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magicno1

Gas Engineer
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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
 
Maybe someone should take this over to the dark side (sparky forum) who's brave enough? Ha ha
 
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.
 
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
 
They have co therm stas. Yes connected correctly live to A and neu to B.
no problem you have to ask I know ,
cheers
 
SimonG said:
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.
Click to expand...
They are titanium!
 
Might be worthwhile to have the sparks fit voltage optimisation unit if they will pay for one, will save them pounds in the long run if they have regular overvoltage
 
magicno1 said:
Hi
One thing is that the voltage today at 5 o'clock was 251 volts permissible apparently at 253!
Click to expand...

You are not wrong here, just looked in the 17th. From 1 January 1995 nominal voltage should be 230V with permitted tolerance of +10%/-6%, which gives us permitted voltage range 216.2 – 253.0V
 
Indeed
an optimiser has been mentioned but would that extra voltage kill,them?
have to wait and see what the RM guys have to say I guess can't keep spending 200 quid every bloody two days can I!!!!
 
Does it coincide with other electrical items being switched on or off ? Neutral earth fault could cause high current flow thru heaters ?
 
Could be but the sparks pretty bang on and I'm sure he would of tested that. He had meters and meggers and all sorts of gear up there earlier testing so I'll assume that's ok!
ill double check,of course
 
magicno1 said:
Could be but the sparks pretty bang on and I'm sure he would of tested that. He had meters and meggers and all sorts of gear up there earlier testing so I'll assume that's ok!
ill double check,of course
Click to expand...

Have you seen this? The book says: If any sterilisation liquid is in the cylinder do not operate the immersion heater/s as this will cause premature failure.
 
dancinplumba said:
Does it coincide with other electrical items being switched on or off ? Neutral earth fault could cause high current flow thru heaters ?
Click to expand...

simple answer NO but the voltage at 251 will make the element burn hotter & shorten it`s life,
On removing the element check for signs of overheating but they should last longer, also what temp was the stat set at did the High Limit trip or not ?
 
Sterilisation liquid????

each time the stats fail. Never trip on the overheat tho!!!! We have about 6 stats by the tank now all :nono:!!!!
 
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dancinplumba said:
Does it coincide with other electrical items being switched on or off ? Neutral earth fault could cause high current flow thru heaters ?
Click to expand...
Simple answer NO to both !
As your sparks would have tested for N - E faults The only case I have had like this in 50+ years was on a 3 phase site where 415 volts was found due to a bad install !
It happened at time of colour harmonisation, Blue instead of black when the blue was a phase colour.
 
Last edited by a moderator:
250v should be fine for an immersion heater and within its designed limits.
 
Have you had street lights in area re-furbed recently ?
( 3 phase is funny stuff when it gets out of balance )

Parents had an electric kiln , is getting it on a different supply an option ?
 
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AWheating said:
250v should be fine for an immersion heater and within its designed limits.
Click to expand...
I agree with that upto a sceptical ( should ) I have had to change hundreds some years have I been supplied with a bad batch ? I have asked that a few times.
Regards Hard Water No not in 24 hours
 
Not sure re the lights but will ask.
regards faulty batch possible but in my opinion pretty unlikely
will pose the question re three phase!
thanks
 
efficiencyman said:
Simple answer NO to both !
As your sparks would have tested for N - E faults The only case I have had like this in 50+ years was on a 3 phase site where 415 volts was found due to a bad install !
It happened at time of colour harmonisation, Blue instead of black when the blue was a phase colour.
Click to expand...
How do you know ? Are you on the job ?
 
Let us know mode of failure, usually gives good clues as to why they have failed in such a short time. Titanium, incaloy or cheapo rubbish, ???? signs of element burn out ?
That 3 phase case I had was a 415 volt wiring mistake ( not mine ) but found it wired like that by original installers.
Ask your sparks to check for any doggy connections or possibility of 415 volts
 
efficiencyman said:
Let us know mode of failure, usually gives good clues as to why they have failed in such a short time. Titanium, incaloy or cheapo rubbish, ???? signs of element burn out ?
That 3 phase case I had was a 415 volt wiring mistake ( not mine ) but found it wired like that by original installers.
Ask your sparks to check for any doggy connections or possibility of 415 volts
Click to expand...


Fitted two two new titanium yesterday. Both set at 50 degrees at 3pm.
both blown today at 11am. Bottom one blew the rcd and the stat but not the overheat. Element was split and burst nearly all the way around.
top one split stat gone but didn't take the rcd or overheat!
previous original heaters two months old incalloy both set roughly the same both shot to pieces again although the bottom one took the rcd and stat but the top one didn't take the rcd just the stat but both never went out on overheat!

previous to fitting this tank they had a megaflo and we were forever changing the elements!
also a lot of the plumbing is plastic barrier pipe connected to copper and I have lost count of the leaks I've fixed there. The copper seems to be corroding in the speedfit joints almost crumbling away.
Do you think this could be related?????
i didn't do the original plumbing it was done about 6 years ago
 
I've no experience of water softeners, have they got one and could that be affecting things?
 
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