If the boiler and the radiant flooring are inside the conditioned space then I don't understand how it could freeze. Am I missing something?

How much is your yearly heating bills and what fuel do you use? Are you trying to save money by using the fireplace?

The boiler is actually in the garage so it does get cold. A couple years ago we switched from a diesel boiler to a propane boiler.

The heat is baseboard radiators in each area. The house came with this setup.

Last year we never set the temp above 65 when we were home. the bill was $3000 for propane. So we got a truck load of wood for $900 this year to try and save.

My last child just started university here in town but hasn't moved out yet. When the kids are all on their own and happy we intend to find something lots smaller and maybe we can afford to stay warm.

You have to make sure the boiler environment stays above freezing.

Your propane heating bill is outrageous. Has the boiler has been checked? It is hard to believe it is operating correctly.

You do have to pay attention to where the pipes are with a hydronic system. If you switch to another source of heat, water can be sitting still in areas where it never has before in the coldest weather. If you have a pipe running through an exterior wall with poor insulation, it could freeze even though it never has before.

Or you could add antifreeze to the system to protect it to at least 25F.

SR

Antifreeze will work, but you add maintenance.

Antifreeze will work, but you add maintenance.

Imagine the 'maintenance' of burst pipes?

SR

Point taken. My aim was to be sure the OP knows that you can't just put in glycol once and forget about it forever.

May be the boiler isn't working fine or the location is not correct. Anti-freezing may seem a good option, but you also cannot oversee the water route. As mentioned above, an exterior wall with a poor insulation won't do well in this case.

Hi Everyone! I had a lot of trouble last year around Christmas time, one group of my tenants left for three weeks over Christmas without letting me know, I then received a call when they returned in early January to say that the boiler was not working and it was quite a lot of hassle and expensive to rectify! I had to get a plumber out and he informed me that the boiler had stopped working due to a frozen condensate pipe. After the situation had been resolved I did some googling on the problem to see if this was a common problem and the best way to avoid it happening again and I actually found a video by a company called corgi homeplan which demonstrates very clearly how to deal with the problem, couldn't believe I hadn't found it first! I have included the link here for everyone else to have a look, it's one of many really useful videos that may save you money by not needing to call out a professional!
https://www.youtube.com/watch?v=v62-ykrNQmk

Here is a link that might be useful: Helpful Video