There are a few changes that need to be made to my central-heating pipework, for which I have to drain the system down. I am fine with all of it, but I am wondering if it is still OK to use the hot water side of the boiler with the heating system drained? It is a Combi by the way.

Although common sense suggests that the heating and hot water systems aren't linked, someone did say to me before that you should try not to use the boiler atall with the heating system not full.

The changes I need to make will only take 1/2 hour and need to be done now but I aren't getting the new rad/valve for a couple of weeks and as the weather is good, I would have like to avoid refilling the system twice.

The boiler does have frost protection, but I can't see it freezing!!

Any help appreciated!!