Lorentz PS600 with undersized wiring

wrdaigle · July 2013

I have Lorentz PS600 that has been worked flawlessly for about 6 years. This year, we have been pushing the pump a bit harder and it has shutting down due to thermal overload. The reason we have been pushing it harder is because we recently planted about 400 trees for a shelter belt. I have a multi-zone drip system in place and theoretically, or pump should be able to handle the need. Actually, it should be able handle about double what I'm throwing at it.

Since the pump has been shutting down, I started running some other calculations to determine whether or not it was set up correctly in the first place. Turns out, it wasn't -- the installer used undersized wiring. They installed 12 awg when they should have used 8 awg. At the end of the cycle, the current is about 8.5amps (48V), which works out to a slightly less than a 10% voltage drop on the 3-phase AC line. So, even though I'm measuring 48V at the controller, the pump motor is probably only seeing about 43V. I am running the pump off 24V battery with a 48V step up transformer, so the controller voltage is pretty constant at 48V.

I guess my main question is: What damage has likely been caused by running the pump this way? I assume if I have caused any damage, it is only to the motor. Anyone know what the ramification of running on a 3-phase AC motor under voltage for a long period of time is? If I upgrade the wire, am I likely to see an immediate improvement? Or should I plan on also replacing the motor in the near future as well?

I'm not looking forward to spending $500 on copper, $1000 on a motor, or having to retrench the well cable...but I guess we gotta have water

Cheers,
Bill

BB. · July 2013

Re: Lorentz PS600 with undersized wiring

Hi Bill,

I am a little confused... 48 volt and 24 volt AC power using a transformer? Or using a 24 to 48 VDC DC to DC converter?

Pump is DC input? AC input? Takes anything (i.e., Grundfos SQFLEX)?

-Bill

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

Sorry for the confusion. Here are a couple of clarifying points.

I am using a 24 to 48 VDC DC to DC converter between the battery bank and the Lorentz PS600 controller.

I assumed the motor was 3-phase AC because I didn't realize there was such thing as 3-phase DC. But the Lorentz pumps actually use 3-phase DC motors. It must have a phase converter of some sort built into the controller.

I may be making this more complicated than I need to. To make a long story short, the wires to my pump are undersized and now my pump has starting to shut down due to thermal overload. If you were in my shoes, what would you do? Simply upgrade the cable and cross your finger, or plan on replacing the motor as well?

vtmaps · July 2013

Re: Lorentz PS600 with undersized wiring

wrdaigle wrote: »

They installed 12 awg when they should have used 8 awg.

How much of the wire length is in the trench, and how much is down the well? Depending on circumstances, it might be possible to upgrade the cable in the well without replacing the cable in the trench. It might be possible to send higher voltage to the wellhead, and then step down to the 48 volts you need for the pump.

--vtMaps

BB. · July 2013

Re: Lorentz PS600 with undersized wiring

More or less, the typical Permanent Magnet motor is a "synchronous 3 phase motor" and would have a VFD (variable frequency drive) built in, or as an external black box. So, you pretty much have all of the right.

The controller (I think) is an external box for this pump family... Is it the controller that is overheating or the pump? I would wounder if the pump can overheat given that (hopefully) it is well cooled as it is a submersible pump (is the well being pumped down from heavy draw--exposing the motor and/or making more lift for the motor/pump?)... Is the controller itself exposed to full sun/hot location? The pump should just slow down (the controller slow the pump down) if there is not enough voltage/current for 100% of rated power (lots of guesses here, I do not know anything about your setup).

If this is a centrifugal pump, if you have more irrigation heads/water flow, the higher flow rate will load the pump/motor more (for centrifugal pumps, you can put a valve on the output and close down the flow to "unload" the pump a bit).

You have a choice--The pump has given good service--But it could be time for a rebuild (mechanical parts). The electronics are probably still good unless they have been running real hot and toasted some parts. Changes to pumping requirements (depth to water, output volume) could mean that your current setup is no longer optimum anyway.

So--Do you spend the money on new wiring and see what happens (size the wiring so that it can run different options down the road--i.e., perhaps even a 120 or 240 VAC pump, or a variable AC/DC pump like the Grundfos SQFLEX family).

Or, do you start from scratch and re-evaluate everything... Battery bank voltage/size, AC vs DC to pump, existing pump pressure/volume. Perhaps put a solar array directly at the pump and skip the whole battery/remote power thing (perhaps a pump+genset for backup power)...

-Bill

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

vtmaps wrote: »

How much of the wire length is in the trench, and how much is down the well?

