Scroll compressors, good or bad??????

[Oregonbythesea]

I had an inquiry today about using scroll compressors in transport units. I know TK has, or at least, had, some of them in a unit. Does anyone have an opinion on their use in transport units? Thanks

[tony2009]

I believe that opinions on them will vary depending on where you are and how they are used.
The scroll compressors here don't enjoy a particularly good reputation but I understand there are those who believe they're very much up to the task. I've seen quite a few scroll compressors replaced over the years for any number of reasons.
Personally, I'd take a unit with a reciprocating compressor any day over a scroll. TK reciprocating compressors generally rebuild well and keep on working; can't say I've found the Carrier compressors to work so well after a rebuild. I believe Carrier is looking to scroll compressors also, so maybe they've discovered the secret to a long and happy life.

[perthtech]

i guess we will see with the Vector 1550, although high ambients could be a problem.....:-)

[vehikool]

Scroll compressors should be fine in transport refrigeration, providing they are not allowed to run in a vacuum as that is where the problems start, they should have an L.P, cut out switch fitted and set up correctly to prevent them running in a vacuum, on the small fridge units Hubbard and Carrier do not appear to have any problems, they are so quiet (compared to a std compressor) when on standby.
Tommycool

[Oregonbythesea]

Thanks for the comments guys. I hope there will be more but I am happy to read these. It will help us with our decisions. BTW, we wouldn't set up any system with out cut-outs.

[NoNickName]

Scrolls are ok for air conditioning, but not so for refrigeration.

[chemi-cool]

Scrolls are ok for air conditioning, but not so for refrigeration.

Please explain, I've never heard that statement before and I'm sure there is more to it.

[NoNickName]

Admittedly, many scroll compressors manufacturers tried to enter the refrigeration market with little success. Part of it is due to the inner features of the scroll compressors, that do not perform as good when subject to high compression ratios (the isoentropic efficiency of scroll compressors peak at design ratio, and worsen very rapidly moving left and right of it. Recips have a flatter isoentropic efficiency graph), part of it is due to the fact that scroll compressors do not forgive liquid hits, while reciprocating compressors may accept a little slugging.
Additionally, recips may be overhauled, while scrolls can't.

[chemi-cool]

So, its all in the system design.
The reason I ask is because I use more and more scrolls in refrigeration, mainly in + temp cold stores and milk cooling. So far the results are very satisfying.
The two firms I use is Copeland and Daffi's.

[NoNickName]

Again, positive temperatures are no problem for Scrolls. I was mainly talking about LT systems.

[chemi-cool]

I get your point.
What your opinion about Copeland scrolls for low temp [-25°C evaporation] with head cooling system?

[Oregonbythesea]

I too need low temp evaporators -37C (-25F). It appears that Copeland and Danfoss both have condenser temperature tx valves into the a middle stage section to prevent the need for head cooling. This approach makes it more like a screw setup and should work fine. One of my concerns has been oil return but it looks to me like they all have oil sight glasses on them. Please keep the ideas coming.