Variable speed exhaust fan

[z28dad]

I finally got my exhaust fan hooked up. Its a Jenny explosion proof variable speed fan. Its the 120Vac version that pulls about 4.3 amps. I have not measured it, but just going by the nameplate. Everything seems to be working fine, but I do have one concerned. The unit was supplied with a solid state variable speed controller. There is an adjustment to set the minimum speed. I ran it for about 5 minutes today and notice that the front metal plate of the rheostat gets really warm. I'm not sure how hot it actually was, but I could only put my thumb on it for about 10 sec, then it would start to burn. This seems to warm to me. I'm talking about the face of the unit that the faceplate screws onto. I didn't have the faceplate on it.

I'm sure its the electronics inside and this metal plate is probably just a heat sink. If I adjust the minimum speed to be a little faster , then it does run cooler, but there is not as much variable speed. If that make sense.

I'm thinking about checking with the manufacture and maybe trying to find a better quality rheostat. I'm also going to pull it out of the box and see how hot the back of the unit gets.

The one they sent me is rated for 6A and looks like this one:

http://www.4hydro.com/growroom/fanSpeed.asp

What do you guys think?

 

[Stuart in MN]

According to the Fantech website (http://residential.fantech.net/resi...s/controls-switches/#variablespeedcontrollers) that controller is rated for 5 amps.

I checked the Jenny fan website at http://www.jennyproducts.com/FanExplosionProof.html and can't find the amp ratings for their explosion proof fans but they appear to all be 1/3 hp. According to the tables in the NEC, 1/3 hp motor will have a full load amp rating around 3.6 amps at 230 volts, but at 115 it will be around 7.2 amps.

If it is a 1/3hp motor, the fan controller isn't big enough.

So, the question is, what is the fan motor horsepower? It should be on the nameplate along with the amp rating If the fan can be wired to run on either voltage, it should have the amps for either voltage on there as well, maybe you're looking at the wrong one.

 

[z28dad]

Stuart, thanks for the reply. It is a 1/3 hp, according to the nameplate its 4.6Amps when wired for 115V. Here is a pic of the nameplate:

I thought I had originally ordered the 230V rheostat, but I received the 115 version. Since we are only talking about 5A, I just decided to use it.

The rheostat that I have is a 6A one. I just showed that link for a picture reference.

Today, I pulled the switch back out and threw and amp meter on it. The minimum speed is suppose to be around 500rpm. I don"t really have a way of measuring it, so I just listen to the unit at full speed and set it about what I believe to be close. I'm pretty sure I'm above the 500 rpm rating just to be safe.

In the max speed setting current draw was 3.6A, and in the lowest setting it was 4A.


I have an infrared thermometer that I used in powder coating. I let it run for about 5 minutes in the low setting. After that I checked the temps and they were about 129-130 degrees. This thermometer doesn't do well on reflective surfaces so I put a piece of tape over the metal.

 

[Sr. WiNdTeCh]

Maybe I'm missing something? Why would you ever need a fan that pulls that kind of amperage?

 

[z28dad]

Maybe I'm missing something? Why would you ever need a fan that pulls that kind of amperage?

Its an explosion proof fan used for painting. To answer your ? "peace of mind" I could have bought a barn ventilation fan at tractor supply, but I wanted this one. I really don't think 5A is a that big for a motor.

 

[Sr. WiNdTeCh]

OK just wondering, as 5 amps seems kinda high for normal "home" use. In your situation I would of went 240v for a painting.

 

[z28dad]

OK just wondering, as 5 amps seems kinda high for normal "home" use. In your situation I would of went 240v for a painting.

I can still re-wire it for 240. I just need a 4 wire rheostat and re-wire the motor in the 240v configuration. If I have to buy another rheostat that will be the way I will go. In the long run it will probably be worth it in current consumption.

I found the manufactures # and will put a call into their tech line in the am. I'm just not sure if this plate is suppose to get this warm.

I'm also going to check my local warehouse supply and see what they stock.

edit" After thinking about it, I believe just switching it over to 240 will solve the problem. It will be less amperage and thus should reduce the heat.