Vaillant VRC470f controls very slow temperature change

[IndigoElectron]

I hope someone can help with a problem we are having.

We had a new Vaillant Eco Tec 831 and VRC 430f controls installed in July. We have had no end of problems with the controls - our installers didn't know how to set them up, and neither did the first Vaillant engineer who came out! We also had issues with the RF signal being weak, but this was resolved by hardwiring the RF unit into the boiler.

It seems to be working ok now, but we are still having ongoing problems with the controls. We have it set to thermostat as advised by Vaillant (heat curve around 2.3, I am still tweaking this though), the problem is that it takes ages to respond to changes in temperature. For example, it felt cold yesterday, and the controls were reading 20.5 (it felt colder than that). I put the heating on and it warmed up noticeably, but when I looked at the controls (at least 30 minutes later), the temperature hadn't changed at all. It only ever reads between 20.5 (heating off) and 22.5 (heating on), even when I have had windows wide open or the heating turned right up (with the house boiling!)

I have mentioned this to Vaillant several times and they said it takes a while to respond, but surely it shouldn't take that long? I tried taking it outside and the temperature did drop lower, but it took some time.

Is this normal for these controls, or have I got a faulty one?

Thanks in advance.

 

[ALEC1]

I would change the control strategy to thermostat or modulating in installer settings...

2.3 is probably way to high for comfort in London, I find most are around 1.7-1.9...it won't matter too much if you use the sensing capability of the table unit...

I would also not fixate either on the controls or the radiators...much better to be comfortable..if you want to monitor room temperature do so with another thermostat...

it is indeed shocking that vaillant don't understand their own controls I agree...

 

[Bunnyman]

Set curve at 2.3 not 1.7 set modulating stat in installer settings as Alec said. If the rads r sized ok temp rise should be gradual, I have a 430 in my house obviously and it's great control. If it says its 21.5 deg inside trust me it is accurate. R u feeling cold because the rads are warm not hot I wonder? This is a common mistake wit the new weathe comp controls, they r supposed to be warm and the flow temp will respond according to the temp differential required

 

[David937]

Just a thought, if the OP's Vaillant was installed in July, should they not have got a VRC470f which replaced the VRC430f?

 

[Bunnyman]

Mmm that's a good point?

 

[IndigoElectron]

Thank you all for replying and sorry for the slow response.

David, it is the 470f

Alec and Bunnyman, why set it to modulating rather than thermostat? The senior engineer who came out to help me set it up said it was better to leave it on thermostat...

Alec, I understand that you mean about concentrating on comfort, but the problem is that I'm not comfortable! When the heating is off I get cold, so the controls should show the lower temperature, and when the set back temperature is reached the boiler should kick in. But the thermostat doesn't seem to respond to the temperature change, so the boiler doesn't come on. The example I gave was when it felt cold, the controls read 20.5 C, I turned the heating on, it warmed up considerably, but the controls still said 20.5 C! Also, it sometimes feels too warm, but again because the temperature on the controls doesn't change, the boiler stays on and I have to turn the temperature down.

Bunnyman, when I said I felt cold, this is when the heating is off, and the radiators are therefore cold. I understand how the weather compensator works and how the flow temperature is adjusted automatically, although I only learned this by looking on the internet, my installer didn't have a clue!

Regarding the heat curve, I thought the idea was to tweak it until we were happy with the temperature. E.g. if the room temp. was set to 22C, but it was taking too long to reach that temperature, we should increase the heat curve. And vice versa, if it was getting too hot.

Anyway, Vaillant are coming out again tomorrow to look at it and possibly replace the controls.

One more thought - does it make much of a difference where the controls are placed? They are in the dining room which goes straight onto the lounge (sort of open plan), but they are above the piano and below the box for the house alarm system. I wonder if they are too sheltered.

 

[Bunnyman]

If the control is showing 20.5 and does not alter wgen u turn the heating on it may well be faulty, i have this setup in my own house (obviously )
It works excellent, the senior engineer may have been making it simpler for u by using stat, but as alec said modulating is better it smooths out all the bumps , keep us posted

 

[ALEC1]

What is the set back temperature?

Modulation works around the curve by a small margin so if the curve is too high modulation won't shut the boiler down

Thermostat shuts things down within a small margin too and ignores the curve.

In an idealised heating system there will always be heat in the rads when it is colder than the two set points...

With a condensing boiler that enhances boiler efficiency..

 

[ALEC1]

also, there are three strategies for set back, Eco, setback and frost protection..

By default it is in ECO, you Ned to change this to setback

 

[IndigoElectron]

Thanks for the replies.

Alec, the temperature is set at 22C for when we want the heating on, the set back temperature is 18C but it never goes down to this.

It was set to ECO until the Vaillant engineer changed it a while ago, it is now on set back and has been for some time.

I don't quite understand the following - could you explain further please? For example, how do I know if the curve is too high?

Modulation works around the curve by a small margin so if the curve is too high modulation won't shut the boiler down

Thermostat shuts things down within a small margin too and ignores the curve.

Thanks

 

[ALEC1]

It gets too hot if its too high and not hot enough if its too low.

It is I am afraid trial and error over time... although I find I can get it correct a lot of the time...

You will become surprised as to how effective heating is with radiators at low temperatures

 

[IndigoElectron]

So, the engineer came and eventually agreed that the controls were faulty - this was after I opened all the windows and doors to get the
house really cold, and the temperature on the display didn't change at
all!

Anyway, he replaced them and said they should work from now on. He also said that the position of the controls may not be that good, because they are quite sheltered, so to move them to a more open position where they can better measure the air temperature.

I tested the new controls that evening - I turned the heat
curve up to maximum, and the desired temperature to 30C, to see what
happened. It still took quite a long time for the temperature on the
display to increase, even when I put the controls near a radiator.
They did eventually get up to 30C, but what is strange is that when I
took them away from the radiator, the temperature continued to
increase and went up to 30.5C. So I have come to the conclusion that these controls are just not very good!

 

[Bunnyman]

No im sorry u just dont understand them, there main fault is they are difficult to understand, i have one an it works perfectly

 

[IndigoElectron]

In what way don't I understand them? Can you give me some information that might help me understand them please?

 

[ALEC1]

lol... It's only software and electronics and my customers are very satisfied with them...and it's pretty well all I install..

Over engagement with out understanding will lead to frustration...


Best to let them do what they need and you get on with your life..