Vaillant ecoTEC 630, UFH, Heatmiser and VR66 for Cylinder Control

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Hello all.

I have a Vaillant ecoTEC Plus 630 system boiler, in an S-plan setup with a HW cylinder and a UFH mixing valve. All of this is controlled via a Heatmiser UF8-HF wiring centre. The Heatmiser boiler enable contact is connected to the 24v RT of the boiler. The Heatmiser wiring centre's hot water contact switches 240v live to open the cylinder valve, and the cylinder valve's auxiliary switch contacts, is also wired to the 24v RT. All works well: when either the cylinder valve is open (and its auxiliary switch closes), and/or the UFH is on (and the heatmiser boiler enable contact closes), the boiler fires up and shows the radiator symbol. The trouble with this setup is that I can only have one flow temperature, which has to be set high enough to warm up the water cylinder: 65C. This means that when the UFH is on alone, and it requires a 35C manifold temperature, the boiler keeps on cycling.

now-Page-1.drawio (1).png


My idea is then to have the boiler modulate its flow temperature: when UFH is on alone, it should be 40C; when the cylinder is on, it should be 65C. Possibly, the boiler should also have different heat partial load settings, which appears to be possible with Vaillant controls.

Reading on these forums, I came across this thread. In it, post #6 suggests that you can use the VR65 wiring centre as a dumb switch which sends a "call for DHW" signal when the CYL contact is closed. He says that "If boiler receives both 240v on RT for heating and eBus command for DHW charging the cylinder charging mode will take priority. When DHW charging is finished the boiler will return servicing RT request."

This is exactly what I want to do with my boiler, but with two variants:
1. Vaillant don't make the VR65 anymore, so I want to use its replacement, the VR66. The manual for the VR66, on page 6, says that you can use it in "Monozone mode (position 1) with VR65 functions". So it sounds to me that whatever was done in the above thread with the VR65 could potentially be done with the VR66 in this mode.
2. Instead of using 240v RT, I would like to keep my 24V RT setup.

Like so:
now-Copy of Page-1.drawio (1).png


Questions:
1. Does anybody have any experience with using the VR66 in this mode? The original poster of the thread above seems to have experience of using the VR65 to do this, but what about the VR66 (in VR65 mode)?
2. Does anybody know if the same priority system works in this situation, or in other words, does this statement hold true? -> "If boiler receives both 24v RT for heating and eBus command for DHW charging the cylinder charging mode will take priority. When DHW charging is finished the boiler will return servicing RT request."

Thank you all.

(DISCLAIMER: I am fully aware that putting my hands inside the boiler invalidates the warranty and would require the intervention of a gas safe engineer)
 
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Hi I’m using a VR65 on my 428 and you should hopefully find enough info on the thread below to get started.

 
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Hi jackthom, and thank you for your reply. That thread is indeed very useful.
In that thread, in post #21, the user "rbranco" mentions using the VR66 in this setup, so that would appear to answer my question #1 positively.
However, everybody there seems to be using 230v RT. Any idea about 24v RT working with that sort of setup?
 
I would think it is pretty much irrelevant which method you use for triggering heating, whether 24V or the mains voltage alternative. I doubt the boiler would operate differently.

Unfortunately I can’t absolutely guarantee that the ebus DHW signal will take priority over the heating signal as I had to use an additional relay to disconnect the CH ON wire going to the 3 port valve whIle the cylinder is calling for heat. Otherwise my valve would be in the wrong state for DHW priority. With this relay the boiler never receives conflicting demands for both DHW and heating so there is no need to set up priority in the boiler settings.

I suspect you may need to similarly disable your UFH valve (or temporarily ditch any UFH Demand) to avoid both valves being open when you really only want DHW as the priority.
 
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What do you mean by "I can’t absolutely guarantee that the ebus DHW signal will take priority"? Do you mean it didn't work in your specific setup, or did you just put the relay in to have additional certainty that it would work as intended?

Do you have a relay to suggest? Considering mine would be switching a voltage-free input, do you know of a cheap enough module that can do that? I have found a relay called Salus RM-16A that seems to be able to do this, but are there any other models that you know?

Also, if I look at the datasheet of the VR65, I see that its consumption is 2W, while the VR66 says it's 20W. 0.02kW*24*365*0.038 = £170 per year to run this. Seems quite a lot for such a simple device! Any idea where I could procure a VR65 at all?
 
I definitely had to use a relay because without it the 3 port valve would have been in the mid position for both heating and DHW when both were calling for heat, probably with the boiler delivering 70C flow temps to both cylinder and radiators. If I had used the VR65 as it is designed with the mid-position valve connected directly to it this would not be a problem, but I wanted to stick with my Nest thermostat and not use a Vaillant one.

I have no personal experience of setting the boiler up for DHW priority although I'm fairly confident it would give the ebus signal priority.
With a relay you don't have to worry about that at all because the boiler will never be presented with both signals at the same time.

Your H/W valve and its associated relay look like they will both be working at mains voltage so a relay with a mains voltage coil is needed.
This sort of thing would be fine.

(Would obviously need to be careful not to mix up the wiring between the low and high voltage sides of the relay, assuming the switching contacts will be operating on much lower voltages.)

You would need to use the normally closed contacts so the UFH demand signal is interrupted when the relay is energised.

