electical shower tripping....

[matt.leung]

I had a phone call with an electrical shower problem..

every time they switch it on and mcb trips out... my thinking at first was that there must be a short circuit, but if there was the mcb would not re-set as the short would still be there...

the client has already changed the mcb to a high value trip and i am due to see the property next week.... any ideas where to start fault finding on this matter... because at first they thought it was the shower so they changed it and the circuit is still tripping. the tripping started when they had some other electrical and building work done...

for me i still keep going back to a short circuit problem, but surly it cant or the mcb could not be reset...

ideas are more than welcome.....

Edit/Delete Message

 

[paul b b]

i went to see a customer with a lighting fault, mcb would trip, they would reset mcb would trip again maybe a day later.

turned out to be a chewed cable and was only shorting every so often.

 

[matt.leung]

i went to see a customer with a lighting fault, mcb would trip, they would reset mcb would trip again maybe a day later.turned out to be a chewed cable and was only shorting every so often.

did u pick this up on a IR test?

 

[paul b b]

yes.

i take it they are not using the shower?

also if they changed the mcb, did they first confirm the cable could take the rating?

 

[paul b b]

i would thake the cables out of pull switch, ir test to the pull then test from pull to shower (making sure cables are not exposed whilst doing ir)

 

[matt.leung]

i have no idea of as yet, i am seeing the client next wed afternoon.. i dont have much experience with electric showers... how easy are they to open up and disconnect so i can preform an IR test...

 

[Bez]

Sound like the short is between pull switch and shower if the MCB is staying in when the switch is off

 

[paul b b]

to open, normaly 2 screws on top and 1 on bottom (put plug in first or you will be scratching about for replacements)

all is there in front of you nothing to much to worry about. if your unsure take your 1 off at home and have a look at so you can look like you have done it before.

having said that, i did one and the bloody thing had mastic all around it, so i ran a stanly around it and re-sealed it when done

 

[Apache]

When you say 'everytime they switch it on' do you mean the shower or the shower isolator?

The Crabtree isolators come highly recomended, maybe there's a cable nipped up there?

 

[matt.leung]

thank you for all ur advice...

 

[Dane]

IR Tests,

I disconnect from shower, first, and switch, then check CU to switch, if all fine check the Switch to shower.

Ask the customer if the MCB Trips when pull the pull chord, or when they press the shower switch. When did it start also.

If its when they turn the shower on at the shower, open the shower up and make sure everything is connected correctly, i recently had a new shower that was tripping exactly how your saying (fitted by plumber)

They had wired it up incorrectly, causing it to only trip when the turn the shower on at the shower.

Also check all seals for water getting into the shower unit.

 

[matt.leung]

this is there second shower that they have fitted and both of them have tripped the mcb...

 

[Apache]

isolator or cable then!

 

[Dane]

this is there second shower that they have fitted and both of them have tripped the mcb...

Have you checked they fitted it correctly? Could still be the shower if its managed to get moisture into it, if its in a bathroom.

 

[SPECIAL LOCATION]

i have no idea of as yet, i am seeing the client next wed afternoon.. i dont have much experience with electric showers... how easy are they to open up and disconnect so i can preform an IR test...

"INS RES" = wrong test...... :_|

IF it is tripping the MCB not RCD, you would be looking at a "LOW RESISTANCE CONTINUITY FAULT"

Consider the following:-

to trip a 32amp MCB resistance will be LESS than 230/32=7.19ohms

to trip a 40amp MCB resistance will be LESS than 230/40=5.75ohms

to trip a 45amp MCB resistance will be LESS than 230/45=5.11ohms

to trip a 50amp MCB resistance will be LESS than 230/50=4.6ohms

Ins Res we are testing for Megohms Thats 1,000,000's ohms!

so say a 0.02Megohm Ins res value will still only draw...

less than 15ma...

not even enough to trip an RCD!

Don't forget shower heating elements can put a low resistance 6ohm load across the circuit... (with no trip).

Don't get your ohms & MegOhms confused.

IMHO you are probably looking for as near as dammit a dead short! :|

Not a high resistance break down in insulation!



Cable knackerd / damaged during installation? could be?