Thermostat circuits are generally Class 2 power limited circuits as defined in NEC article 725. They must be wired with UL listed cable labeled "CL2". Category 5 network cable is usually listed as type "CM" (article 800) but some styles may be dual labeled as "CL2" also. If you're careful to buy the right cable, article 725 (remote control) circuits can be run in the same cable with article 800 (communication) circuits. There are fixed legal limits on the power (not just voltage) that these circuits can supply (think fuses). Read and understand the NEC before doing any wiring in your house. This kind of wiring can burn down houses if done wrong. -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of David Blain Sent: Friday, July 30, 1999 11:33 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: RS485 with a little PIC'up I know very little about National or local building codes, but isn't sending power over Cat5 simular to what is done with thermistats (ie: 24VAC over simular gauge wire)? -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Jeff Barlow Sent: Friday, July 30, 1999 2:15 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: RS485 with a little PIC'up For the final word on this subject look at the National Electrical Code, articles 725 and 800. Your local library should have a current copy. Then check with your local building department for any local amendments. This stuff is a matter of law. In some states (i.e. CA) you are required by law to disclose to a home buyer any known improvements that were not done "to code".