There is actually only about 20' in the trench, another 50' in the house, and I think about 150' in the well (not sure on the depth of the pump). I could probably raise the pump some since the pump has about 100' of water above it. 20' of trenching shouldn't be bad, but this time of year the ground is really dry, hard and rocky. I don't really want to bring in a backhoe or trencher since I have a bunch of buried lines in that area. If I decide to get a new cable, it may just stay above ground until next spring.

NorthGuy · July 2013

Re: Lorentz PS600 with undersized wiring

wrdaigle wrote: »

I may be making this more complicated than I need to. To make a long story short, the wires to my pump are undersized and now my pump has starting to shut down due to thermal overload. If you were in my shoes, what would you do? Simply upgrade the cable and cross your finger, or plan on replacing the motor as well?

Are you sure it is the pump overheating, not the controller? Pump is inside cold water and it is really hard for it to overheat.

The docs says there's no electronics at the pump, and you didn't mention any signal wires between the pump and the controller. Even if the pump was overheating, the controller wouldn't have any means to know that.

If it's a controller, might be as easy as failed fan or obstucted vents.

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

BB. wrote: »

The controller (I think) is an external box for this pump family... Is it the controller that is overheating or the pump? I would wounder if the pump can overheat given that (hopefully) it is well cooled as it is a submersible pump (is the well being pumped down from heavy draw--exposing the motor and/or making more lift for the motor/pump?)... Is the controller itself exposed to full sun/hot location? The pump should just slow down (the controller slow the pump down) if there is not enough voltage/current for 100% of rated power (lots of guesses here, I do not know anything about your setup).

Yes, the controller is an external box. I'm not sure if the pump of the controller is overheating. When the pump shuts down, the "Pump Overload" light comes on. I guess that could mean anything. The controller is in my house, so it's not exposed to the sun. Nor do I think I'm drawing down my well too significantly. The flow test we had done when we bought the house 3 years ago was 10 gals/minute.

BB. wrote: »

If this is a centrifugal pump, if you have more irrigation heads/water flow, the higher flow rate will load the pump/motor more (for centrifugal pumps, you can put a valve on the output and close down the flow to "unload" the pump a bit).

The pump has a helical rotor. I can slow it down (or at least reset it's max speed) at the controller which I could use to "unload" the pump. I haven't tried this yet, but may experiment with this.

In general, it still puts out more water than we require. The only exception is mid summer irrigation. Right now, the pump puts out about 6.5 gallons/minute (~100 seconds to fill a pressure tank with 11.5 gallon draw down). I was running into problems when I tried to irrigate with 4gallons/minute for longer than 30 minutes. I just added some more zones, now I shouldn't have any zones requiring more than 3gal/min.

Since most of our water needs occur in the summer, I'm also considering getting a cistern and booster pump (I don't think I can put it high enough to avoid a pump) for summer time use. I would like to do it eventually, but I'm not quite ready to get both a cistern and a new well pump. Decisions, decisions, decisions!

If I can find a happy medium (i.e. a watering regiment that doesn't overload the pump), is it a bad idea to limp along with my existing pump and undersized wiring?

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

NorthGuy wrote: »

Are you sure it is the pump overheating, not the controller? Pump is inside cold water and it is really hard for it to overheat.

The docs says there's no electronics at the pump, and you didn't mention any signal wires between the pump and the controller. Even if the pump was overheating, the controller wouldn't have any means to know that.

If it's a controller, might be as easy as failed fan or obstucted vents.

You're probably right about it being the controller. The pump is wired with 4 wire pump cable. The only additional wire goes to the low water sensor.

The controller is designed to be outside, so it doesn't have any vents or fans. The enclosure is one big aluminum heat sink. I suspect this is the only thermal management at the controller.

BB. · July 2013

Re: Lorentz PS600 with undersized wiring

A helical rotor pump is a positive displacement pump, so you cannot throttle it by adding a valve on its output. You reduce its output by slowing down the motor RPM (like you are doing).

In terms of electronics, running them hot/wide band thermal cycling is not good for them. So, even if you don't change out the pump, if getting higher voltage to the controller will reduce current flow (and I^2R heating), reducing cable drop will be a help.

Generally, when I trench, I put extra large piping (I am cheap, I just use larger diameter ABS pipe), or even drop several sets of pipe into the trench--Makes it easier to "upgrade" down the road if ever needed.

My last guess--Is it possible that pump bearings (and/or rotor assembly) are starting to fail and require more operating current? I would talk with your pump/Lorentz support folks and see if they have any better debugging suggestions.

-Bill

inetdog · July 2013

Re: Lorentz PS600 with undersized wiring

wrdaigle wrote: »

You're probably right about it being the controller. The pump is wired with 4 wire pump cable. The only additional wire goes to the low water sensor.

