Shop Air Conditioning

[TWISTEDWILLOW]

I’ve seen some folks around here use old semi cabs as tree houses for their kids

[Latticino]

A typical single burner propane forge may have a burner rated for between 80,000 BTUH and 110,000 BTUH.  IF that heat isn't captured and exhausted fairly directly a 12,000 BTUH window shaker air conditioner isn't going to do much.  If it is exhausted, as it should be for fume control at least, you need to deal with the conditions the required make up air brings in (along with any solar load and building envelope load from your walls).  Assuming the building is a simple 20 x 10 cube, the surface area exposed will be around 1,000 SF.  If the building is a generous R-11 (you are insulating your walls and roof, right?), and outdoor conditions are say 90 deg. F,  the envelope load will be on the order of another 2,000 BTUH.  The ventilation heat load would be (for say 10 air exchanges), will be around another 11,000 BTUH.  Note that this doesn't include any solar load calculations, and is a rough approximation at best.

I have seen air conditioned shops.  However, these usually are separated between hot forge areas that are only ventilated, and cold grinding and assembly areas that may be air conditioned.  The cost of heating a room with a forge and then trying to cool it mechanically is prohibitive for most folks.

[Frosty]

20 x 10 . . . CUBE? 

I love it when you speak up with professional information but like humans everywhere deliver some deliciously thought provoking straight lines. 

Thank you, 

Frosty The Lucky.

[Latticino]

Frosty,

Yes originally I thought it was a 20 x 20 space (like mine), then I reread the OP and saw 200 SF rather than 400 SF...  Mia Culpa

[Frosty]

Take the fun right out of it for me why don'tcha? 

I recognize all the factors you detail above but the specifics are so out of my wheelhouse I just nod and read along. 

My shop is 30x40 and I didn't get it finished before the accident so it's uninsulated. Even with the rollup and man door open two 3/4" T burners can make it uncomfortably warm and condensation makes it rain over the forge. One of those large window fans aimed out the man door helps with a breeze but as soon as the sun hits the shop anywhere it turns into an oven. 

A proper fume hood for the forge never got built and I've been forbidden roof time.

Frosty The Lucky.

[jason0012]

My building is 50x90 give or take and the previous owner had the half I use for hot work air conditioned. It was a machine shop and climate control was likely essential, but three years in I have not yet tried to use it. The chimney pulls a lot of air out and it is a bloody huge space to begin with. It just seems silly to have the ac fighting the forge or just blowing the nice cold air out the ventilation system. I am also concerned about coal and grinding dust getting pulled through the unit, tearing up the coils and fan. Now my space is large with high ceilings and big roll up doors. If it is really hot I open all the doors and run several squirrel cage fans and the roof exhaust fans and can get good air circulation. When temperatures get really bad- high 90s-100+ I am likely to take a lot of breaks and it is nice to have ax in the office. I used to have a nice air conditioned break room but it was commandeered for a project of my wife’s. Ventilation is important regardless, so get air moving. Have plenty of water available. If practical, work at night when temperatures abate. I would love to switch to nights in the hot months but I have neighbors and they would likely not appreciate me working at 3 am…perhaps one day I will upgrade to an induction forge and turn the ac on, but something about air containing a forge shop just seems wrong