Vaillant heating predictions etc.

Hi all, I've been trawling the Internet for advice and came across this forum which looks like it's full of helpful and knowledgeable people! We've also tried contacting Vaillant but advice has been inconsistent and I'm not sure it's been altogether helpful.

We had a new Vaillant combi boiler installed in September, along with new radiators and the vsmart thermostat / app. The radiators do get hot and the house is warm. The thermostat is in the hallway on an internal wall. The thermostat works on weather compensation controls and predicts when to turn the boiler on so that the house is up to temp (set at 19 degrees) by the desired time. Our problems are as follows:

1. On a cold morning, such as yesterday, the heating comes on up to 3 hours before the desired time so I'm having to set the desired time later, which seems crazy. Yesterday the desired time was 9am, the heating came on at 7.01 and reached temp at 10.09. Now, really our desired temp should have been 7am but there's no way we want the heating coming on at 4am or even 5am. Does this sound right??? I just can't accept that it's normal for the heating to come on 3 hours before the desired time. We don't want to be sweating in our beds every morning.

2. After researching, we increased the heating curve from 0.9 (Vaillant advised 0.7) to 1.7 but this morning the heating still came on 2 hours before the desired time but this morning it had reached the desired time an hour early. (We had this happen a couple of months ago, Vaillant told us to set the heating curve back to 0.7, set the algorithm to basic / hysteresis and turn heat prediction on (they had previously told us to override heat prediction and use it as a normal boiler). I also reset our weekly schedule by going through the questionnaire on times we get up, go to bed, etc. again and things were a lot better until the mornings turned frosty when it's coming on 3 hours early.....

I hope I'm explaining this well enough, it's all a bit foreign to us and we really need some good solid advice.

Please could anyone advise us on whether this sounds normal, what settings should we use (heating curve, algorithm) and any other advice? Thank you in advance.

SparkeyD

SparkeyD said:

On a cold morning, such as yesterday, the heating comes on up to 3 hours before the desired time so I'm having to set the desired time later,

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You are fighting this function :

SparkeyD said:

heat prediction

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Doing this :

SparkeyD said:

also reset our weekly schedule by going through the questionnaire

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Screws up the unit's ability to learn.

I'm not going to go into my thoughts on Vaillant products, but these intelligent controls do behave in this manner. Think of the schedule as a target and let the controller work to achieve it.

They did work life the old fashioned clocks and twiddly mechanical thermostatic.

Thanks for your reply. How long should it take to learn that it only takes 1 hour to reach temp, not 2? Any further help or advice would be greatly appreciated!

What is you setback temp set to? The colder you let your house get the earlier the heating will come on, especially on very cold nights

I'm not a great fan of the heat prediction capability of my Nest thermostat and switched it off after a few months because, like your Vaillant, it was firing up the heating hours before anyone was due to get up in the morning.

If the vaillant prediction can be disabled in the same way, you may decide to take back full control of when the heating comes on.
The only downside is that it may not quite reach the target temperature, but taking the chill off the house in the morning was always good enough for me.

Lower the curve further or set a higher set back. The idea is to rub the system and boiler at a lower rate for longer to achieve comfort setpoint.

If you expect the rads to be pinging off the wall and glowing hot only 20 minutes before the on time then it won't be compatible with you.

The logic of the unit is continually learning but it should dial in after a few days. One thing all these predictive start thermostats hate is people fiddling.

Thank you for your replies...

If by setback temp you mean the night temperature I've set it yo 12 degrees as I don't want the heating coming on during the night...is this too low?

Re. The heating curve, I read on here that it should be set at about 2.3 whereas ours was 0.9 so I am feeling a little confused as the lower the curve the longer it takes to heat up.

Yes, we can disable the heat prediction but then there's no point having had this type of system installed, but it may be that we do end up doing that in the end.

Today, the desired temp was 19 degrees at 9am. Heating came in at 6.38 and was up to temp at 7.39!!! We were all asleep in bed, I done up sweating and overrode the system so the heating went off. I just can't understand it.

Perhaps @Bunnyman or one of the other Bunnies can shed some light into how these Vaillant specific stats work.

Its doesn't matter what time it comes on - its when it hits set point. Which should be just before the programmed time. If it can't manage that then there is something wrong.

Predictive stuff can work - as can be seen by my system - here's my bedroom:



It is set to be 22 degrees at 6am. It switched that room on at 4:30 ish (i have room level control of my system). The max flow temperature of the boiler for heating is 55 degrees. I very rarely touch my heatign controller.

Thanks for the info. I'm wondering if there's something wrong, have we got a wrong setting set up somewhere or something else. I just feel like we are going round in circles, it's been 4 months now and there's so little info online and we get different answers from Vaillant, if we can get through to them that is. It's very frustrating.

Yes, I agree, it should be at the desired temp at the right time (give or take), however, I don't think it should be coming on 3 hours before, that seems crazy.

Like i said - on time is not important... its the time it hits setpoint.

My parents have a VRC430 and on that you could set the maximum 'preheat' time. I set it up for a maximum of 90 minutes and it works brilliantly, not sure if the same can be done on the newer Vaillant controls.

I've not seen anything that mentions a maximum preheat time. Sounds like it would be a good feature though! There is so little guidance.

If you want a predictive thermostat, then you install it, set the times & temperatures once and then never touch it again. You do not choose anything about how or when it operates, it's totally automatic. That's the whole point of it.

Alternatively get a rotary dial mechanical type and a timer. Then you can tamper with it continually for the rest of your life.

Predictive thermostats are not compatible with some types of people. Often the same ones that buy them, imagining they will save vast sums on their heating costs.

flameport said:

If you want a predictive thermostat, then you install it, set the times & temperatures once and then never touch it again. You do not choose anything about how or when it operates, it's totally automatic. That's the whole point of it.

Alternatively get a rotary dial mechanical type and a timer. Then you can tamper with it continually for the rest of your life.

Predictive thermostats are not compatible with some types of people. Often the same ones that buy them, imagining they will save vast sums on their heating costs.

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then when the fiddlers get someone in and they say they haven't touched it and it was set up like that , god i hate fiddlers , if they do fiddle then say so because its only costing them in the end

I get what you're saying but when you're asleep in bed and the heating comes on at 4am and the house is boiling an hour before you want it to be and everyone is asleep or been woken up sweating....what do you do then??? That can't be right surely?