I want to convert a 240v heating wire to 120v with a transformer(step down). The wire comes from the thermostat on the wall, which also supplies other heaters. Am I able to install the converter at the location where the heater used to be and tie all the wires together at the thermostat?

What exactly are you trying to do?
What do you mean "tie all the wires together at the thermostat"? Wouldn't that make the other heaters on all the time.
Sorry, but I'm confused.

Hi Stanfortyman,

I am adding a sliding door to the outside, my heater used to be there. I would like to install a 120v weatherproof at that location. If I tie through all the wires at the thermostat located in the bedroom it will give me continuous power at the weatherproof. Basically, it would just be a jbox at the thermostat but, still 240v. If I use a step down transformer at the bb heater wire will this allow me to have a weatherproof? I do plan on building a sun room and would just like a little power in there. Getting to the panel to pull a new circuit would not be an easy task.

If you have a straight 240 VAC, you cannot get 120VAC since there is no neutral. If you are only going to have 120VAC, What you can do it to pull the 240 breaker, install 2 120 breakers in it's place and convert one of the hot 120's to a neutral. It is probably wired with a black, white and ground to begin with so make the white the neutral. That frees up another breaker if you want to add. No need to transform the voltage. Just use the thermostat box as a junction box and eliminate the thermostat function.. If you want to keep 240, you will not be able get 120 as the circuit is wired.