Question on 208 Voltage of 3 phase compressors.
TURTLE
I'm into it with the local country Electric power company. They only service
service out side city in rual areas and the got some wild ass ideal as I see
it. Now i could be wrong here but I think I'm right here.
I have 4 --- 10 ton Goodman gas packs in a row on a basket ball Gym with
208 service supplied to them. The power company is letting the 3 phase power
supply to them drop below 200 volts and has told me that there is no trouble
if they drop the power to 195 volts. I told them i have hell keeping them
running on the 208 but when they go for less than 200 they will not start
about half the time. The other part of the story is they let one leg drop to
much as 187 and the others at about 203. They say there is no problem but
this is the 5 th copland compressor I have changed out in 4 years. They
average about one kill a year and I say ok if customer will put up with it.
We raised some hell and they come and got the voltage up to 210 / 209 / 206
reading left to right. These are good but the 195 just won't get it in my
book.
So , is 195 volts good on a copland , New Millium something , 3 phase
compressor rated at 3 phase / 200 volts to 230 volt / 60 Hz. . They did
agree with me on 187 volts being a little low. Am i not up to date on
Voltage rating / loosing it or am I being feed a line of bull ? Yes , every
other school in outline areas I work on has the 208 service and they have
210 to 214 on all legs all the time but with the same power company. This
school is out there in the booneys for they have to pipe sun lite to them.
TURTLE
p...@see_my_sig_for_address.com
wrote:
Local power here is allowed to drop to 197 on nominal 208
services downtown. I think it's a city ordinance. Had a bunch of
equipment that thought the ordinance was a bunch of shit, and refused
to start ( I think they were Forma ultra-lows and such, I forget,
years ago ), had to put a bunch of buck-boost transformers on them.
187 definitely don't get it on nominal 208.
For that piping sunlight, try some fiber optic, great stuff
for it :-)
Paul ( pjm @ pobox . com ) - remove spaces to email me
New HVAC/R program for Palm PDA's !! http://pmilligan.net/palm/
Free demo now available online !!!!
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My personal site is at http://www.pmilligan.net
moonlig...@pop.tcsn.qwest.net
pjm@see_my_sig_for_address.com wrote:
Turtle had similar problem on some ice cream trucks running
onboard generators, overamping and burning windings.
When I contacted Copeland they said not more than 10%
over or under. Also had some TK units that the computer
would not let run on anything less than 200v. BTW check
the contactor, I noticed that when I had low voltage
going to the the pull in coils I got a lot of chatter & burning.
Dave
BOB URZ
TURTLE wrote:
It might b helpful to get a power quality consultant come in and
do a PQ test. They can leave a monitor that will log current and
voltage on all three phases over time. Get the true data and then
confront the power company. If you looked at it over a few days
period, you might be surprised on how bad it might actually be.
You can get a continuous conversion UPS, but the cost of that
for a high current 3 phase power would be high.
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RSCamaro
wrote:
>This is Turtle.
I have 4 RTUs at a job each running 2 - 30 ton Copeland Discus
compressors w/ unloaders. The power this summer dipped as low as 186
volts on one leg with a high pair of 194 and they seem to have come
through it ok. The units are approximately 3 years old. The units
are pretty well protected with voltage monitors that I have set at
200v with a 10% cut out. Try installing voltage monitors for times
when the voltage really drops out.
...Ron
--
68' RS Camaro
88' Formula Bird
http://www.frontiernet.net/~rscamero
Some are wise and some are otherwise
TURTLE
<moonlig...@pop.tcsn.qwest.net> wrote in message
news:3F6B1090...@pop.tcsn.qwest.net...
This is Turtle.
The Power co0mpany sayas they are allowed to go to 195 volts and Goodman say
turn them off at 199 volts or less. The contactor look like a smoke house
where the smoke meat in. I get a volume discount from the warehouse on them
for I buy in Bulk now. I'm working on a volume discount on compressors now.
TURTLE
TURTLE
"BOB URZ" <"sound(remove)"@inetnebr.com> wrote in message
news:3F6B77F9...@inetnebr.com...
This is Turtle.
I don't need a monitor at all for we was looking at 195 to 197 volts on the
boxes and the power company rep. standing there saing it was OK. They got
ball to say We ain't doing anything.
TURTLE
TURTLE
"RSCamaro" <rsca...@hotmail.com> wrote in message
news:r07nmvkecekubj8fs...@4ax.com...
this is Turtle.
My 5 ton scrolls just will not crank on 195 volts and them watching them do
this and volt meter on the box showing the voltage. They are saying That's
no problem to us. I said my shit don't run but it's no problem of yours?
