Can it be saved?

[Russell Nash]

I picked up a wet grinder on ebay.  It ran well.  Yesterday I tried to grind some concrete.  I attached the hose, and got the water running.  The valve on the grinder had been left open, so water shot all over the place and all over the grinder.  When I got the water under control, I turned on the grinder and the circuit immediately tripped. 

I tried it again after leaving it in the sun a few hours, and it did it again.  I tried it again this morning, 16 hours later, and it tripped again. 

1) DId I kill it?
2) If I didn't kill it, what do I need to do?

I'm on the third day of a seven day window to get this grinding done, or I have to scrap this piece and start over.  Thankfully it's not a big piece, but it will still set me back at least a week. 

Thanks

[vtsteam]

Generally you want to dry a wet piece of equipment thoroughly before applying the juice.

It sometimes takes a very long time to air dry a piece of equipment internally. Like inside switches, etc.

It can be shortened by a judiciously applied hair dryer.

Don't melt things.

[Russell Nash]

I went looking in the handle, because I had fixed the switch when I first got it, and figured it was probably my fault.  I found a carbon coated and stinking piece below the switch.  I ran the markings (0,18µF +2x2500pF…) through Google and got that it's a motor condenser.  Most of the ones I find online have only 2 wires, but this has four.  Any idea where I can order one?

[vtsteam]

Sounds like 3 capacitors in one unit. Kinda small ones for a motor capacitor(s). Maybe more for brush arc surpression. You could probably make one up by connecting 3 single value caps of sufficient voltage rating. Probably have one common lead connection and three individual leads. Bu don't quote me!

This is where my partial knowledge stops and others, more electronically expert, step in and correct it, and/or give more accurate specifics.

[Russell Nash]

Here's a picture of the piece:

[vtsteam]

Maybe a 1 megohm resistor in there, too.

Well enough guessing on my part. Where are the real electronics guys?

[Bluechip]

It is a RFI suppressor. The resistor is there to discharge the .18uF cap, otherwise you can get nipped by the residual charge.
 
Could well be unique to that manufacturer/model of grinder.
 
Not likely you will find a generic item like it, not impossible though.
Look for a 'delta capacitor'.
 
What is the make and model of the grinder?
 
You sure that it's gone pop? Mostly they are sealed items, not likely to get water in them.
 
Dave BC
 

[Russell Nash]

Here's the original post on ebay for details about the grinder:
http://www.ebay.de/itm/Gruber-Beyer-Steinpoliermaschine-UWL-375-Schleifmaschine-Steinschleifer-Stein-/261227286137

The piece itself smells burnt and there's a gap between the metal and the resin on one edge.  I don't know how to check it other than that.  I'm thinking that when the water shorted the motor, that current fried this piece.

[vtsteam]

Could have been a mechanical short to case if you fixed the switch and reassembled. Hope you have ground fault circuit protection for your breaker.

[John Swift]

Hi Rusell

once every thing is dry you can test the motor without the filter


   John

[Russell Nash]

Hi Rusell

once every thing is dry you can test the motor without the filter


   John

Where did you get the diagram from?  That seems to be the exact piece.

[John Swift]

Hi Russell

I found a diagram for a chassis mounting filter and cut and paste the diagram to match your filter !

I'v not yet found a wire ended filter just like your original one

 John

PS - this delta network is close http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=DKT1EEWF4VJ3WCQLCIPZK0Q?N=0&Ntk=gensearch&Ntt=delta+capacitor&Ntx=mode+matchallpartial&exposeLevel2Refinement=true&suggestions=false&ref=globalsearch&_requestid=234985

but would need a 1 M resistor adding across the outer two connections - CX
in the diagram in this data sheet -
http://www.farnell.com/datasheets/629964.pdf

[Bluechip]

Much as it grieves me .....         ... not a fan of Maplins ....
 
I have some here, the only one similar I can find is this ...
 
http://www.maplin.co.uk/delta-suppression-filter-501
 
Does seem to have a resistor ?

No need to worry too much about the values, they all seem to work so long as they are 240VAC rated.
 
Only problem is whether the thing will fit in ...

Dave BC

[John Swift]

Hi Dave

I think I know what you mean  ,its turned into a toy shop
its not the Maplin I remember

    John

[Bluechip]

Hi Dave

I think I know what you mean  ,its turned into a toy shop
its not the Maplin I remember

    John

Indeed says I, wallowing in nostalgia. Harking back to their early days of '50 unmarked transistors' for 25p .. 
 
and most of the buggers worked OK ...
 
Anyway, back to Russell's little problem ..
 
Part #s 450543-89  and 450571-89 may do the trick from CONRAD.DE  once more assuming the things will fit in.
 
I got the numbers from CONRAD.UK but I expect they're the same ....

