I reviewed the state of the art in fire rated rooftop ventilators and I found that most of them use belts to allow the motor to be outside of the hot air flow. And I learned that the LorenCook QMXU smoke ventilator can pull 8000 CFM in 1.25 inches of static pressure but it take 4.8 HP to do it! Their application engineer, Ben, said the product data sheet does not show power curves so he relies on software to give him that data.

First, a look at the prices quoted by LC and PB for their fire rated fans.

Loren Cook has many models. Here is their 8000 CFM model – note they need 5 HP! That is at 750 watts per HP or over 3500 watts.

Here is Penn Barry’s quote for a larger fan, the HS24,

Now a look at the range of models and sizes from PB

Here are the Loren Cook designs

Here is a cutaway of Loren Cook’s belt drive.

Here is a design that looks like it has a closed motor compartment. But the enclosure is in the hot air flow so it will be heated quickly.

INVISCO’S INNOVATION – SIMPLE AND LOW COST

This artist conception shows the elegant simplicity that allows Invisco to say this fan will last for hours in 1000 degree air. There is a patent pending on this. The motor is cooled by air pulled in from the outside. The cool air ensures the motor can operate as designed for as long as needed. The simple design reduces the cost of parts and assembly so the price of this is far below competition.

COMPARING RUN TIMES

Here is what PB says about the HS24 –

Here is what LC says about their run times.

Clearly both companies see their designs being limited in run time.

Here is what I say about the Invisco Tornado Fire Fan

Because the motor is cooled by outside air it can run as long as needed.

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