RO high pressure pump

[Clinkis]

I purchased a used commercial RO for water purification that I'm planning on repurposing for sap and I'm wondering if I can reuse the high pressure pump or if anyone uses this style of pump. It's a Pentek submersible style pump, 2 hp, 230V 3 phase. Says max pressure is 275 psi. Unfortunately it doesn't have a GPH rating but I'm guessing it's in the 500-600 gph range. The pump was running five 4" membranes in series. My plan is to reduce it to a 2 post system. Can anyone tell me anything about this pump and if it will work ok for sap?

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[NH Maplemaker]

Clinkis, I'm know RO expert, but that being said. If the pump worked on water it should work on sap ! The membranes are what's going to make it work well with sap. Some of the newer maple RO membranes work very well with lower pressure, But I don't believe you will get any were close to 500 to 600 GPH with that pump! I was running an older SpringTech RO with a 500 PSI pump with three 4" membranes. I would run the operating pressure at 275 PSI. It also had a 1HP feed pump and would only process 250 GPH until warmer sap temps came. Then it would do around 275 GPH !

[Clinkis]

I'm just talking about flow rate for the pump. Trying to determine if it will have appropriate flow to run 2 membranes in series. I found some more info and I believe pump runs at 9 GPM which would be 540 gph which I think should be no problem considering I'm currently running a single xle4040 with a 190 gph procon. I plan on replacing membranes with either MES or XLE 4040's.

Just curious if anyone has used this particular pump or similar in a maple RO.

[mkoehler79]

I have the multistage type pump. The biggest question is what the pump curve is to determine flow at 275 psi. Otherwise if this is already running 5 membrane in series, 2 in series for Maple should be fine with recirculation.

[mellondome]

You will want to have a supply pump. You will need the supply to be able to push 50-80 psi. This will allow you the flow you need before the pump maxes out on pressure and stops flowing volume. When the system was connect to purify water, there was pressure already comming to the pump.

So if you add 60psi supply, then your max output is 335 psi. But @ that pressure level, your flow will be 0. So take the pump performance curve.. find the flow you need.... and subtract the 60psi for the supply pump (or whay ever it rates @ for the same desired flow) and ths will be your target membrane pressure.

[Bricklayer]

I did the same as you and re-purposes a commercial RO that had 3 4" membranes. I called the manufacturer of the RO and they sent me the info on the pump and other components. The RO manual didn't have a pump curve graph in it but I was able to contact the manufacturer of the pump and get that.

[Clinkis]

Thanks for the info. I will contact the manufacturer and see if they can send me the pump specs. I'm used to working with procons that give consistent flow regardless of pressure. I had originally planned on replacing pump with a procon but if this will work then I can save the money.

[Bricklayer]

I've never seen a pump like that. It's submersed in a well. Says right on the decal. Can you take it out or is it a sealed unit. Would be nice if it was removable. Give the well a good cleaning before using it on sap.

[Clinkis]

Yes it's removable. I will take it apart and inspect and clean it.

[Bricklayer]

Does the RO have a VFD for the 3 phase power or are you going to install one?

[Clinkis]

No it doesn't. Don't really see why it would need one. Pump says it's designed for constant use. It came out of a hospital dialysis lab and was running constantly. As far as any energy savings, I doubt for the 2-3 hours a day during the sugar season it runs I would offset the cost of installing one. I have also read that in some cases if the pump is not designed to run with a VFD you can do more harm than good. Is there some other benefit I'm missing?

[Bricklayer]

Do you have a 3 phase power source? That would be one of the reasons a vfd would be needed. It will take single phase 220 and power a 3 phase motor. I'm no expert of vfd's but my neighbour just installed a new 3 phase motor on his drill press and it uses a vfd because he didn't have 3 phase power and it works great. Instead of moving the drive belt to change the rpms of the motor it is all done with a knob on the vfd. Probley a different kind of vfd to control motor speed but same concept.

[Clinkis]

I do have 3 phase power in my barn. My sugar shack is my old milk house. Unfortunately panel is at opposit end so will have to run a new line or at least a neutral to get 3 phase. So with VFD you can run a 3 phase pump off single phase?

[Bricklayer]

Yes, you will have to get the specs on the pump and see if it's able to run off vfd. A vfd might cost less then running wire
The vfd for my neighbours drill press was about $300.

[Clinkis]

Interesting. I may have to investigate that further. I'd really like to know that this pump is going to work properly before I do either. I'll probably rig up a temporary service in my shop and do some testing first. I have 3 phase in there too and the panel is nice and handy.

[maple flats]

When you use a VFD to run a 3 phase motor, you loose power. I've heard between 25-35% loss of power, thus a 2 HP 3 phase will only yield somewhere in the 1.3-1.5 HP. Do some checking. If you have 3 phase I think you will be far better off running the wire. More power when using and use less energy doing it. 3 phase is more energy efficient.

[Bricklayer]

Some info on VFD's and how they can save on energy costs

http://ecovisionslc.org/how-does-a-vfd-save-energy-and-money/

[mkoehler79]

When a VFD is used in a situation where single phase power is used to create 3 phase (via the VFD), the VFD needs to be sized somewhere around 50% larger depending on manufacturer of course. I think this may be what flats is referring to. Otherwise, there is minimal to no power loss using a VFD with 3 phase power supplied to it.

[Clinkis]

There seems to be a lot of conflicting info out there on the benifits of using a VFD vs not. And differing opinions. Not sure what to think.

[mkoehler79]

IMO, a VFD wouldn't do much for you on a RO as you are typically trying to run at Max capacity to get the most out of the machine. On vacuum, this is a different story in regards to possible energy savings.

[Clinkis]

Was kinda my thought as well seeing as how it only runs a few hours a day during a small 4-6 week window. That said, getting to know a little more about them has made me think there are other applications I could use one. Mainly my pool pump which usually jumps my hydro bill about a $100.