solo. Despite Jason's very patient on-site educating... I was still struggling with the wiring and device logic. The solo install forced me to get my head around everything better. Lemonade from lemons.

Jason prepared for the original install by making a diagram. That diagram was really helpful. That inspired me to make a diagram for my solo install, that better reflected the farm's specific pump-control-box situation. Jason had one correction for me — otherwise good. Here's my diagram:

Here's the pump's control box, post soft starter:

If a site has one or more high-in-rush motors (that aren't inverter driven (i.e. variable speed)), a soft starter is a great way to lower the overall cost of an off-grid (or hybrid) system, while also increasing system-component lifespan. I recommend using high-quality well-supported soft starters, from the likes of MES.

Postscript:

Besides the mismash of connector styles and the bastard-rainbow wire colors... Can you spot a FAIL in my wiring work?

...Look at the black and orange wires at the top of the NC unit. The orange wire's 90-degree connector gets it really close to the black wire's connector. Well, that caused arcing that damaged the NC unit and really harshed a Saturday night for the farmer and me. Little by little... learning, and exorcising the dumbass from my soul.

I'll outro with a photo of my fail (a Mike Drop):

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This blog and AI: I use ChatGPT all the time, to understand things better. But I'll NEVER peddle AI writing as my own. These blog posts are 100% written by Mike (for better or worse).

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