Answer No problem to us.
TURTLE
volts500
"TURTLE" <tur...@worldnetla.net> wrote in message
news:bke8ef$pdu0$5...@ID-79743.news.uni-berlin.de...
Sounds like a voltage unbalance problem. A voltage unbalance over 2% is
cause for concern as it will cause a _lot_ of excess heat in a motor
winding. With readings of 187, 203, and 203 the voltage unbalance is about
5.5%. I know it's a real PITA, but it can be verified if you cut the (bad)
compressor open and look at the stator windings......one or two windings
will be blackened......the winding with the largest unbalance will be the
darkest. The third winding will still have a copper look.
As far as the cause, well, it may or may not be the power co's fault.
It's possible that other (unrelated) single phase loads aren't balanced on
the 3 phase system. This can happen over the years when other large
single-phase loads get added to a 3 phase system and nobody checks the load
balance on the system before deciding which phase(s) to put the new loads
on.
Another cause can be that sometimes, if there is a fairly large
_continuously_ running 3 phase motor somewhere on the premises, that if a
main (individual) fuse blows (on a feeder or at the main switchgear) it can
go undetected because the continuously running motor will generate the third
phase and other 3 phase motors (like the compressors) will still start and
run........but a voltage unbalance will exist and eventually burn up the
compressors.
This can happen on the power co. side too.......like at a nearby pump
station........in which case the power co. would need to step up to the
plate and take care of it.
Things to consider anyways.
TURTLE
"volts500" <volt...@tampabay.rr.com> wrote in message
news:QIRab.14136$kg....@twister.tampabay.rr.com...
this is urtle.
There is a lift station at the school that has a pump in it to lift sewarge
out to lines and it can be locked up and no one would know it. i will have
them check it monday morning. The pump does not need to run unless it rains
and extra water enters the system.
Now to the load is not balanced on the service to each building of the
school. well the electric meter is at the service coming into the school but
the power company signed a contract to keep the wires, service, phase, load
balance, and everything before entering each building good and responciable
for it. They play wire switch about every month to keep the power just
running and not fade out. They will tell you that 108 volts to the 120 volt
service is good as gold to them. I think they flip a coin to see what
building is going to get good power this month and flip it again next month
to see who get good power that month.
Now to the Power company steping up to the plate and do something. Well here
in Louisiana our Public service commissioner is going to prison for 30
million in kick backs, ex Governor edwards is in prison for 8 years , in
Dallas Texas, Bobby Odem Housing / erburn developement / Agriculture
Comissioner under indightment for 28 Mill. in kick backs, they have over 200
people under investigation of over 1.3 Billion in kick backs right now, and
Power companys do as they please. The only one we can call is Ghost Busters
i guess for everybody is out of office or town. I guess I'm the highest
public offical in a office to say anything now for I have a volt meter and
know how to read it. You can call the public service commissioners office
and all you get is recording saing. Leave a message and if we come back or
don't go to prison. we will return your call. You will start reading about
in the news soon but around here kick backs is away of life.
TURTLE
gerry
On Sat, 20 Sep 2003 05:37:52 GMT, "volts500" <volt...@tampabay.rr.com>
wrote:
>Sounds like a voltage unbalance problem. A voltage unbalance over 2% is
>cause for concern as it will cause a _lot_ of excess heat in a motor
>winding. With readings of 187, 203, and 203 the voltage unbalance is about
>5.5%. I know it's a real PITA, but it can be verified if you cut the (bad)
>compressor open and look at the stator windings......one or two windings
>will be blackened......the winding with the largest unbalance will be the
>darkest. The third winding will still have a copper look.
With many motor designs, the windings on the low voltage leg will actually
act as a generator, trying to raise the leg! This causes some bizarre
current phasing in the circuit.
>
>As far as the cause, well, it may or may not be the power co's fault.
>It's possible that other (unrelated) single phase loads aren't balanced on
>the 3 phase system. This can happen over the years when other large
>single-phase loads get added to a 3 phase system and nobody checks the load
>balance on the system before deciding which phase(s) to put the new loads
>on.
This sort of thing is easy for the power company to check. What are the
voltages at both ends of the service drop. If the voltages are ok, than
look into a feeder problem. Often the service drop is undersized as are
feeders. The wire gauge can be suitable for the current but wire length
not accounted for.
It's also worth noting that each phase is handled by it's own transformer
by the power company. If the voltage of one leg at the head of the service
entrance is low, possibly that leg's transformer can't cope with the load.
Ther may be other customers on the same transformers with heavy loads on
one phase.
