Vaillant home system boiler - hot water only mode.

[akz786]

Hi Guys

So its a new build house (frowns lol) - moved in last year, just realised when I switch the boiler to hot-water mode only using mode on the boiler. You can see the valve moving upstairs but the boiler will not fire up.

In both heating and hot-water mode, all works fine.

The guys from the customer service team are trying to fob me off by saying it has to work this way.

My argument is that the manual even states I should be able to set hot-water mode only (in summer for example) and then the boiler fires up to heat the tank.

System as follows:

- Valiant Home System 15 boiler
- Thermaq evocyl tank
- 2 heating valves (dual zone) and 1 hot water valve
- Honeywell St9100c water controls.
- Honeywell room stats (upstairs and downstairs)

Any ideas what could be wrong?

 

[ianmcd]

yes you should be able to have HW only, it is still under warranty so tell them to sort it

 

[CBW]

I agree with @ianmcd about the warranty. Are you able to take a photo of cylinder cupboard showing tank and zone valves configuration? We can advise you so you can get them to sort it. Incidentally, which housebuilder?

 

[akz786]

Sure I’ve tried to capture it all in one shot. The builder is Lovell’s.

 

[ianmcd]

Yes your system can give you individual control of all zones , you have a fault tell them to sort it

 

[akz786]

I thought as much, thanks guys really appreciate the prompt response.

They use a contractor called Rolec who came over today and are convinced this is how it works.

I was even told it’s a display from a combi-boiler which I quickly dismissed as I know that’s not the case.


Could it simple be a wiring problem?

 

[CBW]

Sure I’ve tried to capture it all in one shot. The builder is Lovell’s.

- Lovell’s, they built houses for the firm I’m with, put all the 8.5kw showers on 6mm cable, when it should have been 10mm, they wouldn’t put this right, as they said it’s correct.

As for the fault, I would say wiring or pipework configuration, but hard to see from that photo and I don’t have my unvented ticket (not sure I found that’s relevant to the fault).

 

[muggles]

At the risk of disagreeing with various sage minds on here, I think the house builders are correct. The hot water only mode on your boiler, to the best of my knowledge, only works when the full suite of Vaillant controls are used. These have two-way communication between the boiler and the controls, allowing greater functionality which wouldn't normally be included on the kind of basic bargain-basement systems found in almost all new-build homes. You need to use your programmers/programmable thermostats to individually control the heating and hot water, not the boiler display

 

[snb]

you should have your boiler set to heating mode on the front. ( the hot water mode is there but is a universal control panel for use with combi boilers aswell).

your control for heating is via your programmable room stat and your hot water via your programmer in the airing cupboard.

Why do customers have to fiddle!!!!!!

If you read the manual with the boiler it clearly states this.

 

[akz786]

At the risk of disagreeing with various sage minds on here, I think the house builders are correct. The hot water only mode on your boiler, to the best of my knowledge, only works when the full suite of Vaillant controls are used. These have two-way communication between the boiler and the controls, allowing greater functionality which wouldn't normally be included on the kind of basic bargain-basement systems found in almost all new-build homes. You need to use your programmers/programmable thermostats to individually control the heating and hot water, not the boiler display

I think you could be correct, this is what the Vaillant tech support guy said to the Builders supposedly. Hmm ok

 

[akz786]

you should have your boiler set to heating mode on the front. ( the hot water mode is there but is a universal control panel for use with combi boilers aswell).

your control for heating is via your programmable room stat and your hot water via your programmer in the airing cupboard.

Why do customers have to fiddle!!!!!!

If you read the manual with the boiler it clearly states this.

Yes I understand that’s how it works right now, however the manual clearly states as a user, I can select modes of operation. Heating or hot water only or both.

I am struggling to understand how this is customer fiddling with the system?

 

[wannocks]

You have a system boiler without Vaillant controls. In this situation the boiler is a dumb heat producing device and doesn't know what the system is doing. The controls (thermostat and programmer) decide whether that heat goes to the heating or the hot water. The boiler will only operate in heating mode.

 

[akz786]

You have a system boiler without Vaillant controls. In this situation the boiler is a dumb heat producing device and doesn't know what the system is doing. The controls (thermostat and programmer) decide whether that heat goes to the heating or the hot water. The boiler will only operate in heating mode.

Thank you for this explanation. So Lovell's were correct in their statement to me.
Fair enough.

Will I be able to upgrade to Nest/Hive/etc easily?

 

[Harry Bloomfield]

You have a system boiler without Vaillant controls. In this situation the boiler is a dumb heat producing device and doesn't know what the system is doing. The controls (thermostat and programmer) decide whether that heat goes to the heating or the hot water. The boiler will only operate in heating mode.

Correct. One temperature setting on the boiler, for the boilers output temperature - though there are two appearing to be available only one has any effect. Second setting becomes usable when a Vaillant control system is installed [1].

Unless the installer has made an error, you should have the options of HW only, HW +CH, or CH only. It will be able to try to satisfy both HW and CH at one and the same time with basic controls - simultaineously.

If the controls are upgraded to the Vaillant ebus controls, then you will loose the ability to try to satisfy both CH and HW demands simultaneously - with demand for both, there demands will be satisfied sequentially. [1] This due to now having two independent boiler output temperatures settable via the boiler's front panel.