Thank you for your question.
I can understand your concern for not wanting your pipes to freeze.
It will depend on how cold you are taking about. You could have another source of heat if it’s not going to get to 0 degrees. You could use some electric heaters, propane heaters, since no one will be in the house or some other supplemental heat source so you will not have to drain the whole system.
To be sure no damage is done to the plumbing or the heating system you will have to drain the whole water system.
Your house plumbing will have to be drained also, but it is much easier than draining the boiler system
Turn the incoming water supply off and open all the faucets, and drain through the outside hose bibs to drain the water from the house.
To drain the boiler will be more of a challenge since the technician that comes to repair your boiler will want to have water in the system. There should be a drain valve at the lowest part of the system and a relief release at the radiators to open so the system does not get air bound and not completely drain.
You may need to use air pressure to completely drain the system.
The alternative can be a real expense problem if things start to freeze and break.
I hope you will be able to resolve your problem without the extra expense of frozen pipes or system.
Thank you for using Manage My Life.