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

 

[Matt06]

Why Did someone not suggest a gas water heater rather than stored (electric aswell) Electric costs loads and secondary circ elements will burn out pretty often (as they are on constant) i had it last year using element as back up with sec circ burnt out in a week
That was an RM cylinder too, Remember ringing RM and they said a load of crap apparently in the instructions it says somewhere Bypass water softeners for the first 6weeks or 6 months cant remember which (I could nt find it i looked several times after the phone call)