Thread: Festool Rotex 150-slight electrical shocks

Jim

I am a fan of the rotex but are you overdoing it with a rotex. If you restore decks for a living maybe you should be using a big belt sander like the pro's use for timber floors and then finishing with the rotex.

Sorry if I am telling you to suck eggs.

In regard to the zapping issue, could it be an electrical problem with the vacuum if you are using the power through the vacuum?

Mat , Thanks for taking the time to respond. I use a Lagler Hummel 200 mm belt sander to sand out the main body of the deck. However it stops at a wall or along a railing about 200 mm. This has to be removed and I found my 2500.00 Lagler edger useless on decks. The problem with the rotex is the sweat unning into the air vent. The vacuum hose is ani static and it only occurs when you are profusely sweating.

I guess I will continue to suck eggs

Hi Jim,

Like most electrical products your ROTEX will have come with advice about using it in conditions involving moisture. It will advise you not to do so. I expect all power tools will have similar advice and for good reason. So take all necessary precautions to ensure you are safe from electrical shock.

This is taken from the manual: "For reasons of electrical safety the tool must not be damp or used in a humid environment."

Festool products are not water proof, if moisture can enter in enough quantity then there could be a problem. If the sander has been inspected by professionals and there found to be no insulation breakdown or fault then the environment the tool is working in must be looked at.
One other thought. Is the shock from static rather than AC leakage? By your description is may not be static, but this is also something to assess for yourself. Ensure:

1. You are using original Green/Black anti-static extraction hose.
2. You have not added insulation tape to any part of the hose adaptors or tool connection points. This will potentially reduce the effectiveness of the anti-static design and components built into your ROTEX, CT and extraction components.
3. Look for any breaks in the hose or around the adaptor fitting points. Check all fittings are marked AS for anti-static.

If you can eliminate static from the picture, that could help your risk assessment.

Remember, you can always get additional advice in relation to your problem from the Festool Service Department at head office.

Don't endanger yourself - I hope you sort the problem out soon.

Thanks for your reply Anthony,

I was hoping that you may respond as your knowledge of Festool and desire to share is both outstanding and genuine.

All of my tools are Festool. The dust extraction hose is the Festool green and black. It shows no visible signs of cracks or tears. This only tends to happen when I am well and truly sweating and it can be a very bright, sunny and low humidty day. I read in the instruction masnual not to use it in damp high humid environment but the weather hasn't been like this. It occurs when I am sweating fairly profusely and I think it is the sweat running down my arm and into the top air vent. The 125 air vents are on both sides and not on the top. I think the only solution is to wear and change wristbands and to dry off frequently with a towel. They are a great sander and the dust extraction is superb. Nothing else can compete with it . That is why I now have 3 of them.

Thanks again for your help.I sincerely appreciate it.

JimJ www.restore-a-deck.com.au

Hi Jim,

Thanks Jim - my desire to help you out on this one is going to be exceeded by capability..... I whipped the cover off my RO 150 and was reminded again the large amount of electronics it holds for a power tool, in addition to the power switch and plug-it entry-point. All these items located within a short distance of that top vent at the back of the machine. This is going to be hard problem to get around using the RO 150 under your working conditions.

So your assessment as to the cause being sweat ingress seems spot on. The only solution as you point out is process change and risk mitigation. As blocking the vents would be a bad idea especially in your hot conditions.

You will know the best way to manage it, sweat bands, towelling off, etc. I just can't get out of my mind how uncomfortable it must being doing what you are doing in the sun there. I find Melbourne summers enough to cope with.

With respect to safety switches, I am not an electrician or suitably qualified to give advice on these, but my understanding through discussions with my electricians is not all safety switches are alike, some with different triggering methods, and different tolerances. You might want to check into this yourself and have a safety switch that errs on the side of caution. Someone else may have input here as to electrical protection devices.

Thanks Anthony for taking the time to look more closely at the 150 Rotex. Now that I know the conditions to be aware of I can take the necessary precautions. The Rotex is still by a long shot the best sanding machine to use in the situation that I find myself in cleaning off old decking coatings.

Kind regards,


JimJ www.restore-a-deck.com.au

Jim, here's my diagnosis for what it's worth...

You're spot on with your theory regarding sweat ingress. Contrary to popular belief, pure water is actually an effective insulator. However, when contaminated with salts (i.e. sweat) it becomes a potentially deadly conductor. I'm assuming, and correct me if I'm wrong, that your Rotex is the older model with exposed alloy castings as opposed to the newer, more insulating model. Your sweat may be creating a short with the castings of the machine, and some current is intermittently passing through you to ground. If it's the newer model then you're probably getting zapped directly on the body-gripping hand from the enclosed electrics.

