electric outlet for window AC question

On Wed, 08 Jun 2005 11:42:48 -0400 snipped-for-privacy@aol.com wrote:
| On 8 Jun 2005 04:21:48 GMT, snipped-for-privacy@ipal.net wrote:
| |>It could just be that I can't find the part of the code that says |>a 15 amp circuit cannot have a 20 amp receptacle | | Look at 210.21(B)(3) again. The top line says 15a circuits shall have | receptacles "not over 15a"
What code are you looking at? The top line of what I have says "Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform ..."
That very much reads like it does not apply to dedicated circuits with a single outlet. However, 210.21(B)(1) would apply in those cases.
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On 9 Jun 2005 01:17:55 GMT, snipped-for-privacy@ipal.net wrote:

Phil look at TABLE 210.21(B)(3) NEC every year since the FDR administration.
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snipped-for-privacy@aol.com wrote:

Phill has a point. 210.21 (B) (3) would not appear to apply to branch circuits that only have one outlet. I strongly suspect that was not what the code making panel intended but the way 210.21 (B)(1) reads now you could put a twenty ampere receptacle as the only outlet on a fifteen ampere circuit.
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That's the point: you can use a 20A outlet on a 15A circuit, but He argues a 15A outlet can handle the 20A circuit which would toast the recept when & if the load overshoots the 15A on a steady basis.
You see that allot in countertop/shop type businesses where they callously plugging all sorts of things and run extension cords for multiple outlets from them with loads greater than 15A. [well maybe not as common, but I've eliminated a few of these type of violations] Roy /~> From: snipped-for-privacy@mindspring.com (HorneTD) snipped-for-privacy@aol.com wrote: On 9 Jun 2005 01:17:55 GMT, snipped-for-privacy@ipal.net wrote: On Wed, 08 Jun 2005 11:42:48 -0400 snipped-for-privacy@aol.com wrote: | On 8 Jun 2005 04:21:48 GMT, snipped-for-privacy@ipal.net wrote: | It could just be that I can't find the part of the code that says a 15 amp circuit cannot have a 20 amp receptacle | Look at 210.21(B)(3) again. The top line says 15a circuits shall have | receptacles "not over 15a" What code are you looking at? The top line of what I have says "Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform ..." Phil look at TABLE 210.21(B)(3) NEC every year since the FDR administration. Phill has a point. 210.21 (B) (3) would not appear to apply to branch circuits that only have one outlet. I strongly suspect that was not what the code making panel intended but the way 210.21 (B)(1) reads now you could put a twenty ampere receptacle as the only outlet on a fifteen ampere circuit.
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| That's the point: you can use a 20A outlet on a 15A circuit, but He | argues a 15A outlet can handle the 20A circuit which would toast the | recept when & if the load overshoots the 15A on a steady basis.
Do you have a modern 15A UL listed receptacle of USA manufacture that will become toast with 20A of total load?
| You see that allot in countertop/shop type businesses where they | callously plugging all sorts of things and run extension cords for | multiple outlets from them with loads greater than 15A. [well maybe not | as common, but I've eliminated a few of these type of violations] Roy | /~>
More likely cheap plugs making poor contact are arcing inside producing far more heat than if 20A were condtinuously running through the device.
I did disasemble (destructive of the plastic parts) a high quality brand duplex receptacle, one each of 15A and 20A, ever years ago. The metal parts that carry electric current were exactly identical between them, right down to the extra contacts for the "T" side slot on the neutral that would never be used in the 15A version unless you were to drill the plastic out and make such a slot yourself (e.g. "field conversion of a 15A to 20A"). Basically, it's the same thing with one of them having a "lockout to prevent 20A plugs".
Not every receptacle will be like that. I only did that because I could see those "T" contacts in the 15A version. At the time I didn't even know that it was legal to use the 15A version on a 20A (multi outlet) circuit.
The cheaper receptacles may be of lesser quality, but to get the UL listing it is my understanding they _must_ meet the requirement of being able to handle a _total_ of 20A when adding up all the current loads from BOTH of the outlets AND downstream loads on the 2nd set of terminals, all going through the line terminals.
In theory, the contacts of ONE outlet might not handle more than 15A, but it is expect that a device running 16 to 20 amps of current will not have a NEMA 5-20P plug on it. Then that is not that much more heat and is not going to make that much difference. If 20A were to toast it, 15A would be awfully damned HOT ... and that's not safe anyway.
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snipped-for-privacy@ipal.net writes:

