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ERASMO 11-23-2008 07:23 AM

Firing an oven below 32 degrees
When the temperatures outside get down very low below 32 degrees F. are their any possible damages that could occur to my oven?

Any advice on this?


Ken524 11-23-2008 08:00 AM

Re: Firing an oven below 32 degrees
Here's what I do:

Start the fire as you normally would. For the first 30-40 minutes keep the fire low and slow to knock the chill off everything. After an hour, let it rip.

I think this is good advice for anytime of the year. The less sudden thermal shock to the oven the better.

CanuckJim 11-23-2008 08:48 AM

Re: Firing an oven below 32 degrees

Good procedure; couldn't agree more. It's exactly the method I follow here in Ontario during the winter. Sometimes, I'll burn out a medium fire overnight to make sure the chill is off, then go like heck the next day.


ERASMO 11-23-2008 01:12 PM

Re: Firing an oven below 32 degrees
Thanks for the info.
I will definately use your recommendations.

RTflorida 11-23-2008 09:57 PM

Re: Firing an oven below 32 degrees
Not to argue with anyone (I'm simply curious and can't speak from experience). Is thermal shock really that big of an issue? Will it really have a detrimental effect going too hot too fast? We are only talking about a 50-75 degree temp swing (difference between a zero degree evening in winter and a summer evening). It usually takes 10-20 minutes to get a big fire roaring even on the best of days, so the super high temps are not instantaneous and the refractory materials we are using can handle such high temps.....again, does anyone know if it is really necessary to go low and slow? To us with flesh and bones, that 50-75 degrees can make a huge difference is us freezing to death...but are refractory materials greatly affected my subfreezing temps?

This does not apply to me here in FL (I think the coldest evening I have fired my oven has been around 35-40 degrees last winter)....just curiosity on my part.


nissanneill 11-24-2008 02:42 AM

Re: Firing an oven below 32 degrees
I was going to make a suggestion as to how to avoid firing your oven when below 32˚F or 0˚C. There could possibly be ice from condensation in or within the insulation (but that would depend on when it was fired last and the waterproofing properties of the oven). I would think that moisture freezing would cause more problems when freezing/expanding than when thawing out, BUT I would agree with Ken and Jim and plat safe by initially taking the heating easy until some heat has penetrated the bricks and at least got the warm through.
The suggestion was to move to more temperate climates. I am like you with the lowest temps in mid winter around 4˚C or 40˚F here in sunny South Australia.


Frances 11-24-2008 03:03 AM

Re: Firing an oven below 32 degrees
I fired up just as usuall all last Winter - hot and fast :)

And my oven is still standing... so far.

RTflorida 11-24-2008 08:26 AM

Re: Firing an oven below 32 degrees
Neill, my thoughts exactly. I would think the freezing of any moisture would be the biggest concern...not the minimal temp variances. As long as you have taken the steps to make your oven as weathertight as possible (keeping the snow/rain out of the oven, dome, and insulation) you are only dealing with humidity or condensation that could freeze. As you've stated, any damage would actually be caused during the freezing process...not during thawing or heat up. I guess what I was trying to bring up is the question - From a technical standpoint (manufacturers recommendations), Are refractory materials firebrick/mortar) actually damaged from a rapid heat up from below freezing temps?.....I've searched a bit and can only find the detrimental effects of exceeding the maximum temp specs or the introduction of the above mentioned excessive moisture.

Like Frances, I too build my fires up as fast as I can (I have actually been mixing and matching my wood types trying to get faster and faster). Regardless of the outside air temp, I can consistantly get the dome to begin burning white in about 40 minutes...fully clear in just under an hour. So far, no issues other than scaring myself with the sight of the intense flames and off the charts heat.


Ken524 11-24-2008 04:53 PM

Re: Firing an oven below 32 degrees

Originally Posted by RTflorida (Post 45715)
We are only talking about a 50-75 degree temp swing (difference between a zero degree evening in winter and a summer evening).


I agree. Really not much difference between the 20F and 70F starting temp of the oven. As I said in my post, I take it easy all the time. I'm more concerned about the 1000F temperature swing of the oven that occurs during a fast start :)

Neill has a good point about heating an oven that's frozen. It's not the thawing that damages it, it's the freezing. Use your oven regularly during the cold months to keep those bricks DRY!

nissanneill 11-25-2008 01:59 AM

Re: Firing an oven below 32 degrees
Hi Ken,
it's not just heating/melting the ice but also if you have a fierce fire going and a rapid temperature increase, the sudden heating could turn trapped ice/water into steam which can really do the damage.
Lets face it, fire bricks are quite porous and moisture can penetrate well into and through the brick without us knowing, and a fierce fire could/would generate steam which having limited exit area could build up and do serious damage.
The bricks are designed to take the heat and the temp differences but you wouldn't put a fierce fire into a new oven initially would we?


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