You're right, that presents a bit of a problem. Here's how you can handle the transition from the 1" PVC containing your 8-2 UF cable to the 1.5" hub on the RV outlet box

Understanding the Issue

You can't directly connect 1" PVC to a 1.5" hub. It won't be a secure or code-compliant connection.

Solutions

Here are a few options, ranked generally from best/most reliable to least desirable, but all are viable:1. Reducing Bushing (Best Option)



What it is

A reducing bushing screws into the 1.5" hub on the RV outlet box and provides a 1" female threaded opening. This lets you thread a 1" male adapter into the bushing for a solid connection.

How to use

Buy a 1.5" to 1" PVC reducing bushing. Make sure it is threaded, not solvent weld. Thread the bushing into the 1.5" hub of the RV outlet box. Use Teflon tape on the threads for a good seal and easier removal later, if needed. Attach a 1" PVC male adapter to your 1" PVC conduit coming down the wall. Thread the male adapter into the 1" opening of the reducing bushing. Again, use Teflon tape.

Pros

Cleanest, most professional, and most reliable connection. Mechanically very sound.2.

Expansion Coupling (Requires careful measurement)



What it is

A short length of 1.5" PVC pipe that will fit into the hub. A 1" to 1.5" PVC expansion coupling.

How to Use

Glue a short piece of 1.5" PVC into the hub on the power box. Connect the 1" PVC to the 1" side of the expansion coupling. Slide the 1.5" side over the short piece of 1.5" pipe until it is fully engaged.

Pros

Good if you want to future proof for movement.

Cons

Requires precise measurement and a good fitting coupling.3.

Concentric Knockout Reducer



What it is

A metal or plastic reducer designed to convert a larger knockout to a smaller one.

How to use

Remove the 1.5" knockout from the RV outlet box (if it isn't already removed). Install the reducer in the 1.5" hole, creating a 1" opening. Use a 1" conduit connector to attach the PVC conduit to the reducer.

Pros

Can be a good option if space is tight.

Cons

May require some fiddling to get a secure fit. Make sure it's rated for outdoor use.

Important Considerations & Best Practices



Weatherproofing

Since this is an outdoor installation, ensure all connections are watertight and UV resistant. Use appropriate sealant or thread tape. The reducing bushing/male adapter method is generally the most weatherproof.

Grounding

Make sure your ground wire is properly connected to the RV outlet box and to the panel. Refer to local codes for grounding requirements.

UF Cable in Conduit

You are correct to sleeve the UF cable for protection. UF cable is sunlight resistant, but physical protection is important. Make sure to deburr the ends of the PVC conduit so that the sharp edge doesn't damage the UF cable as it's pulled through.

Conduit Fill

Make sure that you are not exceeding the fill capacity of your 1" conduit. Generally, two #8 conductors plus a ground wire should be fine.

Strain Relief

Provide adequate strain relief for the UF cable at the top of the conduit run and inside the RV outlet box. Secure the cable so that there is no tension pulling on the connections inside the box.

Inspection

Before you cover anything up, it's always a good idea to have your work inspected by a qualified electrician or local electrical inspector.

Summary of Recommendation:

I strongly recommend using a 1.5" to 1" reducing bushing and a 1" male adapter. It provides the most secure, weatherproof, and professional connection. Measure carefully and dry fit everything before you make any permanent connections. Good luck! Flag for review