...
FWIW, I have an el-cheapo 15A recepticle that has on its back "FOR 15A BRANCH CIRCUIT ONLY" (and repeated in French) as well as "15A 125V" on the front near the screw hole. I also noticed the holes for back wiring were awful small, and a little experimenting showed they were the exact right size for #14 wiring. Which means that you couldn't use #12 there if you wanted to! Of course you could (should) still use the screw terminals but someone back wiring it must use #14! Take a look at the cheap recepticles at Home Depot which I think is where it came from.
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Roy Q.T. wrote: > That's the point: you can use a 20A outlet on a 15A circuit, but He > argues a 15A outlet can handle the 20A circuit which would toast the > recept when & if the load overshoots the 15A on a steady basis. > > You see that allot in countertop/shop type businesses where they > callously plugging all sorts of things and run extension cords for > multiple outlets from them with loads greater than 15A. [well maybe > not as common, but I've eliminated a few of these type of violations] > Roy /~> >
Roy Step one this is Usenet so please stop top posting. The protocol for Usenet is to add your reply at the bottom of all quoted text and to keep the quotes in posted order.
UL test receptacle outlets to feed through much higher loads then the pattern of the receptacle is meant to supply. A fifteen ampere receptacle will certainly handle twenty amperes without any additional risk of failure. The real danger is that the installation of a twenty ampere receptacle on a fifteen ampere circuit can lead to chronic overloading and nuisance tripping of the over current protective device. That in turn will cause a user to be tempted to replace the OCPD with one that is two high to protect the circuit wiring.
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HorneTD wrote:

