Digital scroll

[archibaldtuttle]

after serious consdieration of adding this at the bottom of the scroll vs. semi thread I decided it deserved its own.

I spent some time on the phone with copeland today in advance of installing a standard scroll and by the time I got done explaining my variant load characteristics they had convinced me I really should have bought a digital scroll.

Has anyone installed one of these and what is the 3 year out service/failure rate for this new technology. Sounds like a silver bullet but maybe it is just a lead ballon. One thing I can't find in copeland's literature is what parameters they monitor to actually set the percentage of compression time - which I understand cycles 3 times a minute, e.g. breaks down into 20 second increments and separates the scrolls for 2 second per 5% reduced capcity desired down to 10%, i.e. 2 sec. on 18 seconds off.

I still am an advocate for a better proportional electric controller to recognize load changes, proportionally modulate chiller delivery temps. compared to outdoor temps and dew point, and set desirable cycle lengths (although the latter might be moot with the digital technology which is designed almost as constanct run). But I'm interested in the digital scroll since my nirvana electric controller doesn't appear to exist at this point.

let it fly.

brian

[Camalla]

Hello Brian

as far as I understood a digital scroll compressor is as reliable as a standard scroll compressor. It goes through all the standard stress and life tests and qualification that all Copeland compressors do + the solenoid valve to modulate the capacity has been qualified with a 40 million cycle test

The capacity is modulated via a PWM signal (either 24V or 230V according to the solenoid you mount) to the solenoid modulation valve, with a period that can be set between 30 and 10 seconds, typically 20 sec, as you say. The modulation percentage must be decided by the main equipment controller depending on how far the system is from the configured setpoint

Let's say the controller is measuring the return water temperature (supposing we talk about a chiller) and the setpoint is 12 with 4 degrees differential. If the measured temperature is 16 then the modulation is off and the compressor is running at full power, 100%. As soon as the temperature starts to decrease the system controller will start modulating the PWM signal. At 14 degrees for example you are exactly at the middle of the differential band and the modulation will be 50%, i.e., with a cycle time of 20 sec, 10 sec on and 10 secs off and so forth

[BritCit_Juve]

You may find your nirvana at http://www.kimo.de/index.php?file=start.html&lang=EN
But be wary as not all scrolls can be controlled so well.
if you have a variable load it is better to use a rotary, screw or recip as they can operate at lower rpms on an inverter drive.
The copeland digital scroll has specific controls developed for it in the form of the ec552 and ec3-62x which are basically superheat controllers
Brit

[gmansparky]

Hello Guys,

Thanks for sharing your knowledge about scrolls. I am trying to come up with a representative model for a discrete Scroll to verify a Controller design. The objective is control of refrigerant pressure. I need to simulate the discharge pressure from a Discrete Scroll (as part of a room air conditioner design -
std Condenser, evaporator, EEV) so I can verify my controller design.

Thanks in advance for your help.

gman.