Changing radiator on Boilermate II sytem?

Hi,

I have attemted to change a radiator in my sytem today but i cant stop water coming out of the radiator system. I am putting a radiator that is larger than the old one that requires pipe work to be moved so thats why i cant just turn the taps off. So how do i go about changing the radiator, do i need to drain down the tank completely or is there a way of just turning it off? Or am i just doing somthing wrong?

Thanks
Tim.

You need to drain the unit and the system.
But you can open up a can of worms.