Hard to believe but apparently true. A single outlet just has to have a higher rating than the branch circuit. Not only can you put a 20 amp single receptacle on a 15 amp circuit you can put a 30 amp, 100 amp ....
This appears to have been in effect at least back into the 1980s.
One way to see check the reasoning behind a code item is to look for proposed changes and see how the code making panel responds. There were no proposed changes to this rule as far back as 1983 (1996 and 1993 are unknown). This rule was invisible?
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| HorneTD wrote: | |> |> |> Phill has a point. 210.21 (B) (3) would not appear to apply to branch |> circuits that only have one outlet. I strongly suspect that was not |> what the code making panel intended but the way 210.21 (B)(1) reads now |> you could put a twenty ampere receptacle as the only outlet on a fifteen |> ampere circuit. | | | Hard to believe but apparently true. A single outlet just has to have a | higher rating than the branch circuit. Not only can you put a 20 amp | single receptacle on a 15 amp circuit you can put a 30 amp, 100 amp .... | | This appears to have been in effect at least back into the 1980s. | | One way to see check the reasoning behind a code item is to look for | proposed changes and see how the code making panel responds. There were | no proposed changes to this rule as far back as 1983 (1996 and 1993 are | unknown). This rule was invisible?
There may have been _other_ rules in place that negated the bad effects of this rule. Note that 210.21(B)(1) allows either an equal rating or a higher rating on the single outlet. Another rule could prohibit the higher rating, resulting in only allowing an equal rating when both rules are in effect together. The other rule may have existed in the past and then was removed.
HOWEVER, the issue is not as simple as that. What if the appliance that needs a dedicated circuit requires 25 amp overcurrent protection, where 20 amps is too low (will trip) and 30 amps is too high (could allow a long term overheating issue). You can put in a 25 amp breaker easily enough. But what size of receptacle do you use? A 20 amp one is too small. A 30 amp would would be safe in that it should not burn up with 25 amps used through it. What 210.21(B)(1) does is allow use of the 30 amp outlet.
What I think the rule should be change to is that for a given circuit rating, the only outlet allowed is one with a _configuration_ equal to the circuit rating for circuits matching a configuration, or the next higher configuration where a matching one is not standardized. Thus:
circuit outlet 10 amp 15 amp (I think 10 amp is still allowed on dedicated circuits) 15 amp 15 amp 20 amp 20 amp (maybe use 20-amp only outlet) 25 amp 30 amp 30 amp 30 amp 35 amp 50 amp 40 amp 50 amp 45 amp 50 amp 50 amp 50 amp 55 amp 60 amp 60 amp 60 amp etc
Such a code change should reference NEMA standards for outlet configuration. Then a 30 amp outlet would be allowed on a 25 amp circuit, but a 50 amp outlet would not be allowed. I think we all (even Roy) would agree this is the way it should be.
One thing I think the code needs to do is distiguish with better terminology the difference between the current capacity rating of a device, and its configuration with respect to the standard plugs it will accept. NEMA X-15R devices do (now days) have a current carrying rating of 20 amps. As long as appliances plugged in are unlikely to create overcurrent situations of more than their own cord-and-plug rating without exceeding the 20 amp trip current, things are safe allowing receptacles on 20 amp multi-outlet circuits that accept 15 amp plugs. The 20 amp configuration accepts 15 amp plugs, so there is no new hazard in this regard by installing a receptacle that refuses to accept 20 amp plugs. You can get 20 amp receptacles that do refuse 15 amp plugs, and that can be useful on single outlet circuits.
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On Wed, 08 Jun 2005 22:44:02 -0400 snipped-for-privacy@aol.com wrote: | On 9 Jun 2005 01:17:55 GMT, snipped-for-privacy@ipal.net wrote: |
|>
|>| |>|>It could just be that I can't find the part of the code that says |>|>a 15 amp circuit cannot have a 20 amp receptacle |>| |>| Look at 210.21(B)(3) again. The top line says 15a circuits shall have |>| receptacles "not over 15a" |> |>What code are you looking at? The top line of what I have says "Where |>connected to a branch circuit supplying two or more receptacles or outlets, |>receptacle ratings shall conform ..." | | | Phil look at TABLE 210.21(B)(3) NEC every year since the FDR | administration.
Read the text of 210.21(B)(3) to see what TABLE 210.21(B)(3) applies to. My copy says it applies to "branch circuit supplying two or more receptacles or outlets". Is yours different?
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From: snipped-for-privacy@aol.com On 8 Jun 2005 04:21:48 GMT, snipped-for-privacy@ipal.net wrote: It could just be that I can't find the part of the code that says a 15 amp circuit cannot have a 20 amp receptacle
Look at 210.21(B)(3) again. The top line says 15a circuits shall have receptacles "not over 15a"
~>Exactly: I do know why Phil argues anything to the contrary., I even explained what could physically happen to a 15A receptacle on a @20A circuit. oy
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15 amp receptacles are legal on 20 amp circuits. The 15 amp receptacle should never have a twenty amp load connected to it because 20 amp loads must use a different NEMA defined plug. Therefore when using plug 'expanders' such as power strip, those 'expanders' must contain a 15 amp circuit breaker. This so that multiple 15 amp appliances do not draw 20 amps through that one wall receptacle.
20 amp loads cannot plug into 15 amp receptacles. Most receptacle used on 20 amp circuits are 15 amp receptacles. The receptacle designed so that only less than 15 amp appliances will be connected. Since power strips can defeat this safety requirement, then power strips must have a 15 amp breaker. These above two paragraphs to clarify for others (lurkers) what is being discussed here.
Back to the original question We still don't see a clean answer. Can 20 amp receptacles be used on 15 amp circuits? Can 50 amp receptacles be used on 40 amps breakers? IOW has the code changed / modified these requirements in different years? Code citations should include the year being quoted.
"Roy Q.T." wrote:

