Vaillant heat only boiler + switched live thermostats + weather comp?

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As a bonus a simple relay, a switch and an indicator lamp.

The lamp shows us that 240v DHW is active.

When 240v DHW is active and when switch is ON the relay breaks 240v live for heating demand, shutting all heating valves that results in immediate removal of 240v from RT terminal of the boiler even if Nest thermostats are demanding heat.

When switch is OFF the relay does nothing, allowing Nests to steal overheated water during cylinder charging cycle for heating.
 
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View attachment 245775

As a bonus a simple relay, a switch and an indicator lamp.

The lamp shows us that 240v DHW is active.

When 240v DHW is active and when switch is ON the relay breaks 240v live for heating demand from RT terminal and shutting all heating valves even if Nest thermostats are demanding heat.

When switch is OFF the relay does nothing, allowing Nests to steal overheated water during cylinder charging cycle for heating.

I like it. Like selecting DHW priority, or feeding both water circuits via your switch / relay.

You have clearly done your homework on all of this. Hats off to you. :idea:
 
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>> Is your outside sensor a 693 that wired to the vr65 or to the ebus directly?

The sensor is wired to boiler PCB via edge connector VRC 252629
Edge connector is normally supplied with VRC 470.

VR65 knows nothing about whether compensation.

Sensor 693 is a basic thermistor sensor.
Sensor on my photo is model 9535 and it also has DCF77 signal receiver from Frankfurt (German radio controlled clock) as a bonus. Boiler's PCB decodes this and sets the time.
Also, 9535 sensor has a bit better chassis than the standard 693 sensor.
Available from German Amazon. Not normally sold in the UK since we are in different time belt.
 
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>> You have clearly done your homework on all of this

Download manuals and just read them. That's all I have done.
Now enjoy heating the way it should've been done from day 1.
Save some money too.
 
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>> Is your outside sensor a 693 that wired to the vr65 or to the ebus directly?

The sensor is wired to boiler PCB via edge connector VRC 252629
It is normally supplied with VRC 470.

VR65 knows nothing about whether compensation.

Sensor 693 also has DCF77 signal receiver from Frankfurt (German radio controlled clock in the boiler) as a bonus.
Also, 693 have a bit better chassis than the standard sensor.
Available from Amazon via Germany. Not normally sold in the UK since we are in a different time belt.
I'm wondering if my boiler pcb has that port to connect it to?
Will have to look tomorrow.
Not sure I need the time signal, as I would set the time on the programmable room stat to sort that out, but maybe the vrc 470 needs the time?
 
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>> I'm wondering if my boiler pcb has that port to connect it to?

It doesn't have that port now. When you buy VRC 470 make sure it is supplied with edge connector and with 3 pin connector for the boiler fascia.
Here's how you do that:
If you choose wired path.

There is wireless VRC 470f thing, but I haven't tried it myself.

I bought 9535 sensor only for aesthetic reasons. Normal 693 sensor looks a bit cheap and crappy.
You will not need time signal since you will set internal Vaillant programmer in VRC 470 for "24/7 on" mode since the demand comes from outside and you use Nest's schedulers for everything.
 
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>> I'm wondering if my boiler pcb has that port to connect it to?

It doesn't have that port now. When you buy VRC 470 make sure it is supplied with edge connector and with 3 PIN connector for the boiler fascia.

Seeing as mine is from 2011, I'll have to open it up and have a look I think.

Whilst wiring up the sensor takes longer, just feels more likely to last longer.

Having it (control box) mounted to the front of the boiler sounds good.
 
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I guarantee you that your boiler comes with no VRC 252629 edge connector fitted.
If you source VRC470 in a sealed new box it will have that connector and a 3 pin connector for in-fascia installation in it.
If you source just a bare used VRC470 you'll just google for VRC 252629 and get it.
Same for 3 pin connector.
 
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>> Whilst wiring up the sensor takes longer, just feels more likely to last longer.

Yes, that's forever. Also, no worries about losing wireless signal. Make sure you have access to shady northern-facing wall.
 
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>> Having it (control box) mounted to the front of the boiler sounds good.

Yes. That will automatically de-active the build-in Vaillant thermostat that you don't need.
 
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