So as a temporary measure so we have hot water we bought a Ariston electrical boiler eco velo and showing water heated up to 70 degrees but no hot water coming out of taps/shower. Was working up to yesterday and only 5 weeks old. We thought airlock so drained it of water via safety valve and boiling hot. We discovered air in system but have now refilled it and showing water hot but nothing coming via taps which are about 2 foot away from boiler. Has anyone had this with an ariston boiler. Can’t believe boiler broken after 5 weeks and was working great. Checked for leakages and frozen pipes. Hot water in tank but only cold coming out. Help please ! We will have to get an engineer out but hoping it’s something simple. Thanks in advance
Hi Carrie… what a darn nuisance…
Mind what you do… as it should be under guarantee… and you don’t want to give 'em any chance of a get-out…
I know , no hot water in this weather 
Told by partner it’s a water heater and not a boiler as I’ve described 
Documentation here if you do not already have it - click on the bit which says the “Notices et Documentations” and then download the Notice d’utilisation
The troubleshooting notes say:
If you are sure the cylinder has hot water the first three are probably OK, but the phrase “bypass pipe” would have me very interested 
Edit: Fixed PDF link.
Thanks that’s v useful and will be studying it. We have been back in the Uk and came back was working fine last night and today is chucking out cold water but when draining is full of hot water so is doing its job but not letting us have it through the taps!
If you have hot water in the tank check that you have not turned off the supply valve. If no water can get in no hot water comes out
I’m guessing this is a "ballon chauffé eau " that you have installed. It is almost impossible to get an air lock in these as they are cold mains pressurised. I would check (as well as the fill tap on the safety valve) that you haven’t inadvertently got the cold feed/hot out mixed up. The cold is on the right, hot on left as you look at the tank with fixing brackets against the wall. The cold is fed in at the bottom and as the tank fills, leave the nearest tap open to vent the air. If round the wrong way, it’s impossible to vent the air.
Given that Carrie said the system had been working, and that the current problem is cold water emerging from the taps with hot water in the cylinder I was assuming that it had basically been plumed in correctly and had a suitable mains water supply.
Worth checking the basics though.
Thanks for all your helpful replies. Can’t get our head round this. Water heater is heating the water inside so presume it’s working , display not showing any faults. Says it’s ready to use and also if we drain it via the safety hose it’s lovely and hot so doing its job but it just won’t go through the hot water hose to the bath which is through the wall , it was doing this before. We have looked at the manual and because it’s an eco heater it remembers usage and we’ve been away for 3 weeks so we reset it but still not working .It only has to move from heater to tap but it won’t , it wants to stay in the tank ! We will look and check if the tap to the bath is faulty altho other half saying not as wd mean sink and bath tap broken at same time which would be weird but will check as both mixer taps . It’s plumbed in correctly. It’s bizarre . Maybe it’s too cold in our bathroom but cold water running out normally at good pressure.
In uk I once called out an engineer as thought boiler broken to find out my batteries needed replacing on my wireless thermostat so don’t want to feel silly again 
Just to clarify - if you open the hot taps in the bathroom does cold water come out, or nothing?
Cold water only whatever way we turn tap.
Tap is a mixer and the same on the sink . It comes out at a good pressure but only cold not even slightly warm
Ok, try this… Turn off your mains water supply to the house, then open a tap in the kitchen or bathroom to drain off any water, turn off tap. Unscrew the hot water hose from the pipe work to the tap. Get a large bucket put hose in the bucket & turn on mains water supply. Hot water should run out of hose into bucket or nothing will come out. If after a few minutes you only have cold water (which should be impossible) then you have a by pass somewhere and you need to turn off the by pass valves & open the hot water supply valves. If no water comes out try turning off the electrical supply to the hot water tank, you may have an electronic valve (though I doubt it) in the heater which has stopped working?
This seems to be the most likely problem - there is a “by pass pipe” explicitly mentioned in the “what to check if you get cold water out” item in the installation instructions - which I referenced above - not sure why it is there. I don’t think it is a normal item on a chauffe-eau but, as Carrie mentioned, this is a “clever” unit which has a complex control panel and it attempts to learn when you use hot water and (presumably) aims to intelligently heat the water for just those periods - it might need it as a safety feature (in fact that is a thought as to why the system might be bypassing the water in the cylinder).
Do you have an aerator on the end of the tap? These frequently block up. The cold comes from around the outside and the hot through the centre (anti scald idea) try removing the aerator and check the flow.
Good thought to check but this wouldn’t affect all taps and would also mean no flow if the mixer was moved all the way to “hot” wouldn’t it?
Agreed Paul, it was a try something that won’t cost anything to check. We had someone on another forum a few years back who had several clogged aerators at the same time. Testing the one showed up the issue.
It’s not easy from the end of the PC, what activates the bypass, back pressure? if so a clogged aerator could cause it to open, is it stuck open?
If I were there I would check the flow with my meter and pretty quickly work out the issue but most seem to be scale breaking off and getting where it shouldn’t.
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I think that our heating has come out in sympathy 
Arriving home after work to be informed by my son that he hasn’t been able to get the heating going all day and discovering that this is because the boiler is not working is not my favourite way to end the day 
In the end it was a couple (more) dry joints on the controller PCB so it, and the boiler, live to fight (or should that be light) another day.
I suppose I ought to get it serviced, it is 23 years old, after all. 
Have you got anywhere with your bypassing chauffe-eau?
Thanks guys for all your helpful hints and we are now convinced the mixer taps are the issue as water is nice and hot and display in heater working fine. We are going to try replacing taps. Bathroom is v old so cd be issue but funny both stopped working. Anyway will try. I’m going back to UK today for work but back when abit warmer. First winter we’ve lived over here and abit of a shocker as soooo cold.
We have another issue now setting up broadband/landline as asking for French mobile to confirm appt next tues. Person needs to just reply YES as we know they are coming tues . Anyone help us with this one and let us have yr French mobile number. May be a bottle of red in it for someone 
If you don’t have a mobile… simply tell them that.
Not everyone has a mobile… yet life does still go on… 
Like Stella writes, tell them instead to contact you by email, had the same problem a while back.