Is 249V on a 220/240 line a problem?
Robert Riley
The external unit was completely replaced 2 yrs ago - then the compressor
was replaced a year ago, then the fan blew about a month ago, then a fuse
blew about 2 weeks ago, and now the thing isn't working again. I noticed
that the voltage reads between 243-249 on my cheapo multimeter. Is this far
enough out of the 220/240 spec to cause problems? If so, who do I talk to
about this?
Thanks
db...@sprynet.com
range of voltage.... you never get the correct voltage on the cheap
ones.. go out to your car and with the engine off check the DC voltage
of your car battery... bet it will not show exactly 12 volts.. its the
cheap parts on the meter the resistor that are used will give you about
a 20 % variance, which is good for most around the house chores...
Speedy Jim
Call the utility. On request, they will bring out precision
meters.
But those appliance devices should be able to work with a
wide voltage range, so don't get too optimistic about it
being a utility problem...
Jim
Eric Lee Green
> I have had several problems with my A/C compressor over the last 2 years -
> The external unit was completely replaced 2 yrs ago - then the compressor
> was replaced a year ago, then the fan blew about a month ago, then a fuse
> blew about 2 weeks ago, and now the thing isn't working again. I noticed
> that the voltage reads between 243-249 on my cheapo multimeter.
Huhn. Is this cheapo multimeter a $5 special from Radio Shack? If so, you
might want to upgrade to the $20 special from Radio Shack before you
panic :-).
> Is this far
> enough out of the 220/240 spec to cause problems? If so, who do I talk to
> about this?
Slightly higher voltage generally isn't a problem for electric motors.
A MUCH higher voltage can be a problem, if it causes them to exceed
the capabilities of their bearings, but 245v should not be a problem
even if it were true (which I doubt). The cheapo multimeters are
mostly just of use for saying "Is there voltage?". If the voltage
indicated is anywhere near reality, that's a bonus that would
surprise me greatly.
--
Eric Lee Green er...@badtux.org http://badtux.org
GnuPG public key at http://badtux.org/eric/eric.gpg
cbhvac
<db...@sprynet.com> wrote in message news:3CF77F...@sprynet.com...
>> > rsri...@hotmail.com
> you answered your own question... the cheapo multimeter will give you a
> range of voltage.... you never get the correct voltage on the cheap
> ones.. go out to your car and with the engine off check the DC voltage
> of your car battery... bet it will not show exactly 12 volts.. its the
> cheap parts on the meter the resistor that are used will give you about
> a 20 % variance, which is good for most around the house chores...
Actually, to be honest...it MIGHT not show 12 volts, and I can tell you now
that mine wont..yours wont....99% of them wont...
When I check mine with my RMS Fluke, or my UEI's, they show 12.9 to 14
volts.....and the reason is that its not a true 12 volt system, since the
alternator, when working correctly, will not charge at 12 volts....but more
like 14.5....if it charged at a true 12 volts, it would be dead in short
order...
but...thats being nitpicky..:)
But, agreed on the cheap meter..
cbhvac
"Robert Riley" <are-es-d...@cox.net> wrote in message
news:JtKJ8.19310$155.6...@news2.west.cox.net...
First, get your electric utility company out there to check it with better
equipment...if there is a line voltage problem, its their problem.
As far as the higher voltage, IF that is the case, hurting the AC unit, from
your list of repairs, it sounds like you got a bad install from the word
go...or a bad unit..
Normally, that is the case...each unit has a pretty wide range of operation
as far as the supply voltage goes..but you cant be sure of the voltage till
you get a good meter on the lines..
Frank
phase service. We find this a lot when installing Engineering copy
equipment. Ck each side to ground should be 110V or probably 120V to ground.
Good luck Frank
"Eric Lee Green" <er...@badtux.org> wrote in message
news:slrnaff0c...@badtux.org...