Asymmetric sized transformers are not unheard of in power distribution -
one upgraded to handle an unbalanced situation.
I final power company possibility is a bad power factor correction unit
or one not matched for the current situation on that leg. Since most loads
are inductive, power companies (and sometimes customers) often use large
capacitors to buck the effects of inductive loads. This is a real PITA if
the load varies. Thus many commercial customers pay different rates
depending upon power factor of their load. I've wired a factory where some
loads has their own power correction. It helped the feeders out as well
:-)
>
>Another cause can be that sometimes, if there is a fairly large
>_continuously_ running 3 phase motor somewhere on the premises, that if a
>main (individual) fuse blows (on a feeder or at the main switchgear) it can
>go undetected because the continuously running motor will generate the third
>phase and other 3 phase motors (like the compressors) will still start and
>run........but a voltage unbalance will exist and eventually burn up the
>compressors.
Yup - I already mentioned one phase of a motor can be a generator before
reading this! Power flow on that leg is reversed.
Voltage is a poor metric by itself, all this can be found by comparing
current and voltage phasing. Can't do that with a simple meter.
>This can happen on the power co. side too.......like at a nearby pump
>station........in which case the power co. would need to step up to the
>plate and take care of it.
If the three phase loads are large enough motors with suitable design (by
chance), one phase can actually be dead and motors are supplying it.
Usually, this situation extreme doesn't survive a power outage.
gerry
--
Personal home page - http://gogood.com
gerry misspelled in my email address to confuse robots
Tekkie
> This is Turtle.
>
> I'm into it with the local country Electric power company. They only service
> service out side city in rual areas and the got some wild ass ideal as I see
> it. Now i could be wrong here but I think I'm right here.
>
Well, I would go to the School Board & say these clowns are costing you
bucks & here's why. Then they would talk to other boards and scream &
hollar at the utility commission loud enough that something would happen.
Plan #2
Mylar ballon(s) directed at pole at suitable time.....
--
Tekkie
Politicians & diapers are filled with it & both should be changed regularly.
TURTLE
"Tekkie" <Tek...@comcast.net> wrote in message
news:MPG.19d6e87e9...@news.pa.comcast.giganews.com...
This is Turtle.
We have got to the bottom of the problem now. The power company has a spec
book that tells all the voltages of all the equipment sold and their voltage
will run all of them with the 195+ volts. now there is one problem about
this is the book does not list scroll or any newer model compressors in it.
it has only the rebuildiable models on 3 phase. I started looking at the
book and it was printed in 1964. They are still using the 1964 version of
the latest compressors and the voltage needed. This is why they can say they
are in all ways giving the right voltage. Damn it is bad when i've been
proven wrong by a book. On compressor before 1964 you only needed 195+ volts
to operate them. I ask them if they ever thought about getting a updated
version one day. They did not say a word. So here we are and i will see what
happens.
TURTLE
gerry
wrote:
>This is Turtle.
>
>We have got to the bottom of the problem now. The power company has a spec
>book that tells all the voltages of all the equipment sold and their voltage
>will run all of them with the 195+ volts. now there is one problem about
>this is the book does not list scroll or any newer model compressors in it.
>it has only the rebuildiable models on 3 phase. I started looking at the
>book and it was printed in 1964. They are still using the 1964 version of
>the latest compressors and the voltage needed. This is why they can say they
>are in all ways giving the right voltage. Damn it is bad when i've been
>proven wrong by a book. On compressor before 1964 you only needed 195+ volts
>to operate them. I ask them if they ever thought about getting a updated
>version one day. They did not say a word. So here we are and i will see what
>happens.
>TURTLE
Another take is "what were those compressor manufactures thinking about"?
The NEC allows a 6V+ drop on 208 feeder and branch circuit wiring. So,
208V can drop to 202V- on premises. That means the power company can only
lose less than 3V at the service drop before you hit 199V!
Pretty unrealistic that the service drop can't be off by 3V and
feeder/branch wiring is always up to current code!
An interesting calculator for 3 phase feeders and branch circuits is at
http://www.acpowerdist.com/calcthreephasevd.asp
gerry
Calculation correction - the 6V+ is just feeder drop. Another 4V+ for
branch the branch circuit.
Thus, on premise 208V wiring can drop a perfect 208V Service to 198V!
gerry
TURTLE
"TURTLE" <tur...@worldnetla.net> wrote in message
news:bke8ef$pdu0$5...@ID-79743.news.uni-berlin.de...
This is Turtle Again.
Question here.
Is there any spec.s on supply voltage in the NEC books? I have to go to my
electrician to look up things for he does all my electric work [big] not
little and asking a hard to find question such as this would be a brain
killer for him.
