viessmann outdoor temperature sensor

[desktop987456]

Hi,
Attached is a basic wiring layout of room stat + programmer working with Viessmann heat only boiler. (pic 1)

I have installed a weather compensation sensor as per schematic (pic2).

When I switch boiler on it shows the display with temperature and CH symbol but it is not igniting.

Is there wiring that I need to change; the room stat clicks, I have put it to 30C but boiler is not firing.

How do I bypass the room stat?
Thanks.

 

[desktop987456]

Can I just put SL from boiler to number 4 on programmer?
1. It should bypass the roomstat;
2. programmer should turn heating on.
3. Weather compensation sensor should work.
Correct?

4. What could be other way if I want room stat to work in conjunction with WC.

 

[desktop987456]

I have tried to bypass thermostat but still boiler won't ignite (it doesn switch on, the display shows temperature with CH symbol but it won't ignite).
I have tried with or without link on port 96 on PCB.
Any ideas? Thanks in advance.

 

[fixitflav]

I have tried to bypass thermostat but still boiler won't ignite (it doesn switch on, the display shows temperature with CH symbol but it won't ignite).
I have tried with or without link on port 96 on PCB.
Any ideas? Thanks in advance.

This was discussed at some length earlier, but without going back into it I can't remenber all the details. Did you install separate boilers for CH and HW? If so I assume this is the CH boiler you're looking at.
On your first attachnent, is (G) the boiler terminals? Just a thought, does the boiler need a permanent live as well as a switched live from the roomstat.

 

[desktop987456]

This is the CH boiler and I installed a WC sensor in it.
Yes (G) are the boiler terminals.
Switched Live is provided to boiler from room stat.
I'm have sent an email to tech support as well but there instructions is what I have followed but it doesn't fire using WC sensor.

 

[desktop987456]

 

[fixitflav]

View attachment 363656

Have you tried powering one of the terminals in 5? At least that might fire the boiler to check it works. What is C? why is a terminal box needed, as well as a cylinder stat?
I'd be surprised if it's not possible to bypass the WC, and just run the boiler on its control-stat.
Do you have a roomstat? I remember this was discussed earlier, as it's not shown on the Viessmann data

 

[polesapart]

Some info, may be relevant to your specific boiler and setup.

https://viessmanndirect.co.uk/files//f814ea2a-5b56-4feb-9166-a43e00f71548/WB1B%20Compact%20Outdoor%20Sensor%20Instructions.pdf?srsltid=AfmBOoq4eudAQtJ9P-ie5EtZlJjGAXusjBXmU7iV9P7BzRsPSsfwX-N3

You may need to download software to configure the heating curve - again model specific.

 

[desktop987456]

Have you tried powering one of the terminals in 5? At least that might fire the boiler to check it works. What is C? why is a terminal box needed, as well as a cylinder stat?

Terminal 5 is for cylinder, the cylinder is not attached with this boiler. C - is cylinder demand box which is required to fire the boiler at maximum power when using weather compensation for CH, it works only if cylinder is present and cylinder demand box is also attached. I don't have any of them attached to the boiler.

Do you have a roomstat?

Yes I do. You and Rob helped me install it last year prior to the WC. I am stuck with this screen when I attach the WC sensor; it shows the CH is on; radiator symbol and temperature of water. That's it. If I bypass the sensor it works as it should in normal mode.

may be relevant to your specific boiler and setup

Yes Sir, I have these instructions and have followed it as I have external controls installed to control the boiler (programmer + stat)

download software to configure the heating curve

The boiler is basic - heat only boiler and I have data ports or anything to configure it via software or computer if that's what you mean.

 

[fixitflav]

I am stuck with this screen when I attach the WC sensor; it shows the CH is on; radiator symbol and temperature of water. That's it. If I bypass the sensor it works as it should in normal mode.

I'm confused here. I thought in your first post you meant the boiler wouldn't fire at all. If you can run it on the roomstat at least you have CH when you need it.
On the WC, without being on site I'm not sure we can add much, if Viessmann can't help. The Viessmann diagram on earlier thread shows a terminal box or strip with 2 contacts unused, don't know whether that is correct, or there's something missing.

 

[desktop987456]

I thought in your first post you meant the boiler wouldn't fire at all.

The boiler does fire in room stat mode. Yes, I have CH working in room stat mode.
When I connect the WC sensor it doesn't fire. See pic 1 of boiler display (pic 1 in post 9).

Viessmann told me to check the resistance of Weather compensation sensor with a multi meter. I have checked it with MM and it shows 6kohms at 20degC which is consistent with their specification. So it tells me that sensor is good.

 

[fixitflav]

Viessmann told me to check the resistance of Weather compensation sensor with a multi meter. I have checked it with MM and it shows 6kohms at 20degC which is consistent with their specification. So it tells me that sensor is good.

Maybe it's something in the WC circuit internal to the boiler. Assuming the burner is On/Off control, the WC contacts will be in series with the control-stat. Might be worth checking the resistance on the boiler side of the sensor, I'd expect zero if the boiler's cold (contacts closed), high if it's hot, but maybe not ∞ as there could be other paths for the current. Worth asking Viessmann.