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Keep blowing an electrical fuse. Eletrical advice please.

Discussion in 'Topical Discussions (In Depth)' started by 00nightstorm, Feb 6, 2014.



  1. 00nightstorm

    00nightstorm Seeker Seeker

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    I have a water pump that I am running that keeps blowing a 20 amp fuse in my house. The pump requires "a 15 amp dedicated outlet for proper operation". Although its a newer house I notice that the electrical wiring might not be too good, I blow fuses if I run two 1500 watt space heaters in the same room. I am electrically challenged so please forgive my ignorance. What options do I have to fix this problem?
     
  2. 917601

    917601 Mother Lode Found Mother Lode

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    Off hand? I would run the pump and check the amps it is pulling. Get a cheapo voltmeter and connect it up in series with the pump, read the amps it is using, if more than 15 amps, that is your problem, also a sign your pump is going tits up.
     
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  3. southfork

    southfork Mother Lode Found Mother Lode

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    You cant run 2 1500 watt space heaters on one circuit, the max is 1500 watts for a #14 line witch is normal, it carrys a 15 am cb which is standard, bathrooms may carry a 20 amp but your still limited on the wattage, regarding the pump it's possible they did not place it on a dedicated line, sometimes they place the garage outlets on it too and if you have a fridge as some do it will still blow, its possible also the cb is bad.
     
  4. Silver Buck

    Silver Buck Gold Member Gold Chaser

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    It's been a bit, so forgive my rustiness and accuracy.

    Power = Current x Voltage.

    therefore

    Current = Power / Voltage

    Power = 1500 Watts x 2 (your heaters) = 3000 Watts
    Voltage = 120 Volts

    Current = 3000 Watts (or Volt-Amps) / 120 Volts = 25 Amps. Definitely too much for your 20 Amp circuit.

    However, since we're talking AC power, I believe that we multiply that 25 Amps by .707 (I don't remember if the 120 is peak AC or RMS/Average).

    So, let's see what we come up with.

    25 Amps x .707 = 17.68 Amps

    That's a bit close to that 20 Amp fuse you're blowing (provided that you are running those heaters on Max). Add anything else to that circuit the 20 A fuse is sure to go.

    Doing a bit of Googling, it seems that my 25 Amp answer is correct (12.5 Amps per heater).

    http://robbieselectrical.com/breakers.html

    As far as your pump goes, it could have some windings shorted out to have it draw excessive current. Or perhaps there are other devices active on that circuit which pushes the current to flow through it to go past 20 Amps.

    Hope this helps.
     
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  5. 917601

    917601 Mother Lode Found Mother Lode

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    As mentioned here on previous posts, check CB, remove it and check the contacts on the buss bars. I had the same problem with a house circuit. I pulled the CB out and there was HUGE amounts of powdery corrosion on the CB contact points and breaker bar. I brushed the bar free of powder and replaced the Circuit breaker. Careful, the bars, ( the part that the CB snaps to, is LIVE unless you cut the power to the breaker box). Also, you will have to pull the CB box cover off to remove the individual CB, be careful.
     
  6. Irons

    Irons Deep Sixed Site Supporter Mother Lode

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    Electricity and I have an agreement. I don't mess with it and it doesn't kill me.
     
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  7. dollars

    dollars New Member

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    However, since we're talking AC power, I believe that we multiply that 25 Amps by .707 (I don't remember if the 120 is peak AC or RMS/Average).

    Brings back memories I believe the 120 volts ac is already RMS

    I would check how the pump runs on a dedicated circuit

    if there are continued problems I would check the current drawn compared with the motor name plate full load rating

    This may help to verify if the pump/motor is faulty (ie breaings on the way out etc) or possible other problems with wiring/circuit breaker/fuse etc

    stay safe
     
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  8. Publico

    Publico Banned

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    Is it a fuse or a breaker?

    If it's a breaker it could be old and worn out.

    If it's a fuse they are kind of expensive to replace so put a penny in place of the fuse.
     
  9. MrLucky

    MrLucky Silver Member Silver Miner

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    Since you already suspect the wiring in your house, I'm going to throw in another consideration. How far away is the pump (feet)? Is it possible the wire is undersized for the distance?
     
  10. Unca Walt

    Unca Walt Midas Member Midas Member

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    As an ole electricabibble type, I just gotta say that ALL the answers here are spot on. ('Cept Publico, and he's teasin')

    Silver Buck: Yer spot on alla way down the line. But I've got a nagging memory from decades (too dang many decades!) back... that is, somehow I remember that FUSES were not rated at .707 (Root Mean Square for the non-elec dudes <-- means since there are gaps betwixt sine waves, ya haveta mathematically "flatten them" to see what the "constant current" is) but at the equivalent of DC.

    The reason for this, IIRC, is most folks see 120V, see 10A, and know the basic power formula (Duh: 120 X 10 = 1200W <-- NOT 848 W). So the custom was to use those straight numbers for fuses.

