Vaillant control optimisation

[DH2]

Hi all.

I'm trying to optimise the working on my new boiler and control system, which is specced as follows:
Vaillant EcoTEC Plus 415 open vent boiler
Vaillant VRT360 room thermostat
Vaillant VR65 control center
which are interconnected using eBus.

Using existing Y-plan hot water 230v controls:
Cylinder thermostat
3-way valve
which are connected to the VR65.

It mostly seems to work well, and is so much quieter than the outgoing Potterton Suprima! But I'm having a few niggles in trying to optimise it, so a small collection questions...

The room stat is installed in the hallway, but it is a small 'room', just 1.5m x 1.5m, with the front door, stairs, and a radiator (no TRV).

1. I'm finding the current temperature reported by the room stat is a little slow to react to changes in the room temperature.
There is an adjustment on the stat called "Control characteristics/route adjustment" which is explained as "For optimum adaptation to the room size or radiator configuration. Default setting: 0. Adjustment range: -5 ... +5 (Positive values: room thermostat switches more slowly; negative values: room thermostat switches more quickly)"
Does this relate to the speed at which the current temperature is updated, or does it more mean the range around the set point temperature that the stat will switch at?

2. I am finding that the boiler gets itself into anti-cycling mode, quite easily. I've not had time to sit and monitor its exact behaviour yet, but I think it heats up quite happily for a while, including modulating itself down, then I assume the return flow gets a bit warm, so it turns off. After the pump overrun, it comes back on, but at full load, so turns off again before it has thought about modulating down. It then sits in anti-cycle mode for a while.
Is there an optimal way to set the flow/return, overrun/anti-cycle settings in order to minimise this? I believe it is going anti-cycle before the room is up to temp (though am not 100% on this yet).

3. It was my understanding that the hot water temperature control on the boiler, should only have any effect if I have a Vaillant UniStor connected using the sensor provided with the VR65. However, adjustment of this control during water heating, causes the boiler to switch out/in. Yet in water heating mode, the boiler appears to run the circulant at 80c regardless of anything else (whilst the cylinder stat is indicating a demand
for heat). What should I set the hot water temperature control on the boiler to?

4. I've read a couple of times on this forum that the radiator flow temperature control on the boiler should be set to maximum, and that the VRT360 will sort the rest out. Not sure I understand how the VRT360 is able to do this? What is the optimum setting for the radiator flow temperature on the boiler? I have it set to 65 and find the rads are really hot to the touch (but I'm a sensitive flower!).

5. What is the "Two-point/analogue operation" mode on the VRT360? I don't know what the difference is between these two modes?

Sorry it's quite long, I am trying to describe things as accurately as possible. Thanks for hanging in until the end, and in advance of any advice.

DH2

 

[gas4you]

The 360 won't adjust the flow temp of the water leaving the boiler.

You would need the VR400 or 430 to do this.

With the VR65 I would set the system temp to 60C on the boiler, then as you rightly point out, the VR65 will increase this flow temp when the HW reheat is demanded.

The system will be slightly confused the way yours is set up as ideally the VR 65 wants the VR10 cylinder NTC and the HW temp would be set on the VRT360, along with the HW on times.

 

[DH2]

The 360 won't adjust the flow temp of the water leaving the boiler.
You would need the VR400 or 430 to do this.

Actually, since my first post earlier, I've discovered the answer to my original question 5. In two-point mode, the VRT360 behaves like a traditional thermostat (i.e. demand / no-demand for heat). In analogue mode, it communicates the required flow temperature to the boiler over the eBus, by comparing the set and actual room temperatures. So it does adjust the flow temp down, as the room temp approaches the set temp. This is visible in d.5 / d.9 on the boiler.

With the VR65 I would set the system temp to 60C on the boiler, then as you rightly point out, the VR65 will increase this flow temp when the HW reheat is demanded.
The system will be slightly confused the way yours is set up as ideally the VR 65 wants the VR10 cylinder NTC and the HW temp would be set on the VRT360, along with the HW on times.

As regards the hot water, I have already set the hot water on the boiler and room stat to 60c (this was Vaillants advice also), as if I lower this, it causes the boiler to turn off, despite an ongoing demand for heat by the cylinder stat. I don't understand why the boiler takes any notice of this setting when the VR10 is not present.
I agree that ideally I'd use the VR10 sensor, rather than a cylinder stat, but that requires an expensive new cylinder! The VR65 seems to simply demand 80c flow temperature when there is a demand for hot water anyway, regardless of what is set anywhere else. This is presumably because the VR65 knows the VR10 is not present.

Now I need to understand the slow reaction of the room stat, as it seems to be getting better at warming things up, but being slow in reacting the the temperature coming back down again (original question 1.), so things aren't ticking over very smoothly yet.

