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  1. #1
    Join Date
    Aug 2007
    Posts
    339

    Confused Ground wire on furnace

    I was talking to a guy in the field the other day about a furnace I worked on that did not have any power to it. It was a weatherking 80pj model and because of a power outage it would not come on. So I did a trouble shoot and discoverd that the ground wire on furnace that leads to the breaker box was not connected. And that the board was not getting any power and I checked the transfromer I was not getting 24v to the board. When I told him this he said thats not the cause of the problem. But when I was in tech school I was always told to make sure everything was grounded before you start a unit. Please can someone prove me right or wrong about this? We talked about this for hours and he still say's that I'm wrong!!
    Thanks!

  2. #2
    Join Date
    Jan 2008
    Posts
    95
    The flame sense on the unit won't work without the ground. All equipment should be grounded.

    The missing ground was not the reason why you didn't have power.

  3. #3
    Join Date
    Aug 2007
    Posts
    339
    Quote Originally Posted by Caveman1234 View Post
    The flame sense on the unit won't work without the ground. All equipment should be grounded.

    The missing ground was not the reason why you didn't have power.
    But if some kind of short where to happened this could effected the board right?

  4. #4
    Join Date
    May 2008
    Location
    North Texas
    Posts
    105
    Two different things going on here.

    One is that with metal cases, they must be grounded. A loose wire, or a wire cut, making contact with that metal case is lethal. With the case grounded, a short should trip the breaker. So school is right, the grounds always go on first, and you should always check to see that the case is grounded.

    Second, power is supposed to be on a hot or both hots, and a neutral. Power current is not supposed to flow on the ground. For residential, the only place that ground and neutral are to be tied together is one and only one place in the service panel. If that rule is not followed, then ground loops will mess up the electrical system.

    So one is life safety, and two is power distribution.

  5. #5
    Join Date
    Mar 2007
    Location
    Sterling Heights, MI
    Posts
    141
    Quote Originally Posted by cook42 View Post
    I was talking to a guy in the field the other day about a furnace I worked on that did not have any power to it. It was a weatherking 80pj model and because of a power outage it would not come on. So I did a trouble shoot and discoverd that the ground wire on furnace that leads to the breaker box was not connected. And that the board was not getting any power and I checked the transfromer I was not getting 24v to the board. When I told him this he said thats not the cause of the problem. But when I was in tech school I was always told to make sure everything was grounded before you start a unit. Please can someone prove me right or wrong about this? We talked about this for hours and he still say's that I'm wrong!!
    Thanks!
    The information quoted makes it sound like this unit does not have a neutral (white), and used either the conduit or the ground (green) wire to make the circuit. By using the term power outage, what do you mean? Every circuit should have a hot (black) and neutral (white) wire, plus a ground (green) to both the switch, convenience outlet and unit. All of these wires are supposed to come from the same panel, not different sources. Installation instructions will tell you to install per NEC (National Electric Code). Insurance company will note such details on a claim investigation. You can never have too much grounding, especially with electronics on board. So what did he offer was the problem?

  6. #6
    Join Date
    Aug 2007
    Posts
    339
    Quote Originally Posted by rfhcms View Post
    The information quoted makes it sound like this unit does not have a neutral (white), and used either the conduit or the ground (green) wire to make the circuit. By using the term power outage, what do you mean? Every circuit should have a hot (black) and neutral (white) wire, plus a ground (green) to both the switch, convenience outlet and unit. All of these wires are supposed to come from the same panel, not different sources. Installation instructions will tell you to install per NEC (National Electric Code). Insurance company will note such details on a claim investigation. You can never have too much grounding, especially with electronics on board. So what did he offer was the problem?
    Well for one thing coming of the toggle switch they had 12-2 wire with a black wire and white wire and a green wire which is the neutral wire. They then wire nutted it with romex wire which had a black wire and white neutral wire and a bare copper ground wire which was not tied to the green wire coming from the toggle switch. The romex wire is leading to the breaker box. Well I install some weatherking furnaces before and in the installation booklet it gives a waring that FURNACE MUST BE GROUNDED. And since I noticed that the ground wire was not connected I asume that that was the cause of the primary side of the transfromer to not have any continuity and the secondary side was find. I have not run into this problem before concerning a ground wire not porperly grounded. There was source power going to the board but no 24v coming out of the secondary side of the transfromer.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,929
    The transforemer does not need the ground connected to work. It will still output 24 volts on its secondary without the ground being connected.

    The board may not function proper without it though.
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