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Does someone know reference to an international standard like IEEE or IEC that could help in determining the time period that should be used for calculating the demand factor of a motor? Also, does any standard allow applying demand factor to motor FLA's for voltage drop calculations? I am in...

Does anyone know if any institute provides training in API RP505 standard - American Petroleum Institute's recommended practice for classification of locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2?

@waross: Thanks a lot. Rule 28-108 & 28-110 of Canadian Electrical Code part 1 is what would apply in my situation.

Hello waross. Can you please give me the reference to the rule in Canadian Electrical Code part 1 that you mentioned in this post - thread238-420754: "Add 25% of the largest motor, 135% of the capacitor loads, 25% of the largest transformer and 135% of the transformer feeding capacitors to the...

@wroggent: My concern is not about the rating of overcurrent protection device in the MCC switchboard, but the rating of the main feeder bus bar in the MCC. @jraef & @padlock01: I am not sure what code you follow, but Canadian Electrical Code part 1 has provision for applying demand factors on...

Hello, I am trying to add an additional load to a MCC switchboard that has a bus bar rating of 800A. I want to verify if adding the load will lead to exceeding the capacity of the bus bar rating or not. I am in Canada and the code that I follow is Canadian Electrical Code part 1. Sum of the...

@waross, are you referring to long time trip setting of a circuit breaker when you say - "inverse time trip"

@waross: when you say 250% of motor current, are you referring to the overload relay settings on a motor branch circuit? Usually like @jraef mentioned, conductors are sized for atleast 125% of total load and breaker is sized to protect the conductor downstream of the breaker. This means the...

Thanks Scotty. That linked helped.

Hi Does anyone know if there are any specific IEC standards which has guidelines for assigning tags/names to electrical symbols? For example, CB for circuit breaker, CR for relay contact, XF for transformer etc.? I referred IEC 61082 & IEC 60617 and couldn't find any specific information...

I would like to thank everyone for their responses. This is a great group.

Hi GPTech Below is an extracted page from CSA code Z462-12 where they recommend Lee's method for determining arc flash boundary & incident energy. They say that Lee's equation becomes conservative over 600V.

Hi Bill (Waross) Please see the extracted page from CSA code Z462-12. The second equation that I quoted is equation D.2(a) What I meant by '*' is 'multiply'. I am not sure if I understood you when you say to replace '*' with '/'.

Hi GPTech & Bill I am having a hard time to get the available bolted three phase short-circuit current (symmetrical rms), kA from our utility. I am trying to calculate the arcing current using the below formula given in IEEE 1584 - Log(Ia) =...

thanks GPTech

Thanks Waross

Hi GPTech Thanks for your quick reply. I am currently in the process of developing a spreadsheet using the formulas in CSA Z462 ( which is in turn referring to IEEE 1584) for calculating the bolted three phase short circuit current. I am not using ETAP or SKM because this is just a one single...

Hello I am conducting an arc flash study of a power distribution system using IEEE 1584. For calculating the arcing current, I need to determine what's the available bolted three phase short circuit current. How is this determined? Is it the utility that provides this parameter? Does this value...