There is no splash screen monitor displays 'no signal check video connection'.
With regards your fan comment that may be an error then as if the power lead is not connected to the card the fan does not spin.
The power supply i am using is the HEC 550TD-PTE (550w)
Understood on the PSU make/model. I am not a fan of that brand due to quality issues I have seen in the past.
This could be the issue here. If the power supply isn't providing adequate power the system, then the GPU is going to be negatively affected.
How old is your power supply? Also, you really can't go by the power rating on some PSUs and older power supplies are less efficient/effective than newer ones. They do wear out.
Regarding supplying power to the video card. Power comes from 2 sources, the motherboard slot and the external power supply. Typically, when you fail to connect external power to a GPU that requires it, a warning is displayed when you first boot the system. In that case, there is enough power provided via the motherboard to allow this to happen.
In your case, I suspect that the video card itself is defective. If you can check out in another system, then I recommend doing so. Also, do you have the option to return/exchange it?