EcoTEC 428 with VR66 d.8 value 'static' with 3&4 connected?

Joined
7 Oct 2016
Messages
2
Reaction score
0
Country
United Kingdom
My first post, sorry it's so long but I'm assuming more information is better?

My system:
EcoTEC Plus 428 (circa 2010)
Megaflo 300L storage tank
2 x 2 port zone valves
VR10 HW tank sensor
VR66 wiring centre set to mode 1
VRT350F Roomstat/timer

Earlier this year, with the assistance of an extremely helpful electrician, I upgraded the control system for my 2010 EcoTEC Plus 428 from a standard tank stat, room stat and timer to the above. We re-purposed the original tank stat set to max as a safety cut out. The house is quite large and on three floors. Two circulation pumps were already in place when we moved in. During the upgrade, we wired the pumps so that the secondary pump only runs when there is CH demand. The primary pump always runs for HW, CH or HW & CH.

The reason for upgrading the controls was because I found the boiler incapable of efficiently heating just hot water (presumably due to being unable to distinguish between demand for HW or demand for CH) due to the boiler just firing up to max and then over-shooting in a never ending cycle until the timer shut it down. I originally got over this by d.0 range rating the boiler down to only 12kW during the summer, but it was only ever a temporary solution.

After fitting the new controls, I was able to d.77 range rate the boiler to 15kW for HW charging mode, plus it is now able to correctly modulate the output as the tank reaches its target storage temperature. The house temperature was managed comfortably. Everything seemed to be running well.

As we hit spring and the need for CH subsided, I set the VRT350f to 'Summer' mode, expecting the CH to stop running. In the main it did, but after a while, I noticed it would fire up randomly for a few minutes from time to time. It would do this even if the room temperature was already well above target, plus I thought Summer mode would inhibit the CH anyway. I couldn't think what was going on, but as a temp fix, I turned the 'Radiator' knob down to minimum on the boiler, which stopped it happening.

Now winter approaches, I'm reminded of this problem and have been trying to work out what's going on. The helpful electrician is coming back to take a look for me, but he's not a Vaillant genius, just a really good electrician and I'm no genius either. I need to do my research into the quirky EcoTEC to guide him before he comes. I'm looking at d.8 to see when there is demand, but note that with terminals 3&4 looped together, d.8 is always 1 and never 0, which I'd expect to see if there is no demand from either the VRT350f or the VR10. Strangely, a wire is connected to terminal 4 in the boiler, which I can't trace back (hopefully my sparky will know what he's using it for) even though theoretically I shouldn't need anything connected there with the VR66 & VRT350f. It might be something to do with the circulation pump arrangement or the tank stat safety cut-out. If I remove the term 3&4 loop, the HW works fine, but the CH will then only run if there is HW demand. I have a sneaking suspicion that the random CH firing is happening when HW is active in the VRT350f time settings, but not necessarily any HW demand via the VR10.

Obviously, we've got some troubleshooting to do around the way we are triggering the two circulation pumps separately and how we use the old tank stat as a safety cut out, but I need to clear up this d.8 issue.

Is it normal for d.8 to be constantly on 1 when using the VR66/VRT350f controls, or should it be dropping to 0 if there is no demand from both CH and HW?

Also, my VR66 makes a high pitched whining sound. Is it about to fail, or is this quite common?
 
Sponsored Links
When fault finding with vaillant ebus controls, is that the controls actually stop the boiler from firing, as the link between 3 & 4 puts a constant demand for the boiler to come on. Another possibility for the heating coming on might be a poor signal between the 350f and receiver. If the connection is lost it can default to on.
If you go into the settings on the 350f it will give you a signal strength reading.
 
Hi gazdaz36, thank you for the reply. So the link between 3 & 4 on the boiler will result in d.8 reading 1 (active/demand) all the time? The RF connection is usually 8-10 when I check it - the 350f is close to the boiler anyway. There's no chance of the boiler being activated by another 350f system because we are in a remote location. The random CH circuit activation only seems to occur when the tap symbol is lit in the display, i.e. 350f timer is ON for HW demand. When it happens, the rad symbol lights up, it'll fire for about three minutes then anti-cycle even at a low circulation temperature. Sometimes it continues cycling for a while, sometimes it stops. It nearly always seems to do it after recharging the hot water storage tank.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top