Vaillant VRC 430f cycling issues - a solution?

[smokebox]

sounds like a lot of the confusions is being caused by poor translation of the user manuals.

Exocet - im sure you had your reasons but i am curious as to why you did not just wall mount the VRC430 instead of fitting a VR81?

Purely for aesthetics. The VR81 is about the size of a standard Room Stat, the 430 is just too big, ugly and confusing to use. In theory at least the VR81 will allow my wife to turn the temperature up, she'd never be able to drive the 430.

Exocet
To begin with (largely because of curious instructions I think) it is easy to be frightened off the VRC430. This is especially true off the inconsistent wording in translation, quite apart from the opaque "meanings " and "descriptions" of functions, but actually this is really only really bad and difficult on the installer or technical settings side of things.

At the up-front "user level" I quite soon found it very clear and helpful! Where else do you get a nice single screen setting out time/ temp periods for a whole day or even week adjustable at touch of button?. I like it now and can race through it with ease, even right through to the "A" level screens, checking things as one goes, and contemplating. It even gives you time to think with each screen before dimming out, and it still holds its place for a while.

Much quicker and neater than operating sequential single button pushes on other programmers for each single item set , (sometimes multiple careful button presses as you approach a desired temp or time), around in general. IMHO !

While quite big, and you clearly don't really like the lovely blue screens and aesthetics [you got to admit you can see them easily] I am now a convert.

Let the wife have a shot at user level, (if you give her control rights on such vital matters!)

smokebox

 

[exocet]

sounds like a lot of the confusions is being caused by poor translation of the user manuals.

Exocet - im sure you had your reasons but i am curious as to why you did not just wall mount the VRC430 instead of fitting a VR81?

Purely for aesthetics. The VR81 is about the size of a standard Room Stat, the 430 is just too big, ugly and confusing to use. In theory at least the VR81 will allow my wife to turn the temperature up, she'd never be able to drive the 430.

Exocet
To begin with (largely because of curious instructions I think) it is easy to be frightened off the VRC430. This is especially true off the inconsistent wording in translation, quite apart from the opaque "meanings " and "descriptions" of functions, but actually this is really only really bad and difficult on the installer or technical settings side of things.

At the up-front "user level" I quite soon found it very clear and helpful! Where else do you get a nice single screen setting out time/ temp periods for a whole day or even week adjustable at touch of button?. I like it now and can race through it with ease, even right through to the "A" level screens, checking things as one goes, and contemplating. It even gives you time to think with each screen before dimming out, and it still holds its place for a while.

Much quicker and neater than operating sequential single button pushes on other programmers for each single item set , (sometimes multiple careful button presses as you approach a desired temp or time), around in general. IMHO !

While quite big, and you clearly don't really like the lovely blue screens and aesthetics [you got to admit you can see them easily] I am now a convert.

Let the wife have a shot at user level, (if you give her control rights on such vital matters!)

smokebox

Smokebox

I actually quite like the blue back lit display....just don't have a nice discrete place to hide it. If it were designed to be recessed into a wall it might we acceptable but instead it stands very proud...probably to allow for accurate temp reading.

Don't see what this would achieve anyway? The 430 has the same option with respect to control as the vr81 I.e you can select Thermostat or Modulation when mounted external to the boiler. Surely the resulting operation would be the same I.e if I select modulating, the boiler will still behave in the way that I have observed?

Are we all clear on what modulating option means? The boiler on its own will modulate according to load. You can set the d0 value to limit max burner rate. Introducing the 430 with external temp sensor will set Target flow temp depending upon heat curve selected. The boiler will then modulate to maintain that flow temp....more or less. The VR81 option extends user control to a more convenient location and acts as an internal temp sensor. Is the consensus that the modulating options provides greater control over the burner I.e a more gentle 'ramp up'?

Surely the boiler gets enough feedback from the CH Return sensor to allow it to modulate effectively? As you can tell, I have lots of questions about this configuration!!

 

[smokebox]

Joemar
I have had an experienced vaillant installer today, but these difficult questions were beyond him, though he was very good and helpful in other rather rarified vaillant wiring matters concerning control of the DHW with the VR61 'mixer' as they call it.

