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Posted by gofish on July 12, 2006, 11:55 pm
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> The last memory for me was a 10 ton 3-phase on a rooftop. (In
>hind site, nobody would have been there to stomp me out.) A green 3-4
>foot fireball that fizzled to softball size after a good 5-7 seconds.
>3 seconds before I was checking voltage at the terminals.
finish your story. were the terminals in your situation corroded?
did you arrive at a conclusion as to why the peckerhead blew?
i myself have seen some mighty corroded comp spade terminals, corroded
to the point that only a split bolt would work in securing a wire lead
to it....though never seen one blow out just because it was
corroded......
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Posted by Jake on July 13, 2006, 7:22 am
gofish@gonefishin.net wrote:
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>
>> The last memory for me was a 10 ton 3-phase on a rooftop. (In
>> hind site, nobody would have been there to stomp me out.) A green 3-4
>> foot fireball that fizzled to softball size after a good 5-7 seconds.
>> 3 seconds before I was checking voltage at the terminals.
>
> finish your story. were the terminals in your situation corroded?
> did you arrive at a conclusion as to why the peckerhead blew?
>
> i myself have seen some mighty corroded comp spade terminals, corroded
> to the point that only a split bolt would work in securing a wire lead
> to it....though never seen one blow out just because it was
> corroded......
Neither have I... so I'd like to hear more.
I have seen them slowly melt more than once due to heat from bad
connections, though... particularly on 3 phase.
Jake
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Posted by zero on July 13, 2006, 12:54 pm
wrote:
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>gofish@gonefishin.net wrote:
>>
>>> The last memory for me was a 10 ton 3-phase on a rooftop. (In
>>> hind site, nobody would have been there to stomp me out.) A green 3-4
>>> foot fireball that fizzled to softball size after a good 5-7 seconds.
>>> 3 seconds before I was checking voltage at the terminals.
>>
>> finish your story.
I thought I did? No problemo.
show/hide quoted text
>> were the terminals in your situation corroded?
Do not know if they were to start with, not able to determine
afterwards.
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>> did you arrive at a conclusion as to why the peckerhead blew?
I feel more exact saying when the discs failed ( the 3 I remember)
either one or more terminals were hot enough to light-off the
oil/refrigerant mix. (makeshift oil burner= atomized over 70 psig,
spray pattern changing as the hole gets bigger, but ready to burn) or
as the disc failed, the now flying energized wire/terminal arced
across ground for ignition.
show/hide quoted text
>> i myself have seen some mighty corroded comp spade terminals, corroded
>> to the point that only a split bolt would work in securing a wire lead
>> to it....though never seen one blow out just because it was
>> corroded......
>Neither have I... so I'd like to hear more.
And of course you both are correct. I didn't mean to imply that
show/hide quoted text
corrosion>disc failure.
The footnote here is the pressure and fuel potential behind the tin
can.
I believe the corrosion and its results are no different than any
other terminal, lug or relay. In saying that, a relay or contact that
has many cycles and suffered contact point degradation along WITH a
bad terminal connection next to it, getting way too hot can cause the
pressured disc to fail.
One of these units that I remember better, was frequently tripping
on internal overload.
So suppose here you have a open peckerhead with a corrosion build
up to cause voltage drop upon start up, causing the Klixon to trip 19
out of 20 times. Should the Klixon fail closed, you've got a hot plate
wire glowing hard until the wire melts or the circuit trips or the
terminal insulator fails.
show/hide quoted text
>I have seen them slowly melt more than once due to heat from bad
>connections, though... particularly on 3 phase.
>Jake
Yes that was the case with myself on the first few I happen across.
Noticing a large oil spray pattern from under the j-box cover… No
problem. Replace compressor, another job done, the end. Man…I REALY
wish someone would have told me about the fire ball potential though.
Messed my mind up for a while. ( More than the average mind
messedupness I wallow through) :-)
Q: Has there been a white paper or analysis that addresses this
failure that anyone is aware of?
-zero
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Posted by Noon-Air on July 13, 2006, 9:00 am
Replaced a compressor yesterday.... Bristol recip... meter said it was ok...
good readings, but tripped the breaker immediately when it was energized.
when I went to put the gages on it to recover the refrigerant, it was dead
empty. turns out that it blew a terminal out of the peckerhead. There were
no outward signs, no oil, no burnt wires... just dead compressor.
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>>>> This setup has a dual cap for the fan and comp. There also appears to
>>>> be
>>>> a factory hard-start built in. The hard-start relay showed closed (as
>>>> it
>>>> should) with the system powered down.
>> Need model and serial number to see if it was a factory installed
>> accessory
> I'll try and get that tomorrow... if I can make it back over there.
>>> I don't recall ever seeing a factory hard start kit on a 2 ton Rheem
>>> unit,
>>> especially from 1991. Something doesn't jive here. I'd rip it out and
>>> install a SPP6 or equalivent.
>> If its immediately throwing the breaker, the SPP6 isn't going to help.
> There is NO breaker or fuse trip. The compressor doesn't draw any current
> even though I can measure resistance across ALL the windings initially.
> The compressor wasn't too terribly hot.
>>>> Put power back to the thing and I don't hear a darn thing but it won't
>>>> run. I never even heard it try to start. 240 V to both run terminals
>>>> and
>>>> 240 V between one run and the start. The other run to start showed
>>>> about
>>> 15.
>> It sounds to me like internally shorted windings.
> The measurements I gave initially sounded about right for that size
> compressor. If I had internal short.... I should get an external OCP trip,
> shouldn't I?
>>>> Why the heck would a internal trip that fast? I can't even see a
>>>> current
>>>> draw when it should be trying to start.
>> Shorted/grounded windings
> Steve, I already measured (and even megged) the windings. I don't find a
> short anywhere. The compressor has V at the terminals but doesn't draw any
> current. I'm going for Paul's thought that the connects are dirty or
> loose. A condenser sitting outside for that long could stand to have that
> crap cleaned up, anyhow.
> My real question, I guess... was how fast a internal O/L trip would
> occur... and thus indicate a mechanical problem in the compressor.. or a
> failure to start due to bad caps?
> Jake
>
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Posted by gofish on July 13, 2006, 7:20 pm
>Replaced a compressor yesterday.... Bristol recip... meter said it was ok...
>good readings, but tripped the breaker immediately when it was energized.
>when I went to put the gages on it to recover the refrigerant, it was dead
>empty. turns out that it blew a terminal out of the peckerhead. There were
>no outward signs, no oil, no burnt wires... just dead compressor.
ok, I'll bite. How could your meter say it was ok (ohming the
windings?) if one of the terminals had blown out?
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>hind site, nobody would have been there to stomp me out.) A green 3-4
>foot fireball that fizzled to softball size after a good 5-7 seconds.
>3 seconds before I was checking voltage at the terminals.