| Author | Message | ||
| ChuckMC9 (Chucks)
Rating: |
OK, if you have a device which the mfgr. specs. says draws 2,000 watts, and the mfgr. says to use a 25A breaker (which I can't easily find), can you use a 20A breaker? I mean, 2,000 watts is 16.66666666666 Amps, so shouldn't a 20 Amp work or will it trip all the time? Don't cream me for this question, ok? Background: 1.) Purchased a GE 125A load center today, on the HD guy's recommendation, but they had no 25A breakers and they don't seem to be common. The load is for a Rheem HWH. (BTW, there were no SquareD QO or Homelite 25A breakers either) Hard to believe that there is no standard interface for breakers after all these years. Haven't those guys learned anything from the computer world??? 2.) The load center is a main lug, with a separate SqD QO main disconnect with two 50A breakers. 3.) 10 gauge between the HWH and the CB, in case you're worried. PS: I have immense respect for engineers. | ||
| Mike (Busone)
Rating: N/A |
Why not just use a 30 AMP breaker. As long as you are using 10 gauge wire. | ||
| James Maxwell (Jmaxwell)
Rating: N/A |
Chuck: The amperage depends upon the incoming voltage and you have figured at 120v. At the resulting 16.67a, you're thinking seems correct w/the 20a breaker, allowing the standard 10% margin. However, I think the industry standard calls for computing at 110v, which results in 18.2, adding 10% yields 20a and pop goes the breaker. I know that my service generally is 120v at most times but I quite often see extended periods where it drops down to 110-112 and stays there for days at a time, especially under summer load periods. I have seen my service voltage into the house as low as 102 per leg before being rotated off. | ||
| John Jewett (Jayjay)
Rating: N/A |
You won't find a 25A breaker- they don't make one in a single pole. Use a 20A, it will take the surge and later if it starts to give problems, then (and only then) use a 30A, but only if you really did use # 10 wire. James M. What are you referring to when you say 10%? 10% of what? Are refering to de-rating factors? Based on what? Percentage of fill in a raceway? Vd? ...JJ | ||
| James Maxwell (Jmaxwell)
Rating: N/A |
JJ: De-rating and VD factors. I was always taught and often read to not run loads to the rated capacity of conductors and breakers, which allowing for normally encountered fluctuations in service voltage, he could well do as far as the rating of a 20a breaker, and that does not consider that they do weaken with use-time and temp. | ||
| ChuckMC9 (Chucks)
Rating: N/A |
Thanks for the counsel, guys. OK, 20A goes in and we'll see what happens. And yes, I really did use #10.  I'll carry a 30 in case it's a no-way situation in problematic low-voltage parks. | ||
| Chris 85 RTS
Rating: N/A |
The purpose of a breaker is to protect the wire not the end device. Assuming the end device shorts out, or some one else puts a new device with a load higher than the wire can handle, the breaker pops to stop the wires from smoking. So, if you put in wire to handle 30A, use a 30A breaker regardless of whether your load is 1A or 20A. | ||
| CoryDaneRTS Rating: N/A |
The load depends on the actual voltage, cable size and length of the wire run. It all gets added in and it all takes power to get the results needed. cd | ||
| Tom Caffrey (Pvcces)
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And, IIRC, the breakers are not supposed to be loaded to more than 80% of their ratings. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher | ||
| John Jewett (Jayjay)
Rating: N/A |
Chris, the purpose of a breaker (or fuse) is to protect the device, and also it shall not be rated greater than the ampacity of the current carrying conductors feeding the device,(including the neutral, and any unbalanced load it may carry.) NEC 210.10(c) He should use a 20A breaker to keep the load from self-destructing, and this leaves him a wide safety margin before the plastic starts to drip off the wires. A 30A breaker on a 20A load is like putting the ubiquitous penny under the old screw fuses. The heater could overload and start a fire long before the breaker tripped. Single phase single pole breakers will "hold" at 125% of rated capacity for about 7 to 15 minutes (depending upon ambient temp.) before tripping if the apmerage goes up slowly, so it could be as much as 37 to 38 amps ( or a bit more) before the 30A breaker tripped,and that would be over 200% of the heater's load. Lot'sa smoke, huh? ...JJ | ||
| John Jewett (Jayjay)
Rating: N/A |
James, Vd (voltage drop) is computed as a function of wire length/AWG, and conductor derating is taken from charts (usually Art. 310) and is based upon the number of conductors in a raceway. Neither are based upon a percentage. ...JJ | ||
| chris Rating: N/A |
John, how does the guy that wired my house know what load I planned on plugging into the circuit he just wired? Let's say I had a 20A household circuit, and I am running a 1000W space heater. Should I go out and remove the 20A breaker and install a 10A breaker to protect the heater? If it were that important to protect the load, would we not have either adjustable breakers or a much wider selection of breakers available? | ||
| Richard Bowyer (Drivingmisslazy)
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Richard | ||
| Jack Conrad (Jackconrad)
Rating: N/A |
When we built our house about 7 years ago, The code required a 20 amp breaker for any circuit using 12 ga. wire, a 15 amp breaker for any 14 ga. wire and a 30 amp breaker for any 10 ga wire. I was allowed a maximum of 10 outlets and/or lights on a 15 amp circuit and a maximum of 15 outlets and/or lights on a 20 amp circuit. Inspector said this is based on the assumption that it is unlikely you would be using all of the outlets/lights on a circuit at the same time. (I put 9-10 per 20 amp circuit) However most appliances and any motor 1/2 HP or larger such as dishwasher, garbage disposal, and garage door openers require a dedicated 20 amp circuit. When I installed my garage door openers, each had a dedicated 20 amp circuit 12 ga wire (per code). The plate on the opener said the motor draws 6 amp. I asked the inspector about this telling him there was no way the 20 amp breaker could protect that motor that a has draw of 6 amp. He smiled and said "well, that's that code". The door opener does have an internal thermal overload. NOTE This was per code in Florida 7 years ago, and as we all know codes change. Hope this Helps, Jack | ||