    Alla that said. I could be fulla sh!t. :cheerful::thumbs_up:

    Really doesn't make. OP should be happy as a demented goat, 'cause if'n that fargin fuse didn't blow, yer 24 gauge wire will eventually become a long, hot filament.

    And I agree: If you've got coils that are now shorted (but the pump still pumps), you are gonna draw a lotsa more current.


    LATE SANITY EDIT: :bowdown::bowdown: Dollars:bowdown::bowdown: straightened out my memory!!!! He is right! 120V IS the RMS. The AVERAGE would be less (.637 X 120)
     
    Last edited: Feb 6, 2014
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  11. itsamess

    itsamess Silver Member Silver Miner

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    If plugged into outlet you might want to buy a Kill a watt plug in meter (cheap, safe and great for checking draw on older appliances or your infrared heaters). They are about $20 here or HD etc
    82-715-001-05.jpg

    If initial draw is high at first on then drops off a cheap option is to install start capacitor like on ac compressor units. These are also great for lowering startup draw for running items off generators.
     
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  12. 00nightstorm

    00nightstorm Seeker Seeker

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    It trips the breaker plugged into any outlet. The outlet it is plugged into right now is about 25 ft away from the fuse box. The manufacturer said it will run fine plugged into any normal wall outlet but that does not look like the case. Maybe the motor is out of wack. It looks like I will probably have to have a dedicated line installed. No idea what that will cost but a local electrician is coming by here tomorrow afternoon to take a look and give me an estimate. Maybe I will have him see how much the draw is on the motor first? Thanks for all the advice guys...
     
  13. 00nightstorm

    00nightstorm Seeker Seeker

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    I never run it for longer than 10 minutes and often times it does not trip the breaker at all. Other times it will trip it in about 15-30 seconds.
     
  14. southfork

    southfork Mother Lode Found Mother Lode

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    Your pumps not on an extension cord is it? If so that could be the problem having an undersized cord.
     
  15. Rusty Shackelford

    Rusty Shackelford Midas Member Midas Member

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    Surprised that no one mentioned going redneck and use a bigger fuse!!

    Curious, what newer home uses fuses? I would have assumed any newer home would be protected by breakers.
     
  16. Goldhedge

    Goldhedge Modal Operator/Moderator Site Mgr Site Supporter

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    From my limited knowledge on the subject...


    Typically houses have 14ga wire and 15A circuits (for lights and plugs NOT the heavy appliances washer/fridge etc. they're usually 12ga/20A. The electric stove is 220vac)


    Commercial has 12ga wire and 20A circuits.


    But if you have an electrician coming over, pick his brain on the subject...
     
  17. Rusty Shackelford

    Rusty Shackelford Midas Member Midas Member

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    I figured 12/2 or 12/3 wire was standard in newer homes.
     
  18. Publico

    Publico Banned

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    I am not teasin'. A breaker rated at 20 amps can get "pleasure bent" to engage at a lower amperage.

    And the replacing a fuse with a penny solves the problem with a new house paid for by the home owner's insurance payout.
     
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  19. TN_Preacher

    TN_Preacher Silver Member Silver Miner

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    You need to describe your situation better... Is it a sump pump? A septic tank pump? And if it is a newer house, you have all breakers, not fuses, correct? The breaker is doing what it is designed to do when you are running 3000 watts (25 A) on a circuit designed for only 20 A. One heater is all you should run on that circuit.

    "Dedicated circuit" means that there should be nothing else on the same circuit, because the water pump requires all the current that the circuit can supply. I would definitely use a 20 A circuit (12 AWG) in that situation.

    If you are blowing a breaker on the sump pump, see if the breaker is on a GFI circuit. If so, then there is current flowing to ground, meaning that somewhere in the circuit the insulation may be breaking down. Breakers also fail, the metal fatigues over time, contacts corrode, etc. Pump motors also fail.

    Please describe your circuit the best you can, and if you don't know what something is called, take a picture and post it. Like Johnny 5 says... 'need input.'


     
    Last edited by a moderator: Dec 26, 2015
  20. Spectrism

    Spectrism Seeker Seeker

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    If your fuse or breaker is rated for the load, a tripped circuit means you have a short somewhere.... or, you are not getting a proper power feed. Someone mentioned corrosion on the main bar or a fuse holder. If you have corrosion at connecting parts of the feed line, they act as resistance. At resistance there is a voltage drop. When a load is pulled, the voltage supplied to that load will drop severely.

    Let's say you have a 120VAC pump. It wants to use 3000 Watts. The current draw will be:
    3000/ 120 = 25 amps.

    Let's say there is corrosion or a broken wire feeding this line. When the pump is turned on, instead of seeing 110 or 120VAC to feed the 3000Wts, it drops down to 90 volts. Here is what it does to the current:

    3000/ 90 = 33.3 amps.

    Fuses trip on current.



    DO NOT get a cheap "voltmeter" and hook it up in series with the pump. You will surely let smoke out of the voltmeter that should never come out. You will likely see fireworks too.

    Measure volts first. It is easier and safer. If you want to measure current, get a current sensor that goes around the wire. If you are not sure about what you are doing, don't do it. You don't get second chances.
     
