Random occurrences of no hot water

[fm1979]

Hi all,

I posted a few months ago about a 'no hot water' problem, and it turned out that it was a diverter valve problem.

But still, from time to time, not too frequently fortunately, we have only lukewarm/cold water in our taps/showers. What could be the problem?

- sometimes, the trick to have hot water in the shower is to open the tap and run the water in the adjacent sink. It 'forces' the water in the shower to come hot. It is just a bit wasteful to do that...
- sometimes this trick doesnt work.

It is a bit surprising as the programmer says that the hot water is on. Also, I can see that when it happens, the boiler (Vaillant home system 15) displays a temperature of 40-45 degrees. So not hot enough.

Eventually, the hot water comes back, maybe an hour later. So there is a delay. Again, it is very random and fortunately not too frequent, but still a bit annoying.

Any clue? Thanks in advance for your thoughts.

 

[Deleted member 120897]

I’m a little confused by this, as you mention a diverter valve and system boiler. If you have a system boiler, the chances are there’s a control fault, so possible 2/3 port valve issue.

 

[fm1979]

I’m a little confused by this, as you mention a diverter valve and system boiler. If you have a system boiler, the chances are there’s a control fault, so possible 2/3 port valve issue.

well, I was a little confused too when the engineers fixed the thing. He really changed a 'diverter valve' as he said, and we do have a 'system' boiler.

 

[Deleted member 120897]

Can you post a photo of your cylinder cupboard?

 

[fm1979]

I have attached some pictures. Again, I'm no expert, but I'd like to understand my system. Thanks!

 

[Deleted member 120897]

You have an unvented hot water cylinder, so likely a system boiler, and an s plan plus. Valve looks like Honeywell, so if it’s been replaced it’s unlikely it’s failed, although not impossible.

 

[Chuck]

You have an unvented hot water cylinder, so likely a system boiler, and an s plan plus. Valve looks like Honeywell, so if it’s been replaced it’s unlikely it’s failed, although not impossible.

The OP mentioned that he has a "Vailant home system 15" boiler, which IIRC has a 3-position internal diverter valve that can be CH only, both CH and HW, and HW only.