Block of 200+ flats, eleven single channel hot water timers blown this week alone.

[GBDamo]

It is often possible to identify the root cause from close forensic examination of the damage. Is there any way you can get and post high res pics and / or get a sample open on the bench and take some measurements?

Terminal burnout is not normally caused by a supply fault like a floating neutral. It is more likely to be from incorrect installation or faulty units. Overvoltage will usually kill the internal DC supply dropper and one can often tell from which components failed in which way, whether it was a 'surge' or a long low overvoltage from a floating neutral.

Your quite right, it's time to get CSI on it.

The fact these faults have occurred across most floors leads me to lean towards a supply issue or early distribution issue.

I'll try to get back there today and swap out a couple, get some better pictures and do an autopsy.

 

[plugsandsparks]

Might be worth checking the rating of the controller against the load of the immersion, just in case they are maxed out

 

[Mikegh]

Must be supply overvoltage

 

[GBDamo]

Might be worth checking the rating of the controller against the load of the immersion, just in case they are maxed out

That's on my list, cheers.

 

[Julie.]

I would contact the manufacturer, ask them if an almost 6% failure rate is normal, wording the conversion well, I have no doubt they will ask for one of the failed units and do the post mortem.

Especially if you highlight that even if there were some form of supply problem, it didn't impact anything else other than their timers, nothing from other supply equipment/other makes of timers through to sensitive electronic equipment, only their kit.

 

[littlespark]

Is there a batch number printed on the failed units? Maybe worth a check

 

[Mikegh]

Must be supply overvoltage

Could be jumping on conclusions , some other good suggestions posted

Re: checking timers for type of physical damage , rating , batch number etc.

 

[LukeD]

I missed the rating bit of the timer. This is important

 

[GBDamo]

I missed the rating bit of the timer. This is important

They are rated at 16A. The hot water cylinders are on a dedicated circuit off their own 16A MCB, isolated via a 20A double pole switch, length is a couple of meters.

Couldn't see a rating on the element but looking into that now.

Edit to add,

The elements are 3kW but looking at the plumbing I think they're on a central hot water system as there seems to be a coil on the cylinders.

I'm back there tonight two replace a couple and grab some more info.

 

[Yozza19]

They are rated at 16A. The hot water cylinders are on a dedicated circuit off their own 16A MCB, isolated via a 20A double pole switch, length is a couple of meters.

Couldn't see a rating on the element but looking into that now.

Edit to add,

The elements are 3kW but looking at the plumbing I think they're on a central hot water system as there seems to be a coil on the cylinders.

I'm back there tonight two replace a couple and grab some more info.

I would also see if the affected units are on the same phase still can’t rule out floating neutral