Looking for a spec to say there is a certain lower level of voltage that can
be supplied. And yes , don't tell me to call the power company or Public
service commission to get answer. they are all tring to stay out of jail.
TURTLE
gerry
wrote:
\
>> So , is 195 volts good on a copland , New Millium something , 3 phase
>> compressor rated at 3 phase / 200 volts to 230 volt / 60 Hz. . They did
>> agree with me on 187 volts being a little low. Am i not up to date on
>> Voltage rating / loosing it or am I being feed a line of bull ? Yes ,
>every
>> other school in outline areas I work on has the 208 service and they have
>> 210 to 214 on all legs all the time but with the same power company. This
>> school is out there in the booneys for they have to pipe sun lite to them.
>>
>> TURTLE
>
>This is Turtle Again.
>
>Question here.
>
>Is there any spec.s on supply voltage in the NEC books? I have to go to my
>electrician to look up things for he does all my electric work [big] not
>little and asking a hard to find question such as this would be a brain
>killer for him.
>
>Looking for a spec to say there is a certain lower level of voltage that can
>be supplied. And yes , don't tell me to call the power company or Public
>service commission to get answer. they are all tring to stay out of jail.
>
>TURTLE
>
NEC only controls premise wiring, it's published by the National Fire
Protection Association. It allows 3% drop for feeders + 2% drop for branch
circuits. That means the premise wiring can have over a 10V loss on a 208
circuit and meet code.
This doesn't allow for power company issues INCLUDING old standards. For
example nominal 120V once was 117V and is still 110V in some older areas.
That's single phase data, I don't have history data on hand for 3 phase.
gerry
On Sun, 21 Sep 2003 21:05:22 -0500, "TURTLE" <tur...@worldnetla.net>
wrote:
>This is Turtle Again.
>
>Question here.
>
>Is there any spec.s on supply voltage in the NEC books? I have to go to my
>electrician to look up things for he does all my electric work [big] not
>little and asking a hard to find question such as this would be a brain
>killer for him.
>
>Looking for a spec to say there is a certain lower level of voltage that can
>be supplied. And yes , don't tell me to call the power company or Public
>service commission to get answer. they are all tring to stay out of jail.
>
A few standards and references:
- NEMA MG 1, 12.44 indicates induction motors must tolerated +- 10%, Thus
a nominal 208V motor must handle 197V.
http://www.usmotors.com/products/ProFacts/1-133.htm
- Pacific Gas has cumulative data of interest - a 208V device should
expect to see 181-220V!!!
http://www.pge.com/002_biz_svc/powerquality/pdf/voltage_tolerance.pdf
- Power companies are state regulated, not national.
An example is PA which doesn't state any specific voltage, but that a "A
public utility shall adopt a standard nominal service voltage for the
entire territory served by the public utility" They then allow +-10%!
http://www.pacode.com/secure/data/052/chapter57/s57.14.html
- The ANSI standard for 208 is 197-218 (standard but not US law)
http://www.pge.com/002_biz_svc/powerquality/pdf/voltage_tolerance.pdf
If you worst case ANSI low with NEC allowed feeder and branch circuit
loses (10%), you get 187 volts! That requires present standards are being
met an no oddball state allowed low voltage.
TURTLE
"gerry" <gerrr...@gogood.com> wrote in message
news:ggttmvoa8apbmn6iu...@4ax.com...
This is Turtle
Now you said you could have 10 volt drop on 208 volt sevice but is 195 volts
delivered to meter pan acceptiable. This would be a 13 volt drop before you
got to the switch box and then you can drop another 10 volts to 185 volts.
I'm making a load answer here but does it have any merreit to it or is off
the wall?
TURTLE
RD
wrote:
>This is Turtle
>
>Now you said you could have 10 volt drop on 208 volt sevice but is 195 volts
>delivered to meter pan acceptiable. This would be a 13 volt drop before you
>got to the switch box and then you can drop another 10 volts to 185 volts.
>I'm making a load answer here but does it have any merreit to it or is off
>the wall?
>
>TURTLE
>
>
Did you clamp an ammeter on those feeders?
Up the thread you made a comment about the power co. being responsible
for balancing the load....
I suppose this is true on the primary side, but you may want to check
the amperage on each phase at the service entrance.
Rick
gerry
wrote:
>> >
>> >This is Turtle Again.
>> >
>> >Question here.
>> >
>> >Is there any spec.s on supply voltage in the NEC books? I have to go to
>my
>> >electrician to look up things for he does all my electric work [big] not
>> >little and asking a hard to find question such as this would be a brain
>> >killer for him.
