Shower circuit tripping

[Scott 12345]

Shower circuit (40a mcb 10mm cable 8.5kw shower ) tripping after 5 mins RESET trips after 2 mins...changed shower /cable /isolator still tripping I'm stumped

 

[DPG]

Does it trip if the line conductor is removed from the MCB?

Has the MCB been weakened by someone repeatedly closing it on to a fault (which may no longer be there)?

What was the initial failure? Has the customer had a faulty shower which has been replaced but caused damage to the MCB?

Welcome to the forum by the way.

 

[westward10]

Randomly replacing parts without knowing the cause is not the way forward and is costing money. What tests have you done?

 

[Scott 12345]

Randomly replacing parts without knowing the cause is not the way forward and is costing money. What tests have you done?

 

[Scott 12345]

Drawing 34.7a when in use
Changed cable as cu to isolator was simple and only 2m away cable to shower was only 6mm again easy change. IR on cable disconnected from shower ⁹>999

 

[James]

Cable change was probably not required
if the current is constantly below 40A then a faulty breaker is likely, assuming it is just an Mcb.
if it is an rcbo then of course there could be other root causes.

 

[Scott 12345]

Cable change was probably not required
if the current is constantly below 40A then a faulty breaker is likely, assuming it is just an Mcb.
if it is an rcbo then of course there could be other root causes.

Mcb on order only changed cable as easy swap and showed signs on damage and stripped to far back not long enough to re terminate.is there a way to test mcb is faulty?

 

[James]

Put a clamp meter on the outgoing cable, if it is tripping before it’s rated output, it has had its day.