Immersion heaters 3 blown in two days!

[magicno1]

Hi
I installed an RM 180 lt direct unvented 2 months ago. It serves a deli and kitchen area so the elements are on 24/7.
Saturday both elements faied and took the rcd. Both were blown as you would expect after say a year or so. Spoke to RM and they advised fitting titanium elements due to heavy constant use so replaced them both yesterday around 3 pm. 11 o'clock today the shop rings no hot water! Drained tank off to find both elements blown apart again!
The electrician is testing the electrics and they all are fine, correct wiring etc! One thing is that the voltage today at 5 o'clock was 251 volts permissible apparently at 253! Could it be over voltage causing this in such short time or crappy elements do you think????? I believe the heaters to be fine and there must be some underlying issue electrically!
We are speaking to RM in the morning if their tech guy answers the phone!!!

any ideas guys please we are stumped.
yes I am cert unvented!
cheers

chris

 

[AlexGas]

Sparkies will tell you more.

 

[dancinplumba]

Possibl voltage surge ?

 

[magicno1]

A surge possible yeh but I've never had this in 31 years has anybody???

 

[dave1]

Possibl voltage surge ?

I was thinking that, what could cause that tho?

 

[dave1]

Maybe someone should take this over to the dark side (sparky forum) who's brave enough? Ha ha

 

[magicno1]

God knows! What the hell would rip apart a titanium heater in under 24 hrs????

 

[SimonG]

The immersions that are supplied with the cylinder are only rated for domestic use. If they are in a commercial environment then they need to be upgraded.

Amazing what you read on a rm label

Dont mention where you have installed it.

 

[gasmanrob]

Just going to throw it out there you are connecting to the right side of the stat if I remember rightly the immersions fitted as standard have external overheat stats. Not insulting you just clearing the obvious

 

[magicno1]

They have co therm stas. Yes connected correctly live to A and neu to B.
no problem you have to ask I know ,
cheers