Does anyone know as the mentioned compare to inverter comp.?
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Does anyone know as the mentioned compare to inverter comp.?
No, a digital scroll is a compressor with a ON.OFF scroll operated via a solenoid valve. When solenoid is energised, the scroll is not connected to the motor. The motor still runs, virtually with no load at all.
When the solenoid is denergised, the scroll is returned to operation. By modulating the number of ON and OFF in a given time, the required cooling capacity can be achieved.
This is Copeland Patent and it is the greatest piece of BS ever seen in the refrigeration market.
That's means motor still run at fixed speed but varied tourq,
and consume power from low to high. Is it correct? And it still use R-22 which will be fade out soon?
Yes, correct for the first part, but no R22 models as far as I know.
It sounds like a Brysch variable capacity compressor used in an old commercial unit. It used a solenoid to hold the intake valve open, so the compressor can "freewheel" cycles as necessary. There is also a magnetic pickup coil mounted near the crankshaft that pulses every time the crankshaft comes around (right before the suction valve opens). Of course, the controller switched the solenoid on and off many times a second (as opposed to once or twice a minute for the Copeland Digital Scroll), which made it pretty noisy.
The power curve is almost linear: 100% Capacity = 100% Power consumption, 10%Capacity = 20% Power Consumption.
The idea is there is energy still required to run the motor.
There are 4 models; 4&6HP for R22 and R404a.
THis compressor takes advantage of the axial compliance between the fixed and orbiting scroll. A tube connects the discharge side of the compressor above the scroll set to the suction port. A solenoid opens and closes to control capacity. When it opens the orbiting scroll moves up several thousandths. The scroll still orbits, but doesn't compress.
I have used them in small chillers and they work quite well. We have achieved +/- 0.2 F at low loads.
I am sorry I don't have any real detailed power consumption data.
I was recently given the opportunity to install a 6hp digital scroll in a Hussmann Protocol unit on a +25f header carrying multi-deck dairy and produce cases. The controller is an E2 version 2.41f01. I have installed 30 or so Einstien 2 controllers on existing equipment in the last year. Utilizing VSD control for condenser fan/tower control and for Compressor capacity modulation. Where the digital scroll is unique is in the fact that you can go from 10% - 100% capacity. Most of the compressors under VSD modulation are recips and that limits you to a 50% - 100% to prevent oil pressure issues. The digital scroll I installed was literally tagged "Sample" and the install was supervised by an engineering crew from Emerson (Copeland). It has been 4wks of smooth and trouble free operations. The compressor is best suited for interface with Emerson's E2 and they go together well. The E2 has a specific algorythm that is written for digital scroll control.
In summary, it appears to be a well thought out quality product and a great option for energy savings and better system performance (due to steady suction). If you are extremely experienced with the E2 and a good refrigeration tech the install is easy. I am eager to see them in the 15hp line so I can fix all of these piss poor design applications that Hussmann put out on their racks. I mean 5 - 15hp per suction header and no stepping!!!
Azeotrope
Azeotrope,
What do You think to install a inverter for 15 HP Scroll for HVAC, to save more energy !?
Sure that the other parameters how,EVaps and Conds are Prepared too!
Are there matters with oil pressure!? (maybe!)
All informations will welcome!
thanks!
Energy saving of Digital scroll/
I think uppon load characteristic and control device.
Please explain why the Copeland Digital Scroll is the biggest peice of BS on the market?Quote:
Originally Posted by NoNickName
Also - does anyone have ANY power consumption data for the Digital Scroll at lower steps than 100% capacity?
Thank you
The digital scroll has a solenoid that when energized pulls one of the two scrolls out disengaging its pumping capacity. I think the better term would be energize no pump and de-energize pump. The more times a minute the scroll is not pumping this reduces compressor capacity. You are right there is no power savings because the motor continues to run at a high RPM. The compressors were designed for the Sea container to maintain tighter temperature control but don't misconstrue this to being a energy saving compressor. If you want to save energy a VFD on a scroll would be a better idea but I don't know due to the oil pump or lack there of how much a scroll can be ramped down. I tend to believe the other poster who wasn't impressed.
The Inverter System has more capacity steps than hot-gas bypass or multiple circuit systems, but capacity range is limited by minimum motor speed. The capacity change is slow because motor frequency changes must be performed slowly to avoid damage due to insufficient compressor lubrication where as the Digital Scroll system has the most precise capacity matching capability because it provides continuous modulation between 10% & 100% capacity with widest available capacity modulation range available. Also the oil management issues are negligible, since compressor motor runs at constant speed. So with this in mind i'm sure it saves energy but I don't have any numbers
You obviously don't know much about electrical motors and digital scroll compressors.Quote:
Originally Posted by 128cyclist
First, contrary of what you are saying above, every electrical motor, when is not loaded, pulls less current than when it is loaded. Hence, digital scroll power consumption falls when is unloaded to 10% that of full load capacity.
Second, inverter loss accounts for approximately 15% of total power consumption. Inefficient hot gas bypass method must be used for low capacities. Liquid injection must be used under conditions of high ambient temperature.
And last, compressor have optimum performance only on one speed, and other speeds are less efficient, hence, in practice are at VRF/VRV multiple compressor setups of which one is inverter and others are fix speed as optimum solution rather then one bigger inverter compressor (what would be cheaper).
To add to that, inverter system can run at high frequencies for only short period of time since this increases both oil circulation rate and the motor temperature.
http://www.ishrae.in/journals_200420...article03.html
It seems that he doesn't have explanation.Quote:
Originally Posted by snowed_in
Probably, because he works for other compressor manufacturer. ;)
Or just because I didn't notice the question. I will be back from holidays with a due answer. Until then, :o cheers.Quote:
Originally Posted by nike123
I would like to see some independant part load perfromance data for leading digital scroll & VRF manufactures
Its no good just looking at the manufacturers own data & comparisons because they will always pick the best data for their own system & choose the worst data from the compared competitors data.
Manufacturers will always put some spin on available information to make their system look as good as possible & try to hide any disadvantage.
So if any one has some independant performance data to compare DS with VRF please post a link on this thread.
Untill there is some hard data enginners can debate untill the cows come home about the advantages & disadvantages.
Becasue power consumption for variable capacity system also fluctuates from full to part load, it is also best to guage the performance of a VRF system through IPLV or Integrated part load.
ARI has a test method to measure IPLV which is quite similar with COP, ONLY the system is tested at 4 capacities (25%, 50%, 75%, 100%).
I've came across some values, the Digital Scroll is 3.56 while other VRV/VRF systems are 3.45 and 3.