Mike Dolt Enterprises
Mike Dolt Enterprises
User: Talvinder sidhu, Location: Seattle Washington
Asked on: Tuesday, April 22, 2025 at 1:58 am EDT
Answered on: Tuesday, April 22, 2025 at 5:24 am EDT
Question: Hello, I have a question if someone wants to know any code Reference that would be helpful.Hypothetically speaking when I was doing load calculations, I came across situations where in the standard method and optional method for multifamily and single-family dwelling, and even in some duplexes that they would not give no dryer calculation.I understand that we always assume two small appliances at 1500 VA each. And that we also assume one laundry circut at 1500 VA.Unless they state no laundry provision or that the laundry is calculated as a house load in multi family calculation. Then it’s included in the end. However what if they don’t give you no number figure for a dryer and don’t mention a dryer do you assume each unit has one at 5kw?Does this mean in our calculation let’s just say hypothetically on an exam that if the dryer is not given as a calculation that we automatically include a dryer @ 5kw ? For single/multi family calculation.Would the same apply if they did not include aRange figure/calculation? Would we just assume the min 8kw per dwelling.I also further understand that if they say the heating and cooking appliances are gas that we do not calculate a range figure. Any clarity would be much appreciated and code references would be appreciated per the 2020 nec.Thanks for taking the time to read.
Okay, let's break down these load calculation scenarios and the applicable sections of the 2020 NEC. You're asking about how to handle situations where specific loads (dryers, ranges) aren't explicitly stated in a load calculation problem, particularly in exam scenarios.
General Principle
In the absence of specific information, you're generally expected to assume the minimum loads required by the NEC for typical residential dwellings. This ensures a safe and adequate electrical system.
Dryers
NEC Assumption
The NEC doesn't mandate assuming a dryer load in every dwelling unit calculation. However, practically speaking, it's highly unlikely that a dwelling unit, especially in a multifamily building, wouldn't have a dryer.
Your Question (No Dryer Mentioned)
If the problem doesn't explicitly state "no dryer provision" or that the laundry is handled centrally, and it's a typical residential dwelling, you should
assume a dryer load. Default Dryer Load
The NEC doesn't specify a fixed wattage for a dryer in load calculations unless the actual rating is known.
Therefore, assume a 5,000 VA dryer load. NEC 220.54
This section covers electric clothes dryer demand factors. It doesn't establish a mandatory load, but it's used to reduce the calculated load when you have multiple dryers (e.g., in a multifamily building). The absence of a dryer mention means you're calculating for a single dwelling and don't use the demand factors.
Exam Strategy
On an exam, explain your assumption: "Since the problem doesn't state that there is no dryer provision, I am assuming a 5,000 VA dryer load per NEC best practices. " This shows you understand the principles.
Ranges
NEC Assumption
If a range is not mentioned, you need to assume one based on the dwelling type.
Your Question (No Range Mentioned)
If the problem doesn't explicitly state "gas cooking" or that there is no cooking appliance, you should
assume a range load. Minimum Range Load
This is where NEC Table 220.55 becomes crucial.
Table 220.55
This table is your primary reference for range loads. If the rating of the range is not given, you must use the demand factors in Columns A, B, or C.
Column C is the default if the range is not over 12kW. Therefore, the minimum is 8 kVA (8,000 VA). If the range is over 12 kW you need to select Column A or B Gas Cooking
You are correct. If the problem specifically states "gas cooking," you do not include a range load in your electrical calculations.
Exam Strategy
On an exam, clearly state your reasoning: "Since the problem doesn't state 'gas cooking' and doesn't provide the rating of the range, I am assuming a minimum range load of 8,000 VA per Table 220.55, Column C, of the NEC."
Multifamily Dwelling Unit Calculations and Common Areas In multifamily dwelling units, you will be figuring out the feeder/service calculation. So that means common area loads will be added to the final figure. Laundry, Range and Dryer calcuations may not be assumed for each individual unit. So the problem will state if each unit has Laundry and a Dryer. Or you will just include the laundry in the feeder service calculation.
Important Code References
Article 220: Branch-Circuit, Feeder, and Service Calculations
This is the ENTIRE article you need to master.
220.12: General Lighting Loads
Specifies VA per square foot for dwelling units.
220.14(H): Receptacle Outlets
Specifies the 180 VA rule for non-dwelling receptacle outlets.
220.52: Small-Appliance Branch Circuits
1500 VA per circuit for kitchen/dining areas.
220.53: Appliance Load – Dwelling Unit(s)
Covers fixed appliance loads (other than ranges, clothes dryers, air conditioning, and space heating). You apply a 75% demand factor if you have four or more fixed appliances.
220.54: Electric Clothes Dryers – Dwelling Unit(s)
Demand factors when you have multiple dryers.
220.55: Electric Ranges and Other Cooking Appliances – Dwelling Unit(s)
Critical for range load calculations. Memorize Table 220.55.
220.82: Optional Calculation – Dwelling Unit
If the problem states you are using the optional calculation method, you follow the steps in this section.
220.84: Optional Calculation – Multifamily Dwelling
If the problem states you are using the optional calculation method for multifamily dwellings, you follow the steps in this section.
Key Takeaways for Exams
Read Carefully
Pay close attention to the wording of the problem. Look for phrases like "gas cooking," "no laundry facilities," or "shared laundry."2.
Default to Minimums
When information is missing, default to the minimum NEC-required loads to ensure compliance and safety.3.
State Your Assumptions
On an exam, explicitly state any assumptions you're making and why you're making them, citing the relevant NEC section if possible. This demonstrates your understanding.4.
Know Table 220.55
This is crucial for range calculations.5.
Practice, Practice, Practice:* Work through numerous load calculation problems to become familiar with the different scenarios and how to apply the NEC rules.I hope this comprehensive explanation is helpful! Let me know if you have any more questions. Flag for review