This is a dangerous, and potentially deadly, situation. Almost all modern power tools are "double insulated", meaning that there exists additional insulating and or isolating elements within the design. They have no direct earth connection as such, apart from the resistive/conductive "anti static" dust extraction hose and fittings, which are grounded at the vac's earth connection (if it has one).

You're being zapped with a current smaller than that which will trip the RCD on your safety switch (typically 30mA.) Current >30mA. is sufficient to kill if sustained for more than a few milliseconds, and may cause damage anyway. This is why the triggering current of RCDs are legislated to a max. of 30mA. RCDs work by monitoring the current in both the active and neutral conductors, and will trip when an imbalance occurs >30mA. (i.e. when the current finds an alternative path to ground).

Don't tape up the air intakes. If you're getting hot, then so will the machine. If you restrict the ventilation cooling in hot weather, you'll be placing enormous thermal stress on the armature and windings, effectively shortening the machine's life.

You haven't mentioned which hand is getting zapped: the hand holding the body of the sander, or the hand at the front of the tool. Perhaps both sweaty hands are creating an alternate current path from the live electrics to the exposed alloy frame at the front, or are you using the insulating side handle?

Either way, your suggested use of towels and sweatbands to prevent the ingress of salty water sounds spot on. There's other less practical alternatives, such as using Cat III insulating matting to kneel on. But I don't think it's a realistic solution, as you'd need to be constantly mobile while sanding a deck. Best of luck.

Dear Ratbag,

Thanks for your great response. I am right handed and hold the body close to the air vent with my right hand with the heel of my left hand placed on the roundish head of the sander located above the sanding disc. I found this provides the best sanding angle, pressure and control . I do not find the detachable handle works as well. Until a better sander comes along I will be using the Rotex as nothing can clean and smooth off weathered exterior timber decking as well and as quickly. The second Rotex that zapped was just puchased 2 months ago whilst I sent my first one was sent back to the Festool repair facility ( and has now been there for 10 weeks). I had the shop where I buy my gear call the repair shop and they said it checked out fine with no problems diagnosed and it will be back soon. That was 3 weeks ago. I hope it doesn't take as long to get back as their warranty papers take to process.

I guess if I was to offer a suggestion to Festool . Maybe they could(if possible) realign the vents to open on both sides like the ROTEX 125 and close the top opening vents.

I am grateful to both you and Anthony for taking the time to listen to my problem, research it and confirm what is indeed happening. Any chance that we could alert Festool to this issue?

I forgot to add that I am only getting zapped with my right hand and have not been zapped with my left. I wear very good knee pads called nailers that have a hard plastic cap on the front where your knee is on the deck. You are correct that I need to be fairly mobile whilst moving around on a deck. I know that at the end of a long hot day of sanding off the edges my back hurts and the first few beers in the shed don't even come close to touching the sides.

Originally Posted by jimj

Any chance that we could alert Festool to this issue?

It's already been done Jim. I did it yesterday.


Hi Ratbag, have I been misinformed or misunderstood about there being differences in safety switches? Are all RDCs created equal, have they always been? And can the RCD protection be somewhat circumvented by non-earthed appliances?

When installing a RCD the neutral is in fact earthed so non earthed products are still protected.

As all of you are way ahead of my feeble mind concerning the finer points of electrics can you help with my methodology. I always plug my safety box into the wall outlet of the house. I then have my Festool ct33 plugged into the safety box and then the Rotex into the extractor. Is that the best method or should I plug the Rotex directly into the safety box and the extractor into the safety box and run it in the manual mode. I hope this makes sense.

Thanks again to all of you have offered advice and suggestions.

Anthony can you let us know if you hear back from Festool on this issue.

JimJ www.restore-a-deck.com.au

Will do.

Jim,
Everything downstream of the safety box is "protected", so it sounds like you are OK.

One thing to keep in mind with RCD's is that they will only protect you if the current leakage is to earth. So if you were isolated from earth and completed a circuit between active and neutral, the RCD would NOT trip and you could be dead.

So if your on a timber deck (and effectively isolated from earth) and via your sweat you complete a circuit between active and neutral parts inside the tool, you could get a tingle (or much worse) and the RCD would NOT trip and protect you.