Shop Vac tripping GFI?

[Cdshakes]

I have a shop vac-- maybe 15 yrs old, recently hooked to a dust deputy.  It's worked fine all these years for collecting dust--don't think i've ever used it to suck up water.

Suddenly it's tripping the GFI outlet that it's plugged into-- no water around it.  I tried cleaning it all out, removing the dust deputy, and plugging into a gfi on another circuit--tripped that one too.  Any idea why it would do this?

There is no water anywhere around it.

Colin

[Roly]

Does it have a three wire plug on it ?     Roly

[Cdshakes]

Does it have a three wire plug on it ?     Roly

yes.

[Roly]

The unit has current going to ground either internally in the motor or a wire or connection is going to ground.    A GFCI does not need water to trip,  it compares the current in the hot lead to the current in the neutral, if they do not match it trips.   Roly

[fredhargis]

I suspect Roly has it.

[daddo]

Roly is right. If I have an appliance or tool turned on before I plug it in or unplug it, it will mostly trip since the neutral might be unplugged first.

[Snipe Hunter]

I have a turbine paint sprayer in my van which I plug into various outlets all over town. One of my clients has a GFCI which I plug into once a week. It's a problematic receptacle and will trip when I switch on my turbine. For whatever reason, it trips when I start working but once I reset it, it will work all day.. till next week and I start the process all over. A turbine sprayer uses a motor nearly identical to a shop-vac motor.

[Robert Adams]

Gfci outlets are sensitive to motors and will nuissance trip. As they age they get worse at nuissance tripping.

[Roly]

When you have two different gfci's both tripping where it worked before , it is most likely a problem that is causing it rather that a bad gfci.    Roly

[JTTHECLOCKMAN]

Brushes are sparking from wear and this throws an imbalance current. It is the age of the motor. Commutator maybe wearing down causing the arking or the brushes are just wearing down to point of need replacing. Being GFCI outlets are frequency sensitive that is why many times motors will not work well with them. They have improved GFCI outlets over the years but yours maybe of vintage age. You could try changing the outlet with a better quality one such as Hubble.