I have been ill and am to go into hospital tomorrow.
Hope to be in touch again

smokebox

 

[UpgradeME]

Joemar
I have had an experienced vaillant installer today, but these difficult questions were beyond him, though he was very good and helpful in other rather rarified vaillant wiring matters concerning control of the DHW with the VR61 'mixer' as they call it.

I have been ill and am to go into hospital tomorrow.
Hope to be in touch again

I hope all is well and we see you again on here soon!

exocet, I believe that without an "intellegient" control such as the VRT392/VRC430 the ecoTEC boilers WILL modulate based on the return water temp. i.e. lower the gas kw/ouput as necessary

However, this will be based on a static water temp. Using a modulating "Intelligent" control (such as VRT392/VRC430) the WATER temp will modulate along with the GAS usage i.e. Boiler will modulate gas kw based on return temp and will modulate water temp based on VRT392/VRC430 request.

Although slightly different, there's some intesting discussion on this in my threads from last year here , here and here!

 

[exocet]

Thanks UpgradeME.

I understand the principle of modulating the water temp by using the VR 430 with external temp sensor. This has been working well for me for over a year.

So, the boiler can modulate according to return flow temp. The Target 'set point' can vary according to external temperature which in turn will influence the burner rate (modulation). So what else is there to modulate when you select the modulation option on the Room Temp Control Parameter? And, when I select this option, why does my boiler fire up when there is no apparent demand for heat (Target room temp set to 20 deg, actual measured room temp as indicated on VR 81 is 21? Setting this parameter to thermostat, the boiler behaves are I would expect i.e room temp higher than Target temp, no demand, boiler does not fire up.

Perhaps I should have left it to work that out for itself? I only tried it twice, leaving the boiler to run for a couple of minutes eqch time. Trouble was, house wed warm enough already!

Thanks for your input. I'd love to write my own user guide one day, once I've worked it out.

 

[David937]

I would have thought it was trying to run continuously to maintain your selected room temperature, your minimum flow temperature of 39ºc is likely to still have been too high to maintain this so the house began to overheat, I'm guessing it would have eventually switched itself off.

 

[JoeMar]

Joemar
I have had an experienced vaillant installer today, but these difficult questions were beyond him, though he was very good and helpful in other rather rarified vaillant wiring matters concerning control of the DHW with the VR61 'mixer' as they call it.

I have been ill and am to go into hospital tomorrow.
Hope to be in touch again

smokebox

hi
i hope you feel better soon.

joe

 

[JoeMar]

Thanks UpgradeME.

I understand the principle of modulating the water temp by using the VR 430 with external temp sensor. This has been working well for me for over a year.

So, the boiler can modulate according to return flow temp. The Target 'set point' can vary according to external temperature which in turn will influence the burner rate (modulation). So what else is there to modulate when you select the modulation option on the Room Temp Control Parameter? And, when I select this option, why does my boiler fire up when there is no apparent demand for heat (Target room temp set to 20 deg, actual measured room temp as indicated on VR 81 is 21? Setting this parameter to thermostat, the boiler behaves are I would expect i.e room temp higher than Target temp, no demand, boiler does not fire up.

Perhaps I should have left it to work that out for itself? I only tried it twice, leaving the boiler to run for a couple of minutes eqch time. Trouble was, house wed warm enough already!

Thanks for your input. I'd love to write my own user guide one day, once I've worked it out.

hi all

i've been doing a bit more reading on this...here is one thing i found interesting in the VR61 manual. On Page 9 (4.4 - hydraulic drawing 4) in bold letters it says that 'Thermostat' must be set for both zones to ensure proper temp control. in this diagram, both Zones are controlled by 2 Port motorised valves.

in all the other diagrams Zone2 is controlled by a motorised mixer valve. here's how i think this works (please dont quote me on this): assume VR81 is installed in Zone 2, set to 'modulating' - it will try to maintain the target room temp by constantly adjusting the flow temp via the motorised mixing valve. the key component here is 'motorised mixing valve' - not to be confused with 3-port valves.

in 'thermostat' mode, it is simply a case of - shut valve when target temp is met and open valve when room temp falls below a certain level - 2 port valve behaviour.

