New Vaillant boiler problems

[Roger Chapman]

I returned to Usenet too late to see more than the tail end of the 'New Boiler - controls' thread and I lack the nous to seek out the earlier part on-line so my apologies if any of that covers my query below.

I have encountered a couple of problems with my new Vaillant ecotec 418 boiler. Since I no longer consider myself competent to do gas work I had to ask the builder to get a plumber in to do the installation but I had no such worries about electricity so I did the wiring myself only to be disappointed to find that there is no easy way to connect up the domestic hot water zone valve to the separate temperature control for that aspect.If I understand the documentation correctly the only way to connect this is to purchase Vaillant's own no doubt expensive control system that from what I have read elsewhere would not suit the rest of my system which consists of 2 UHF zones downstairs, a radiator in the kitchen on its own zone and another radiator zone upstairs.

While I am happy to play with substantial wires I am not at ease with really fine wire and am reluctant even to touch printed circuit boards. The route to the other control appears to be an an edge connector on the PCB and I might just about manage that but further than that I do not want to go. So is it feasible just to obtain a suitable edge connector and link that via a single wire to the to be segregated control signal from the zone valve?

The other problem - that is a human one. The plumber having fired up the boiler left saying he would be back the next day to do the commissioning tests and complete the paperwork but hasn't been seen since. The story is that he has left his wife and cannot be found in his usual haunts or indeed anywhere else. Where that leaves the guarantee is anyone's guess but I am reluctant to approach Vaillant at this stage while there is still a faint change the plumber might resurface.

And getting a builder in! I am sorry but there are some jobs that are just not possible on your own even if young and fit (and I am neither). I am doing as much as I can to assist when I can but not as much as I would have liked.

[dennis]

It should have a mains boiler on connection. I use it for my zone valves.

See fig 4.8.2 in the manual

[Roger Chapman]

That is what I used to wire up the boiler. Or at least in part since I wired the pump direct to the boiler rather than too the external junction box.

My problem is the separate control for the DHW. 4.4 of the owners manual states "The control of domestic hot water is only available if you have fitted the optional accessories (VR 65, VRT 360, VRC 400)."

The suggestion is that the connections are to the ebus (whatever that is) which is a complication I could do without since that seems to be at

12V but presumably surmountable with suitable advice but the above mentioned VR whatevers are out of the question.

I see the separate control as a useful facility as circulating water through the DHW zone will reduce the chances of the boiler actually condensing to next to zero.

[newshound]

I am just struggling with similar issues, when I installed my 637 I found out too late that the digital timer didn't do what I had expected, and had to get a VR65 and then do some fiddling (e.g. the diverter valve needs to be the "wrong way round").

Now my VR65 has part-failed, it is not responding to the DHW demand.

This seems to be one of the down-sides with the otherwise mechanically excellent Vailant ecotec boilers.

I have not yet decided exactly how to resolve my problems, I am probably going back to the basic mechanical timer perhaps with an additional relay or two to sort the logic. (Personally, I think diverter valves should be powered when there is a demand from the cylinder, rather than the other way round).

[dennis]

I don't use the ebus at all. I just wire ored the end switches on the zone valves together and connected them to the 240V boiler on. If I had used the 24V loop it would have meant having 24V and 240V down the cables into the zone valves. The ebus could have made using solar hot water controller work the boiler input to the cylinder but I decided a simple single channel programmer was going to be easier so I connected another zone valve into the hot water circuit. As it has a 16+kW heat exchanger coil it will still condense.

[John Rumm]

One of the difficulties is that the language used by the manuals is often a little ambiguous - If you run the boiler using a traditional wiring plan and with mains controls, then you should be able to do what you want in the same way as with any other boiler. i.e. you set one flow temperature on the boiler, in effect logically OR together all the various calls for heat, and let the stats and programmer sort out what valves etc are opened.

However, armed with some extra toys the boiler can also do other stuff (i.e. so called "control of domestic hot water"). But this is optional.

You will note that the boiler has separate knobs for CH and DHW temperature. Hence if it is wired up so that it "knows" that its being asked to heat the DHW and not the CH, it can be set to run at a different flow temperature and make use of an analogue feedback from a thermistor, rather than just a binary call for heat from a cylinder stat.

