Why would it become live?

[RPM]

Hi,

Another elec question I'm afraid!

I have a power washer and 3 of the 4 head housing bolts snapped.
Upon removal of the third bolt I found that it had stripped the tread and gone into the housing of the motor ( a bit of oil came out).

I re-tapped the hole and heli-coiled it. When I tried the machine it worked fine...full power etc.....

Then!! when I came to remove the screw thread (to remove the lance) I got one hell of a belt from it.

Has anyone any Idea as to why the machine is live?


I understand that any reply will be treated as the opinion of the poster and
will not hold anyone responsible for any action I take on said machine.

I can post some photos if that is of any help. I need this machine for my work.


Thanks

RPM

 

[jasonB]

Did you get any swarf into the motor when re tapping the thread?

Are you using an RCD device?

Jason

 

[RPM]

Did you get any swarf into the motor when re tapping the thread?

Are you using an RCD device?

Jason

Hi Jason.

Thanks for the swift reply. It is possible, In fact more than likely that swarf may have fallen in.

I have got an RCD, but it was not in use at the time.
Would the swarf act as a conductor? I never thought of that.

Wonder if there is any hope for this machine now?

 

[Woody Alan]

It sounds as if the initial problem was caused by freezing ( or an extremely hard life) and the force of expansion is what caused these bolts to shear. if that is the case there is a fair chance that all sorts of cracks may exist that you can't see and you are simply getting water into the electrics (or electrics into the water) past the seals or around the seal housings.
I would also go direct to the point, and say you absolutely should be using an RCD device (25mA max trip rating) with an outdoor electrical appliance it will more than likely save your life in such circumstance.

As you say that is only my opinion

Alan

 

[RPM]

Hi thanks for the replies.

A strange twist to my "shocking" experience. This power wash has a shut off
switch that stops the motor when the lance is released.

I decided to remove the cover to it and found "what looks like" water marks.
The shock came from the brass tube (to the right) as I removed the lance.

The pic shows the machine motor upside down. From looking into the method of seal, for water to ingress in there, it looks non-existent?




I sent Silverline mail today to see if they could help (sponsor wise) no reply as yet tho.

Alan

I think the bolts may have snapped due to vibration :?: Although this machine has had a hard life I have noticed a few other parts of it have worked loose.

Again...thanks for all your help on this.






Cheers

RPM

 

[Losos]

Hi,
I don't have any instant answer but, as mentioned please start using an RCD everytime. We don't want to loose you

Also, those 'spade' connectors should have insulated sleeves, the bottom one is a bit too close for comfort to the metal bits :roll:

Have you an airline you could blow out (or try to blow out) the swarf from the motor.

Did you make sure all the 'earths' went back after working on the motor (These should be the green / yellow wires if you're not sure)

Just a few thoughts

 

[OLD]

'Then!! when I came to remove the screw thread (to remove the lance) I got one hell of a belt from it.'

Has anyone any Idea as to why the machine is live?

Its live because the power has come into contact with the metal work this should normally be earthed and cause the power to trip out /blow fuse so make sure the earth connection is there and continuous (this will also get rid of any static charge) then check mcb/fuse for correct rating.
You may find that the portable rcd does not trip normally but it will if you connect the metal work to a temp. earth ,indicating lack of permanent wired earth continuity.
Fixing the connection power to metalwork is then up to you or a expert who can use test equipment to fix it.

 

[Woody Alan]

Whilst the earth is an inherrent part of the safety of a piece of equipment containing metal it is of little or no value (don't take that to mean it can be left off) in a lot of fault conditions. It is quite possible for up to 13 Amps to be going to earth without tripping anything if there is no protection on the main board, this means if you come into contact with that earth and you provide a better or parallel earth path you will share some of that current, and you only need 100mA to kill you that's 0.1 of an Amp.
a safety trip works in a different way relying on a simple fact that the current flowing through the live is the same as the current flowing through the neutral, as soon as that deviates by 25mA or greater it cuts the power,it works on the basis if it's not coming back on the neutral it's going somewhere it shouldn't, very likely to earth via a human body. These trips should really be tested from time to time as not only the current value at which they trip is important, the time it takes is critical too.
I am not an expert so if anything I have said is incorrect then please feel free to say and I will edit post. The last thing I want is erroneous info on this subject

Alan

 

[davy_owen_88]

An RCD will NOT trip if you don't have, or have an insufficient earth connection from the main earthing terminal in the consumer unit to your means of earthing whether that be an earth rod, the metal sheating on the supply cable or a combined neutral and earth conductor. It is a vital safety feature which is relied upon by both RCDs and MCBs to disconnect the supply in the event of all earth faults.

An RCD works on the principal that if the earthed metal work becomes live some current will flow from live to earth and when this current is 30mA or more it will trip. I'll repeat if the earth connection at the CU isn't sufficient not enough current will flow to trip the RCD and will do nothing until you give it a path of lower resistance, it should never get to that point where you have a lower resistance than your earth terminal.