Thanks for your help.

DH2

 

[DH2]

Sorry to keep whinging on, but its really annoying me now.

I'm running in analogue mode, so the stat is giving a required flow temperature to the boiler over the eBus. However, this evening, the current temp read by the stat, was above the required temp, but it was still requesting a flow of 30-odd. This caused the boiler to cycle like it is going out of fashion.

The room stat is real slow to react to the room temp falling, it is currently reading 18.5c, the room temp is actually 17c, the set temp is 18c, and its requesting a flow temp from the boiler - that can't be right?!?

I thought this new boiler and controls would mean I could keep the house temperature ticking over better than the non-modulating boiler with basic room stat it has replaced. In the end, I've had to switch it off, as the cycling is just annoying.
I guess I need to find someone who knows how to configure this Vaillant kit, unfortunately, that doesn't seem to be Vaillant themselves (so far).

DH2

 

[Guzzles]

Hi DH2,

the problems you are experiencing sound familiar to my situation. I have the Ecotec618, VR65 and VRC430. The instructions are poor and the support from Vaillant is just as bad. I think the units are quite complex, and can probably perform really well, but unless they are setup correctly, they are usless.

In answer to 2, have you balanced your radiators? If you have one rad returning hot water your boiler will cycle frequently. Also can the speed of your boiler pump be adjusted. My setup is 15 rads on 2 floors, and I set my boiler to always be on full speed. ( non-default).

I'm still having problems with my VRC430, but I will plod on. I wouldn't mind paying someone to sort it out, but all the Vaillant approved fitters round here have little knowledge of the units.

 

[simond]

You can use the thermistor control if you want, just slip the sensor under the insulation. Ideally there would be a dry pocket in the HW cylinder but this method is at least as accurate as your current cylinder stat.

Your problem does sound like a radiator balancing problem. If the hallway can't get up to temp as quickly as the rest of the house there will be cycling. Especially if there are trvs in every other room, if this is the case a bypass should be fitted.

It is true that the Vaillant controls will confuse most customers, which is why we are really careful who we recommend them to. VRC430 is the easiest to use, VRT360 the most difficult (ignoring VRC400 which has been replaced by VRC430)

90% of our Vaillant installs get Honeywell controls.

I suggest, and you are not going to like this, returning the boiler and the VRT360 to defaults, and see how it goes. You will not get anywhere trying to fine tune the controls if something else is wrong.

We fitted one of these set ups for an 'engineer' who altered everything and then expected us to come out and assist him. In the end we could only offer him support if he ran it in default (eg: factory) mode, because every time we went there all the d settings had been changed and the boiler was not behaving how we would expect.

It is the installer's responsibility to get the sytem working properly but any 'tuning' you do thereafter must be at your own risk. Many of the settings in the Vaillant manual can have deleterious effects if used in combinations; if you are not sure what you are doing, leave it in default mode.

 

[DH2]

You can use the thermistor control if you want, just slip the sensor under the insulation. Ideally there would be a dry pocket in the HW cylinder but this method is at least as accurate as your current cylinder stat.

I had wondered about that, but wasn't sure how it worked with the UniStor. I guess I can plug it in and see what temps it is reporting at the boiler. As you say, it can't be any less accurate than the electro-mechanical stat that is already fitted.

Your problem does sound like a radiator balancing problem. If the hallway can't get up to temp as quickly as the rest of the house there will be cycling. Especially if there are trvs in every other room, if this is the case a bypass should be fitted.

You could be right, balancing has always appeared to be a black art, and I'd be surprised if the developers ever did it when installing the system (house was built 9 years ago).
There are TRVs on 4 out of 8 radiators, and I have an automatic bypass valve installed. It's not really that it isn't getting things up to temperature, it just doesn't seem very good at keeping it there at the moment, as the room stat stays warm for longer than the room.

It is true that the Vaillant controls will confuse most customers

I can imagine, but I feel I understand it now, except its really not clear what "Control characteristics / route adjustment" actually does (in plain english!).

I suggest, and you are not going to like this, returning the boiler and the VRT360 to defaults, and see how it goes. You will not get anywhere trying to fine tune the controls if something else is wrong.

I hear what you are saying, but I've not changed anything, other than swapping it to analogue, rather than two-point, mode. I've even swapped that back now, as I'm beginning to believe the implementation of the analogue control is flawed because it requests a low flow temperature from the boiler when the current temperature is above the required temperature? For example, it woke me up early this morning, and when I checked what it was up to, the room temp was 1c above the set-back temp, and it was requesting a flow of 25c from the boiler (which it obviously achieved in about 2 seconds of burn).

I'll go and try to find out some information about balancing radiators.

Thanks for your input, it is very much appreciated, and hopefully useful to other people reading.

DH2