Send Single Calculated with airSlate SignNow

Electrical load calculation worksheet form

let's now work an example 9.9 optional load calculation what is the service size using optional method actually this is the one we had worked out earlier on the standard method they came out to be 147 amps or something like that if we're looking for the optional method here's what we do this is beautiful you add it all up general lighting three VA per square foot to small appliance circuits a laundry circuit dishwasher what's that disposal value 1,000 okay the disposal the water heater the dryer remember this is nameplate sometimes people wonder well when do you use the 5000 won your two optional its nameplate standard over than 5 KW and then we have the range if the standard method okay and a standard method this dryer would have been what value so that's good right and a standard method the 14k degree range would have been at what value point eight eight point eight because it had been 10 percent more so we just add up the total loads not including AC and heat take the first 10 kW at 100% that's 10 kW so 34,000 minus the 10 gives you 24,000 take that at 40 percent gives you 9600 then we have to add the AC versus the heat and that to 20 80 to see said heat was at 65 percent which is 5200 the AC was at 100% and that would be the bolt times the amps so the AC is still smaller so then we can simply add the heat that comes out to be a hundred and three amps from a hundred and forty-one amps so that's considerably smaller let me review this all you do is add up all the loads not AC and heat take the first 10 kW undred percent and the remainder forty percent and it add the heat the larger up heat 65 and the AC 100 now if we had four more supply control units then it would have been 40% for the heat and if you had heat plus a heat pump then you might be adding them depending upon the condition how do you size for service well 24800 / to 4103 110 amp service that means you have to take it at 83 percent of the service which we need 91 amp wire then you go to Table three 1015 b16 and it would then be three gauge wire so if we look at this graphic here three 1015 be seven one four services says that once you know the service rating you take 83 percent of that if the service conductors carry the entire load supplied by the service which it does then you take 83 percent of 110 which is 91 amps and you have it on 110 amp protection device now question comes up is like oh wait a minute now I have a question here by a streamer and it says how can you have 90 whatever how do you put a hundred amp wire on a hundred and ten amp breaker you can't go there it's just real simple the code says you get your calculated load demand load once you know you demand load then you obviously have the size of service which is a certain size breaker 125 refused whatever you going to use there once you know that you go to 3 10 15 B 7 and this tells you how to size the conductor to that specific overcurrent device and you're saying that doesn't make any sense and my answer to you is you're absolutely right but it doesn't matter why can you put a wire that's smaller that 83 percent smaller than rating of the breaker I don't know I'm thinking this how about we do an optional calculation we come up with a hundred three instead of 141 then we take 83% of that and then that's how we size the breaker to wire but know you size the breaker at a hundred percent of the optional method then you size the wire to 80 80% of the rating of the breaker so the overcurrent protection of the conductor is not in compliance with the rating of the ampacity and if you do too much thinking that it makes no sense at all or you could just simply say I'm not going to a whole bunch of thinking I calculate the server's using the optional method once I know the server's I go to 3 10 15 B 7 B 7 1 and it says for the service take 83% of the service calculate load and that's how you size the conductor and then that's what sides over current device you put on it it doesn't make any sense now the next question comes up is Mike you made a comment that well you know you don't really need to worry about the standard method because you go to optional method I got two quick comments in there like what yeah you do how do you think you figure out the neutral conductor on a service for a dwelling unit you can only to use it at the standard method I'm like duh of course you have to know the standard method the size and neutral conductor that's the only way you can size a neutral conductor is using the standard method to get the data to size the neutral conductor but then you size the ungrounded conductor based upon the optional method and then you size the service and then you take 83 percent of the service decides the conductor this all is this real smooth system and how it all works together I know it's kind of crazy and and and you know it's it's just crazy and I know that but it's are crazy it's our world is what we have to deal with let me review it again you sized the servers I recommend you using the optional method which can be smaller so that gives you service conductor and you know what size protection device and 83% of that your wire now if you want to get a neutral size to the unbalanced load then you have to know the standard method and go through those calculations get your neutral size which we're going to be doing again in a few minutes okay or you can simply say nope I don't wanna mess with that service standard size I'm just going to size a service conducted based on the optional method well then size your neutral conductor full size but Mike when I buy cable is the neutral conductor full size and a cable or is it generally a little smaller I'm not sure how that works anybody know how either way it could be either way full size about two sizes smaller are smaller okay get a couple size but so it's just a matter of ordering it out so me personally yeah I would know the standard calculation I make my own little spreadsheet I would know how to do the optional calculation I'd make my own little spreadsheet a matter fact I did make my spreadsheet and I'll show you what it well I don't have my calculator here what I did was I made my spreadsheet it actually did both the standard method and the optional method all at one time so I can get both information so I can double check my work question came up what about the water heater is at 125 percent no water heaters and appliance and the water heater is going to be sized as an appliance which is one of the four if it's four or more at 75 percent okay we're going to go to an XD example D to C we'll use that as an optional method we got 2,000 square feet 12 km arranged 4.5 kiddie water heater 1.2 dishwasher 5 kW dryer 24 amp heat pump and a 15 kW backup heat oh so we're going to have the heat pump and the heat run together here all right 2,000 square feet at 3 v8 per square foot is 6000 VA we have two small appliance circuits is 3000 VA we have a laundry circuit 1500 we had a dishwasher given a 1200 water heater was given at 4500 the dryer was at 5000 the range was at 12 add up the total connected load take the first 10 at 100% 33 2 - 10 is 23 - at 40 percent is 19 - then we have the heat at 65 percent let's take a look at that let's go into the code book that's on 220 82 C 220 and of course those you better watch the DVD you're going to put this on pause - 20 80 to see talking about Heat number one it's 100 percent of the heat rating in the air con a percent of the of the air conditioning - is 100 percent of the heat pump without supplementary three is 100% of the nameplate of the heat pump and 65% of the supplemented heating all right so that would be able to be number three there then so I'm going to go one hundred percent of the heat and sixty hundred percent of the heat pump and sixty-five percent of the heat well there's a hundred percent of the heat pump sixty-five percent the heat that comes out to be a hundred and forty five amps is the calculated load the demand load the calculated demand load okay so the calculated demand load is 110 amps by taking the power divided by the voltage then I would put a hundred and ten amp service once I know the service I then go and get eighty three percent of the rating of that service that's ninety one amp wire it's three gage rated 100 amps that is how we size a conductor now I understand as I'm getting the feedback from the streamers that people are saying well wait a minute now using the optional method you're already getting a break and how can you take eighty three percent it doesn't matter that's what the rule is you do the optional method come up with 110 get your service 110 go to three ten fifteen be seven it says take eighty three percent by the way this is no different than it's always been is that right make it's been this way since forever so nothing has changed so that's eighty three percent is confusing you I'm sorry but that's the way it is and it's always been that way nothing has changed here so looking at this graphic here if it's a resonant and you see 110 amp service then you take eighty three percent of that and you would put three gauge wire rate 100 amps on 110 F breaker and that's what the rule is just like if it was some other load sometimes they don't always match the same ampacity