Depending on your earthing system you must have a 30mA RCD protecting all sockets likely to supply outside equipment and in the case of a TT supply (use of an earth rod) you must have a 100mA time delayed RCD as an incomer protecting everything.

You obviously have an insufficient earthing connection and lack of permanent RCD protection which must be remedied immediately. You were lucky that your resistance to earth was high enough to prevent a fatal shock, you might not be so lucky next time.

Davy

 

[RPM]

Hi all and thanks.

The more I read this, the more I am tempted to put this thing in the bin.
I have checked all the wires,earths,leads etc..... and they all seem fine?

I can only think that it must have been something to do with the bolts that snapped.

There is only one thing that I have not checked and that is the earth in the plug.

If I do decide to keep this, how do I get it checked out?
Do I need a tool shop or a household electrician? (sorry for the dumb question) :roll:

Thanks.

RPM

P.S My dad was right "never mess with leccy lad.....you can't see it and you can't smell it"

 

[davy_owen_88]

Check the plug for loose connections, then check the consumer unit for earth cables leaving it. How many do you have and how big are they?

If you let me know I can offer you more advice. Usually a shock like this indicates a more serious problem as the circuit should never have remained on when the casing became live.

Davy

 

[RPM]

Thanks Davy.

I have not checked the plug as it is a sealed one.

All I can do is post another photo to see if you can find anything.
There is a sort of "glue?" on some of the wires. I thought it was burned at first, but it's not.

The pic shows the motor the right way up. The black box under it is the pic I posted showing water marks.

I was looking to re-place this...but at around the £100 mark I could do with fixing it.

 

[davy_owen_88]

Does the earth cable connect to the metal casing directly? Should be connected via a screw through the metal casing.

If all the cables have those push on connectors take them out one at a time and inspect the insulation for signs of damage. The only way the casing becomes live is when the live conductor touches the metal directly or indirectly (if full of water or metal filings etc.)

You really need to confirm the earthing arrangements at your consumer unit. Like I said before, you were lucky this time but adequate earthing and suitable RCD's should have stopped this fault well before you had a chance to touch it.

Davy

 

[RogerS]

looking at what seems to be the incoming cable, Im looking at what looks like a cable gland support thingie on the cable and wondered where that came from as it's not doig much where it is.

I'm then thinking if it's that old you might cut the incoming cable around where that gland is and remake the connections. I have seen problems where the clamping strip has, over time, caused the cable to break underneath the clamp...bit of a longshot but worth checking.

 

[RPM]

Thanks guys,

Rest assured this thing is NOT going to be plugged in again until I sort it out.
I think that it must be some sort of short?
I will test all the wires in the morning and let you know how I get on.
The multimeter that I have should give me some sort of idea of continuity on the wires.

I will look into the clamp on the wires, the motor sits in a case, hence the missing bit for it to go to.



Sorry, I do try to reply to each sugestion, but it would take me an age to figure out the
"quote" thing! Yes, I have read the post on it too....still don't understand it?


Cheers all, thanks for your time on this.

RPM

 

[RPM]

Does the earth cable connect to the metal casing directly?

Yes it is screwed in to the motor housing.


( I am trying to "quote") hope it works? it will make it easier to reply

 

[davy_owen_88]

Righteo, that's causes me some concern because if there was an adequate means of earthing you would never have got that shock because the supply would have been disconnected within mili-seconds of the case becoming live.

You either have a dangerously high earth fault loop impedance from a poor connection somewhere or a badly installed earthing point or worse still no earth connection atall.

As I have said you need to check this asap, as it is a vital safety feature which you can not safely do without. Unfortunately it is only when something goes wrong that it comes to your attention. The pump itself is of little importance, I'd worry more about checking the state of your existing electrical installation.

If you need any more help on this feel free to ask away, it's unusual my knowledge is useful on a woodworking site

Davy

 

[Losos]

Davy,

Talking about electrical installation, I have never been sure if it's essential, or even desirable, to have an earth rod (By which I mean a copper rod one metre or so long in the ground) connected at the distribution / CB box in the house.

I know that the mains feed into the house will have an earth, and that obviously goes back to an earth point somewhere, but do you recommend earthing to earth at the house??

 

[davy_owen_88]

It isn't desirable to earth via a rod because they are not very good at making good contact (high resistance). Theresistance (when installed correctly and to current standards) is still about 200 times more than the maximum allowable resistance from the cable sheath or combined neutral and earth conductor.

If you have a connection via the incoming supply cable use that and nothing else. If you don't then that is the time when you have to use a rod but supplemented with extra RCD protection.

Davy

 

[RogerS]

Losos

There's more to read here if you're masochistic :wink:

http://en.wikipedia.org/wiki/TN-S

Roger