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| Subject - 20 amp curcit | |
| relbas |
My question is how many outlets on 20 amp cuircuit can be installed? The location is bed recepticals in the hostipal. |
| kbsparky | To determine the number of allowable outlets per circuit, one has to know the load per outlet. In cases of convenience outlets, where no specific load is given, the default load for calculating purposes is stipulated to be not less than 180 VA. See NEC 220.14(i) In this case, you would be allowed to install 13 outlets on a 20 Amp circuit. -Ken |
| lctrc789 | Actually they should have a total number of outlets per circuit on a print for you. However 180 VA x10 =1800 and 80% load on a 20 amp circuit is 1920 so ten would be the maximum allowed on a dirty circuit. |
| kbsparky | It was my understanding that the 80% limitation on circuits applied only to continuous loads, as per 210.20(A). I have made the assumption here that convenience outlets are considered non-continuous loads for purposes of branch circuit calculations. Do you have a Code reference available to support the assertion that convenience outlets are to have the same limitation placed on them? -Ken |
| lctrc789 | Ken, actually article 210-20(a) states That the branch circuit that supplies a continuous load or any combination of a continuous or non continuous load the rating cannot be less than the noncontionuous load plus 125%. Not 80% What I was referring to was that article 210-21 b (2) the maximum cord and plug connected load to a recpt. is 16 amps or 80% of a 20 amp load. |
| kbsparky | quote: Ok, here is the text of 210.21(B)(2) (emphasis added): Where connected to a branch circuit supplying two or more receptacles or outlets, a receptacle shall not supply a total cord-and-plug connected load in excess of the maximum specified in Table 210.21(B)(2). The table then shows the Maximum Cord-and-plug-Connected Load to (a) receptacle (on a) 20 Amp circuit with a maximum load of 16 Amps. The word receptacle is listed as a singular item, and I read that to mean that you can't have more than 80% of the load of that circuit on any one receptacle connected to that circuit. Taking that thinking one step further: You are permitted to install a single 20 Amp receptacle on a dedicated 20 Amp circuit, and connected to a 20 Amp load. But if you have more than one receptacle on that 20 Amp circuit, then the maximum allowable per receptacle is 80% of the rating of that circuit. Reading the Code further, you will find Table 210.24 Summary of Branch Circuit Requirements. Circuit rating of 20 A shows minimum conductor size of 12, and max load 20 A . As for the issue of 80% VS 125% it all depends on which way you do the math: 80% of a 20 Amp circuit = 16 Amps. 125% of a 16 Amp load = 20 Amp circuit. We are referring to the same thing.  Best regards -Ken |
| lctrc789 | Yes you are right but as a matter of good practice I never over do the 80% rating. Less problems and head aches and you never know what any one will plug in to a circuit, I would rather add more then to have to go on service calls or call backs because of an overloaded circuit. |
| kbsparky | What is allowable under the rules of the NEC may be more than you are willing to install. As a matter of practice, following the 80% limitation is good practice. We are in complete agreement on this aspect. 
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