Varible speed controller

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inspector 102

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Northern Indiana
Because I am only an inspector, I am having trouble with this issue. A ventilation fan was installed having a 5-amp rating. A variable speed controller was used also having a 5-amp rating. Apparently when the varible controller is set to a lower setting, the ventilation fan stops working. Since 5-amps translates to 550 watts, does it sound like the controller needs to be increased to a 1000 watt controller or is this the motor causing the issue. Because this is located at our local fire department and used for exhausting dust from the fire extinguisher work area, I am trying to assist them in figuring out which component is the cause, the controller or the motor. I believe that the 1000 W controller will solve the issue and allow the motor to operate at the lower speed because the resistance at slow speed is causing the controller currently to overheat and cut-out. Any comments appreciated.
 
I'm not very knowledgable with single phase variable speed components, but I wouldn't be scared to write down a couple of part numbers and call the manufacturers to verify that motor will work with that controller.

Usually doesn't take longer than 5 min. to look up manufacturer tech support numbers on google if it isn't on the equipment already.
 
I appreciate that fact the this did not get locked because this is not a DYI guestion. I was trying to simply get opinions from this group that has helped in the past some many times. I have an electrician coming in to look at the set up and adjust accordingly. It might simply be the nature of the equipment. City governments have no money to work with and I was trying to assist in trouble shooting this problem with them. In the future, I will try to keep my questions code related and not ask for technical assitance so I do not disrupt the forum.
 
I apologize that my question might not have been properly posted from the start. The controller is a fan contoller with a 5 amp rating. It operates a single phase motor rated at 5 amps that operates a ventilation fan. This is the type of fan normally used in out buildings to exhaust and move air during the summer months. Because it was rated at 3000 CFM, the fire department felt that it would work well for the minimal dust that occurs when they are re-filling fire extinguishers for the public. Apparently when the speed control is set on low speed, the fan will shut off after a short time. They ask me if the motor might be shutting down, or does the controll er need a higher wattage rating. I told them I thought I knew of a group that could answer this real quick and save them some money by guessing. Next time I will be more specific on my request for infomation for the forum.
 
If the motor is getting hot, when it shuts down, then I would say it's not designed to run slower, not common with most shunt armature fan motors, it should take awhile before it can get hot enough to trip it's thermo-overload.

If the above is not the case, then look at the speed control, there is a minimum speed trim pot on there, most are under the knob or cover, but I have found some in the back or on the sides, it will be a little hole which you will need a very small flat head screw driver, it should be marked "Min. speed Ajus." just outside the hole.
 
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