Gilbert Smith
Plus or minus 5 percent is within the tolerance for most electric utilities, and
no way +9 volts is going to damage a 240v. compressor. I'd rather have that then
-9 volts which could cause a hotter running motor. My own service measures
126v/252v because I'm near the distribution transformer, and my AC hasn't blown
up yet! ;>)
SteveR
<in...@carolinabreezehvac.com> wrote:
>As far as the higher voltage, IF that is the case, hurting the AC unit, from
>your list of repairs, it sounds like you got a bad install from the word
>go...or a bad unit..
Also, it may be useful to keep in mind that 15% undervoltage has far
more potential to damage motors than 15% overvoltage. HVAC
compressors are a reasonable example of constant-power devices.
Undervoltage them and they'll draw proportionally more current, and
correspondingly dissipate more power in I-squared-R losses. Assuming
constant R, a 15% undervoltage causes ~17.6% higher current. Losses
will thus be 1.176 squared higher or ~38.4 % higher. This is what
burns up motors and relays, and blows fuses.
OTOH, overvoltage, within small limits, may reduce current draw
somewhat, and produce marginally lower losses. One important limiting
factor in taking advantage of higher voltages is that the motor
magnetics will eventually saturate and cause high current spikes. All
things considered, you're best off running within the nameplate
ratings and manufacturer-recommended tolerances.
SteveR
db...@sprynet.com
out anything, look at the post.....
cbhvac
<db...@sprynet.com> wrote in message news:3CF7BA...@sprynet.com...
I did, and I still stand by my original statement....just because the car is
turned off, the battery voltage does NOT drop suddenly back to 11.9, or
12.0..
I believe, and I might be wrong...but I believe the term used for it is
called a surface charge...at least thats what I heard it called in dealers
all across the country for years...
VåìrXpêrt
>
>i have never saw a car with the engine off and the alternator putting
>out anything, look at the post.....
A typical car battery has a float charge of 13.2 to 13.8 volts. If
you read 12 volts the battery is partially discharged.
maddog
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jriegle
240v. When the unit was operational, the voltage at the compressor is likely
to be lower when it is running.
To toss another scenario into the mix, have the voltage checked at the
compressor with a similar load. If the supply wire is undersized and is a
good distance from the house electrical box, The compressor may have a hard
time getting started and may pop fuses or fail.
John
Gilbert Smith <gws...@worldnet.att.net> wrote in message
news:3CF7B234...@worldnet.att.net...
scrook
bulbs not 120V) Over 10% over/under, call your utility. The nominal spec is
120V/240V (or 120V/208V for commercial 3 phase wye systems) "220V" (or
"110V") is a misnomer. Motors will generally say 115, 200, and/or 230 on
their nameplates however, as at nominal 120/240 may be as mish as -15%/+10%
what w/ brownouts etc. some moters may be rated to run at either 200 or 230
(a 115/230 moter will require reconnecting the interal wiring for the
desired voltage however.
"Robert Riley" <are-es-d...@cox.net> wrote in message
news:JtKJ8.19310$155.6...@news2.west.cox.net...
Clifton T. Sharp Jr.
> <db...@sprynet.com> wrote in message news:3CF7BA...@sprynet.com...
> > cbhvac wrote:
> > > <db...@sprynet.com> wrote in message news:3CF77F...@sprynet.com...
> > > >> > rsri...@hotmail.com
> > > > you answered your own question... the cheapo multimeter will give you a
> > > > range of voltage.... you never get the correct voltage on the cheap
> > > > ones.. go out to your car and with the engine off check the DC voltage
> > > > of your car battery... bet it will not show exactly 12 volts.. its the
> > > > cheap parts on the meter the resistor that are used will give you about
> > > > a 20 % variance, which is good for most around the house chores...
> > >
> > > Actually, to be honest...it MIGHT not show 12 volts, and I can tell you now
> > > that mine wont..yours wont....99% of them wont...
> > > When I check mine with my RMS Fluke, or my UEI's, they show 12.9 to 14
> > > volts.....and the reason is that its not a true 12 volt system, since the
> > > alternator, when working correctly, will not charge at 12 volts....but more
> > > like 14.5....if it charged at a true 12 volts, it would be dead in short
> > > order...
