Hmm.... Thermaltake's website clearly shows two. If you only have one, then your PSU must be different than the TR2-500 on their website and I don't know what kind of output it is capable of.
What does the +12V ratings say on the PSU label? Most importantly, how many watts are dedicated to the +12V rails?
It's deffo the TR2-500 ATX 12V 2.0
Can you not see the screenshot I took above? It has all the label info on there..
DC output +12v 14A, +12v2 15A?