| niles steckbauer (Niles500)
Rating: N/A |
I'm not an electrician - but we always use the simple 15 'points' per 15 amp CB and 20 'points' per 20 amp CB - a duplex recep is 2 points and a dedicated light switch (one fixture) is 1 point - if your electrical system is installed per code (i.e. no more than 10 feet distance from a recep to any point in your structure - thereby removing the need for extensin chords and expansion jacks) you will never overload the circuit under normal conditions - Niles | ||
| Chris Rating: N/A |
I confirmed my assertation with a current FL state certified and licensed electrician, who agreed with me 100% that the breaker protects the wires and not the load. If a load needs protecting, it will have it's own protection. | ||
| ChuckMC9 (Chucks)
Rating: N/A |
Off Topic, but GE Industrial has the lousiest web site imaginable. All sorts of useless junk except what you're looking for. I might call my electrical supply house as a last try, otherwise wait till I get to a campground to see if 20 will work. Good grief, there is *nothing* that's not a hassle with this dang conversion 'hobby'! | ||
| John Jewett (Jayjay)
Rating: N/A |
Chris, you (and your electrician friend) are correct IF it is a branch circuit. BUT the original post was about a single load i.e. a hot water heater, and as such it should have a dedicated, properly sized, circiut breaker. Care must be taken in these posts to not get sidetracked about the original issue. Oh, BTW the distance to the nearest receptacle on a branch circuit is 6 feet, NOT 10 feet. Jack C.-none of the issues you covered have changed under the newer NEC. ...JJ | ||
| niles steckbauer (Niles500)
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Ooops - was that 10 feet along any wall? - told you I wasn't an electrician - sorry for the misinformation - thanks for the correction - Niles | ||
| FAST FRED Rating: N/A |
"I confirmed my assertation with a current FL state certified and licensed electrician, who agreed with me 100% that the breaker protects the wires and not the load. If a load needs protecting, it will have it's own protection." And the best way to protect the load is with a FUSE , tailored to the exact requirements of the load. Keep the smoke inside!! FAST FRED | ||
| CoryDaneRTS Rating: N/A |
FF, you are correct. Assuming a #12wire can normally be protected with a 20amp cd/fuse.... It would be really dumb to use a 5 amp cb/fuse on a #12 conductor wire, limiting your use to very low loading, likewise, It would be really dumb to put a 30 amp cb/fuse on a #12 conductor as the wire can't handle the load of 30amps. think of it this way. When a car is wired, the cable has a fusable link, I think it is around 60amps, which feeds the fuse box. Now most items are fused directly from the fuse box but if you add a CB, notice it has its own fuse for protection, and it is usually about 3 amps, same with an AM/FM radio aftermarket installation. The CB/fuse protects the wire and the accessory, if it is a very low load item, is protected by an additional fuse/breaker. Most of your household items have the additional protection built in them these days. Interesting subject, isn't it? I was never more amazed at the power station when they told me that we harness electricity to make money and yet, though we successfully contain the product, we really don't know everything there is about it. That explains the occasional flashovers and such that occurr. I sometimes thought that we, as a producer, sometimes stretch the limits when manufacturing the equiptment that contains this product. This reflects well with how we build our conversions, though, the station delt with voltages from 120v up to 140,000v. A nice span of area to work with. In the far stretch of the mind, it is similar to our bus wiring. Good luck cd | ||
| ChuckMC9 (Chucks)
Rating: N/A |
While out getting all manner of electrical whatnot today, lo and behold, I DID find a 25 Amp household FUSE, for which I paid $.89 in honor of Fast Fred. Sure would be nice if there were such a thing as an inline holder, like a much larger version of the one for the CB that CoryDane mentioned. I sure don't want to add yet another full enclosure/conduit all that jazz for the fuse, which would be downstream of a 30A breaker, by the HWH. Just like the CD above. Anyone know of an inline holder or something like that? | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
There are 30 amp in-line fuseholders and I believe the fuses for them can be found up to 250 volts, both 25 and 30 amps in AGC sizes. You should be able to find them at many hardware and parts stores. Just be sure to look at the fuses before you buy them. Common voltages are 32 and 250. They look the same as the older style car radio fuseholder. Good luck. Tom Caffrey PD4106-2576 Suncatcher | ||
| CoryDaneRTS Rating: N/A |
Hold on here.... If the main feed is 30AMP, then why are you trying to protect with 25Amp down stream? if we are protecting a HWH, the 30 will do the job with no damage to the cable(providing you have the proper cabling. Or if the device has a really cheap electrical box where electrical failure is a concern. One thought comes to mind, Aren't the HWH circuits dedicated, that is, only the HWH is on the ckt? If so, then the line could be protected at the source. And again, the HWH devices I have seen have two types of protection, over heat, which opens the ckt and overload which pops when the current goes too high. Sorry, perhaps I don't understand the circuit involved that well but I have tried to explain the charactoristics... Good luck cd | ||
| John Jewett (Jayjay)
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Hey Gang, just remember that ALL electrical manufacturers are required to pre-install a certain amount of smoke in their products. This smoke comes in multiple colors, odors and flavors, and leaves stains of varying types, that are extremely difficult to remove. When we screw up, or the device gets old then it blows and lets the smoke out, and then it won't work any more. Some devices can be recharged with new smoke via a warranty, but selsom without much frustration and expense. Like FF said...keep the smoke in!!!!!! Cheers...JJ | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
That's a good idea, JayJay. Tom Caffrey PD4106-2576 Suncatcher |
