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Home > Archive > Electrical Engineering > June 2006 > A/C Disconnect
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| I have an A/C Disconnect which i am not sure is wired properly. There
is a 30amp double pole breaker in the inside panel which has a RBG wire
connected (and a white wire nutted and capped). At the disconnect
(Eaton 30A a/c disconnect), the red and black connect to the line
terminals and the ground connects to a 2 terminal ground bar. From the
disconnect, the R & B run to the a/c unit and the ground is connected
to the other terminal in the ground bar. I have a cheap volt meter
which shows a 120 volt when i connect to either hot wire and the
ground, but doesn't respond when connected to both hot wires. I am not
sure if the volt meter 240 light is broken, or if it is possible that
while each leg would produce 120, no current is produced by the tandem
wires? If it is possible, what is the fix?
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| gfretwell@aol.com 2006-06-13, 3:21 pm |
| On 13 Jun 2006 08:01:29 -0700, "CO" <conwuegbu@elliottmahoney.com>
wrote:
>I have an A/C Disconnect which i am not sure is wired properly. There
>is a 30amp double pole breaker in the inside panel which has a RBG wire
>connected (and a white wire nutted and capped). At the disconnect
>(Eaton 30A a/c disconnect), the red and black connect to the line
>terminals and the ground connects to a 2 terminal ground bar. From the
>disconnect, the R & B run to the a/c unit and the ground is connected
>to the other terminal in the ground bar. I have a cheap volt meter
>which shows a 120 volt when i connect to either hot wire and the
>ground, but doesn't respond when connected to both hot wires. I am not
>sure if the volt meter 240 light is broken, or if it is possible that
>while each leg would produce 120, no current is produced by the tandem
>wires? If it is possible, what is the fix?
Is this really a 2 pole breaker that takes 2 slots or a single slot
tandem breaker on one phase rail?
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gfretw...@aol.com wrote:
> On 13 Jun 2006 08:01:29 -0700, "CO" <conwuegbu@elliottmahoney.com>
> wrote:
>
> Is this really a 2 pole breaker that takes 2 slots or a single slot
> tandem breaker on one phase rail?
It is a General Electric 30 Amp, 2 Pole Thin Type THQP General Electric
Circuit Breaker
Model THQP230
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| gfretwell@aol.com 2006-06-13, 4:21 pm |
| On 13 Jun 2006 10:30:25 -0700, "CO" <conwuegbu@elliottmahoney.com>
wrote:
>
>It is a General Electric 30 Amp, 2 Pole Thin Type THQP General Electric
>Circuit Breaker
>Model THQP230
Pull the breaker out and be sure it is actually hitting 2 rails. Some
small GE panels only have 240v on the center two positions and one
rail extends horizontally out from there. I have one of these in my
garage.
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gfretwell@aol.com wrote:
> On 13 Jun 2006 10:30:25 -0700, "CO" <conwuegbu@elliottmahoney.com>
> wrote:
>
>
> Pull the breaker out and be sure it is actually hitting 2 rails. Some
> small GE panels only have 240v on the center two positions and one
> rail extends horizontally out from there. I have one of these in my
> garage.
There is a horizontal bar, with a smaller vertical bar below it. the
breaker has a large split down the middle, two smaller connectors which
line up with the vertical bar. All appear to be contacting properly. Is
it possible that because the neutral wire is not attached to the
neutral bar (because the disconnect doesn't have a way to connect it)
it is not operating correctly. I am just perplexed because each hot is
drawing 120, but i can't get the 240 to show.
| |
|
| CO wrote:
> I have an A/C Disconnect which i am not sure is wired properly. There
> is a 30amp double pole breaker in the inside panel which has a RBG wire
> connected (and a white wire nutted and capped).
The red wire should go to 1 pole on the breaker, and the
black wire should go to the other pole.
> At the disconnect
> (Eaton 30A a/c disconnect), the red and black connect to the line
> terminals and the ground connects to a 2 terminal ground bar.
And the white wire is ...?
> From the
> disconnect, the R & B run to the a/c unit and the ground is connected
> to the other terminal in the ground bar. I have a cheap volt meter
> which shows a 120 volt when i connect to either hot wire and the
> ground, but doesn't respond when connected to both hot wires. I am not
> sure if the volt meter 240 light is broken, or if it is possible that
> while each leg would produce 120, no current is produced by the tandem
> wires? If it is possible, what is the fix?