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NEC 210.21 [(B)(1)] ~ Receptacles: A single receptacle installed on an individual branch circuit shall have an ampere rating "not less" than that of the branch circuit. oy
From: snipped-for-privacy@aol.com On 8 Jun 2005 04:21:48 GMT, snipped-for-privacy@ipal.net wrote: It could just be that I can't find the part of the code that says a 15 amp circuit cannot have a 20 amp receptacle Look at 210.21(B)(3) again. The top line says 15a circuits shall have receptacles "not over 15a"
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| NEC 210.21 [(B)(1)] ~ Receptacles: A single receptacle installed on an | individual branch circuit shall have an ampere rating "not less" than | that of the branch circuit.
What part of "single" are you having trouble understanding, Roy?
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050616 0130 - Roy Q.T. posted:

So, what if you put a 20 Amp duplex receptacle on a 15 Amp branch circuit?
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| 050616 0130 - Roy Q.T. posted: | |> NEC 210.21 [(B)(1)] ~ Receptacles: A single receptacle installed on an |> individual branch circuit shall have an ampere rating "not less" than |> that of the branch circuit. |> ?oy |>
|> It could just be that I can't find the part of the code that says a 15 |> amp circuit cannot have a 20 amp receptacle |> Look at 210.21(B)(3) again. The top line says 15a circuits shall have |> receptacles "not over 15a" |> | | So, what if you put a 20 Amp duplex receptacle on a 15 Amp branch circuit?
That is not permitted by NEC 210.21(B)(3). See table 210.21(B)(3). But this only applies to circuits with 2 or more outlets. A duplex receptacle is 2 outlets, so it applies. However, I see no rule that would prohibit this for a _single_ outlet circuit.
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snipped-for-privacy@ipal.net wrote:

I would agree with the interpretation of 210.21(B)(3)as applicable. The NEC language is a little different with regard to "outlets" and "receptacle". Although people often refer to a receptacle as an outlet, they are treated as two different things in the NEC.
Here's three definitions from the NEC: "Outlet. A point on the wiring system at which current is taken to supply utilization equipment."
"Receptacle. A receptacle is a contact device installed at the outlet for the connection of an attachment plug. A single receptacle is a single contact device with no other contact device on the same yoke. A multiple receptacle is two or more contact devices on the same yoke."
"Receptacle Outlet. An outlet where one or more receptacles are installed."
Ed
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050616 2113 - snipped-for-privacy@ipal.net posted:

So, is the sky going to fall if a 20 amp duplex receptacle is installed on a 15 amp branch circuit with other 15 amp duplex receptacles?
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| 050616 2113 - snipped-for-privacy@ipal.net posted: |
|> | 050616 0130 - Roy Q.T. posted: |> | |> |> NEC 210.21 [(B)(1)] ~ Receptacles: A single receptacle installed on an |> |> individual branch circuit shall have an ampere rating "not less" than |> |> that of the branch circuit. |> |> ?oy |> |>
|> |> It could just be that I can't find the part of the code that says a 15 |> |> amp circuit cannot have a 20 amp receptacle |> |> Look at 210.21(B)(3) again. The top line says 15a circuits shall have |> |> receptacles "not over 15a" |> |> |> | |> | So, what if you put a 20 Amp duplex receptacle on a 15 Amp branch circuit? |> |> That is not permitted by NEC 210.21(B)(3). See table 210.21(B)(3). |> But this only applies to circuits with 2 or more outlets. A duplex |> receptacle is 2 outlets, so it applies. However, I see no rule that |> would prohibit this for a _single_ outlet circuit. | | So, is the sky going to fall if a 20 amp duplex receptacle is installed on a | 15 amp branch circuit with other 15 amp duplex receptacles?
Depends on your AHJ/inspector. If it was me, you'd get a red tag.
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The odds are that it will be about the same as what you paid for the air conditioner.
I note that Walmart sells 240 units when you get to the 10,000 BTU/hour size. If you have room for another two pole breaker in you box, it may be about the same charge from the electrician and you may be happier with a larger a/c.

If you run a new circuit, the electrician likely would want to connect it to a new breaker.

Likely, that's a 15 amp "lighting" circuit. Find an unswitched wall outlet. You CAN use a heavy duty extension cord. See if it still "trips." You can save some money.

As I said, if you are starting from "scratch" then consider going to a 240 unit.

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