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240 Volts - AC Not working - Getting 68 volts b/w one line-phase

240 Volts - AC Not working - Getting 68 volts b/w one line-phase

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  #1  
Old 06-15-05, 06:56 PM
Kuldeep24
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240 Volts - AC Not working - Getting 68 volts b/w one line-phase

Hi,

I started my AC this season for the first time but it didn't start. Last season it was working perfectly. It is connected to an outer junction box. The box has four points. I'm assuming two-live (say L1 and L2) and two ground (G1 and G2). I checked the voltage between all points. Here is the summary:
L1, L2: 240V
L1,G1: 120V
L2,G2: 68V
G1,G2: 0V

Does this reading make sense? I was expecting voltage b/w L2, G2 to be 120V also. Actually even L1,G2 is 68V.

Also, I did expect G1,G2 to be 0V but someone at my work said it should also be 240V. Is it?

Is there a fault with the supply or everything is ok and it's the AC that has problem. If there is a fault, can you please point me in the right direction?

Thanks in advance
KC
 
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  #2  
Old 06-15-05, 07:47 PM
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Join Date: Oct 2004
Location: USA
Posts: 719
I thinking,
L1, L2, N = neutral, G = Ground

L1 to L2 = 240
L1 to N = 120
L2 to N = 120

L1 to G = 120
L2 to G = 120
==========
What's L2 to G1 ?
What is the colors of the wires ?
Did you check the breakers / fuses ?
How many breakers are used for your air con ?
Is this a single house ?
Can your AC be 3 phase unit ?
 
  #3  
Old 06-15-05, 09:14 PM
Kuldeep24
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It's a townhouse, about 14 yrs old. The air conditioner is single phase so I guess supply is 1 phase too (unless 1 phase AC can be connected to 3 phase supply, I dont know much about that).

The wires in the box going to AC are all white, no red/green etc. There are two breakers used, each 30 Amp. When I started the AC and it did not start I checked the breaker and it was OFF. I dont know whether it was set to OFF and it happenned when I started the AC. But I turned it back to ON. After that whenever I turn on the AC to check it etc, breaker stays ON.

Also, I hope this 68 Volts is not showing any hazardous condition in the house

Any help would be appreciated. Thanks
 
  #4  
Old 06-16-05, 12:02 AM
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Join Date: Aug 2004
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Posts: 1,065
There is no neutral in a 240 volt A/c circuit. There is also no G1 or G2 there is just ground. Nothing in the description sounds like three phase. However it does sound like you have lost one leg of your 240 volts. If these are individual breakers and not a double pole with handle tie then reset them by moving them all the way to the off position then back on. The outside box is a disconnect....does it have fuses or is it non fused?
 
  #5  
Old 06-16-05, 02:25 AM
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Join Date: Oct 2004
Location: USA
Posts: 719
General setup would have the two breakers located inside your townhouse.
A second disconnect located at the AC unit. as stated in post # 4.
I had a friend with a condo, that had the neighbors stealing the fuses out of his AC every summer and replacing them with bad ones.
Look for a pull out ring attached to a square fuse holder turn Off the Power First then pull out the fuses and check them.

----------------------------
The 68 volts May-May be a phantom voltage.
Wire sometimes, picks up static voltage charges or induced voltage from other wires.
Digital volt meters put such little load on the line, the charged wire does not discharge and you get an false reading.

Most, but not all analog meters put a higher load on the wire discharging or reducing the static voltage reading, giving less error when encountering phantom voltages.

ANY voltage measured phantom or not must be considered Dangerous.
------------------------------
Sometimes they mark the hot lines with black tape, do you see any other markings on the wires ?
 
  #6  
Old 06-16-05, 10:43 AM
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Join Date: Aug 2004
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You may also have a problem with your controll circuit (thermostat).
 
  #7  
Old 06-16-05, 11:39 AM
Kuldeep24
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The box is a no-fuse box(written on it). I guess I can do upto this much only (being a novice in these matters). Thanks for all your help. I'll call an electrician and see what he says/does. Will try to post the cause here once he figures it out.
 
  #8  
Old 06-16-05, 12:04 PM
Ed Imeduc's Avatar
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Location: Mountain Williams Missouri
Posts: 18,389
Wink

Is there a fault with the supply or everything is ok and it's the AC that has problem. If there is a fault, can you please point me in the right direction?
First do you have power at the blower unit?? is the transformer 24V good Power at the tstat. When you call for cool does blower come on inside ? You have got a lot of ifs ifs ifs here. With your meter ring out what and where you have power on this AC.

ED
 
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