yes, just drain the heating,make sure everything is switched off ,pump etc.
depending how it is plumbed you may only have to drain the upstairs pipework
make sure you isolate the feed /expansion tank in loft or turn off the
mains stop cock ,then you can drain down the system from anyone of the downstairs d.o.c on radiators
best open bleed valve in upstairs rads in order to allow all water to drain off.
you will still get a little water from what is standing in the pipe when you disconnect the port valve
hope this helps..... : :P :) :)