Rosco Fogger stops working in three minutes.

[Bryce Foster]

Hi all, I have a Rosco Vapour Fog Machine that lately will run full blast when I bring it to full, but within three minutes it goes dwindles to a putter of smoke. After twenty minutes or so it's fine again and does the same thing all over again.
I know the heating chamber is clean, It shouldn't be overheating in three minutes, there is a 2" gap between the exhaust and the tube for oxygen, I've read through community boards and the manual, I'm stuck

Can anyone tell me why this Fog Machine almost completely stops after three minutes?

 

[sk8rsdad]

Foggers work by transferring energy from a heating block into the fog fluid converting it to vapour. At full, the heating element is unable to put energy into the heating block as fast as the fluid is taking it out. Eventually the temperature of the heating block drops below the point where the fluid will vaporize. When that happens, most fog machines shut off the pump to keep from spitting out hot fluid.