>
1) RE: not sure if your volt meter is broken
If you know how to do this *safely*, connect a 120 volt,
60 watt test lamp to the load side red and black, then
turn the Eaton on. If the bulb glows extremely bright or
blows, your meter is bad. Or buy a new meter.
2) RE: possible to have 120 to ground from red and 120 to ground
from black, but nothing from red to black?
Yes, it is possible if the wiring is wrong. At your main
service panel, the power comes in like this:
120------0 A
ground---0 B
120------0 C
I added the ABC labels. Voltage from A to B is 120; voltage from
C to B is 120; voltage from A to C is 240.
A typical panel distributes the voltage so that 12/ the breakers
are connected to A and the other 1/2 are connected to B, like this:
A B
B A
A B
B A
etc
Your Eaton disconnect should be wired to an AB pair. If
it is miswired so that both red and black go to A (or
to B) then you will get the symptom you describe.
The double pole breaker in your main panel should have 240
volts across its poles.
Please be very careful with this. If you are messing around
in the main panel or the disconnect, you are in danger.
If you are unfamiliar with these, the danger is magnified.
Ed
| |
| Skenny 2006-06-13, 9:21 pm |
| You should read 240 (approx.) volts between the two hot wires.
Make sure your tester is wroking properly first, you can try it on another
240 volt appliance outlet, such as a dryer or stove. If you are sure it is
reading 240 volts like it should, then proceed with this next suggestion, if
it is not reading, stop and get one that does work.
If you are reading on the bottom of the disconnect, try reading on the top.
If you read 240 volts on the top, then the disconnect is bad and needs to be
replaced.
Or if the disconnect has fuses, one is probably blown. Put your test leads
across each fuse , you should read nothing with power on.
If you read nothing between the top, or incoming wires, then go back to
wherever this is fed from, you either have a bad breaker, or a blown fuse.
This is probably fused in your main breaker or fuse panel. (The one for the
whole house.)
Or you could have a wire broken between the disconnect and the main fuse or
breaker.
You are reading 120 volts on each conductor to ground because the voltage is
going from the "live" conductor, through the AC unit, back to the conductor
that is "dead", through your tester, to ground.
Pretty common problem.
Hope this helps..
"CO" <conwuegbu@elliottmahoney.com> wrote in message
news:1150210889.376537.249550@y43g2000cwc.googlegroups.com...
>I have an A/C Disconnect which i am not sure is wired properly. There
> is a 30amp double pole breaker in the inside panel which has a RBG wire
> connected (and a white wire nutted and capped). At the disconnect
> (Eaton 30A a/c disconnect), the red and black connect to the line
> terminals and the ground connects to a 2 terminal ground bar. From the
> disconnect, the R & B run to the a/c unit and the ground is connected
> to the other terminal in the ground bar. I have a cheap volt meter
> which shows a 120 volt when i connect to either hot wire and the
> ground, but doesn't respond when connected to both hot wires. I am not
> sure if the volt meter 240 light is broken, or if it is possible that
> while each leg would produce 120, no current is produced by the tandem
> wires? If it is possible, what is the fix?
>
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| |
| Tom Horne, Electrician 2006-06-14, 12:21 am |
| ehsjr wrote:
> CO wrote:
>
> The red wire should go to 1 pole on the breaker, and the
> black wire should go to the other pole.
>
>
> And the white wire is ...?
>
>
> 1) RE: not sure if your volt meter is broken
>
> If you know how to do this *safely*, connect a 120 volt,
> 60 watt test lamp to the load side red and black, then
> turn the Eaton on. If the bulb glows extremely bright or
> blows, your meter is bad. Or buy a new meter.
>
> 2) RE: possible to have 120 to ground from red and 120 to ground
> from black, but nothing from red to black?
>
Yes, it is possible if the wiring is wrong. At your main
service panel, the power comes in like this:
120------0 A
ground---0 N
120------0 B
I added the A,N,&B labels. Voltage from A to N is 120; voltage from
B to N is 120; voltage from A to B is 240.
A typical panel distributes the voltage so that 1/2 the breakers
are connected to A and the other 1/2 are connected to B, like this:
1 A A 2
3 B B 4
5 A A 6
7 B B 8
etc with each number representing a breaker position and each letter the
buss bar it is supplied by.
