SteveC5088 said:PPL, I have seen people warn about homeowners insurance refusal cover issues based on DIY / un-permitted / non-NEC / non-UL-approved work and equipment.
But I have not seen anyone actually quote a policy that really does have words to that effect. I've gone searching myself, and cannot find anything. I even found people calling such warnings Urban Legend.
When in doubt of policy coverage, please do check with your insurance agent. If you are lucky enough never to had to use your home insurance policy, I am glad for you. In our last house, we had a major roof leak during a major storm that caused water damage in the internal wall. I certainly saw then the fine print on what is covered and what is not.
The National Electrical Code (2005) is easily downloadable by anyone.
https://law.resource.org/pub/us/code/ibr/nfpa.nec.2005.pdf
There is a specific section 250.140 that covers that covers "bonding" of Grounded to Grounding conductors (that the 10-30 adapters use) which details what constitutes approval. Even the gauge of the wires used are defined.
As I said, safety is a personal choice. Just be educated on your decision instead of accepting someone's view on what is safe enough.