Myth or Fact?

[cretan]

According to manuals,a compressor should not be bumped/started in a vaccum.I read a thread a while back that said the comp. could explode if stared in a vac.Is this true or false? PS:installed a new tecumsy cond. unit and while it was in vac,turned on breaker and it tripped.sounded like a dead short.also,compressor should not have started if system was in vac.(pressure control).checked the pins and compressor is open between all.220v/single phase.supplier is blaming my boss.what do you guys think?

[Phase Loss]

fact.

scrolls can be nasty.

[shaka]

fact..

u should not turn it on when its in a vacuum..

when unit is in a vac the internal resistance will be a lot lower
So if you turn it on it will usually jump from terminal to terminal direct short.

if you are lucky it will be okay. if your lucky

[shaka]

if I was the suplier I would blame your boss too.

you dont have to have both leg to short it to ground..

sorry im with the supplier with this one

[cretan]

Thanks guys.

[shaun66]

i tried it once on a 15 hp discus, for the hell of it. took out compressor breaker, 2 of 3 200 amp fuses on rack, and 200 amp breaker in rack house. definately a dead short

[dangpgt97]

Thats kind of an odd situation you got there. Ive seen more than 1 stuck closed pressure control take out a comp. But whats the point of throwing the breaker while its in a vacuum anyway. I wouldnt think it would take long for the motor to overheat and die with no load at all on it and no cooling. Plus I dont know that oil would make its way up to the cylinders when the systems in a vacuum?

[jdwendling]

I have been told that it can arc at the fusite (where the leads leave the compressor motor into the electric box) and burn it out,wasting the compressor

[Joe Harper]

The copeland manual states that applying power to compressor in a vacuum will burn fusite plugs.

Why was the breaker turned on anyway? If you are trying to heat up the crankcase pull the compressor plug out before powering up.

[MikeySq]

How much of a vacuum are we talking about before this carnage happens???? I've seen compressors run in their own vacuum due to a jumped pressure switch for a long time

[Joe Harper]

It is probably on a compressor that has never been in use. Im sure some oil on the terminals has some insulating effect.

[Airmechanical]

it takes at least 3 things for an EXPLOSION

fuel, spark, oxygen

compression helps as well to make a nice explosion

in a vacuum, there is no oxygen or compression

so no, it won't explode



.

[Tiger93rsl]

I had a compressor start on me while it was in a 500 micron vacuum. The short was so bad it blew all 60 amp fuses coming into the RTU, triped the 80 Amp main breaker and weilded the contactor shut.

[mspanky]

it takes at least 3 things for an EXPLOSION

fuel, spark, oxygen

compression helps as well to make a nice explosion

in a vacuum, there is no oxygen or compression

so no, it won't explode
.

We're not talking combustion explosion here. A big spark by itself will blow the terminals out of the crankcase followed by oil. Then you may have a fire. Think of throw a nitro tank in a fire. No fuel or oxygen inside either, but will still explode.

[itsiceman]

http://202.56.127.90/nacg/ServiceBook/general.pdf

Never saw an explosion yet but have seen

terminal venting with what lawyers now call a "thermal event"