>
> Your Eaton disconnect should be wired to an AB pair. If
> it is miswired so that both red and black go to A (or
> to B) then you will get the symptom you describe.
>
> The double pole breaker in your main panel should have 240
> volts across its poles.
>
> Please be very careful with this. If you are messing around
> in the main panel or the disconnect, you are in danger.
> If you are unfamiliar with these, the danger is magnified.
>
> Ed
Ed
I changed the labeling of your reply to make the labeling consistent and
to mimic the breaker pattern most commonly found in North American
panels. This change may make your reply easier for the OP to understand.
I'd also like to suggest that the OP go and buy a Wigington type
solenoid voltage tester such as the one shown in this document.
<http://ecatalog.squared.com/pubs/El...5013-100-17.pdf>
There is a good reason that electrical workers are required to use them
on the job rather than use a multi meter. A solenoid voltage tester
places 10 milliamperes of load on the circuit in the form of the testers
solenoid coil. The vibration of the solenoid is palpable in the tester
and increases as the voltage increases. This leads to both a palpable
and visual difference in disparate voltage readings and unlike high
impedance multi meters a Wiggy will not falsely indicate a voltage from
induction from adjacent circuits.
--
Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison
| |
| Phil Scott 2006-06-14, 5:21 am |
|
--
Phil Scott
Ideas are bullet proof.
"CO" <conwuegbu@elliottmahoney.com> wrote in message
news:1150210889.376537.249550@y43g2000cwc.googlegroups.com...
>I have an A/C Disconnect which i am not sure is wired
>properly. There
> is a 30amp double pole breaker in the inside panel which has
> a RBG wire
> connected (and a white wire nutted and capped). At the
> disconnect
> (Eaton 30A a/c disconnect), the red and black connect to the
> line
> terminals and the ground connects to a 2 terminal ground
> bar. From the
> disconnect, the R & B run to the a/c unit and the ground is
> connected
> to the other terminal in the ground bar. I have a cheap volt
> meter
> which shows a 120 volt when i connect to either hot wire and
> the
> ground, but doesn't respond when connected to both hot
> wires. I am not
> sure if the volt meter 240 light is broken, or if it is
> possible that
> while each leg would produce 120, no current is produced by
> the tandem
> wires? If it is possible, what is the fix?
sounds like a bad meter.... if the AC unit runs then thats
probably the case.. you can also try the meter on a known live
220 source to see if it reads.
Typically the two colored wires would be line 1 and line 2, as
you assume... white is neutral and goes to the neutral bus or
is not connected on a 220 supply, but the ground is connected.
110 to ground indicates you have a line 1 and 2 probably in
tact.
by the way a cheap meter is not rated for use close to the
panel or in proximity to the main house feeders which connect
to the often oversized pole transformer.
search 'arc flash hazard' on google..its an old issue, getting
new play these days.
The closer you are to the mains the bigger the potential to be
electrocuted by a cheap meter..
Phil Scott
Mech/ elect contractor
>
| |
|
| Tom Horne, Electrician wrote:
> ehsjr wrote:
>
> Yes, it is possible if the wiring is wrong. At your main
> service panel, the power comes in like this:
>
> 120------0 A
> ground---0 N
> 120------0 B
>
> I added the A,N,&B labels. Voltage from A to N is 120; voltage from
> B to N is 120; voltage from A to B is 240.
>
> A typical panel distributes the voltage so that 1/2 the breakers
> are connected to A and the other 1/2 are connected to B, like this:
> 1 A A 2
> 3 B B 4
> 5 A A 6
> 7 B B 8
> etc with each number representing a breaker position and each letter the
> buss bar it is supplied by.
>
>
>
>
> Ed
> I changed the labeling of your reply to make the labeling consistent and
> to mimic the breaker pattern most commonly found in North American
> panels. This change may make your reply easier for the OP to understand.
Yes! Much better!
Ed
>
> I'd also like to suggest that the OP go and buy a Wigington type
> solenoid voltage tester such as the one shown in this document.
