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Thread: Max Breaker

  1. #11
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    Max breaker?
    I don't want to break Max.......

    Sorry mods...........

  2. #12
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    Quote Originally Posted by Little Bill View Post

    Now I'm back doing trim-out .
    Quote Originally Posted by Dennis Alwon View Post
    Leave the 30 and if the customer has a call back or something else for you then change it out. I would not make the extra trip unless you were in the area.
    I wouldn't make an extra trip to change that breaker either. That would defeat the purpose of the change (save time and money). But if he is there doing a trim out.

    Edit: you can't buy much gas for the price of a two pole 40 amp breaker ( not to mention the drive time).
    The 95% of people that you can't trust give the other 5% a bad name.

  3. #13
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    Many new units have a voltage range, my current unit has a range of 197-253 volts, MaxOCPD 30 amps, MCA 18.6 amps. I would assume that the 18.6 takes into account the unit running at 197 volts. If it's operating near the top of the range say at 240 volts the current will be much lower than the MCA/125%.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  4. #14
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    Quote Originally Posted by kwired View Post
    If it will hold the starting surge it will likely be fine. If you are running on some temp service and then later switch to permanent service, there is a chance there is less overall circuit impedance in your permanent service and that could lead to higher starting surge from that arrangement - increasing the chance it trips upon starting.
    It's not a "temp service". That get's replaced by the permanent service when you receive a "service release". As I said earlier, the "service release" just allows the POCO to energizes the service before final is ready. This allows the HVAC to run and also allows finish workers to plug in inside without dragging an extension cord across a finished floor. Also, have to have power of some sort to get a final. So basically, it's the main service without everything hooked up. All that's required for a "service release" inspection is grounds made up in the panel and one 120V GFCI circuit, whether that be one receptacle or several on the same circuit. The impedance doesn't change from "service release" to "final" .
    If you aim at nothing, you will hit it every time!

  5. #15
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    Quote Originally Posted by infinity View Post
    Many new units have a voltage range, my current unit has a range of 197-253 volts, MaxOCPD 30 amps, MCA 18.6 amps. I would assume that the 18.6 takes into account the unit running at 197 volts. If it's operating near the top of the range say at 240 volts the current will be much lower than the MCA/125%.
    Running current is well under trip range, it is starting current that is going to be a potential nuisance tripping issue. Starting current is going to be impacted by overall circuit impedance during starting conditions. Same HVAC unit may trip the 30 amp breaker in one location because there is a pretty stout source, maybe short service run and short branch circuit length. Another install with same unit may never trip same breaker because the source is higher impedance, maybe has long service run to the source, but same install maybe sees more severe dimming of lights when this unit is starting compared to the first example.
    I live for today, I'm just a day behind.

  6. #16
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    If you Amprobe the unit when it's running the current is probably close to 15 amps @ 240 volts. A 30 amp inverse time circuit breaker sized at near 200% should not trip on a normal start up. I do get that the warm fuzzy feeling when I size the OCPD at the maximum but won't loose any sleep using a 30 amp CB in this application.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  7. #17
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    I have a 3 ton heat pump in my house, 45A MOCP. I have taken readings when in heating mode and it is only pulling around 6 amps.

    I don't know what peak starting current is, but I can tell you it starts up pretty quickly on utility power, if I try to run it on my generator, it really bogs it down trying to start, and won't start it if there is much for other load running at same time. Runs fine once you get it started on that generator.
    I live for today, I'm just a day behind.

  8. #18
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    Why didn't you swap it out when you noticed the issue. It was cheap then.

    Don't sweat it now. Blame it on the AC guy.

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