I first did business with Dupont Heating & Air Conditioning more that 20 years ago, and have been very happy with their service. However, my recent experience has been quite negative, and so I wanted to share it with others who might be considering the company.
About 12 years ago, I purchased a water heater from Dupont H&AC on their recommendation. The water heater broke while (barely) under warranty, and then this year, broke again (not under warranty).
When I contacted the company and expressed my concerns about the repairs this water heater required, I was told that they thought this was a good brand at the time they sold it to me, but that they later learned that it was not. When I asked for some financial accommodation for the necessary repair based on their recommendation, the response i received was (paraphrasing) that they thought the product was good at the time, and that subsequent repairs were my problem.
I didn't feel this was an appropriate response, and asked to be put in touch with a manager/owner. I was told that I could email the person I was already in contact with, and they would forward my communication.
It might well be that this was something they would do, but this response definitely left me with the impression that there was some serious gatekeeping going on, and that my concerns were not being taken seriously.
I'm currently in the process of contacting other companies to get quotes for either repairing or replacing my water heater. I don't know for sure that any of these companies will be better. However, based on my recent experience with Dupont Heating & Air Conditioning, I can confidently say that if you are looking for a long term relationship with an HVAC company, this is not the company for you.
Hope this is helpful!