[TheForge] Hot box

Sat Jul 27 17:59:01 2002

Dave,

I have worked with a lot of commercial and industrial ovens. Most of the gas fired
paint drying ovens I have worked on had a fire box that is similar to a home
heating furnace, except the blower motor and are outside the unit. The combustion
gases and exhaust are not passed through the oven. Instead a heat exchanger is used
to heat the air that is then blown into the oven. The fire box is often located
above the oven and duct work carries the heated air to defuser baffles along the
sides if the oven.

The oven is usually a large sheet metal box that resembles a walk in cooler. Most
industrial units are insulated with ceramic fiber. Some lower temperature ovens use
a high temperature fiberglass insulation.

You might want to check into the maximum operating temperature of fiberglass duct
board that is used to make HVAC ducts. It is foil faced on one side, rigid and
light weight. I made a 24 x 36 x 48 hot box out of it to pre heat molds, but we
only operate it to about 200 F.

Jay

Dave Brown wrote:

> I want something larger than a kitchen oven.  I've already got one of these
> outside in the shop, now I want something bigger.
>
> I'm thinking that common convection oven is my best bet.
>
> What's the best method of heating?  It's for powder coating, so would the
> H2O byproduct of the flame be a problem with the coating as it cures?
>
> Dave
>
> At 12:31 07/27/02 -0500, you wrote:
> >I'm told that is about what my oven gets
> >to when set to "clean". It would seem
> >that monitoring the "air and walls "
> >might be easier than monitoring the
> >surface temp of the item. Discarded
> >ovens are a dime a dozen.
> >
> >Mike Graf
> >
> >Dave Brown wrote:
> > >
> > > I need/want to make a hot box or oven capable of around 500-600
> > > degrees.  How would you go about a project like this?  I'm assuming that
> > > you could install one or more electric oven heater elements.  But, would
> > > heat lamps work, since it's the piece that needs to get to that temperature
> > > more than the air and the walls?
> > >
> > > This would be for powder coating.  Would a soft flame propane burner (such
> > > as is used in a barbecue grill) under a diffuser plate work, or would the
> > > H2O by product of the flame present a problem in curing the powder coat?
> > >
> > > Any thoughts appreciated.
> > >
> > > Dave Brown
> > > Heritage Smithing
> > > Green Bay, WI
> > > ABANA, UMBA, GoM, MODA, ARG
> > >
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