RCBO ---shower --- lightning

[GavinK]

Shower MBC is on part of the consumer unit that is protected by an RCBO. Since yesterday following a thunder storm the RCBO trips whenever the shower is turned on. If MCB for the shower is switched off then RCBO doesn't trip so look like its the shower that is causing the problem. Could the lightning storm have caused this (shower was used briefly during the storm) ? How to trouble shoot / or replace shower unit ?

Thanks.

[lopburi3]

Most showers have a built in ELCB. If that is tripped you likely have to push up a plastic rod at bottom of unit. Not sure if that trip would cause your issues but easy first place to check.

[Crossy]

The possibilities.

1. The shower
2. The cable
3. The RCBO
4. Something else

Some things to look at.

Can you swap the shower for another unit? Does it work correctly?

Does the RCBO trip with the shower set to 'cold'?

It's possible the wet has got in somewhere and is causing a N-E (yes Neutral) fault, this would have the effect of causing the RCBO to trip when a load comes on the system.

What test gear do you have?

Let's pop this over to Electrical

[bankruatsteve]

Also...

With your shower heater turned off, can you then open the "shower MCB" without tripping the RCBO?

Do you have any other outlets on the same circuit as the shower?

[GavinK]

RCBO doesn't trip if shower is running cold. I have a Double Pole Switch between the Consumer Unit and the shower. RCBO doesn't trip when DPS is on. It's only when I turn the shower on for warm warer that the RCBO trips straight away. The showers built in ELCB doesn't trip. The MCB doesn't trip. No other outlets on the shower circuit. It also has its own earthing rod. MCB can be opened with shower running cold and RCBO doesn't trip.

Took a look inside the shower unit and no water or unwanted creatures inside.

Could the lightning have damaged the shower ???

[Crossy]

Do you have a multimeter?

It is possible that the shower has been killed by a surge, particularly if it was already old and possibly already weak.

As the internal RCD doesn't trip I would like to verify that there's no N-E fault on the installation.

You really need to get the beast to someone who has an insulation tester, failing that a replacement is on the cards.

[GavinK]

No multimeter yet - any recommendations that can be bought here ?

Shower is about 3 years old.

Would it be worth just connecting up a light bulb to the circuit and disconnecting the shower to see if the RCBO trips when I send supply to the bulb via the DPS ? Would be easier than connecting up another shower from the other bathroom.

[Crossy]

You really need a similar load, the other shower would be best. A bulb may not draw enough current to cause a trip if there's a N-E fault.

Simple digital multimeters are available in Tesco and other large stores, more than adequate for our purposes. Don't get a cheap analogue meter (with a needle) they really don't cut the mustard.

[bankruatsteve]

Beat the hell out of it with a rubber hammer - try not to damage anything. That works some times.

[lopburi3]

Does the RCBD have adjustable sensitivity? If set for 5ma it may trip without a shower unit (which is likely 25-30ma) tripping. But as said a cheap meter is a good investment and will help troubleshoot now.

If shower is fried note advertisement from HomePro this week for Panasonic DH3JL2TH model for 2650 baht (have one for last year and find it the best of the about 10 units have had in last decade).

[eyecatcher]

Its a long shot but you are assuming the storm was the cause.

It may be pure coincidence.

I had a similar problem myself and thr first thing i replaced was the pole switch.

Problrm solved for 100bt.

Possible scenario....the storm and thunder vibrated the switch cover loose allowing humidity steam to ingress and triggering the ecb.

May sound far fetched but strange things happen often dont they?

[GavinK]

I replaced the shower unit with one from the other bathroom and that works fine, so I assume it's the shower unit that is damaged. It's a Stiebel so just need to find somewhere to take it. I can't help thinking it was the storm that caused the problem so wondering if that means something has blown that can be replaced or it's dead Jim.