>> >
>> >Looking for a spec to say there is a certain lower level of voltage that
>can
>> >be supplied. And yes , don't tell me to call the power company or Public
>> >service commission to get answer. they are all tring to stay out of jail.
>> >
>> >TURTLE
>> >
>>
>> NEC only controls premise wiring, it's published by the National Fire
>> Protection Association. It allows 3% drop for feeders + 2% drop for branch
>> circuits. That means the premise wiring can have over a 10V loss on a 208
>> circuit and meet code.
>>
>> This doesn't allow for power company issues INCLUDING old standards. For
>> example nominal 120V once was 117V and is still 110V in some older areas.
>> That's single phase data, I don't have history data on hand for 3 phase.
>This is Turtle
>
>Now you said you could have 10 volt drop on 208 volt sevice but is 195 volts
>delivered to meter pan acceptiable. This would be a 13 volt drop before you
>got to the switch box and then you can drop another 10 volts to 185 volts.
>I'm making a load answer here but does it have any merreit to it or is off
>the wall?
>
>TURTLE
Actually, the voltage at the service drop is state regulated, so that
voltage was just an example. The feeder/branch drop is what is allowed ny
the present National code.
That's why I posted the Pacific Gas data in a 2nd post, as low as 181V! I
used them since it is a publicly available reference, not just my opinion.
That's pretty extreme but could happen. One reason the power conditioning
industry is so big.
BOB URZ
gerry wrote:
So, does that mean your suggesting something like a continuos conversion UPS to
solve his problem? Or maybe a tapped autoformer or step up 3 phase transformer?
All possible, but expensive solutions. All on the building end, not the utility
end.
BOB
>
> gerry
>
> --
>
> Personal home page - http://gogood.com
>
> gerry misspelled in my email address to confuse robots
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
volts500
All the NEC references to volt drop are fine print notes
(FPN's).....210.19(A)(1) FPN#4, 215.2(A)(4) FPN#2. FPN's are _not_ a part
of the NEC.......recommendations only. In fact, in practice it's not
uncommon to see volt drop's much higher than the minimum _recommended_ by
the NEC. That's why it best to feed a school with 3 phase 277/480 volts
(Wye).....use the 3 phase 480 for large motor loads and the 277 for
lighting. There are some pretty sharp power engineers over in
alt.engineering.electrical who can tell you more than you'll ever want to
know about power co. supply requirements......I believe it's plus or minus
10% allowed.
While we all know that running a motor at the limits of the plus or minus
voltage rating of the motor is not the best thing, as long as the voltages
are balanced, the only effect should be that the average life expectancy is
reduced as compared to a motor operated at the correct voltage. When
running at a lower voltage extremes AND having an unbalanced voltage (187,
203, 203), you can expect premature burnouts. I'd go so far as to guess
that the AC units only have OL protection on two phases and the unprotected
phase is _also_ the phase that is unbalanced. That can be verified. For
example, if the phase with the unbalance is "*"..............if existing is
A, B*, C, (where A and C are connected to the OL's), switching to A, C, B*
puts the unbalanced phase on the OL's but now the motor is reversed, then
switching to B*, C, A puts the rotation back to where it needs to be with
the unbalanced phase on an OL now. Of course, if unbalanced voltage is
indeed the problem, that will lead to nuisance tripping.......but at least
the compressors won't be getting burnt up and you can then show all
interested (or disinterested, in the case of the power co.) parties what the
problem is.....but, like I said in another post, the problem may be on the
load side of the main gear, making it the school's problem to fix.
Hope you get it resolved.
gerry
wrote:
>>
>> Actually, the voltage at the service drop is state regulated, so that
>> voltage was just an example. The feeder/branch drop is what is allowed ny
>> the present National code.
>>
>> That's why I posted the Pacific Gas data in a 2nd post, as low as 181V! I
>> used them since it is a publicly available reference, not just my opinion.
>> That's pretty extreme but could happen. One reason the power conditioning
>> industry is so big.
>>
>
>So, does that mean your suggesting something like a continuos conversion UPS to
>solve his problem? Or maybe a tapped autoformer or step up 3 phase transformer?
>All possible, but expensive solutions. All on the building end, not the utility
>end.
>
>BOB
Not really, as in a previous note, I'm suggesting compressor manufacturers
get in the real world. Forgetting phase imbalance, Turtle posted that
Goodman required 199V and had a bunch of scrolls that wouldn't work with
195V.
Phase imbalance is another game. Since one can assume that the branch
circuit only feeds the compressor (major part of the load anyway),
imbalance has to be a service drop (power company) or feeder issue.