The controller is designed to be outside, so it doesn't have any vents or fans. The enclosure is one big aluminum heat sink. I suspect this is the only thermal management at the controller.

In addition to BB's good advice, consider these points:

If the three phase VFD in the controller is capable of providing a constant (regulated) output voltage over a reasonable range (check the specs), then the pump will be seeing exactly the same voltage and current when the controller is getting low voltage as when the controller is getting high voltage.
But the controller will have to pull more current from the DC source to do that, and so it will cause even greater voltage drop and also increase the power losses within the controller. That could overheat the controller.
If the motor is getting a lower voltage, then it will try to draw more current to maintain its output speed, and that could overheat the motor, the controller, or both.

NorthGuy · July 2013

Re: Lorentz PS600 with undersized wiring

wrdaigle wrote: »

When the pump shuts down, the "Pump Overload" light comes on.

Is it "pump overload" or "thermal overload"? Does the controller feel hot?

You wire doesn't seem so bad. According to the docs maximum distance for #12 wire is 170 feet. Yours is not much longer than this, so it shouldn't be that much of a problem.

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

NorthGuy wrote: »

Is it "pump overload" or "thermal overload"? Does the controller feel hot?

You wire doesn't seem so bad. According to the docs maximum distance for #12 wire is 170 feet. Yours is not much longer than this, so it shouldn't be that much of a problem.

The light is called "Pump overload". So I'm not sure. Will need to get back to you on whether or not the controller gets hot.

As suspect the #12 at 170ft is assuming 0' of head. I have about 50' up to the surface and pressure tank set to 22-38psi (100-130' of head total). I did talk with a Lorentz dealer. He ran the numbers through their calculator and came out with an 8. His recommendation was to upgrade the wire. He didn't really have any thought as to whether or not there would be any long term damage.

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

BB. wrote: »

In terms of electronics, running them hot/wide band thermal cycling is not good for them. So, even if you don't change out the pump, if getting higher voltage to the controller will reduce current flow (and I^2R heating), reducing cable drop will be a help.

That's a great idea. I just realized my 24V to 48V Step Up DC/DC Converter has an adjustable output voltage range. I just maxed it out at 53V. I'm sure it won't solve my problem, but every littl e bit helps.

BB. wrote: »

Generally, when I trench, I put extra large piping (I am cheap, I just use larger diameter ABS pipe), or even drop several sets of pipe into the trench--Makes it easier to "upgrade" down the road if every needed.

Me too! ABS is cheap compared to physical therapy. This wouldn't be the first time I've cursed our installer!

Texas Wellman · July 2013

Re: Lorentz PS600 with undersized wiring

Put a clamp on amp meter on the output to the pump and measure the amps. The controller converts the output to 3 phase A/C. Also, I was going to suggest upping the voltage at the controller but I see you've already done that.

Good luck.

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

Well, thanks for all of the suggestions, but I think it's all for not. My pump problems are becoming more and more frequent and each time it shuts off I become less and less convinced I'm going to get it up and running again. So, it's time for a new pump. I'm opting for something a little more conventional -- a 230V 0.5hp Franklin. But I am going to incorporate a constant pressure driver for it. It seems like the only downside is the 35watt idle power on the driver. I'm hoping to hook it up to a pressure-sensor activated countdown timer. I may need some suggestions on how to set this up, but I will start another thread for that topic.

BB. · July 2013

Re: Lorentz PS600 with undersized wiring

My one generic warning with "electronic" controllers of any time (refrigerator, pumps, networking, etc.)... Some will either lose their parameters on power off, others will reset back to zero on timers (such as a fridge which will start a defrost cycle on every power up), my require manual reset/turning on after power is reapplied, etc.

Just understand what may happen with this controller on power cycling.

-Bill

wrdaigle · July 2013

Re: Lorentz PS600 with undersized wiring

Understood. I talked with a technician at Franklin and they verified that my plan should work. But I will do some testing and verify what happens when I turn the pump on and off once I get everything installed.

richardimorse · October 2018

I just had a new PS600 control board delivered (previous one was not earthed), it has an internal earth wire on the connector block with a hole in the lug that is smaller than the screw and hole on the connector plate and the chassis body, it is the right size to connect to the main control board mounting screws but that sounds like a bad idea, but then again it will take any induced load away from the board quickly, it could be a design error so my feeling is to just use a smaller screw and mount the internal earth lead to the chassis and the external side of the same connector to a ground rod. (The earth I am talking about is not the motor earth on the Right but the ground rod earth on the left next to the panel connectors, it comes with an internal facing earth fly lead)

Lorentz PS600 with undersized wiring

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