Okay, let's break down the pull box sizing requirements for your scenario. You are correct that this is an angle pull, and that affects the calculation.

Understanding the Rules



Angle Pull

For an angle pull (where the conduits enter one wall and exit a different wall), the minimum dimension of the pull box in the direction of the pull must be at least 6 times the trade diameter of the largest conduit.

Conduit Spacing

You'll also need to consider the physical space required for the conduits, couplings, and hubs, especially with PVC-coated conduit, which tends to be bulkier.

Calculations


Angle Pull Dimension

Largest conduit: 4" Minimum dimension for angle pull: 6 x 4" = 24"This means the dimension of the box in the direction of the pull (from the bottom where the conduits enter to the side where they exit) must be at least 24 inches.2.

Conduit Spacing/Arrangement

This is where we need to consider the number of conduits (16) and the physical size of the conduits, couplings, and hubs. This is where your experience comes into play, as you'll have a feel for the space needed between each. Here's a way to approach this:

Estimate Conduit Diameter with Hubs

PVC-coated conduit with hubs adds significantly to the overall diameter. A good rule of thumb is to add at least 2-3 inches to the conduit's trade size to account for the hub and spacing. So a 4" conduit with a hub might effectively need a 6-7" space.

Arrange Conduits

Think about how you'll arrange the 16 conduits entering the bottom of the box. Will it be a single row, multiple rows, or a grid pattern?

Calculate Minimum Box Width (Based on Arrangement)

Let's assume you're trying to minimize the box size and arrange the conduits in two rows of 8. If each conduit/hub needs 6" of width, then you'll need at least 8 conduits 6" = 48" wide for each row, and 48" overall. If you are able to stagger conduits and make it one row of 16, the width would need to be 96".3.

Combine Requirements

You need at least 24" in the direction of the pull (bottom to side). You'll need likely 48"- 96" minimum in width, depending on conduit arrangement.

Evaluating Your Suggestion (50" x 30")



30" Dimension

This works for the direction of the pull (bottom to side) and satisfies the 6x rule.

50" Dimension

If you are able to do two rows, 50" satisfies the width requirements, if you did one row of 16 it does not.

Recommendations & Important Considerations


Account for Bending Radius

Consider the bending radius of the conductors within the box, as this will affect the depth and overall size needed.2.

Working Space

Remember that you need adequate working space inside the box to pull and train the conductors. Cramming the box to the bare minimum will make the job significantly harder and potentially create safety issues.3.

Manufacturer's Data

Consult the specific dimensions of the pull box you plan to use. Internal dimensions can vary between manufacturers.4.

Grounding

Ensure you have adequate space and provisions for grounding within the box.5.

Future Expansion

Think about the possibility of future conduit additions. It's often better to slightly oversize the box now to avoid a costly replacement later.6.

Local Codes

Always check with your local electrical inspector for any specific requirements or interpretations of the NEC in your area.

Final Thoughts

Your initial estimate of 50" x 30" might be a minimum starting point, depending on the exact arrangement of the conduits. I strongly recommend:1. Lay out a mock-up

Use cardboard cutouts representing the conduit and hubs to physically arrange them in the planned configuration. This is the best way to visualize the space requirements.2.

Consult the Manufacturer

Get the internal dimensions of the pull box you intend to use, and double-check that it will provide adequate working space.3.

Consider Going Larger

If there's any doubt, err on the side of a slightly larger box. It's much easier to work in a box with ample space than to struggle in a cramped one.4.

Verify with Local Inspector: Before finalizing the size, run your plan by the local electrical inspector to ensure it meets their requirements.Good luck with your project! Let me know if you have any more questions. Flag for review