 
 
Dave BC
 
 
EDIT at least one does ... 
 
http://www.conrad.de/ce/de/product/450543/?insert=89&insertNoDeeplink&productname=Funkentstoerkondensator-XY-K042201051-01-F-250-VAC
 
Just needs a new Funkenwotsitten ... it seems ... but don't we all ???     

[lordedmond]

Russell
the part is not needed to run the machine only to comply with the RFI regs

quick and dirty test just remove it and strap it out that will prove where the fault is  ( you will not be watching the tele while using the machine  )

but you may need to replace it to keep the domestic harmony intact


Stuart

[Russell Nash]

Part #s 450543-89  and 450571-89 may do the trick from CONRAD.DE  once more assuming the things will fit in.
 
I got the numbers from CONRAD.UK but I expect they're the same ....

 
 
Dave BC
 
 
EDIT at least one does ... 
 
http://www.conrad.de/ce/de/product/450543/?insert=89&insertNoDeeplink&productname=Funkentstoerkondensator-XY-K042201051-01-F-250-VAC
 

The numbers on these all look right, but can I use them/how would I wire them in.  The piece is like the diagram John posted earlier.  It has four wires and no ground wire.  The pieces you linked to have two wires plus a ground wire.  Should I get two of these and put one on the live(?) wire and one on the neutral(?) wire, and then wire both to the ground?

[John Swift]

Hi Russell

this version of the filter Dave found is a closer match to your original

http://www.conrad.de/ce/de/product/450646/Funkentstoerkondensator-XY-K042202050-02-F-250-VAC/?ref=detview1&rt=detview1&rb=1

this filter has 5 wires two live wires two neutral wires and an earth wire

on the original filter the earth connection is made by fastening the metal case of the filter to
the earthed metal case of the tool

do you have a picture or a note  of how the grinder was originally wired ?



   John

[Russell Nash]

Thank you so much for all the help.

Back to the other part of my original question.  Did I do any damage to the motor by shorting it out?  Does the fact that it still shorts out mean that it's just still wet, or that I permanently damaged it?  I have it sitting in my workroom with a fan blowing into the vents right now. 

[John Swift]

Hi Russell

I think its going to take a long time blowing warm air into the vents

I would of disassembled the motor

remove the carbon brushes and remove the gearbox from the motor
then you can remove the armature and see just how much water has found is way inside

if possible remove the end cover to gain access to the brush holders and the wiring

I expect the field winding to be in two halves
so the mains supply current flows through one half of the field winding . through the armature and then the second half of the field winding

with water entering via the rear vents
the brush holders will need drying and checking for burning caused by any current tracking acrorr the wet surface to the earthed case

any damage to the motor winding would be more of a problem


  John 

[Russell Nash]

Hi Russell

I think its going to take a long time blowing warm air into the vents

I would disassemble the motor

remove the carbon brushes and remove the gearbox from the motor
then you can remove the armature and see just how much water has found is way inside

if possible remove the end cover to gain access to the brush holders and the wiring

  John

THat would be my first time taking apart a motor, and I kind of need this thing soon, so I think I'll skip taking it apart. 

The question is more of if I killed it or not.

[John Swift]

Hi Russell

that all depends on just where the fault current is going ,how large is the fault  current and  how long the supply is on

If the tracking is across a  brush holder to earth
and is just enough to trip a 30mA residual current circuit breaker in under 40 ms
 ( 2 cycles at 50 hz)
your likely to get away with it

but you may have to remove carbonised residue left by any arcing that occured or possibly in an extreme replace the brush holder

a multimeter on its resistance range may not detect any high resistance path to due  damaged insulation
insulation testers use 500 or 1000V instead of the 6V or so of a multimeter

damage to any of the windings would be a  more expensive  problem 

 John

[tekfab]

I dont think you've killed it, its just taking longer to dry it out that's all. Sometimes the switch takes longest to dry out because of its size and shape, yeh water gets in but doesn't like coming out !
As you can guess i've "drowned" a few grinders and drills etc and they've always been okay it's just unfortunate that you need it in a hurry . . . .  patience !   

Mike

[awemawson]

Do you have any sort of vacuum pump? Put it in a heavy duty poly bag taped to a vacuum pump and lower the pressure as much as you can - it will accelerate the drying very markedly as the water evaporates at a much lower temperature

[Russell Nash]

Current status:

I had the grinder lying out in the sun for a good part of the day.  The body heated up a lot, so I hoping that did something.

I'll be heading pretty close to a Conrad tonight, so I'll make a detour in and pick up the last filter you guys pointed out.

I'll let the grinder go until Monday, and then try to start it up.  If it doesn't work on Monday, I'll have to trash the concrete.  It won't matter if it ends up taking a week to dry out after that.