RO phase conversion.

[madmapler]

What type of phase conversion is used in the larger ROs with 5hp pumps and up? I'm assuming most of these motors are 3 phase. From my research so far it seems that a VFD is the best solution but I have never really looked at a larger RO with this in mind. Thanks.

[GeneralStark]

If the RO has a 3-phase motor than the way to go is definitely a VFD. Been using them for several years on vac. pumps without issue and have been very impressed with their capabilities. I would imagine there are many ways a VFD could be programmed to run an RO ie high pressure shut off, low flow shut off, etc...

That said I have no experience with 3-phase ROs, but I certainly would like to have one.

[wiam]

I believe unless they are built to run on 3 phase they have single phase motors. Thad has 3 phase machines as he has it in his sugarhouse

[madmapler]

I guess my next question would be why not? The amp draw would be considerably less(31 to 35 amps 220) as opposed to 20 or less on a 3 phase 7.5hp motor. You could soft start the 3 phase w.VFD which is another plus and as G. Stark says, there could be many other options possible. Another thing is 3 phase motors are far more durable.

[500592]

I think to get one in three phase is more expensive and it's not like the motors run 24/7 365 days a year.

[mountain man maple]

If using vfd to take single phase to 3 phase a ro would need a vfd for each motor. If your using single phase to make 3 phase then amp draw would still be the same on single phase feeding vfd as it would be with a single phase machine.

[madmapler]

I think to get one in three phase is more expensive and it's not like the motors run 24/7 365 days a year.

I'm planning on building one and from what I've seen so far, the motors are cheaper and they are far more bullet proof. The added expense of the vfd is'nt that big a deal.

[madmapler]

If using vfd to take single phase to 3 phase a ro would need a vfd for each motor. If your using single phase to make 3 phase then amp draw would still be the same on single phase feeding vfd as it would be with a single phase machine. I would only use a VFD on the pressure pump. The smaller pumps would be single phase. I was under the impression that there would be less of an amp draw using a vfd on a 3 phase motor as opposed to going with a single phase motor of the same size. You could still curb the amp draw at start up thus decreasing the amount of power that had to be available which is a consideration in my case. (5/4... I did some more looking around and apparently there is'nt as much savings power wise as I originally thought. If anybody had some experience in this regard I'd like to hear. Thanks)

[maplwrks]

Sounds overcomplicated to me

[madmapler]

They're really not difficult to incorporate. I'm just exploring the possible benefits and options they can provide before I start building my RO. I appreciate the feedback.

[Rossell's Sugar Camp]

Three phase motors are much cheaper. Due to less mechanical components inside the motor. They are also less likely to fail under a load. And as far as saving money on your bill, you will not make a difference at all unless you have a three phase entrance put in. Bottom line. Unless you have plans on running the motor at less than the nameplate rpm, the vfd is not worth it. But if you have a three phase entrance by all means go three phase.

[BreezyHill]

It would be much cheaper and easier to utilize a few pressure switches for low pressure and high pressure for unit protection.

Ben