Voltage Measurement

Reply

  #1  
Old 01-06-05, 10:42 AM
justlaffer
Visiting Guest
Posts: n/a
Voltage Measurement

I disconnected a baseboard heater that wasn't working and tested the wire that was connected to it. I wanted to determine whether the heater was broken or the wires connected to it were dead.

I used my multimeter to test the voltage between the live and neutral wires and it displayed 0V. So I was convinced that the wire was not live.

I continued to work and by chance tested the voltage between the live and ground and it displayed 120V. I was surprised! I could have electricuted myself!

If there is 120V running through the live wire shouldn't the multimeter show 120V when I test between the live and neutral wire? Otherwise how can one test the the voltage of the live wire in a situation when there is no ground?

The bottom line is I want to figure out if there is something wrong with this circuit and in the future how can I make sure that a wire is not live.

Justin
 
Sponsored Links
  #2  
Old 01-06-05, 11:02 AM
GTBaker's Avatar
Member
Join Date: Jan 2005
Location: Newfoundland
Posts: 81
Test the RED against the ground...should be 120v and the same with the BLACK and ground...120v. If you go across the RED & BLACK should give 240v. Sounds like one of the wires has worked it's way loose in the panel off the breaker. If you're comfortable with taking the panel plate off go for it and see. For safety make sure the main breaker is OFF. After that just wiggle the wires on the breaker that controls this heater. Should be tight. Also check the GROUND wires to make sure they are all tight.

Another synopsis is if this heater in question gets it's power from another heater. Not all heaters have there own dedicated breaker. If it does share...you will have to back track.

But safety first....turn OFF breakers.
 
  #3  
Old 01-06-05, 11:25 AM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
When you say "neutral", do you mean "white wire"? They are not the same thing. In fact, the white wire to a baseboard heater is usually hot, not a neutral. Baseboard heaters usually do not use a neutral.

But test whatever you called "neutral" for voltage to ground.

Other than disconnecting the unit, have you made any other changes, especially in the panel?

Remember, there are lots of ways to get zero volts between two wires. They both might be dead. They both might be hot. One may be open.
 
  #4  
Old 01-06-05, 11:37 AM
Member
Join Date: May 2001
Location: Dry Side of Washington State
Posts: 738
Does a thermostat control the baseboard heater? Make sure you turn the temperature up at thermostat so the second hot leg has voltage. If you get a 240 volt reading between the baseboard's hot legs and the heater doesn't work, then the heater has failed.
 
  #5  
Old 01-06-05, 11:37 AM
Member
Join Date: Sep 2004
Location: NW Ohio
Posts: 188
justlaffer,

Does this unit have a wall thermostat? If so it could be that one leg of the ckt is controlled/switched by it and it is turned down. If this is the case, maybe you can turn it "on" and check your voltage between each wire that was connected, and each wire to ground and see what you get. That would at least tell you if the ckt is good and the unit is faulty...
 
  #6  
Old 01-06-05, 01:18 PM
justlaffer
Visiting Guest
Posts: n/a
Clarification

The baseboard heater has been disconnected so it is out of the equation. I am testing the wire coming out of the wall which I presume is connected to the main panel.

The wire is standard electrical cabling that contains three distinct wires: black (live), white (neutral) and copper (ground)

When I test the voltage between black and white I get 0V
When I test the voltage between black and ground I get 120V
 
  #7  
Old 01-06-05, 01:28 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
I say again, white does not equate to neutral!

Please test for voltage between white and ground.
 
  #8  
Old 01-06-05, 01:39 PM
GTBaker's Avatar
Member
Join Date: Jan 2005
Location: Newfoundland
Posts: 81
If you have white in your 3 wires...what gauge is this wire. You should be getting 240v between the black and white...if it's hooked up right. How many amps is the breaker/fuse for this circut?
 
  #9  
Old 01-06-05, 02:35 PM
Member
Join Date: May 2001
Location: Dry Side of Washington State
Posts: 738
Is the heater controlled by a thermostat? You'll have to turn it up to get a voltage reading between the white wire and ground, white wire and black wire.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'