Three phase heavy duty conditioning is very expensive, but it exists. Thus
somebody isn't doing their job very well.
gerry
wrote:
\
>While we all know that running a motor at the limits of the plus or minus
>voltage rating of the motor is not the best thing, as long as the voltages
>are balanced, the only effect should be that the average life expectancy is
>reduced as compared to a motor operated at the correct voltage. When
>running at a lower voltage extremes AND having an unbalanced voltage (187,
>203, 203), you can expect premature burnouts. I'd go so far as to guess
>that the AC units only have OL protection on two phases and the unprotected
>phase is _also_ the phase that is unbalanced. That can be verified. For
>example, if the phase with the unbalance is "*"..............if existing is
>A, B*, C, (where A and C are connected to the OL's), switching to A, C, B*
>puts the unbalanced phase on the OL's but now the motor is reversed, then
>switching to B*, C, A puts the rotation back to where it needs to be with
>the unbalanced phase on an OL now. Of course, if unbalanced voltage is
>indeed the problem, that will lead to nuisance tripping.......but at least
>the compressors won't be getting burnt up and you can then show all
>interested (or disinterested, in the case of the power co.) parties what the
>problem is.....but, like I said in another post, the problem may be on the
>load side of the main gear, making it the school's problem to fix.
>Hope you get it resolved.
NEC requires current limits on all legs, not just two.
Also, current limiters are strange beasts. They can't tell what direction
the power is flowing. You can have two legs drawing power and one leg
reverse feeding (acting as generator) yet trip nothing.
Simple clamp on current meters don't tell much of the story with three
phase motor loads. You just can't tell the difference between load and
back feed.
gerry
wrote:
>I'd go so far as to guess
>that the AC units only have OL protection on two phases and the unprotected
>phase is _also_ the phase that is unbalanced.
NEC 430/32 An overload shall be installed on each conductor that controls
the running of the motor rated more than one horsepower.
NEC 430/37 plus the grounded leg of a three phase grounded system must
contain an overload also. This Grounded leg of a three phase system is the
only time you may install an overload or over - current device on a
grounded conductor that is supplying a motor.
volts500
> [original post is likely clipped to save bandwidth]
> On Tue, 23 Sep 2003 14:20:00 GMT, "volts500" <volt...@tampabay.rr.com>
> wrote:
>
>
> >I'd go so far as to guess
> >that the AC units only have OL protection on two phases and the
unprotected
> >phase is _also_ the phase that is unbalanced.
>
> NEC 430/32 An overload shall be installed on each conductor that controls
> the running of the motor rated more than one horsepower.
Point taken, however, there is an asterisk (*) in Table 430.37 next to "one
in each phase" (3 phase) that refers to: "*Exception: An overload unit in
each phase shall not be required where overload protection is provided by
other approved means." The manufacturers usually put in a CB or fuse (at
125%) as the "other approved means". The NEC Section that should be
referenced, 440.52(A)(4) is even more ambiguous by stating: " a protective
system, furnished or specified and approved for use with the motor
compressor..." The reason that I brought it up was because it's not
uncommon (in my area anyway) to see units like that.
> NEC 430/37 plus the grounded leg of a three phase grounded system must
> contain an overload also. This Grounded leg of a three phase system is the
> only time you may install an overload or over - current device on a
> grounded conductor that is supplying a motor.
That's because a 3 phase Corner-grounded Delta connected system uses a
"solid neutral" instead of a fuse in the grounded phase.....basically a
piece of copper tubing with a UL sticker on it. It would be rare, indeed,
to see a corner-grounded Delta distribution in a school or any commercial
building for that matter.........a mine, yes.
gerry
wrote:
>
>"gerry" <gerrr...@gogood.com> wrote in message
>news:fn41nv0r2ogs4nb1c...@4ax.com...
>> [original post is likely clipped to save bandwidth]
>> On Tue, 23 Sep 2003 14:20:00 GMT, "volts500" <volt...@tampabay.rr.com>
>> wrote:
>>
>>
>> >I'd go so far as to guess
>> >that the AC units only have OL protection on two phases and the
>unprotected
>> >phase is _also_ the phase that is unbalanced.
>>
>> NEC 430/32 An overload shall be installed on each conductor that controls
>> the running of the motor rated more than one horsepower.
