Quick Hits

⚡ NEC Article 120 — Load Calcs Won't Kill You

🚜 Episode 38 — Welcome to the Farm: Part V Begins

Article: 120 — Load Calculations
Part: Part V — Farm Loads
Section: 120.100 / 120.102(A)
Format: Quick Hit

🎯 What You'll Learn

Farm electrical installations have their own load-calculation rules. But the farm dwelling itself generally follows the load-calculation methods we've already covered — with one important exception involving electric heat and grain-drying equipment.

📖 The Quick Hit

🚜 Part V Begins

Farm loads are covered under Part V of Article 120.

The important thing to understand is that the farm dwelling doesn't automatically get a completely new load-calculation system.

Under 120.102(A), the dwelling's load is calculated using the applicable methods from Part III or Part IV.

🏠 The Farm Dwelling

For the dwelling portion of a farm installation:

Part III — Standard feeder/service load calculations
Part IV — Optional feeder/service load calculations, where permitted

So far, this should sound familiar.

But there's an important exception.

⚠️ The Grain-Dryer Exception

If the farm dwelling has:

⚡ Electric space heating
🌾 Electric grain-drying equipment
🔌 A common service supplying both

...the Part IV optional dwelling method cannot be used for the dwelling load.

In that situation, the dwelling load must be calculated using Part III.

Remember:

Electric heat + electric grain drying + common service = Part III

That's the farm-load gotcha.

🧠 Why This Matters

Farm installations can combine large agricultural loads with residential loads.

Don't automatically assume the optional dwelling calculation is available just because the building contains a dwelling unit.

Always check whether the conditions in 120.102(A) allow the optional method.

🎯 Test Yourself

A farm dwelling has electric space heating and shares a common service with electric grain-drying equipment. Which load-calculation method must be used for the dwelling?

A) Either Part III or Part IV
B) Part IV only
C) Part III only
D) A separate farm-specific calculation