OSO UNVENTED WATER HEATER

[fabsurf]

Hello
I have an OSO unvented water heater 20 RD which gives me a lots of problem.
It is 4 years old, and the immersion has gone 3 times for the last 3 years.
350 pounds to fix all the time, the immersion completely split in 2 each time.
I m really desperate to understand beyond the water quality what can cause this. I have also bought an limescale reducer (strong magnet) but still failing.There are 2 immersion, always the bottom one failing. It can't be that an immersion only last a year??
It s becoming very expensive and I wonder whether i need to buy a new boiler or something is wrong with the electric. It is a brand new boiler and fitted by OSO recommended engineer in a new building.
Thanks for any recommendation

 

[canduit]

I am by no means experienced with these systems. First thoughts are loads of scale deposits can build up in the bottom of the cylinder, which is hard to remove due to lack of access. If the bottom immersion is sitting in this it will reduce lifespan. Is the thermostat(s) functioning correctly? Are genuine OSO parts being used?

 

[RF Lighting]

I'm sure you can buy stainless steel immersion elements for where corrosion of copper elements is a problem

 

[flameport]

It's not the water, because if it was, the top element would have failed as well.
Magnetic limescale reducers will do nothing.

Could be limescale collecting at the bottom of the cylinder and covering the element, however this would be obvious when the element was replaced, and a fair amount of it could be cleaned away at the same time.
More likely is that the original element was faulty, and subsequent ones are either also defective, damaged when being installed or are the wrong part.

£350 also seems rather high, given that the element is about £100 and changing it should only be a couple of hours.

 

[fabsurf]

I'm sure you can buy stainless steel immersion elements for where corrosion of copper elements is a problem

Thanks I have contacted OSO themselves and they sent me the actual original part the previous time. So i guess what you are saying is to get those more expensive part coated, that will definitely something I will try.
The time before that, the plumber just ordered the part. Why don't they talk about it or advise accordingly especially when I specified the issue

 

[fabsurf]

It's not the water, because if it was, the top element would have failed as well.
Magnetic limescale reducers will do nothing.

Could be limescale collecting at the bottom of the cylinder and covering the element, however this would be obvious when the element was replaced, and a fair amount of it could be cleaned away at the same time.
More likely is that the original element was faulty, and subsequent ones are either also defective, damaged when being installed or are the wrong part.

£350 also seems rather high, given that the element is about £100 and changing it should only be a couple of hours.

It is a very fair point and all the time the top one keeps working, even ran it for weeks before the plumber could turn up will ALL that is needed.
First those boiler require a unique key 1 inch 1 quarter or something like that.
£350 was without the part as Oso sent me a free replacement but yet they charge me for the drainage (3H and something) and he did not even wait till the end so all the limescale i guess remained ! Is there any specific tool to remove inside the limescale?

 

[fabsurf]

I am by no means experienced with these systems. First thoughts are loads of scale deposits can build up in the bottom of the cylinder, which is hard to remove due to lack of access. If the bottom immersion is sitting in this it will reduce lifespan. Is the thermostat(s) functioning correctly? Are genuine OSO parts being used?

Yes genuine Oso part as I called them direct and one of those replacement was from them. The picture is quite shocking when you look at the immersion completely split ...

 

[canduit]

Is there any specific tool to remove inside the limescale?

I helped someone change both immersions on an OSO. Not too sure about the scale on the inner wall of the cylinder, but for the loose deposits we used a wet n dry vac with all kinds of bendy hoses on the end. Took about 2 hours and we got a total of about half a black bag full. Also, the bottom immersion on this was shot to peices too. It was causing the circuit breaker to trip.

 

[kai]

It may be worthwhile just scrapping your OSO unit - so unreliable - just replace it with a standard unit if possible, with widely available standard immersions - cost of ownership works out cheaper over a ten year period.

 

[fabsurf]

It may be worthwhile just scrapping your OSO unit - so unreliable - just replace it with a standard unit if possible, with widely available standard immersions - cost of ownership works out cheaper over a ten year period.

Thanks I m tempted but will probably sell my flat in less than 10 years..
I might try to clean the bottom first to buy me hopefully 2 years.