Thermal Cut Out On Fan Motor

[undertaker]

I have just acquired a 1.5hp bouncy castle blower. It will run for about 4 minutes then trip the thermal cut out. you can let it stand for a few minutes then press the button and it will go again, for a few minutes.

Just wondering if anyone had any ideas? I would naturally think the thermal cut out function however as it has been stood in a damp garage for about 5 years I'm wondering if the bearings and motor is just generally rusted up.

Thinking of a dismantle and clean first then see if I can temporarily bypass the thermal cut out to see if that diagnoses it. Then take it from there??

I'm not a huge expert in electric motors.

Any suggestions would be welcome!

 

[rtbcomp]

Does it make a lot of noise - dried & rusty bearings will scream. Does the motor feel hot?

If it has a centrifugal switch on the start winding that's sticking it could trip the cut-out. Standing in the damp could easily cause the switch to stick.

 

[Robotstar5]

Bypassing the thermal cutout will probably reveal the fault, just look for where the smoke/flames are coming from so not advisable.

 

[normspanners]

Try blocking the inlet to the fan, if not possible block the outlet and fit a smaller fuse ie 5 instead of 13 run it unloaded and see how long it will run, if it is damp causing the problem it can dry it out by running The other possibility is the capacitor has dried out worth replacing it just in case.

 

[undertaker]

Been running it a few times now outside. I have opened the case now and the motor is warm to the touch. So this can't be normal surely? Maybe thats why the THERMAL switch is kicking out

I have opened the actual motor case and there was a little damp in there. Also no screeching bearings. Shaft spins freely.

What is the next test stage on it?

 

[DrNik]

has it 1 or two capacitors wired to the motor???

 

[rtbcomp]

..........Maybe thats why the THERMAL switch is kicking out

.......

Thermal cutout can be a bit ambiguous, sometimes it just means the cutout operates by an element heating up under overload conditions, othertimes it can be because something is getting too hot.

It can also be a combination of the two.

 

[undertaker]

Thermal cutout can be a bit ambiguous, sometimes it just means the cutout operates by an element heating up under overload conditions, othertimes it can be because something is getting too hot.

It can also be a combination of the two.

Just seems like a button wired in the neutral from the socket to the motor.

 

[rtbcomp]

It should be wired in the live not neutral. If it is connected to neutral when it opens the motor will be live and there is a risk of electric shock.

 

[the snooper]

it should only be run under load ie attached to the bouncy castle, a mate of mine had one and it would always trip when not attached to the inflatable

 

[brightspark]

it should only be run under load ie attached to the bouncy castle, a mate of mine had one and it would always trip when not attached to the inflatable

as said it might be the case as the fan running in free air takes more current to run restricting air flow with castle conected runs at a lower amperage

 

[BrokenBiker]

as mentioned above, cutout should be connected to live, otherwise when it does cut out, if you open it up to have a look and bridge between live and and part of the neutral after the switch, or ground, you're going to know about it.

also it should have some form of load on it when running, i.e. give it something to blow up and see if it still cuts out like it is now

 

[eil]

The overload could well be on the neutral as its the neutral that heats up when the capacitor is weak or open circuit, You should isolate everything electrical before taking the cover off to just have a look anyways.

 

[normspanners]

actually,

it should only be run under load ie attached to the bouncy castle, a mate of mine had one and it would always trip when not attached to the inflatable

when connected to the castle they are NOT under load they are under the most load when they are running open ! thats why I said to block the inlet or the outlet. to run it unloaded
note to self, UUPS READ ALL POSTS when there are two pages norm!!

 

[undertaker]

actually, when connected to the castle they are NOT under load they are under the most load when they are running open ! thats why I said to block the inlet or the outlet. to run it unloaded
note to self, UUPS READ ALL POSTS when there are two pages norm!!

I have shoved a car sponge up the outlet and put it up against a wall and it again trips out after a few minutes.

My local alternator guy told me to take it to parts, clean the rotor edges and stator. If there is dirt on it (from being stood up for years) it could be running tight.

I'd have thought if there was a bad winding or something it would trip almost straight away??

 

[normspanners]

thought you said it turned freely if so then I cant see it running tight

I'd have thought if there was a bad winding or something it would trip almost straight away??

I would agree but a bad cap can give exactly the same fault.
you need a clamp on ammeter to tell you what current the motor is drawing
to accurately determine the fault, but a new cap is cheaper and will only do good for the motor. Then if it is still tripping as I said put a smaller fuse in and run it blocked if that fuse does not blow then it could be the motor overload has gone weak it is quite common for them to weaken when they have tripped a few times due to running with a big air leak or wrongly as a cooling fan, drawing full load for extended periods

 

[undertaker]

Changed the capacitor for another 16uF 400v jobbie and it now just trips quicker. 2 minutes now instead of 5 or 6 minutes.

Thinking thermal trip button next?? Someone said once they've tripped a few times they're bad???

Any other ideas?

 

[rtbcomp]

As a matter of interest, are you running it through an RCD? If not it might be worth a try, if it trips you're leaking current to earth which would suggest faulty windings.

 

[undertaker]

As a matter of interest, are you running it through an RCD? If not it might be worth a try, if it trips you're leaking current to earth which would suggest faulty windings.

Going though a RCD on the plug and also an RCD in my workshop fuse board.

 

[brightspark]

theres 2 possibilitys either the windings are shorting and overloading or the cutout is tired .a clamp on ameter is realy needed to test full load current otherwise its guesswork. if its just the mcb tripping and not the rcd theres no leakage to earth just a short