Re Ariston under-sink water heater install

[Adrian]

HI All

The Studio saga continues...... After much thought, and with grateful thanks to all those who offered suggestions, we finally decided to go with the electric under-sink water heater.

This one is by Ariston, and stores 10 litres of hot water, thermostatically controlled.....

The installation manual's in 12 languages (!) - but I'm stuggling to understand the English info....

It seems to suggest that there are two ways to install the pipework to the thing.... being 'open outlet' and (I assume) conventional tap outlet.

I have taps for the new sink - so I was hoping to do the tap outlet thing....

The heater has a red outlet connector and a blue inlet connector. The instructions and diagram for this shows the following connections on the cold inlet side of things....

From the mains water to the heater.... Pressure relief valve (8 bar - supplied)..... .......Drain c*ck .......and then into the cold inlet of the heater.

Nothing is shown on the outlet side - but I'm guessing that it's simply pipework to the hot tap ?

This is the first time I've installed one of these units - and I'd like to get it right (very much aware of the expolsive power of steam in the event of a failure !) - so am I right in that the pressure relief valve goes on the inlet connection, rather than (as you might expect) on the outlet side ....?

Maybe the idea is that, in the event of over-pressure, the first thing that comes out is cold water... before the steam.... ? Dunno ??

There are also diagrams for an 'open' system - but that uses 'valves' rather than 'taps', and I don't particularly want to go that route....

Any comments / suggestions please ??

Thanks Adrian

[Adrian]

C'mon - somebody must have installed one of these things !

Regards Adrian

[Donwill]

Polite suggestion---- These things can be DANGEROUS and can EXPLODE, If you don't know how to proceed, then DON'T, get someone in who is familiar with the installation of electric under-sink heaters. They are meant to be installed with an open vent tap which are very expensive, the water expands when heated and drips out of the open vent tap, the outlet is always open and the tap controls the inlet side of the heater, I recently purchased a tap for my heater which cost me approx £90. Donwill

[Adrian]

Thanks for the warning....

OK - understand that. The bit I didn't understand was that the information supplied with the heater seems to offer the option of either an open vent OR a conventional 'tap on the hot water outlet' install.

In fact, the section of ths installation instructions that don't refer to the 'open outlet' connection say 'The safety valve has a calibration value of about 8 bar. A slight drip during the heating phase is quite normal,.....'

Which sounds to me as if, in this mode, there is a tap on the hot outlet of the heater, and the increased pressure caused by the heating of the water is vented through the safety valve....

All I was looking for was confirmation that this plan is correct ....

I've now emailed the manufacturer just to confirm that I've understood their manual correctly...

Many thanks Adrian

[Tony Bryer]

I will agree about the potential for danger but in many cases you no longer need an open vented tap. The requirement is either for an expansion vessel or for a suitable length of pipe between the heater and incoming main. You also need a safety valve.

[Adrian]

OK - thanks....

The heater came with a little safety valve. The instructions require that a 'T' untion be fitted to the cold inlet. One end of the 'T' goes to a drain valve, other end goes to the safety valve, and then on to the incoming water mains 'via a flexible pipe'.

In my case, the water 'main' is fed from a private deep-bore well, with a pressurised expansion vessel - situated about 12 feet away as the pipe runs.

Wonder if this sounds suitable ? The installation is in a timber Studio - I was planning on installing the safety valve outside the building (freezing isn't going to be an issue - we're in South-West Ireland) - the valve can then 'leak' to outside, if it needs to.

The current pipework to the well is 3/4" black Alkathene, so I was going to tee from that into the water heater, also fit an additional tee before or after the safety-valve to feed the cold tap on the sink.

I've a fair bit of (amateur !) experience in plumbing & wiring - but this is the first time I've come across one of these devices - and I'd like to get it right

Regards Adrian

[<me9]

And IIRC the capacity of the heater has to be below a certain volume.

[Tim Lamb]

I have something similar but not Ariston. I suspect these are imports from a country with rather different rules on plumbing installation.

I fed the output from the over-pressure relief valve to the *washing m/c* input on the sink waste trap. Overflow outlets are meant to be visible to avoid waste!

The other issue is that of expansion. My instructions, translated from whatever, required a minimum length of connecting pipe on the input side.

The third issue, which I probably should not mention:-) is the requirement to connect to the cold feed. The whole purpose in my installation was to overcome a problem with overlong piping from the hot water cistern. This is a hard water area and it seemed really stupid to not use pre-heated softened water.

regards

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[Adrian]

Thanks for the comments

Do you mean that the Ariston is from a country with different plumbing regs ?

That was my thought in putting the overflow 'outside'....

Hmmm - no mention of that requirement in my instructions...

Not an issue here. Water's soft 'out of the ground' - but pretty darn acidic before it's been though our dosing plant..... after that it's a fairly constant pH7.....

Thanks Adrian

[Tim Lamb]

In message , Adrian writes

Mine came from Screwfix!

IME anything with more than one language on the instructions is likely to be an import.

I spoke to one UK manufacturer (forgotten who now) in an attempt to establish why it was necessary for the feed to be from the cold supply and failed to get a clear explanation. The obvious issue is the risk of a local *shut off* valve leading to over pressure. ISTM a thermostat failure is more likely, where putting hot water/steam back into the mains supply system ought to be less attractive than into a vented hot water cistern. Oh well! None of this is relevant to your borehole set up.

regards

[Donwill]

It makes no mention in the instructions of the one I recently installed ( Zip Tudor 2) of an alternative to the permanently open outlet installation. In fact it expressly forbids using any other type of installation, I quote "UNDER NO CIRCUMSTANCES SHOULD THE SPOUT OR OUTLET BE CONNECTED TO A TAP WHICH IS CAPABLE OF BEING CLOSED"( their capital letters) Maybe the Zip is not constructed to withstand mains pressure?

My experience is limited to the Zip only, so cannot help further. Good luck & Best regards Mot

[Adrian]

Thanks....

Adrian

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[Adrian]

Certainly - looks as if the 'native' langauge for this piece of kit is Italian...

The only reservation I have is that my deep borehole feeds a pressure tank to provide the initial water feed before the pump cuts in. Quite how this pressure vessel would feel about having 8 bar pushed back up its outlet (!) I do not know.....

...but then, I'm not sure how a conventional mains supply would react either. I guess in either case the condition only applies until the pressure release valve blows - which, if the tank's decided to boil due to a stuck 'stat, will not be for very long....

Complicated, innit ??

Still waiting to see what Ariston's Irish tech support people have to say (probably along the lines of 'Shure - you don't want to be worryin' about that now.....'

Regards Adrian

[Clive Mitchell]

In message , Adrian writes

My guess is that it would make your neighbours toilets toot like steam whistles and turn their ablutions into brown vapour.

[Adrian]

Now there's a picture to conjure with ! How to win friends & influence people

Adrian