Electrical Calculations Pdf

[Michael]

Forthose of you that perform electrical load calculations or panel schedules for the electrical service on your projects, what resources have been helpful to you? Have you created any templates or worksheets for yourself to make this an easier process? Would you be interested in having a template in chief architect that another user has made?

I'm curious who would be interested in sharing tips/tricks or anything that could be shared to used in chief architect. I have some things I've developed for my own use but not sure if others would find this useful or how many users incorporate this into their plans and services.

If you use a combination of polylines for hips, that report to a custom schedule, as well as outlets, in conjunction with custom fields in your OIP, you can make an auto generated panel schedule and could even do load calcs using macro

Thanks for the input but you're speaking martian to me Let me know if you want to collaborate on creating something new for this.. I think other calculations like attic ventilation, crawlspace ventilation, natural ventilation and glazing calcs could be simplified with a step by step table in chief if load calculations could be.

I have not seen this addressed anywhere else, but have noticed that Revit's electrical current calculations are incorrect and have been since at least 2013. I have made custom panel schedules with my own calculations to make it show up right, but since no-one else seems to have noticed and it hasn't been fixed in this many versions, I'm starting to wonder if I just don't understand the parameters or am missing a setting somewhere.

I created a schedule based on a dummy project (Revit 2020) with 120V circuits that I set up as an example, image attached. The first column is the Apparent Load Phase A parameter for each circuit, second is Apparent Current Phase A, straight from Revit. The third column is a calculated parameter with the formula: Apparent Load Phase A / 120V, which gives the actual current for the load. Notice that five of them match Revit's number, but the rest are off by varying amounts. My thought was that maybe Revit is using another number for the voltage, like 115V or 110V, so I added a fourth column that backs out what voltage Revit would be using to come up with the current it's calculating, using the formula: Apparent Load Phase A / Apparent Current Phase A. This gives varying voltages that seem to have some sort of pattern, but I can't figure out anything.

Has anyone noticed this or figured out what the issue is?

I have not had this issue. It could be something in the families that you are using or in some of the electrical setting. We did spend a considerable amount of time to configure these to report everything correctly for our engineers. I would need to see more information to help troubleshoot, and I think most of the community here would be in the same situation.

@David_Robison thanks for the article, it helps but I had to do some more thinking on this to figure it out. I attached a panel schedule (Panel B, I'll get to Panel D later) that more clearly shows what my question was. I was able to come up with the Revit numbers for this panel using the calculations below. The numbers do appear more accurate than just dividing each phase kVA by the phase-N voltage, which is what our Excel schedules do. The currents should be calculated separately for balanced load and for unbalanced loads connected line-line. The L-L single-phase currents are 30-deg out of phase with the L-N voltage, so these would be kVA/(L-N voltage * cos 30). Let me know if you agree with these calcs.

Hi, i am completly new to this Autocad "toolset". And i do not know much about electrical components. My question is: Is Autocad Electrical able to make wire sizing calculations? For example if there is a pump with say 5 hp. Can this software tell me what kind of wire it will need or any specification on it? If so or not so; What calculation capabilities can i get from Autocad Electrical?

Like i said im no experienced user but it seems it does what i was looking for. Which is have a motor with its defined HP and get a suggested size acording to standards, i see that it has a standards database.

I checked Mep Trimble and sure looks good. In my case i am an employee who can suggest its aquiry, but the best course of action is to save as much money while extending our reach of engeniering solutions with what we have now. I saw that as of March of this year Autocad 2019 is now uniting all "specialized toolsets" as in MEP, Electrical, Plant 3D, etc.

The following calculators are provided to help you determine the size of generator required for your specific application. Other calculators on this page are for unit conversions and other power related calculations.

