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Saw this with Food Lion in the early 90's. You dont have lubrication issues? Sentronics are rated at 12psi differential. I have found every VFD used in this application, unhooked and bypassed....

Originally Posted by Phase Loss

this market in particular is a organic green we love mother nature store. who like to buy all the fancy stuff for their equipment.

I saw an article in Supermarket News about them a month or so ago. The article did not mention any specifics, only that new strategies were being implemented. Very cool. If it pays off.

Energy savings will eventually catch up to all of us.

Energy prices aren't trending downwards.

this market in particular is a organic green we love mother nature store. who like to buy all the fancy stuff for their equipment.

everyone in California is hopped up on energy savings.

VFD's on condensers, air handlers, compressors, lower head, raise suction, dim sales floor lights, use motion detection for case lights.

a lot of stuff does get bypassed. But eventually the stores want it fixed. Or the contract changes hands, and the new service providers want it fixed.

I've seen that setup before.

Seemed fairly common in late 80s early 90s around here, then it just disappeared.

Drives failed and weren't replaced or guys bypassed them because they were too stupid to finger them out.

Now, most just run 100%

I've started seeing a few pop up on condensers and air handlers, but not compressors, yet.

I mean, 1 compressor per suction group has a VFD. each suction group has at least 3 compressors total.

Originally Posted by Phase Loss

yeah it's on a supermarket rack system. 1 compressor per suction group. and they are using stepper valves too.

Only one compressor per group?

Hmmm.

No redundancy?

I'm already not a fan.

yeah it's on a supermarket rack system. 1 compressor per suction group. and they are using stepper valves too.

Huh. I'd heard that recips were being ramped up & down, don't recall that I've actually seen it anywhere outside the transport world, and they weren't using VFDs. How's it working out for you? The potential for energy savings could be very high, especially in supermarkets. Are you also using the stepper valves as well?

Originally Posted by engineerdave

Interesting question. What prompted this and how would a guy actually verify rpms?

I was setting up some Copeland recip's to run on VFD's. And the VFD's motor parameter settings call for an RPM input.

RPM's are not listed on the nameplate information.

I knew there is a calculation for RPM= 120 X supply frequency(Hz) / number of poles

I just didn't know how many poles are in Copeland's 3D, 4D recip's. It turns out there are 4 poles

So 120 X 60Hz / 4 poles = 1800 RPM synchronous speed.

However, induction run motors don't run 100% synchronous speeds, they have a slip...so the RPM is actually around 1750 for a 4 pole motor at 60Hz.

It's some screw compressors that have 2 poles which run the 3450 RPM

Originally Posted by Phase Loss

Anyone know the typical RPM on a Copeland 3D,4D reciprocating compressor? Something in the back of my head is telling me 3450 RPM...but I cant remember for sure...1750 also comes to mind, but that seems too slow, more like a fan motor.

Interesting question. What prompted this and how would a guy actually verify rpms?

Sorry for that, those are displacements in (CFH) not rpm.

Originally Posted by craig1

Welded compressors have 2 pole motors and run at 1450/3600 RPM.

This was supposed to say 3450/3600 RPM

I agree with craig1 on the RPM's.

It appears -frozen-ocean-'s numbers are actually Copeland's compressor displacements in cu.ft/hr (CFH).

All Copeland semihermetics have 4 pole motors which means they run at 1750/1800 RPM. Welded compressors have 2 pole motors and run at 1450/3600 RPM. This is why semi hermetics make a deeper noise when running compared to welded hermetics which make a buzzing noise.


If you ran any compressor at 7721 RPM, the parts on the inside would quickly be on the outside.

On a side note, its not possible to run an induction motor above 3600 RPM on a 60 hZ source without a VFD

Originally Posted by -frozen-ocean-

3D 1370 rpm to 2127
4D 2386 rpm to 3603
6D 4136 rpm
8D 6463 rpm to 7721

Above min max readings depend on which model is being used

Can you show me where you got these figures? I've been looking all day and seem to find 1750 everywhere.

Thanks

3D 1370 rpm to 2127
4D 2386 rpm to 3603
6D 4136 rpm
8D 6463 rpm to 7721

Above min max readings depend on which model is being used

Copeland 3D, 4D RPM?

Anyone know the typical RPM on a Copeland 3D,4D reciprocating compressor? Something in the back of my head is telling me 3450 RPM...but I cant remember for sure...1750 also comes to mind, but that seems too slow, more like a fan motor.