> <http://ecatalog.squared.com/pubs/El...5013-100-17.pdf>
>
> There is a good reason that electrical workers are required to use them
> on the job rather than use a multi meter. A solenoid voltage tester
> places 10 milliamperes of load on the circuit in the form of the testers
> solenoid coil. The vibration of the solenoid is palpable in the tester
> and increases as the voltage increases. This leads to both a palpable
> and visual difference in disparate voltage readings and unlike high
> impedance multi meters a Wiggy will not falsely indicate a voltage from
> induction from adjacent circuits.
| |
|
| CO wrote:
> gfretwell@aol.com wrote:
>
>
>
> There is a horizontal bar, with a smaller vertical bar below it. the
> breaker has a large split down the middle, two smaller connectors which
> line up with the vertical bar. All appear to be contacting properly. Is
> it possible that because the neutral wire is not attached to the
> neutral bar (because the disconnect doesn't have a way to connect it)
> it is not operating correctly. I am just perplexed because each hot is
> drawing 120, but i can't get the 240 to show.
>
It's the wrong breaker. It contacts only 1 phase, and
distributes that phase to two wires via the two poles.
You need a regular width 2 pole breaker that takes up
two positions in your panel - or you could use 4
"skinnies" in 2 positions with appropriate toggle ties.
Easisest to use a regular two pole if you have the
positions available.
Ed
| |
| Bob Ferapples 2006-06-20, 3:25 am |
| Whoa whoa whoa!
He said he has a "thin" GE breaker, which means it is the type that
gives 2 x 1-pole breakers off of a single 1" slot. You CANNOT get 240V
from that breaker, it is 2 x 120V from the same phase! The reason he
is reading nothing now Line-to-Line is because there is no difference
between the 2 breaker circuits, but both of them will read 120V
Line-to-Neutral or Ground. There is nothing wrong with the meter.
What is needed is to put in a true 2-pole breaker, which will be TWICE
the width of a 1 pole breaker. That way it will span the 2 phases of
the load center bus bar and have 240V Line-to-Line. If you are out of
slots, you need to buy a 4 pole breaker set which has 2 x 2-pole thin
breakers configured so that the 2 on the inside make up 1 x 240V
circuit and the 2 on the outside make up the other 240V circuit. If
you need the other 2 circuits to be 120V, just remove the bracket that
joins them together.
If you don't understand any of this, hire an electrician!
| |
| gfretwell@aol.com 2006-06-20, 3:25 am |
| On Tue, 20 Jun 2006 02:51:34 GMT, Bob Ferapples <licku45@yqahoo.com>
wrote:
>He said he has a "thin" GE breaker, which means it is the type that
>gives 2 x 1-pole breakers off of a single 1" slot. You CANNOT get 240V
>from that breaker,
It still depends on which slot he uses in the panel. They do make a
thin 2 pole but there are usually only a couple slots in a panel where
it works. I have a small GE panel and there are only two 240v slots,
the rest are on the same rail so you get 120v, no matter what breaker
you use.
The label says you only use single pole breakers anywhere but the two
center slots.
| |
| TURNTABLIST 2006-06-30, 9:25 am |
| WRONG!!
"tandem" vs "double-pole"
A single pole "tandem breaker" IS 2 breakers that will fit in an
opening designed to fit one breaker. = same phase.
He listed the model# THQP230 = Q Line Circuit Breaker, 30 Amps, 2
Poles, 120/240 Vac. "Double Pole" Thin
That breaker will not fit a single 1" slot. It straddles the middle of
two 1" slots connecting the opposite phase and only using "THE AMOUNT
OF SPACE" not the opening, of a single 1" slot leaving spaces for a 1/2
single pole on either side.
If you don't understand any of this, hire an engineer!
Bob Ferapples wrote:
> Whoa whoa whoa!
> He said he has a "thin" GE breaker, which means it is the type that
> gives 2 x 1-pole breakers off of a single 1" slot. You CANNOT get 240V
> from that breaker, it is 2 x 120V from the same phase! The reason he
> is reading nothing now Line-to-Line is because there is no difference
> between the 2 breaker circuits, but both of them will read 120V
> Line-to-Neutral or Ground. There is nothing wrong with the meter.
>
> What is needed is to put in a true 2-pole breaker, which will be TWICE
> the width of a 1 pole breaker. That way it will span the 2 phases of
> the load center bus bar and have 240V Line-to-Line. If you are out of
> slots, you need to buy a 4 pole breaker set which has 2 x 2-pole thin
> breakers configured so that the 2 on the inside make up 1 x 240V
> circuit and the 2 on the outside make up the other 240V circuit. If
> you need the other 2 circuits to be 120V, just remove the bracket that
> joins them together.
>
> If you don't understand any of this, hire an electrician!
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