Valiant Ecotec 615 Plus - no hot water

[Ciderspace]

Just signed up having searched for answers but not sure what difference my system has on things so... Apologies in advanced for the long post but I've tried a few things so have detailed them here..

System installed 2012 - new build - I am first owner.
Valiant Ecotec 615 Plus
Danfoss programmer
Santon Premier Plus unvented mains water heater
2 floor (zone) heating.

Issue - no hot water currently. Heating is fine - been noticing that our hot water supply doesn’t last us as long just lately.

When we moved in the builders recommend that we keep the hot water programmer on from 7am to 10pm, allowing the water to heat when required but I never liked the idea as felt like a waste of energy but also, we'd hear the boiler in or bedroom as its installed directly below in the kitchen.

So I re-programmed the timer to come on at 8pm every night for just an hour - this has lasted us fine since install - showers, washing up etc etc. I've only ever had to click the 1 hour override button a few times to top up if we've needed it.

Despite no other issues since then, we had no hot water one morning recently. I researched solutions and figured Id check the external expansion vessel - no pressure! A quick push on the valve and nothing, no air, no water (which might indicate it was faulty). So I shutdown the water, ran a tap to alleviate any pressure and pumped up the expansion vessle to its recommended 3.5bar. Hit the hot water override and the boiler fired, and we had really good hot water - much better than usual, obviously! Felt great to fix the issue, brownie points etc although slightly confused why the expansion vessel would cure this issue as figured it was more for the heating system....

This has lasted about a week however as last night, despite the usual 8pm heat up, when my partner went for a shower about 2 hours later, there was no hot water. She was not happy!

This morning I checked the expansion vessel again and this showed 2.7bar, down a bit from its recommended 3.5 so I hit the 1hr override - but the boiler did not fire.

I tested the heating - worked fine, which means the boiler is ok as I understand it - is that right?

When I press the override button I can hear the zone value working.

As the weather is so warm, our heating isn't on at present and programmer is set to manual - but this cant have a bearing as its been like this for several weeks now.

I've also read that this particular boiler doesn't heat the water - which would seem right as there is no "tap" symbol on the boiler display, only a radiator symbol. I've always understood this to be the case but what confuses me is why does the boiler come on when programmed to heat at 8pm, and when I hit the override? I understand the Santon heats the water but how does it do this, what relation does the boiler have to it?

So I believe the boiler is ok, the expansion vessel and programmer - so it must be the Santon - but what could it be?

Please can someone advise what the issue might be? I thought I had it sussed by pressurising the expansion vessel (although must admit I wasn't sure why this would make a difference - but it did last week) but with that seemingly ok (despite being down a tad), we still don't have hot water.

Many thanks in advance..

 

[Ciderspace]

Right, bit of progress having found the Santon troubleshooting manual! Tried the classic power off/on of the Santon heater itself (had tried the boiler previously). Hit the override on the programmer and the boiler fires! Should mean we have hot water shortly... So will see how long this lasts but think will get the Santon guys in for a checkup....

 

[Gasguru]

You are completely misunderstanding your heating/hot water system.

The white expansion vessel has nothing to do with whether the boiler will heat the water.

The boiler heats water that is then circulated through a coil within the cylinder...heat transfer takes place between this water and the domestic water within the cylinder.

Have a read up on S plan systems...although you will have a 2 port zone valve for the cylinder and another 2 for the heating zones.

Simplifying it...when there is a programmed on time (or you hit the overide) AND the cylinder thermostat is calling for heat (ie. the stored hot water is below the thermostat setpoint) the cylinder zone valve operating motor is energized. The motor opens the zone valve and once the valve is open a microswitch inside operates sending a 240V AC signal to the boiler/pump to fire up.

I suggest you take a look at the cylinder zone valve...it's probably a Danfoss and there could be a problem with either a weak motor (valve doesn't open sufficiently), a failing microswitch or a partially seized spindle (it rotates 180 degrees and should be relatively easy to turn).

 

[Ciderspace]

Thanks Gasguru, for confirming my clear misunderstanding of this! And thanks so much for your response.
Ok, so the cylinder zone valve is a Honeywell 272848 t50 brass ts88. It is very hot to touch - is that normal?
The boiler is still operating - have not tested for hot water as yet...
At the rear of the cylinder zone valve is a switched which is in the "Auto" position.
I am (clearly) unqualified to make any changes to the system and will call someone in, I just wanted to get a better understanding on the issue before I get fobbed off with this/that.

 

[Ciderspace]

We have very hot water.....
Re the Honeywell cylinder zone valve - when I first checked, I was able to move the manual override freely - no resistance. Having had the boiler firing for the past 25 mins or so (its since gone off), I now feel resistance when moving to manual, at which point it then works its way smoothy back to Auto. I can hear it working (a very nice sound I must admit!) and I understand this is set to a Hot Water System only). I assume this is a good sign at least.
Surprised the boiler went off after just 25 mins though so I'm sure there is still an issue, just need to isolate it but at least I have a better understanding of where the issue might be.
I am not electrically qualified but having read up here (http://www.freeheatingadvice.com/articles/honeywell-motorised-valve-faults/#manual_lever) - I might be able to do a bit more digging - possibly replacing the valve motor/powerhead (a 4000 3916 - 001) looking at this page (https://heatingcontrols.honeywellhome.com/products/Valves/Motorised-Valves/V4043-Motorised-Valves/) - this is what I have.
Any more thoughts greatly appreciated...
Thanks

 

[ianmcd]

If you are calling someone out, tell them that you have an unvented cylinder as a separate qualification called G3 is required to work on the cylinder if the fault lies there, leave the expansion vessel alone that is not the fault and you are doing it completely wrong, mention to who you call out that you have messed with the expansion vessel and they should be able to sort it they way it should be

 

[Ciderspace]

Thanks ianmcd, I will do.

Re the expansion vessel - when I had the boiler last serviced, the guy showed me how to repressurize it, hence why I thought Id fixed the problem last week when we had hot water again.