> >
> > out anything, look at the post.....
>
> I did, and I still stand by my original statement....just because the car is
> turned off, the battery voltage does NOT drop suddenly back to 11.9, or
> 12.0..
> I believe, and I might be wrong...but I believe the term used for it is
> called a surface charge...at least thats what I heard it called in dealers
> all across the country for years...
1. A "12V" battery is not a 12.00000 volt battery. A 12V car starting
battery is made up of six "wet" cells, each of which has a *nominal*
voltage of 2.3V when charged. A new battery with a full charge will
thus read about 13.8 volts. But if they called it a 13.8V battery,
every jerk in town would be returning his because his brand new $400
Fluke DVM read 13.797V or 13.802V.
2. When the car is running and the alternator is in charge mode, the
battery voltage can range to nearly 16V in *normal* use. Electrical
noise from other things connected to the battery, plus the inductance
of wires in the harnesses, can put noisy spikes of many, many more volts
on top. It is not unusual to find fifty volt spikes at the cigarette lighter
socket in some cars with the heater blower motor running.
3. "Cheap" meter is ambiguous. "Cheap" meters are generally not bad in
accuracy for general use. They might be inaccurate with noisy voltages,
and they certainly won't take much rough handling or environmental change,
but if pampered, out of the box a "cheap" meter will compare favorably
with the expensive ones for simple, non-noisy voltage readings. "Cheap"
digital meters are generally pretty accurate; I have a $20 Sears meter
that compares well with my Fluke 77.
4. That said, it's ridiculous for a guy who buys the best tools to spend
money on a cheap meter. I know guys who chase the Matco truck because they
won't tolerate mere Craftsman tools, yet they'll buy a cheap meter because
they "don't use it often." They don't use their reciprocating saws or
routers often, either, but they won't buy cheap ones. The first time you
forget and plug your meter into a wall socket while it's set to a resistance
scale, you'll be glad you bought a good meter. THAT is where the cheap
meter falls down.
--
If spammers weren't stupid, they'd be the idle rich instead of spammers.
- Morely Dotes
Gfretwell
more effort to read but the answer is potentially just as accurate and they
don't have the "random number generator" effect when you have spikes or
transients on the point you are reading.
Digital meters demonstrate the classic difference between precision and
accuracy. You can get a totally inaccurate reading, precise out to 3 decimal
places.
Tony Hwang
True. DVMs are so sensitive, it can be a minus in some situations.
I always double check with analog meter(Simpson 260) when in doubt.
Tony
Gene Bruce
This is an interesting thread. I'll add my two cents' worth.
Most folks don't realize that you power voltage coming into your house is
actually regulated only by the load that the generator down at the power plant
sees.
As demand increases, they have to put more generating capacity online or see
brownouts occur. The other way around, voltages can go way up.
Its been a long time, but my power theory professor, who loved to tell stories
in class anyway, told us of a very large industrial facility whose main breaker
tripped very suddenly. They consumed a significant percentage of the local
grid's power. All of a sudden, there was all this capacity looking for a place
to go. It found that place. Many electric motors that were unfortunate enough to
be running at the time all of a sudden had much more voltage to work with than
normally expected. Many motors all over town went poof that afternoon. The power
company had to replace 'em all.
There is now a _very_ large bank of resistive load adjacent to the industrial
facility. It wasn't there before. So now the main breaker switches the load to
the resistor bank instead of simply opening up.
Names and towns omitted to prevent the (maybe not so) innocent.
On Fri, 31 May 2002 13:00:25 GMT, "Robert Riley" <are-es-d...@cox.net>
scribbled the following wisdom:
Gene Bruce Ph/Voice Mail: (972)952-4937
Raytheon Systems Company FAX: (972)952-4275
2501 W. University, MS 8056 McKinney, Texas 75070
UNIX is a very user-friendly operating system.
However, it is very particular about just who it makes friends with.