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Variable Makeup Air by Fantech with Best Range Vent Hood Issues – Need Circuit Diagram?

Steve Mackay | Posted in General Questions on

I’ve got an interesting problem with my Fantech MUAS 750 Makeup Air System hooked up to the Best vent Hood Model CC34IQSB  (Links to the products at the end).

The hood is a variable speed 800 CFM max and the makeup air is a variable speed up to 750 CFM max.  The reason I specified the Fantech is because it uses a hall effect current sensor to detect the current being used by the hood and then adjust its speed accordingly.  Once it is calibrated it should bring in the amount of makeup air necessary given the speed selected on the vent hood.

However here is the problem.  The vent hood includes 4 LED lights that we use all the time (often without the extractor fan being on).  The current draw of the LED lights on bright is about 0.8 AMP however the current draw of the extractor fan on low (without the lights) is also 0.8 AMP.

If I calibrate the system to start the makeup air system at 0.8 AMP I’ll get makeup air when the lights come on only.

Ideally I’d want to put the hall effect sensor inside the vent hood directly on the motor power line.  However the motor is a DC motor.  I somehow need to decouple the AC supply line to the AC-DC rectifier for the motor from the current used for the lights.  It’s difficult to figure out what’s going on without a detailed circuit diagram for the hood.

Long story short, does anybody know where I can get a detailed enough circuit diagram for the Best Vent Hood Model CC34IQSB?  I’ve tried their tech support to no avail.

I’m considering calibrating the makeup air to only come on when the current draw is greater than 1 amp (although I’m not 100% sure this is possible).  IIRC the second setting on the vent hood draws about 1.2 amps.  I’ll not have makeup air at the low setting (IIRC it’s about 100 CFM) but I don’t think that will be a problem and I can always open a window if necessary

Does anybody have any other suggestions?



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  1. Steve Mackay | | #1

    Anybody have any tips on where I can go to find the info I need? Another forum?

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