Advice Needed - Ariston Undersink Water Heater Install

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Hi - First Post so hello and thankyou in advance for any help/advice!

The undersink water heater has packed up in the kitchen, I'm guessing it's been there since the extension was done 20+yrs ago.

I recently plumbed in a new kitchen sink and it was all working fine for a few weeks. I live in SW London so the water is very hard - so I wouldn't be surprised if that was the issue. The existing setup is really straight forward with a power feed, cold water feed and hot water outlet. See pic attached of existing setup.

I've bought an Ariston 15 Lux as a replacement. I had assumed that I could just wire it up and connect the inlet & outlet pipework (15mm braided flexi). However a couple of queries;

1.) The existing electrical feed cable is probably not long enough so I will need to extend it. I've bought a cable jointing box so I can do this, but I don't know what size cable I need to use to extend it.

2.) The user manual talks about the need for an expansion tank? The existing setup doesn't have an expansion tank, so I'd assumed I wouldn't need this on the new system?

Any help on the above is much appreciated!
Plumbing.jpg
Plumbing1.jpg
 
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You need to follow the MI explicitly. It's really important to ensure you have the relief valve fitted properly, emptying through a visible connection (tundish), into a larger pipe size and that you have a suitable amount of cold water supply pipework for expansion.

It is also a usual specification that copper should be used, plastic is not a recommended material as it's is not rated to the required spec. Distance to the nearest draw off is also important to ensure there isn't a danger of excess expansion pressure compromising the valve, so unfortunately that spaghetti junction of plastic/flexi pipes would not be recommended either.

When your old one was installed then these regs were probably not as important, they are now. It's purely for the safety of you and yours, as these heaters are miniature pressure vessels and as such, if everything did go wrong, it could explode.

Cabling is straightforward and needs to have a current capacity of at least 13A, breaks in the cable should be avoided.
 
I've bought an Ariston 15 Lux as a replacement. I had assumed that I could just wire it up and connect the inlet & outlet pipework (15mm braided flexi). However a couple of queries;
You cannot do that with the Water heater that you have bought, it is completely wrong and dangerous, read the Manufacturers instructions for the install of the new one which you shouldnt be installing as you are not G3 qualified
 
Thanks - looks like I was a little naive and optimistic so thanks for your input. Can you advise on the approximate cost of a professional supply and install? I can return the Ariston unit and get a refund (or would I be better off keeping it and supplying to whoever I get to do install?)
 
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2.) The user manual talks about the need for an expansion tank? The existing setup doesn't have an expansion tank, so I'd assumed I wouldn't need this on the new system?

Any help on the above is much appreciated!

Anyone who touches that, is required to be G3 qualified. You cannot do any work on it at all without the G3.
 
You need to follow the MI explicitly. It's really important to ensure you have the relief valve fitted properly, emptying through a visible connection (tundish), into a larger pipe size and that you have a suitable amount of cold water supply pipework for expansion.

It is also a usual specification that copper should be used, plastic is not a recommended material as it's is not rated to the required spec. Distance to the nearest draw off is also important to ensure there isn't a danger of excess expansion pressure compromising the valve, so unfortunately that spaghetti junction of plastic/flexi pipes would not be recommended either.

When your old one was installed then these regs were probably not as important, they are now. It's purely for the safety of you and yours, as these heaters are miniature pressure vessels and as such, if everything did go wrong, it could explode.

Cabling is straightforward and needs to have a current capacity of at least 13A, breaks in the cable should be avoided.

The distance quoted is so no hot water expansion enters a branch to a cold water outlet.
 
Anyone who touches that, is required to be G3 qualified. You cannot do any work on it at all without the G3.
As far as I remember, anything up to 15L doesn't fall under G3 so doesn't needs notified and doesn't need G3/UVHW to install, tbh though I think all unvented should, if nothing else than for safety's sake.
Anything above 15L does fall under the regs and requires a 'competent' person (G3/UVHW) to install and notification.
 
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I usually wouldn't disagree with other pro's on here so I need to go and check but when I did my unvented refresher a year odds ago I'm sure it was still the same as far as the 15L requirements.
 

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