Okay, let's break down this sawmill electrical setup. You've got a good handle on the basics, but let's clarify the classification and look at the motor starting and other issues.1. Hazardous Location Classification



Class III, Division 1 is highly probable for a sawmill. This is due to the presence of easily ignitable fibers (sawdust, wood shavings, wood flour) that are normally in suspension in the air in sufficient quantities to produce ignitable mixtures. Division 1 means those ignitable concentrations exist under normal operating conditions. Important

You absolutely MUST consult with someone with expertise in hazardous location classification. This is not something to guess at. Incorrect classification can have catastrophic results. Check with the local AHJ or an engineer experienced with this type of industrial environment. They will consider factors like the type of wood processed, the dust collection system (if any), ventilation, and the overall cleanliness of the mill.



Dust Collection is Key

A properly designed and maintained dust collection system can significantly reduce the risk of explosions by limiting the amount of airborne dust. This might even potentially allow for a Class III, Division 2 classification (where hazardous concentrations exist only abnormally). However, don't assume this – get professional advice.

General Safety

This is also important to note that even if you are able to get away with a lower classification, it is of utmost importance that you and your customer are always aware of the danger of dust ignition and implement general safety practices to mitigate those risks.

2. Generator and Voltage Considerations

The 480V 800A generator is a good starting point for the 480V loads. The existing single-phase power should not be connected to the same loads as the generator. You'll need a transfer switch system to ensure there is no backfeed of power.

Dealing with 208V Motors

You have a few options:

Rewire for 480V (Best Option)

If possible, rewiring the 80HP and 17HP motors for 480V is the preferred solution. It simplifies the overall system, reduces the need for transformers, and improves efficiency.

Pro

Avoids transformer losses, simplifies wiring and overcurrent protection, potentially lower initial cost compared to a transformer.

Con

Requires rewinding the motor (if possible), potential downtime for rewinding.

Step-Down Transformer (For the 1HP, Maybe the 17HP)

For the smaller 1HP motor, using a small step-down transformer is probably the easiest. The 17HP might be a candidate, but rewinding is likely still the better option.

Pro

Simpler if motor rewinding is difficult or not cost-effective.

Con

Transformer losses (though minimal for a small transformer), additional equipment cost, more complex wiring.

Considerations

Make sure the transformer is appropriately sized for the motor's inrush current during starting.

3. 150HP Motor Starting



Slamming it on with a disconnect is a terrible idea. It will cause a huge voltage sag, stress the generator, and likely damage the motor over time. You need a reduced-voltage starting method. Here are the typical options:

Solid-State Reduced Voltage Starter (Soft Starter)

This is probably the best balance of cost, performance, and ease of installation. It gradually ramps up the voltage to the motor, reducing inrush current and mechanical stress.

Pros

Smooth starting, adjustable acceleration, can reduce peak demand charges, relatively compact.

Cons

More expensive than a basic autotransformer starter.

Autotransformer Starter

Uses a tapped autotransformer to reduce the voltage applied to the motor during starting.

Pros

Effective inrush current reduction, relatively simple.

Cons

Stepped voltage increase (not as smooth as a soft starter), physically larger and heavier than a soft starter, can be less efficient.

Part Winding Starter (If Motor is Designed For It)

This requires a specially wound motor. Not generally recommended for new installations unless you already have the motor.

Variable Frequency Drive (VFD)

While more expensive, a VFD offers the best control over the motor's speed and torque. It also provides the smoothest starting and can offer significant energy savings if the motor doesn't always need to run at full speed. However, it may be overkill for a simple sawmill application.

Recommendation

I strongly recommend a solid-state reduced voltage starter (soft starter) for the 150HP motor. It's the most practical choice for most applications.

4. Motor Controllers and Disconnects



50HP Motor Controller

Ensure the existing controller is properly sized for the motor and the voltage. Verify it's in good working condition.

All Motors

Each motor needs a properly sized disconnect switch, ideally lockable for safety during maintenance. If you have a hazardous location classification, you'll need appropriate hazardous location disconnects and starters.

5. Future Expansion (Second Building)



Planning for Future Expansion is Key



Dedicated Conduit and Wiring

Run a separate, appropriately sized conduit and conductors from the generator area to the second building now, even if you don't immediately terminate them. This saves a huge amount of hassle later.

Distribution Panel

Place a distribution panel near the generator. This will be a central point for distributing power to both buildings. It should have appropriately sized breakers for each feeder to the buildings.

Consider Overcapacity

Plan for more capacity than you currently need. It's far easier (and cheaper) to run larger conductors now than to have to upgrade later.

Separate Metering (Optional, but good practice)

If the two buildings will be used for different purposes or rented out, consider installing separate metering at the distribution panel.

6. Hazardous Location Considerations (Continued)



All electrical equipment within the classified area must be rated for the specific Class, Division, and Group of hazardous location. This includes motors, starters, disconnects, lighting, wiring methods (conduit, fittings, etc.), and enclosures.

Sealing Fittings

Sealing fittings are critical in hazardous locations. They prevent the passage of flammable dust from one area to another within the conduit system.

Grounding and Bonding

Proper grounding and bonding are even more important in hazardous locations to minimize the risk of static discharge.

Lighting

Use explosion-proof lighting fixtures.

Summary of Recommendations


Hazardous Location Assessment

First and foremost, hire a qualified professional to assess the hazardous location classification. This will drive all your electrical decisions.2.

Rewire for 480V

Prioritize rewiring the 80HP and 17HP motors for 480V if possible.3.

Soft Starter

Install a solid-state reduced voltage starter for the 150HP motor.4.

Plan for Expansion

Run conduit and wiring to the second building now. Install a distribution panel near the generator.5.

Hazardous Location Compliance

Ensure all equipment and wiring methods are compliant with the hazardous location classification. This is non-negotiable.6.

Safety

Implement and enforce strict dust control measures and electrical safety procedures.7.

Review by Qualified Professional

Have your entire electrical design reviewed and approved by a qualified electrical engineer experienced in hazardous locations.

Important Considerations



Local Codes and Regulations

Adhere to all applicable local electrical codes and regulations, in addition to the NEC.

Documentation:* Keep detailed records of all electrical work, including the hazardous location classification, equipment specifications, and wiring diagrams.This is a complex project, and it's crucial to get professional help to ensure a safe and reliable electrical system. Don't cut corners, especially when dealing with hazardous locations. Safety is paramount! Good luck. Flag for review