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Thread: Dimming lights

  1. #27
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    being a licensed master with over 20 years experience & pilot carries a lot more authority and respect than a patch wielding youngster, hows that for experience..........

  2. #28
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    Feb 2006
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    Originally posted by electricbuzz
    Dont a 40 amp breaker seem a little small for a 4.5 or 5 ton heat pump?
    No.

    240x40 = 9600W. Say the COP is 2.5, this is effectively 24kw (~82k BTU) which is more like 6.8 tons.

    Of course, any electrical strips would be on a separate breaker wouldn't they ... but, in my experience, it is very highly inductive loads (load motors and hence compressors) which cause voltage droop (and hence flicker).

    Paul.

  3. #29
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    The Stealth doesn't come in 4.5 ton, its either 4, or 5 ton.

    Min circuit amp is 18.9, and max fuse is 60 for the 5 ton.


    It can also dim the lights starting in second stage if they over charged it.
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  4. #30
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    Jan 2004
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    Just checked the breaker it's 50

  5. #31
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    Did the HP come with start gear?

    I had to add start gear to a couple of Lennox units with scrolls last summer. Streight cool.
    Beware of advice given by some guy on the Internet.

  6. #32
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    Originally posted by Milk man
    Did the HP come with start gear?

    I had to add start gear to a couple of Lennox units with scrolls last summer. Streight cool.
    Thats standard on the Stealth.
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  7. #33
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    I'm not really an electrician anymore since I got my electrical engineering degree, but maybe I can help.

    The ground is a safety device, there should never be any electrical current flowing in the ground except if something bad is happening. The purposes of the ground is to keep any part of the unit that a person might touch at the same electrical potential as the ground you are standing on and other things around it. A "weak ground" is definitely not the problem, although a "weak ground" could cause somebody to get hurt if some other failure causes an electrical short to the case of the unit.


    The lights will always dim by some amount whenever a load is placed on the electrical service, the question is how much. Are the lights only dimming during startup or do they remain dimmed the whole time the compressor is running? I will assume here that they are dimming more then they should the whole time the compressor is running and that the current draw of the compressor is within reason. I don't know the size of the service but the fact that the 40 amp breaker isn't tripping makes me suspect that the run current isn't overly excessive. Keep in mind that sagging voltage can cause the run current on a motor to increase. We all know what sagging voltage can do to a motor, especially when it is starting . The lights in the house are all on a separate circuit from the HVAC system. This means that the current draw from the compressor is pulling down the voltage on the buss bar where the breakers supplying the lights are connected. The problem, therefore, has to be upstream from the compressor circuit breaker. It has to be the buss or the service and connections supplying it. If some lights dim while others brighten then the problem is a voltage drop across the neutral line due to some sort of poor connection there.


    One very common place for a problem to occur is where the service connects to the top of the panel or meter. This wire is usually aluminum, which has a tendency to creep over time and oxidize. When I was in the business, I would always give those screws a turn, sometimes with fresh anti-oxicant. They were always loose. Often there is visible signs of heating such as melted insulation, etc. I wouldn't touch those wires if I were you, if one of them broke off and shorted against the box or ground it can supply hundreds of amps and there is no circuit breaker to stop it. I once saw a guy get burned that way. The smoke oozing up from the ground from the fried service wire was interesting to watch. Another possibility would be accidentally disconnecting a loose neutral which could fry a house full of electrical equipment and start a fire. Seen that happen too.

    Another possibility, if it is a buried service, is that the wire insulation was damaged during installation or later. Electrical leakage into the ground will corrode the wire until it eventually breaks. The symptoms will be dimming and flickering lights.

    One thing is certain, whatever is causing the dimming is causing heat. If there is a lot of dimming, there is a lot of heat. Using an infrared thermometer while the compressor is running would be a good way to spot a problem like this if it is in the breaker box. I just wouldn't wiggle or mess with anything in a breaker box having this sort of problem due to the possibility of some defective part failing and causing an insurance issue.

    The trick in this situation would be to determine what the compressor startup and run current is, and how much that current is pulling down the voltage on the breaker panel buss. Personally, if I were in your business, I would carry a multimeter and clamp meter with min/max capability (peak hold) so I could capture how low the voltage is sagging or what the peak current draw is when a motor starts up. That way I could phone my favorite electrician when I suspected a problem and ask him if a particular reading is normal.

    George.



  8. #34
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    yes use

    a meter

  9. #35
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    No current should be going to ground but since your Nuetral is tied to ground, the grounding rod or main ground to the house has to be a good one. It can very well have something to do with dimming lights.

  10. #36
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    Since neutral is generally tied to ground, Older systems might use the neutral to bond the chassis to electrical ground by tying neutral to ground at the breaker panel and the chassis at the compressor. You aren't supposed to do that any more, you need to run a separate ground wire. Since the compressor is a 220V unit the neutral is unused, unless there are 120V circuits on the unit, so the neutral might be used to bond the chassis to ground.

    You are right, a small current will always flow through the ground rod as a result of the voltage drop on the neutral wire to the service transformer. If the neutral line from the transformer to the house were severed then a significant neutral current would flow through the ground rod to return to the transformer. The quality of the ground would affect dimming of the lights in that situation. This would be a very bad situation because the neutral has failed and the final fallback system, the ground rod, is preventing dangerous voltages. Hopefully this isn't what is happening here. If you ever clamp a meter around a ground rod and see significant current flow, be afraid. It is a bad situation.

    Funny story. Long ago, as a mere child of 26, I worked for an electric company. I watched a guy open a breaker panel on the outside of a house which was having problems with dimming, flickering lights. He grabbed the service neutral and wiggled it to see if it was tight. The neutral wire popped out. He stuck it back in but it was too late. There was an immediate bang from inside the house and the sound of a lady cussing and yelling as loud as she could. A few seconds later, a guy came storming out carrying a hachet, raging mad. I recognized a few of the words, %^#%$@ moron were two of them. I was downwind and could smell smoke. I don't have a clue what happened inside the house, but an active imagination could conjur up all sorts of scenarios. Nobody was hurt and it reportedly cost the utility $11,000. We all sat and laughed our asses off later, though it really wasn't funny.

    George

  11. #37
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    Originally posted by gstein


    He grabbed the service neutral and wiggled it to see if it was tight. The neutral wire popped out. He stuck it back in but it was too late. There was an immediate bang from inside the house and the sound of a lady cussing and yelling as loud as she could.
    George
    Thats a great way to put 240 volts through any running 120 volt appliances.
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  12. #38
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    Forget the neutral or ground as being anything to do with the problem. Your dealing with a balanced 240v load.
    Run a larger wire to the heat pump. Check the start components.

  13. #39
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    Originally posted by rsmith46
    Forget the neutral or ground as being anything to do with the problem. Your dealing with a balanced 240v load.
    Run a larger wire to the heat pump. Check the start components.
    And the run capacitor under a load.
    Beware of advice given by some guy on the Internet.

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