>
>Point taken, however, there is an asterisk (*) in Table 430.37 next to "one
>in each phase" (3 phase) that refers to: "*Exception: An overload unit in
>each phase shall not be required where overload protection is provided by
>other approved means." The manufacturers usually put in a CB or fuse (at
>125%) as the "other approved means". The NEC Section that should be
>referenced, 440.52(A)(4) is even more ambiguous by stating: " a protective
>system, furnished or specified and approved for use with the motor
>compressor..." The reason that I brought it up was because it's not
>uncommon (in my area anyway) to see units like that.
"Overload" protection for a device should not be confused with branch
circuit fire protection. Perhaps you are referring to device overload
protection rather than branch circuit protection? Many three phase devices
can be protected for overload with just two leg devices.
Another NEC issue comes in play - all ungrounded conductors must have over
current protection before they exit the panel they originate at. Overload
protection at the load does not cover this. One can then can get in an
interesting conversation regarding short vs overload protection.
Basically, you can't run unprotected, ungrounded legs around a premise.
(GFI's can bring in more complications) There are a few exceptions for
short feeders. Inspectors around here interpret this as requiring over
current protection for all ungrounded conductors at the panel where the
branch circuit originates.
It is true, wire can be oversized to reduce voltage drop and the panel
protection can be rated above that required by the load but not exceeding
that required to protect the branch wiring. At that point, it is just fire
protection for the branch or feeder.
>
>
>> NEC 430/37 plus the grounded leg of a three phase grounded system must
>> contain an overload also. This Grounded leg of a three phase system is the
>> only time you may install an overload or over - current device on a
>> grounded conductor that is supplying a motor.
>
>That's because a 3 phase Corner-grounded Delta connected system uses a
>"solid neutral" instead of a fuse in the grounded phase.....basically a
>piece of copper tubing with a UL sticker on it. It would be rare, indeed,
>to see a corner-grounded Delta distribution in a school or any commercial
>building for that matter.........a mine, yes.
I really doubt HVAC folks will see these ;-)
RD
wrote:
>[original post is likely clipped to save bandwidth]
>On Tue, 23 Sep 2003 20:12:45 GMT, "volts500" <volt...@tampabay.rr.com>
>>
>>That's because a 3 phase Corner-grounded Delta connected system uses a
>>"solid neutral" instead of a fuse in the grounded phase.....basically a
>>piece of copper tubing with a UL sticker on it. It would be rare, indeed,
>>to see a corner-grounded Delta distribution in a school or any commercial
>>building for that matter.........a mine, yes.
>
Schools...no
Commercial.... yes.
Albeit a salt mine it is, rhetorically speaking.
I'm not sure how rare they are around here, but we have such an
entrance. It was installed in the last four years.
>I really doubt HVAC folks will see these ;-)
Oh they have and they will again. Next time our chiller goes on the
fritz.
Rick
TURTLE
this is Turtle.
i have been bussy as hell keep the aligator beat down on the hvac business
and just now got time to come back and look at this. The info you stated
here is very helpful in the problem of the voltage at the school 10 ton
cooling units. We are at this point now as stated below here.
The power company says , We can supply as low as 195 volts and be OK for us
to do so.
The school board / Maintaince dept. head of school board / the manufactor of
Air conditioning system / ME says , We will turn the Air conditioning
systems off to the basket ball Gym when voltage goes to 199 volts or less.
We will be installing a voltage monitor to set a alarm off when voltage
drops to 199 volts or less or there is a voltage inbalance of a acceptiable
percent. This will be installed at the 600 amp main switch box for the Gym
and Welding Education shop. when the alarm goes off we will call you every
hour / on the hour till the problem is looked at by one of your service
people. During this time all cooling systems will be turn off. We will
expect you to show up with in 1 hour of calling for you have been informed
as to what will be taking place.
After this was stated to the power company. i went back to the job and i can
read now 214 / 214 / 214 . I wonder how this happen? They have a recorder
on the phases for a week to see that they are suppling good voltage to the
gym now. They have a man check the voltage to the school every morning at
7:00 am & 4:00 pm and can make adjustments to keep the voltage correct in
any way. They must be doing this because the like us so much.
Do you know of any devices that will read the voltage on 3 legs and set a
alarm off if it goes under 199 volts. i can use a phase protector for the
enbalance but what about the low voltage and setting the alarm off on 199
volts or less?
TURTLE
p...@see_my_sig_for_address.com
wrote:
>After this was stated to the power company. i went back to the job and i can
>read now 214 / 214 / 214 . I wonder how this happen? They have a recorder
>on the phases for a week to see that they are suppling good voltage to the
>gym now. They have a man check the voltage to the school every morning at
>7:00 am & 4:00 pm and can make adjustments to keep the voltage correct in
>any way. They must be doing this because the like us so much.
