New hot water shower unit works OK but indicator not coming on.

[NanLaew]

After around 15 years, the auto shut-off button on the 4.5kW Panasonic wall shower started sticking. Otherwise the unit was OK but decided to replace it.

 

Looking at various different brands and models to replace and the criteria was not having to extend the original power wiring as it comes out of embedded conduit in the wall. I went with the same brand, current model but without the auto shut-off. It has a different footprint so needed new mounting holes drilled. Plumbing was the same as the old one and the wiring was one for one the same as well, L, N and Ground. The unit flows OK and the water heats OK and the manual RCB test works OK.

 

However, the RCB LED on the front panel never lights up like it did on the previous model when power is switched on. The only reference in the installation manual is if this LED fails to light, don't use it and call an electrician. The L, N polarity is correct (tested before on the old one to make sure nothing had gotten reversed somewhere else over the years).

 

Open for suggestions and for any other tests that I can do.

 

Thanks

NL

[Crossy]

Is your ground known good??

[NanLaew]

5 hours ago, Crossy said:

Is your ground known good??

I knew YOU would ask that!

 

Unfortunately the grounds in my old pile are as dubious as the 'electrician' that did the work unsupervised fifteen years ago. I suspect that the earth leakage detection and/or indicator circuitry in the new shower unit doesn't accommodate what is probably one of those dangerous 'bootleg grounds' and we've been dodging the proverbial on that one.

 

Mrs NL had the other bathroom's old Panasonic shower unit changed abut 2 months ago, same sticking auto-switch problem. She chose the budget Astina brand from HomePro and once I swapped the inlet/outlet over (the installer didn't look at the diagrams and assumed that all shower units have inlet on right, outlet on left!), it works great. The LED's function normally on that one. Lower sensitivity circuitry? It's only about 3-5 meters from the main CU whereas the one I'm having issues with is on the other side of the house, probably 20-25 meter run?

 

Looking at the shambles of our house wiring, the main CU is not MEN compliant but I was assured by the only qualified electrician* that helped us with a ground issue in the extension a few years back that the ground busbar in the CU is connected to a good ground. I will see about running a new ground wire from the shower unit to the CU.

 

* He said the quickest and safest fix was to rip out all the existing wiring and have the home rewired with a new CU as the existing one was a budget model as well as being undersized. Trying to guess what the other clown had done in the walls and roof space and patch it up wasn't an option. Ten day job he reckoned and we would have had him do it except he went off to wire the Burj-al-Arab and has never been back.

[bankruatsteve]

9 hours ago, NanLaew said:

I will see about running a new ground wire from the shower unit to the CU.

Before you start extreme measures, I suggest you do some testing at the shower unit.  Measure voltage between L & N.  Then, measure voltage between L & E.  If the measurement is the same or within 5 volts or so, it is likely your ground is OK as is.

 

Check for loose or disconnected wire at the indicator light.  

[BritManToo]

15 hours ago, NanLaew said:

Open for suggestions and for any other tests that I can do.

Faulty LED, return shower unit to supplier for exchange.

[NanLaew]

3 hours ago, bankruatsteve said:

Before you start extreme measures, I suggest you do some testing at the shower unit.  Measure voltage between L & N.  Then, measure voltage between L & E.  If the measurement is the same or within 5 volts or so, it is likely your ground is OK as is.

 

Check for loose or disconnected wire at the indicator light.  

Not too extreme but from previous experience, I really do doubt the grounding in the home. I will have the cover off the unit to check the LED connections but I noted it's soldered directly onto the PCB. I'll also check the PCB plugs are all seated OK and I'll check those voltages too, thanks.

 

Since I will have the cover off, I can also take the cover off the CU. Then I can disconnect the existing ground and run a direct wire from the ground tab on the unit to the ground buss in the CU. Check the voltages and/or see if the light comes on?

 

Failing all that...

 

2 hours ago, BritManToo said:

Faulty LED, return shower unit to supplier for exchange.

Yes, it's possible. The store's only a 15 minute drive away.

 

Thanks for all the tips.

[bankruatsteve]

16 minutes ago, NanLaew said:

Check the voltages and/or see if the light comes on?

I doubt ground has anything to do with the light but you do want to have a good ground.

[Crossy]

48 minutes ago, bankruatsteve said:

I doubt ground has anything to do with the light but you do want to have a good ground.

 

It might be acting as a "ground good" indicator.

[NanLaew]

A quick update. It appears that the RCB LED is coming on but it's very dim compared with the previous model of shower unit. I noticed this when I was in the bathroom with the lights off and saw the green LED dimly illuminated as the unit hadn't been switched off by the last user (they'd just turned off the water inlet and it auto-stopped). I recall that the pcb with the LED is further recessed from the front escutcheon than the previous, slimmer unit so that may be the way it is rather than an indication of a 'weak' ground.