Fire soon after installation

[JimmyMcJim]

I recently had a cast-iron wood burning hearth installed in my home (a Victorian grate fire held in to the opening with mortar).
We weren't able to light a fire for a week as we were waiting for a cap to be removed from the chimney – so around a week after we had the fire installed we lit our first fire, and had it burning for around 3-4 hours.

I’ve since read that the first fire you have in a new fire should be small, otherwise you’ll overheat the new mortar before it cures properly - so I’m a bit worried that our first fire was too hot (the whole hearth and the room got really warm!).

I’m looking for some expert advice here - is this likely to have caused a problem with the mortar behind the insert? What sort of damage can this cause. Will having left it for a week before we had the fire made any difference?

 

[logger]

Cast iron needs a break-in period. For our stove the first fire's goal was to reach 200 deg for 1 hr then allow to go out. 2nd fire was 300 deg for 1 hr then allow to go out. 3rd was 400 deg for 1hr then allow to go out. After that we were ready to go. Its hard to give you any advice without knowing how hot your fire reached. I guess its a good sign if you didnt hear any major cracking. Best of luck.

 

[JimmyMcJim]

Thanks for replying. I don't know exactly how hot it got but like I said it was burning for a long while so probably got very hot. I thought I heard some small 'ping' type noises as it cooled down that first time. Could this have been motar cracking?

We've had 4-5 fires since and all seems fine, and the cast iron insert still feels securely in place.

However, if mortar has become cracked what are the implications long term?

 

[SteveKG]

The ping noise I would guess is the iron contracting as it cools. The best case is to burn a series of smaller, cooler fires, yes, but that option is out and you may as well just carry on. Hope you enjoy your new installation,.

 

[firefighterjake]

Having the room "really warm" is relative . . . similar to saying the fire looked really hot . . . the only real way to tell just how warm it is in the firebox is with a thermometer or Infrared Ray Temperature Gun . . .

That said, cast iron should be broken in slowly . . . partly for the mortar. Waiting for over a week certainly would have helped if you did some recent mortar work . . . but while it would have been better to do a series of small fires, what has been done has been done.

If you're concerned you can look for cracked mortar or mortar pieces in the firebox . . . and if needed reapply more mortar.

The pinging noise is not a big deal . . . normal expansion and contraction of the cast iron as it gets hot and then cools down.