Hello - this is my vision of your logo. The idea behind was to incorporate 3 important elements of the logo: plumbing, heating and air conditioning as 3 pipes. Each one is represented by different colour that matches the name. Plumbing - dark blue, Heating - red and Air Conditioning - light icy blue.
When connected [like versions #17, #18] - it shows the complexity of your services. When disconnected [like #19, #20] - create something like a smiling face. It might represent customer satisfaction and it's a little bit, maybe more friendly approach.
I hope you like them. Please let me know your thoughts.
One more thing - because everything is symmetrical it emphasizes the name of the company "Central". Also - the simplicity and elegance make the logo very versatile and highly scalable. Modern and out of the box.