Shopsmith Forums

I recently picked up a NOS DC3300 that was never used. I hooked it up in my shop and after about 2 hours of running, the motor got extremely hot...so hot, one can smell plastic overheating. I took the entire assembly apart and nothing seems wrong...it truly was never used as eerything is clean and shiny...although the foam seals are rotted. I am wondering if it may have been wired for 220? Does anyone know what pins on the motor are for 120 and what ones are for 220? Or, other theories why it overheated? Thanx!

I have one I can look at later in the week to see how it is wired.

I did find one old thread about the wiring.

Link: viewtopic.php?t=3473

On a sample size of one, my DC-3300 motor is not dual voltage capable and there is only one way to hook it up. That is not to say that SS did not make a dual voltage, 220/230 V, and/or a 50Hz version. There is a label on the outside of the DC listing its power requirements, easier to check than the label on the motor but perhaps not quite as reliable. If yours was built for a market other than North America I suppose that label would say so. But since that seems unlikely here are some other thoughts:

It is a capacitor start induction motor, likely has a centrifugal switch inside. That switch MUST disconnect the start windings of the motor once it reaches a certain speed. If that switch does not disconnect the start windings the motor will get hot.

Excessive load will also cause the motor to get hot. Possibly something stuck in the impeller? Bad motor bearings are possible, but seems unlikely for NOS.

- David

It may have been the load. I was using my CNC and had it hooked up to a 2" dust line hose. The other two inlets on the dust collector were capped. Possibly it was trying to draw too much through the cnc hose and that caused the overheating issue. Going to re-try today and leave the two inlets open when the cnc dust line is connected. I'm thinking it had nothing to do with the wiring.

Looks like they would have a cooling fan on this motor anyway.

If it is "new" and old, the smell MAY be simply the insulating varnish off venting voc. As for the cooling fan, is it moving air?

Finally how hot is extremely hot? What were you cutting with the CNC? Could debris from the leaky seals made it into the motor?.

This is definitely a plastic smell, not varnish. There is no cooling fan on the motor. It is so hot that it will burn skin in a flash. I also replaced the dry-rotted seals and sealed up all the typical leaky spots...around the motor housing and around the intake. I took the fan housing apart to check and see if anything was inside, or binding, and it was almost spotless. It's obvious that I am the 1st user. I read in another thread that sealing the extra intake ports will reduce the load and keep it from overheating. This is counter-intuitive. Seems like leaving the two unused ports open would reduce the load. My main load is through a 1 1/4" hose that leads to the CNC and I've been leaving the 2 unused ports open.

Fire41fighter wrote: Wed Sep 04, 2024 8:19 pm This is definitely a plastic smell, not varnish. There is no cooling fan on the motor. It is so hot that it will burn skin in a flash. I also replaced the dry-rotted seals and sealed up all the typical leaky spots...around the motor housing and around the intake. I took the fan housing apart to check and see if anything was inside, or binding, and it was almost spotless. It's obvious that I am the 1st user. I read in another thread that sealing the extra intake ports will reduce the load and keep it from overheating. This is counter-intuitive. Seems like leaving the two unused ports open would reduce the load. My main load is through a 1 1/4" hose that leads to the CNC and I've been leaving the 2 unused ports open.

Yes it seems counter-intuitive until you understand what is going on. The load on the motor is directly related to the amount of the air it is moving. More open ports means more air and more load. Reducing the amount of air being moved reduces the load on the motor. That is why, when you block the hose of your shop vac it starts to scream. The motor speeds up because it is not moving any air ( no load ).

jsburger wrote: Wed Sep 04, 2024 10:09 pm Reducing the amount of air being moved reduces the load on the motor. That is why, when you block the hose of your shop vac it starts to scream. The motor speeds up because it is not moving any air ( no load ).

...And if you were to put a ammeter on it, you'd see that when you block the hose, the current draw goes down. No load.

https://www.youtube.com/watch?v=CJlrbMHLBd4&t=1155s

I am not sure a vacuum cleaner motor is a good example of how the DC motor responds. I am curious what running with all ports open results temperature wise. I am also suspicious regarding the 1 1/4" inlet hose. No cooling fan makes no sense - I think it is on the internal end of the motor blowing out the rear vent.

I did some testing when I 'upgraded' my DC-3300 to DC-6000. (DC6K puts a TEFC motor in the same motor housing.) I found both motors get uncomfortably hot if run for an extended period of time. And both are slow to cool, so run times are somewhat cumulative in terms of temperature. In both cases the motor housing is essentially a box enclosed on five sides and with a grate on one side. So if you think of a cooling air path, a motor fan is going to create some recirculation because the 'warm' exhaust air must exit through the same grate that the 'cool' intake air goes through. I thought the DC-3300 motor had an internal fan, but to my surprise this is not easily proven with a picture.

Based on my testing I concluded that the DC-6000 is not suited for continuous operation, at least not in my shop. It reached a case temperature of 235 degrees F in about 70 minutes of continuous operation, and was still rising. I shut down the test because it was not intended to be destructive. My DC-3300 testing was not as detailed, but I recall thinking that temperatures were similar.

Question for the OP, how long are you running the DC? Based on my limited testing, I would not be comfortable running mine more than one hour out of four without modifying it. Modification could be pretty simple, use the DC to pull warm exhaust air out of the motor housing.

- David