3 phase scroll

[bodhisatva]

Can you have a scroll compressor run backwards? A co-worker tells me he was an a job where he changed out a three phase scroll and when he turned it on he got no compression-the gauges stayed equalized. He switched two of the legs and it ran fine. Was the rotation backwards? I don't see how. Wouldn't the vanes inside do the same thing even if the motor rotation was reversed? My buddy says there's a spring inside and reversed rotation would make the thing jam (lock rotor in other words). Who's right? Or are we both wrong? What do you guys think?

[mdp]

Mechanically a scroll compressor can run backwards but you'll get no change in pressures. Left reversed the compressor will overheat and burn out the windings. Scrolls don't have vanes, they have two machined plates one of which is stationary and the other rotates on it. Check out one of the websites concerning scrolls and you'll get a better picture on the mechanics involved.

[maxster]

when you start them do it manually...push the contactor in and if your feeling any rise on the suction line within seconds stop the compressor and flip 2 legs.when they run backwards there are no safties except for the internal winding stat...i have seen armaflex on the suction of the compressor flake off like stail bread and the compressor tag melted off the casing.with guages their is hardly any guage movement from being equalized from the first start,and they are quiet! go to hear the difference on the bristol site http://www.bristolcompressors.com/default.htm

[Edited by maxster on 07-18-2004 at 11:10 AM]

[airworx]

scrolls can run backward but youll be replacing it shortly. compressors are loud and amps are low when running backward, change any two leads.

[tonymjr]

yes they can. they must be phased correctly.

[chs]

Also have heard a start kit on a single phase can cause them to start the wrong direction. Any one seen or heard the same.

[caosesvida]

This is where the directions that come with compressor come in handy, they are very obvious and want you to know that you can run it backwards, with troubleshooting info to let you know immediately that it is running bacwards such as little pressure difference between hi and lo side also noisy..

[basser]

Three phase Copeland scrolls are directional. They must run the correct rotation for pumping. Have your gauges installed like previously mentioned and watch your pressures.

However, running a scroll backwards will not cause damage unless it is for a extended period of time. Since no compression is taking place, no cool return gas is entering the compressor. No cooling means the motor gets hot and trips the overload and the overload will protect against a burnt motor here. The real concern is after an extended time some of the oil will be leaving the compressor with no oil returning. Bad news.

Proper single phase components will not make the scroll operate backwards.

[service guy]

Sometimes you can get a three phase compressor to start if it's locked up you can try reversing leads and it may start I've got them going for a day or two till it can be replaced but they really won't last long after they have locked up, replacement is a must.

[deanm]

On all 3 phase equipment you should check phasing with a Phase Meter. Scrolls can run backwards & checking phasing with a phase meter will eliminate ANY guess work!

[AIR PRO]

Originally posted by maxster
when you start them do it manually...push the contactor in and if your feeling any rise on the suction line within seconds stop the compressor and flip 2 legs.when they run backwards there are no safties except for the internal winding stat...i have seen armaflex on the suction of the compressor flake off like stail bread and the compressor tag melted off the casing.with guages their is hardly any guage movement from being equalized from the first start,and they are quiet! go to hear the difference on the bristol site http://www.bristolcompressors.com/default.htm

[Edited by maxster on 07-18-2004 at 11:10 AM]


RE: your link....Bristol put that crap up about copeland scrolls? I'm freaking dying here!!! No way in hell is that a copeland scroll unless someone closed BOTH service valves on it.Are you kidding me....a QUIET Bristol compressor??? No such animal! If ANY scroll is running backwards, you can hear the differance...PERIOD!


STILL laughing my ass off on Bristol calling out Copeland!!!! HAHAHAHAHAHAAAAA Can you say major marketing ploy?? I need to forward this to them, that sound clip is NOT a copeland scroll....actually sounds more like a bristol recip IMO.

[edward301]

They got the Bristol, and the Copeland Scroll reversed
on their website.

The only loud Copeland I have ever heard, is when you
start a 3phase backwards.

[maintmankc]

yeah they will run backwards, if you have never heard one running backwards just kill the power to one while it is running or wait for a shutdown, they spinbackwards as the pressure equalizes (kind of a knocking sound) if you hear that (inly extended) on a start up then it is backwards.

[loosewire]

Hawk,

The sound comparisons are real. Ask anyone that attended the ASHRAE and/or ACCA shows and visited Bristol's booth. They had an actual sound room that demonstrated their new Benchmark recip and Benchmark scroll against a Copeland scroll. The Benchmark recips are running as low as 69 dBA, 71 dBA on average. This has aslo been verified by independent test labs.

[AIR PRO]

Originally posted by loosewire
Hawk,

The sound comparisons are real. Ask anyone that attended the ASHRAE and/or ACCA shows and visited Bristol's booth. They had an actual sound room that demonstrated their new Benchmark recip and Benchmark scroll against a Copeland scroll. The Benchmark recips are running as low as 69 dBA, 71 dBA on average. This has aslo been verified by independent test labs.




loosewire
New Member

Registered: Jul 2004
Posts: 1


Hmmmm, you don't happen to work for Bristol do you?

[AIR PRO]

Originally posted by loosewire
Hawk,

The sound comparisons are real. Ask anyone that attended the ASHRAE and/or ACCA shows and visited Bristol's booth. They had an actual sound room that demonstrated their new Benchmark recip and Benchmark scroll against a Copeland scroll. The Benchmark recips are running as low as 69 dBA, 71 dBA on average. This has aslo been verified by independent test labs.




loosewire
New Member

Registered: Jul 2004
Posts: 1


Hmmmm, you don't happen to work for Bristol do you?

[ericnyc]

yes they can run backwards...carry on.

[Sunnyphx]

Changing the topic some but still related to 3-phase scrolls .... why are the amp draws different on the three legs of a scorll? Seems they should be balanced, but I've heard this is not uncommon with scrolls. Is it the type of 3-phase service. Ours is delta. Does the same thing happen in wye installations too?