Variable Frequency Drive/ Inverter

[Crabb]

While I know most probably use a simple pump to circulate water and then either cut flow by recirculating it through the sump or half-cocking a ball valve, some motors come with the ability to vary flow. The Vectra series comes to mind as a good DC pump that can do this. I thought about switching, however due to other reviews I've heard of unreliability and that it imparts a lot of heat (great in winter, bad in summer) prevented me.

I currently run an Iwaki MD70-RT, and it has been super reliable for the last 2 1/2 years without so much as a hiccup. I have a basement sump and pump from there against about 10 ft of head and I still have WAY too much flow through the sump at 100%. Not only is it running a couple of reactors, but the ball valve is half-cocked. So it should come as no surprise then that cost efficiency for this motor leaves something to be desired.

Running a motor 24 hours a day and 7 days a week adds up quick. Therefore I've been keeping my eye out for a variable frequency drive (Invertek Optidrive E2 specifically). Found one on ebay and have decided to give it a try. I spoke to Iwaki already and they said they run one in their lab, although they gave a few pieces of advice for optimal running.

I've calculated the potential savings, and it should save me approximately 10-20 dollars a month in electric expense (for what I paid it will pay for itself in 9 months). I will monitor this and let you all know. I will post pics and the whole experiment so if anyone is in the same boat they can benefit.

 

[Ron Reefman]

So you are just making an AC pump run like a variable speed DC pump, right?

 

[mcgyvr]

So you are just making an AC pump run like a variable speed DC pump, right?

Yep..
The VFD will allow speed control of the pump..

Very few use them as the VFD's aren't cheap..

 

[Crabb]

Yes, I will be using it to change the speed of the pump similar to a D.C. Pump. As was mentioned they aren't cheap... brand new. But I found 5 on eBay for less than a 100 bucks. That coupled with my Iwaki 70 which I got off of eBay (it said it was "leaking", but the person was speaking about fittings that had been added not about the pump) for 100 bucks. So altogether I'm in at 200, which ain't bad, and probably more reliable than a Vectra. If anyone has a Vectra I'd be interested to know their energy usage change if they had been running a Iwaki, Reeflo, or similar pump previously.

As was mentioned I will post pics before/after install.

 

[Agostinone]

I'm impressed with the savings. Must be some good sized pumps. For reference it costs me about $30/ month to run my hot tub in the winter.

 

[Aqualund]

Are you sure about your calculations? Typically, a VFD uses 3 phase AC input and converts it to a DC signal, and then inverts that DC into a modulated 3 ph "AC" signal which works best on a 3-phase motor.

However, there are some exceptions (at a cost):

1. You can use single phase input to output to a 3phase motor at a cost of about 30% efficiency.

2. You can use 3Phase input to output to a single phase motor at about 50% efficiency of the motor.

3. You "can" use single phase input to output to a single phase motor, but the derating at this point is so extensive (about 80%) that it is not worth it.

Additionally, the Iwaki Motor appears to be a variation of an Interior Permanent Magnet design, and this would need to be accounted for with regard to the VFD commutating the motor correctly. Typically VFD's are set to operate a Squirrel cage design which has the electromagnetic stator surrounding the conductive rotor, rather than a magnetized rotor.

But, advancements never come without people willing to at least try new things...and with that, I am curious to see your results

 

[Crabb]

Thank you Aqualund, I appreciate the info. I'm using a single phase input to single phase output Invertek Optidrive E2 which I hooked up today. I'm running the motor at it's stated amperage and voltage at 48 HZ. I was told by Iwaki that they do not recommend running the motor below 850 rpm. I now have the valve fully open, and so am no longer "throttling" the flow. I will post the before and after electric bill results, as well as photos.

As far as efficiency is concerned and reduction of electricity use, I'm not quite sure what you are referring to with derating since the E2 is specifically meant for single phase input/ single phase output, rather than a VFD for single phase input/three phase output. In such case is derating (other than for altitude and other factors) needed? I would like to hear your take, since I called their technical support and they stated that since the VFD/inverter is specifically designed for single phase motors from single phase input no derating calculation is needed so long as the VFD is appropriately sized, temp controlled, and is not at altitude higher than 1000m.

I agree with you, unless we try it's all just theoretical. Since I could get the VFD used off eBay for 100 bucks it seemed like a good investment. According to the efficiency calculator I used from Honeywell it would pay for itself in less than six months, so I'm interested too! Haha. We shall see, I'm hopeful. Either way it did make the motor much quieter, and both are still running cool even this morning, so at least one positive?

 

[Crabb]

Oh and as far as the payback on the VFD I re-ran the calculation using what I paid for it and the actual settings I'm using. I didn't know before and had only been guessing at HZ. But I'm running it at 48HZ.

 

[Aqualund]

Well I am definitely Interested now. In looking at the specifications of the VFD, I can see that you either need the split capacitor or shaded coil Induction motor for the VFD to work. I assume that since you talked to Iwaki about this, that their motor must have one of these features integral to their design. (which I didnt know)

If that is the case, and this works (like it should) I am equally excited for you now. I mostly deal with servo motors and regular VFD's that have the de-rating I spoke to before...but having this option for single phase solutions is a great addition.

Please keep me posted!

 

[zachfishman]

I've calculated the potential savings, and it should save me approximately 10-20 dollars a month in electric expense (for what I paid it will pay for itself in 9 months). I will monitor this and let you all know. I will post pics and the whole experiment so if anyone is in the same boat they can benefit.

Have you put a meter on that pump to see what the actual power draw is? When restriction is applied to our AC water pumps (via head pressure and/or dialing back via ball valve) the power draw will drop. In terms of power use, dialing an AC pump down via a ball valve vs a VFD might not be very different...

 

[RegalAngel]

Just put in an Ecotech Vectra L1 on my 300g closed loop. Replaced a Pan World 200ps...very noisy.
The pump is very quiet has about 85% the flow and is very valuable in varing flows especially at night....all automatically with ecosmartlive software.
Very pleased I made the switch.
May get one for my open loop as well.

Sent from my SAMSUNG-SM-N920A using Tapatalk

 

[Crabb]

Cool, I appreciate the feedback on the Vectra and the helpful comments. Thus far its been working about a week. I no longer have the ball valve half-cocked, and the motor is putting out the same amount of flow at about 48HZ. I won't know about the energy usage until the month of March. Since I started it mid February I have not really changed much as far as energy usage around the house and I don't have electric heat (although I do have electric air-handlers). My house is well insulated though and very efficient.

If there's little to no change in usage then I might assume the same as far as the ball valve is concerned. But to be honest the motor even sounds more subdued and there's not as much pipe turbulence or noise coming from the basement (I'm getting more sensitive to that kind of junk).

Btw, I also bought a 3K Icecap Gyre to remove four MJ1200's and a Red Sea Wavemaker I had stopped using. Gotta say it moves a lot of water, but it's got a soft annoying sound when spooling up and down in certain modes. Max energy for that is 40W for 12 hours. But it's nowhere near that at 50%, so I'm guessing more like 25W for 12 hours.

Will let you all know of the outcome and post pics.