Exocet - i think this may answer your question - "So what else is there to modulate when you select the modulation option on the Room Temp Control Parameter?

of course this is MY interpretation/opinion from what i've read and understood and may need correcting.

Joe

 

[exocet]

I would have thought it was trying to run continuously to maintain your selected room temperature, your minimum flow temperature of 39ºc is likely to still have been too high to maintain this so the house began to overheat, I'm guessing it would have eventually switched itself off.

I can understand your thinking but my question would be "why try to maintain a preset flow temp (39 deg) if the desired room temp has already been reached"?

 

[exocet]

Thanks UpgradeME.

assume VR81 is installed in Zone 2, set to 'modulating' - it will try to maintain the target room temp by constantly adjusting the flow temp via the motorised mixing valve. the key component here is 'motorised mixing valve' - not to be confused with 3-port valves.

in 'thermostat' mode, it is simply a case of - shut valve when target temp is met and open valve when room temp falls below a certain level - 2 port valve behaviour.

Exocet - i think this may answer your question - "So what else is there to modulate when you select the modulation option on the Room Temp Control Parameter?

Joe

That sounds like a plausible interpretation - surely they should state this in the manual though i.e. When using single zone heating, set this parameter to THERMOSTAT?

 

[smokebox]

There is much that should surely be said in and about the Vaillant manuals!
smokebox

 

[David937]

I emailed Vaillant technical and their reply was:

The VRC430f should be set to 'Thermostat' and mounted in the main living area. They did not explain what 'Modulating' is even though I asked quite nicely. Anyway, I'm not too fussed about it now as my system is running really smoothly now with the VRC430f set to Thermostat. It's only on for 2 hours in the evening and 2 hours in the morning (3 on weekends) at the moment.

 

[Gary27]

I would have thought it was trying to run continuously to maintain your selected room temperature, your minimum flow temperature of 39ºc is likely to still have been too high to maintain this so the house began to overheat, I'm guessing it would have eventually switched itself off.

I can understand your thinking but my question would be "why try to maintain a preset flow temp (39 deg) if the desired room temp has already been reached"?

I am new to all this but have been trying to understand what is going on in my new installation. But I did think the idea of this cleaver system was that it could maintain a temperature based on conditions such as outside temperature and not just switch on and off like a regular thermostatat, although still modulating.

 

[Agile]

Weather compensation in its simplest form does just that, looks at outside temperature and sets a boiler flow temperature which is expected to provide the required temperature. It can do this because the heat loss is expected to be proportional to the outside temperature. Getting this to work well requires adjusting the curve used by the device, e.g. when its 5 C outside the boiler flow temperature might be 60C.

In reality its not always so good. For example a force 9 gale greatly increases heat loss and draughts.

Another way the simple concept falls down is when the outside temperatures are changing rapidly such as at sunrise and sunset.

Its possibly that some controllers do take those changes into account and modify the boiler control. Unfortunately it seems a general principle that makers do not want to give any details of exactly their products work. Maybe thats because of commercial fears, others copying their ideas or just because they think that all plumbers are thick!

Alex, our forum expert on WC is currently on holiday in Thailand otherwise he would be adding pages on the topic.

Its best for the controller to also look at inside temperatures as well. The excellent Worcester controller enables the user to set the percentages that the unit assesses the inside and outside temperatures.

Tony

 

[Gary27]

I emailed Vaillant technical and their reply was:

The VRC430f should be set to 'Thermostat' and mounted in the main living area. They did not explain what 'Modulating' is even though I asked quite nicely. Anyway, I'm not too fussed about it now as my system is running really smoothly now with the VRC430f set to Thermostat. It's only on for 2 hours in the evening and 2 hours in the morning (3 on weekends) at the moment.

I called Vaillant technical today as well and they confirmed that if the VRC430 was away from the boiler and used as a thermostat you should also set it as thermostat not modulating. They said modulating was for when you had no thermostat and it would use the outside temperature and the curve setting to set the temperature. So I presume you would keep altering the curve until it gives you an exceptable temperature.

They also said for me the curve should be set at 2.3.

Also I have set my minimum temperature to 50c and that seems to stop most of the cycling.