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  21. andial

    andial Sir Midas Member Site Supporter ++

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    I am in full agreement with what numbers posted, in post #2 .
     
  22. obilly

    obilly Silver Member Silver Miner

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    i would think you have a queer breaker if it keeps blowing fuses?
     
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  23. JustPassinThru

    JustPassinThru Gold Member Gold Chaser

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    I was going to suggest the one-cent solution, but Publico beat me to it.

    It does have some things to recommend it. Cheap initial outlay, and a very, VERY permanent solution. At minimal cost to you, but...a bit inconvenient.
     
  24. Goldhedge

    Goldhedge Modal Operator/Moderator Site Mgr Site Supporter

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    Not since the cost of copper went bonkers!

    14 is much easier (and cheaper) to pull.
     
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  25. ttazzman

    ttazzman Midas Member Midas Member Site Supporter

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    really need to know the pump motor size.....

    but its highly possible the pump STARTER is weak or out...

    pump motors have a high starting amp draw.....then lower to run...

    A. assuming the pump worked at sometime on the circut in question...then

    #1...a starter problem or a load problem has developed in the pump (replace pump..or starter...or brushes etc.)
    #2 ...the pump is fouled and overloading on startup (clear fouling)(make sure pump is free and turns)
    #3....the circut breaker is getting weak...(replace with delayed trip breaker)

    B. the pump is new to you and never been run by you before..

    #1 and #2

    #3 your home circuts are not rated for the pump starting/running load (consult label on pump motor to determine)

    FWIW...pump motor starting loads can be as high as 2.5 times running loads

    Since you state your pump requires 15amps to run....any modern home under 20yrs old should have that (15amp) as a minimum circuit capacity, would be good to make sure not much else is on the circut

    if it is blowing while runing on a 20amp breaker as you state.......its probably something else on the circut cycling such as a deep freeze ..etc..
     
    Last edited: Feb 6, 2014
  26. Ragnarok

    Ragnarok I'd rather be Midas Member

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    Best to keep the load on a fuse/breaker to about 75% of its rating imho (15amps max on a 20amp fuse/breaker).

    And imho no discussion about fuses should be without this handy guide: ;)

    Fools Guide to Fuse Replacement.jpg

    2c,
    R.
     
    Last edited: Feb 6, 2014
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  27. brosil

    brosil Gold Member Gold Chaser Site Supporter

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    I had a similar problem once and replaced the breaker with a hi-mag breaker. They will accept a higher starting current. It does kind of sound like a cheap starting cap on the motor, though.
     
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  28. Unca Walt

    Unca Walt Midas Member Midas Member

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    (*snork*) Hadn't thought of that... butcha better tell the OP to remove the penny after the house is gone but the insurance guy has not shown up yet. :s13:
     
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  29. Publico

    Publico Banned

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    If the OP isn't smart enough to remove the penny before the insurance adjuster shows up then the OP isn't smart enough to deserve an insurance settlement.
     
  30. 00nightstorm

    00nightstorm Seeker Seeker

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    The electrician told me the problem was arc-fault breakers. I have some GFI breakers at a few locations in the house so I will just run an extension cord to one of these to run the pump while I am out of town.
     
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  31. Bobthetomato

    Bobthetomato New Member Seeker

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    Is it a dedicated circuit or is something else on it? Could the wire be damaged?
     
  32. SWRichmond

    SWRichmond Seeker Seeker

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    If the pump used to work ok and not pop the breaker, then you should probably suspect the pump motor is starting to go bad and is drawing more current than it was when it was newer.
     
  33. TN_Preacher

    TN_Preacher Silver Member Silver Miner

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    If you want to be sure the pump won't fail when you are out of town, make sure it has a battery backup with sufficient capacity for the duration of your time away. GFCIs are known to trip when used with water pumps just like arc-fault breakers can trip with motors.
     
  34. CiscoKid

    CiscoKid They all look good through beer goggles... Gold Chaser

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    I had some of those GFI breakers start to go bad on me and was told by an electrician that I trust that they were crap and that hardly anyone uses them any longer. The smart setup is to run a standard breaker and have the first outlet in the circuit be a GFI outlet. Replaced the GFI breakers and never had another issue. Also, what Publico says about breakers getting weak after so many trips is true. At least, in my experience. And, for what it is worth, I never waste time installing anything less than 20 amp breakers with 12 gauge wiring and I install a fair amount of new electric.
     
  35. southfork

    southfork Mother Lode Found Mother Lode

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    Did he mean an arcing gfi breaker, gfis's are very fussy and go bad, check to see what wire size you have, if its #12 make sure they have a 20amp gfi installed, some builders are cheap and will use a 15gfi on a #12 wire.
     
  36. TN_Preacher

    TN_Preacher Silver Member Silver Miner

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    The arc fault breaker is a relatively recent requirement of the NEC, required for all bedrooms in residential dwellings. They are designed to prevent fires due to bad connections (hence arcing), but they are prone to nuisance tripping,which I believe was the issue with the OP.
     
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