Had a look around for 2nd hand vr65 but don't see any at the moment, however In the installation manuals it looks like both units have 20W power consumption.
 
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I definitely had to use a relay because without it the 3 port valve would have been in the mid position for both heating and DHW when both were calling for heat, probably with the boiler delivering 70C flow temps to both cylinder and radiators. If I had used the VR65 as it is designed with the mid-position valve connected directly to it this would not be a problem, but I wanted to stick with my Nest thermostat and not use a Vaillant one.
Aha, but my setup is S-plan, so no 3-port valve to worry about being stuck in the wrong position. The two 2-port valves operate independently.

The heatmiser wiring centre will still remain the brain of the system. It normally takes care of closing the UFH valve and Boiler contacts, that is regardless of the demand for HW. The UFH manifold has a mixing valve, so whatever temp the boiler's flow may be (45 or 65), the mixing valve will take care of stabilising the manifold temp to 35C.

So:

Boiler contact
(Heatmiser)
HW contact
(HW valve auxiliary switch)
Flow Temp
(Boiler dependent on eBus signal)
UFH Valve
(Heatmiser)
HW Valve
(Heatmiser)
YesNo45OpenClosed
NoYes65ClosedOpen
YesYes65OpenOpen

I have no personal experience of setting the boiler up for DHW priority although I'm fairly confident it would give the ebus signal priority.
With a relay you don't have to worry about that at all because the boiler will never be presented with both signals at the same time.
Got ya, but in my setup it may not be needed. I will keep in mind your suggestion though, in case it doesn't work as expected.

Your H/W valve and its associated relay look like they will both be working at mains voltage so a relay with a mains voltage coil is needed.
This sort of thing would be fine.
My H/W valve has a switch inside which is voltage-free if you don't put any voltage through it. I *could* connect it to a 240v live contact, but I would rather work with low voltages throughout if it can be avoided.

Had a look around for 2nd hand vr65 but don't see any at the moment, however In the installation manuals it looks like both units have 20W power consumption.
The VR65 manual says power usage 2VA, which at power factor 1 should be 2W. Am I missing something?
 
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I was thinking that it simply wasn’t good to have 65C water going to the UFH but I now understand that isn’t a problem for your system when both heating and HW are required together, so apologies for the diversion and no need for a relay.
 
No need for a vr66 or any other Vaillant controls call for DHW using the C1C2 connection on the boiler harness (close to call, no volt) this creates a priority call for DHW at the set power and temperature. Exactly as you want!
You'll have to cutoff the plug and put one of your own on to connect - contact is a legacy of the old solar thermal controllers and the storage combi's -I keep expecting to see it deleted each time the model gets an update but it's still there and damn useful for accessing the twin stats with a Sundial plan!
I think the harness colour changes on current models so check in the right manual.
 

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It would have made things a lot easier if my 428 had the same connections for triggering DHW.
Just had another close look at the manual in case I’ve missed it; unfortunately I don’t think so.
 
I was part of those original threads and can confirm the VR66 works exactly as the VR65 does in mono mode. Although given the post above from scw, it seems your boiler may not require the VR65/66 to boost flow temps for HW.

Whichever method you choose, you will need to clamp your CH temperature using the radiator dial on the boiler, and use the VR66/boiler connection (scw's post above) to boost flow temps when HW is being called for. In this setup, if both zone valves are open, you will inevitably have a slight compromise, but given your UFH manifold blends temperatures down, this will probably be acceptable.

If you want PDHW (priority hot water), you will need the ability to turn off your UFH valve whilst the HW valve is open. For this, I used a simple relay and you can find more info on the following posts:

 
Hi @peredelkin I have been trying to buy a VR66 but it's out of stock everywhere, where did you get yours?
 
@jackthom No, you've not missed it, never there on the 400 series, as this was a UK only product with a totally different build Hex and electronics to the 600/800's and nowadays its only a rebadged Ecofit for more money and a nasty ali hex that's almost impossible to open for servicing because of the primary connections wrapped round the rear left burner nut.

In fact if you want to use a VR61 (and possibly a VR66, I never had the pleasure being a hardened WC man :) ) on a 400 you need an adaptor lead (pcb edge connector to choc block) to make in the VR10 of VF1 DHW sensor into the main PCB as it was never deemed UK domestic installers were forward thinking enough to use such controls (or such features as analogue compensation on 7,8,9), good luck finding one of those in a reps case nowadays it was the only place to get them!!
 
My 428 is over 15 years old now and I’ve no idea what I might replace it with when it packs in. If there are boilers which have separate connections so they can easily be fired up in either Heating or DHW mode, with associated temperature and power settings, I’d be interested in finding out.
 
No need for a vr66 or any other Vaillant controls call for DHW using the C1C2 connection on the boiler harness (close to call, no volt) this creates a priority call for DHW at the set power and temperature. Exactly as you want!
You'll have to cutoff the plug and put one of your own on to connect - contact is a legacy of the old solar thermal controllers and the storage combi's -I keep expecting to see it deleted each time the model gets an update but it's still there and damn useful for accessing the twin stats with a Sundial plan!
I think the harness colour changes on current models so check in the right manual.
Reeealllly? I will try that today, 100%. If it works it will save me 70 quid + 20W running all the time.

Hi @peredelkin I have been trying to buy a VR66 but it's out of stock everywhere, where did you get yours?
It's on order.
 

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