Yup ebus is a power and serial comms bus for talking to electronic controls etc. The VR65 is a way to interface traditional mains controls to it.

Yup, just go for a "normal" S or S+ style wiring (but let the boiler drive the pump):

[Roger Chapman]

snip

" Note! The VR 65 is designed to control one 3-port valve or two 2-port valves. Systems requiring more zone valves or a combination of 3-port and 2-port valves are not possible."

So that wouldn't be any use to me anyway.

The pump is wired directly to the dedicated boiler connection.

I have a version of S plan plus with separate 2-port valves for the DHW, the upstairs radiators, the kitchen radiator and the UHF mixing valve. Two UHF zones lurk behind the mixing valve.

What I need is a terminal on the boiler to take the 240V from the DHW valve when the tank thermostat calls for heat. I appreciate that while the DHW is being heated the CH will get the hotter water but since the DHW is only on a few hours a day and even then doesn't always need a full recharge the CH could operate at a much lower temperature if only I could find a way to control the second dial.

[fred]

In article , Roger Chapman writes

Do you know if the boiler ebus and 240V controls can operate in parallel?

If they can, perhaps you could use the VR-65 to control only the H/W demand/activation and leave your existing controls to operate the C/H side. As the manual shows the ebus room stat as optional, I'm guessing this should be possible.

Obviously it's a lot to spend on the off chance (how much!) but I see there are some being punted on ebay that could be acquired more cheaply to try this out.

[Roger Chapman]

I am afraid I don't have a clue. The nitty-grity of electronic boiler control are a closed book to me. If there is not a 240V terminal for me to use then I will just have to put up with having a useless feature on my boiler.

ISTR that when I checked out the price of a VR 65 the cheapest I could find was a smidgen under £75. It would take more years saving the odd half a per cent (or less) on the annual gas bill to match that than there are years in several boiler lifetimes. ;-(

It is having a potentially useful feature on my boiler and not being able to use it that really gets my goat.

[Roger Chapman]

I have now heard from Vaillant technical:

When using external 230V controls the only switch live terminal is 4 and the only temperature selector is the bottom dial with the radiator symbol, the hot water dial has no function, the only way of separating the heating from hot water utilising both temperature selectors is with Vaillant ebus controls."

So not a lot of help there then. I suppose it would be technically possible to rig up a low voltage control system for the DHW if the required input is a straight on/off signal but even that is a bit above my skill level and there is always the possibility that the Vaillant gubbins uses a variable voltage to fine tune the temperature control and I would be completely lost on that.

[John Rumm]

Yup thinking about it, that much I knew - I setup the controls on a mate's 416 open vented C Plan system. The CH temp knob let you set the primary flow temp, and the DHW knob did nothing.

I think the more interesting question would be, what happens if you have say a weather compensating control (e.g. VR470), but then also use the normal switched demand input. Does it then ignore the weather comp information? (it would be handy if it did - since you could then run other zones at the temp specified by the knob, and the main heating zone under the control of the compensator).

[newshound]

I've been waiting for someone to post that they are doing all this clever stuff with a Raspberry Pi!

The VR65 has been superseded by the VR66 which does two zone control. To be fair to Vaillant, the new timers and controllers do seem to be backward compatible with my 2010 ecotec.

[dennis]

So you can subdivide one zone using multiple zone valves and use the other for HW?

You really only need to run the HW at about 70C but vary the rads according to the ambient temp.

[Paul Whitehouse]

replying to Roger Chapman , Paul Whitehouse wrote: Sounds like a hard time you're having there. My Vaillant had a few problems also, and I struggled on how to fix it - I think it was heating up then cutting out at random. I got the guys from STL Heating to come out and fix it, and I was grateful when they did. Transpires they had to do somthing to the boiler but it's been working well ever since. Man, there's no way I'd try a DIY fix !!!

Anyway, so if you're still stuck and live in the north west - give 'em a go. Or you could try a local firm if you don't live up here - but - don't forget some small one man bands can sometimes skimp on service though.

[Roger Chapman]

Thanks but they are on the wrong side of the Pennines for me and I don't want to see a bill which starts with 3 hours traveling time.

Most of the gas safe engineers in this neighborhood are one man bands. I have several within walking distance of my house but know nothing at all about any of them so it is going to be a matter of pot luck.