Yes, that is probably why :-)
>Do you know of any devices that will read the voltage on 3 legs and set a
>alarm off if it goes under 199 volts. i can use a phase protector for the
>enbalance but what about the low voltage and setting the alarm off on 199
>volts or less?
>
>TURTLE
>
These will give a dry contact, which you can do whatever you
need with - both shut down and alarm, even if different circuits, etc.
http://www.nationalcontrols.com/SSR5-4.htm
http://www.macromatic.com/products/voltage-monitor-relay.html
others at
http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=%22voltage+monitor%22&btnG=Google+Search
Tekkie
> >After this was stated to the power company. i went back to the job and i can
> >read now 214 / 214 / 214 . I wonder how this happen? They have a recorder
> >on the phases for a week to see that they are suppling good voltage to the
> >gym now. They have a man check the voltage to the school every morning at
> >7:00 am & 4:00 pm and can make adjustments to keep the voltage correct in
> >any way. They must be doing this because the like us so much.
>
> Yes, that is probably why :-)
>
Maybe they saw the mylar balloons waiting for inflation...
Jabs
I'm wondering, are the control transformers on these units 24 volts? If so,
are the primary's for the 24 volt transformers wired for a 230 volts primary
or are they wired for a 208 volts primary. Units usually come from the
factory wired for a 230 volt primary on their 24 volt transformers. This
can make a big difference.
Jabs
"TURTLE" <tur...@worldnetla.net> wrote in message
news:bkggn1$1h7lp$1...@ID-79743.news.uni-berlin.de...
>
> <moonlig...@pop.tcsn.qwest.net> wrote in message
> news:3F6B1090...@pop.tcsn.qwest.net...
> >
> >
> > pjm@see_my_sig_for_address.com wrote:
> > > >So , is 195 volts good on a copland , New Millium something , 3 phase
> > > >compressor rated at 3 phase / 200 volts to 230 volt / 60 Hz. . They
> did
> > > >agree with me on 187 volts being a little low. Am i not up to date on
> > > >Voltage rating / loosing it or am I being feed a line of bull ? Yes ,
> every
> > > >other school in outline areas I work on has the 208 service and they
> have
> > > >210 to 214 on all legs all the time but with the same power company.
> This
> > > >school is out there in the booneys for they have to pipe sun lite to
> them.
> > > >
> > > >TURTLE
> > > >
> > >
> > > Local power here is allowed to drop to 197 on nominal 208
> > > services downtown. I think it's a city ordinance. Had a bunch of
> > > equipment that thought the ordinance was a bunch of shit, and refused
> > > to start ( I think they were Forma ultra-lows and such, I forget,
> > > years ago ), had to put a bunch of buck-boost transformers on them.
> > > 187 definitely don't get it on nominal 208.
> > >
> > > For that piping sunlight, try some fiber optic, great stuff
> > > for it :-)
> > >
> > >
> > >
> > > Paul ( pjm @ pobox . com ) - remove spaces to email me
> > >
> > > New HVAC/R program for Palm PDA's !! http://pmilligan.net/palm/
> > > Free demo now available online !!!!
> > > --
> > > Free superheat charts for 38 Ref's online at
> http://pmilligan.net/pmtherm/
> > > My personal site is at http://www.pmilligan.net
> >
> > Turtle had similar problem on some ice cream trucks running
> > onboard generators, overamping and burning windings.
> > When I contacted Copeland they said not more than 10%
> > over or under. Also had some TK units that the computer
> > would not let run on anything less than 200v. BTW check
> > the contactor, I noticed that when I had low voltage
> > going to the the pull in coils I got a lot of chatter & burning.
> > Dave
> >
>
> This is Turtle.
>
> The Power co0mpany sayas they are allowed to go to 195 volts and Goodman
say
> turn them off at 199 volts or less. The contactor look like a smoke house
> where the smoke meat in. I get a volume discount from the warehouse on
them
> for I buy in Bulk now. I'm working on a volume discount on compressors
now.
>
> TURTLE
>
>
TURTLE
"Jabs" <nos...@nospam.net> wrote in message
news:aprfb.29327$T46....@twister.socal.rr.com...
> Terry,
> I'm wondering, are the control transformers on these units 24 volts? If
so,
> are the primary's for the 24 volt transformers wired for a 230 volts
primary
> or are they wired for a 208 volts primary. Units usually come from the
> factory wired for a 230 volt primary on their 24 volt transformers. This
> can make a big difference.
>
> Jabs
>
This is Turtle.
Yea, That is the first thing I look at everytime i go there for we have some
turkeys working for the school Board that will change anything to the wrong
settings.
TURTLE