Even if you work with stamped drawings, you'll eventually need to do commercial load calculations in the field or on a licensing exam. The National Electrical Code (NEC) covers commercial calculations in Art. 220, but other Articles also apply. For example, you must know the definitions in Art. 100, be familiar with what Art. 210 says about continuous loads, and understand the overcurrent protection requirements set forth in Art. 240.

Dryers. Size the branch-circuit conductors and overcurrent protection device for commercial dryers to the appliance nameplate rating. Calculate the feeder demand load for dryers at 100% of the appliance rating. If the dryers run continuously, you must size the conductor and protection device at 125% of the load [210.19(A), 215.3, and 230.42]. Table 220.18 demand factors don't apply to commercial dryers.

Let's apply what we've just learned. What size branch-circuit conductor and overcurrent protection does the NEC require for a 7kW dryer rated 240V when the dryer is in a multi-family dwelling laundry room (Fig. 2)?

Electric heat [424.3(B)]. Size branch-circuit conductors and the overcurrent protection device for electric heating to not less than 125% of the total heating load, including blower motors. Calculate the feeder/service demand load for electric heating equipment at 100% of the total heating load.

To determine the service demand load for commercial kitchen equipment that has thermostatic control or intermittent use, apply the demand factors from Table 220.20 to the total connected kitchen equipment load. The feeder or service demand load can't be less than the sum of the two largest appliance loads. The demand factors of Table 220.20 don't apply to space-heating, ventilating, or air-conditioning equipment.

Lighting. The NEC requires a minimum load per square foot for general lighting, depending on the type of occupancy [Table 220.3(A)]. For the guestrooms of hotels, motels, hospitals, and storage warehouses, you can apply the general lighting demand factors of Table 220.11 to the general lighting load.

Assume the general lighting load for commercial occupancies other than guestrooms of motels, hotels, hospitals, and storage warehouses is continuous. Calculate it at 125% of the general lighting load listed in Table 220.3(A).

Multi-outlet receptacle assembly. For service calculations, consider every 5 feet (or less) of multi-outlet receptacle assembly to be 180VA. When you can reasonably expect a multi-outlet receptacle assembly to power several appliances simultaneously, consider each foot (or less) as 180VA for service calculations. Normally, a multi-outlet receptacle assembly isn't a continuous load [220.3(B)(8)].

Number of receptacles permitted on a circuit. The maximum number of receptacle outlets permitted on a commercial or industrial circuit depends on the circuit ampacity. To calculate that number, divide the VA rating of the circuit by 180VA for each receptacle strap.

Bank and office general lighting and receptacles. Calculate the receptacle demand load at 180VA for each receptacle strap [220.3(B)(9)] if the number of receptacles is known, or 1VA for each square foot if the number of receptacles is unknown [Table 220.3(A) Note b].

The NEC requires each commercial occupancy that's accessible to pedestrians to have at least one 20A branch circuit for a sign [600.5(A)]. The load for the required exterior signs or outline lighting must be at least 1,200VA [220.3(B)(6)]. A sign outlet is a continuous load. You must size the feeder load at 125% of the continuous load [215.2(A)(1) and 230.42].

In addition, you can't reduce the neutral demand load for nonlinear loads supplied from a 3-phase, 4-wire, wye-connected system, because they produce triplen harmonic currents that add on the neutral conductor. This situation can require the neutral conductor to be larger than the ungrounded conductor load (220.22 FPN 2).

Knowing the correct way to do commercial load calculations makes you more valuable because you can play a key role in the field design, inspection, and implementation process. It's one more skill that helps you do the job right the first time.

The City of Bakersfield, California, is a city of approximately 400,000 residents, located in the Southern San Joaquin Valley, about 100 miles north of Los Angeles. We are an extremely busy jurisdiction for solar photovoltaic (PV) installations. When I first started as the chief electrical inspector for the city back in 2005, we inspected one to two PV systems per week. The weekly average has now increased to 100-150 residential PV installations. Since 2005, we have had the opportunity to permit, inspect and approve more than 40,000 systems total.

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