• Welcome to PlumbersForums.net - The international free plumbing advice forum. Professional plumbers sharing advice with fellow plumbers and DIY alike. Register for free today! - Checkout the Plumbing Advice forum and then our Plumbing Videos area which still needs populating.

Discuss CH not switching off - Nest/Viessmann in the Central Heating Forum area at PlumbersForums.net

vikdab

Messages
2
Hello

I have a NEST with Viessmann system boiler with unvented cylinder.
I have a mid position and two position valve

You don't have permission to view attachments. Attachments are hidden.



I thought the mid position valve was faulty as it was not switching off
I got new actuator - the right one (40003916-003/U) . The manuals do make a reference to v4073a1039 so I'm sure it is the right one.

However my CH does not turn off when I switch it off in the app (when there is no HW on).
If HW and CH are on and I turn CH off it does work

I think my NEST is connected ok

App status Nest wiring status Mid posn valve wires

Both off 1245 live Grey live

Ch on 2345 White/Grey Live

HW on 1256 Neither live

Both on 2356 White live

I also notice some spurious voltages for eg after I turn Ch off 3 on nest has 55v (white wire as well)
When both CH and HW are on 4 on nest has 72v (also Grey wire)


Any clues on what is going wrong here
 

Attachments

    You don't have permission to view attachments. Attachments are hidden.

vikdab

Messages
2
The spring does bring lever back to mid position when there is no power (I switch mains off) so i doubt the spindle is getting stuck.

When I turn power on with CH/HW off on app and force the lever all the way to left (feel spring resistance) the boiler comes on and valve remains open (loose lever)
 

Reply to CH not switching off - Nest/Viessmann in the Central Heating Forum area at PlumbersForums.net

Similar threads

P
Thanks, this is really helpful. Has it been useful or more efficient to have the connection via opentherm?
Replies
3
Views
1K
profarvin
P
plumberhelp!
Thank you so much I reset to pumped and its fixed it!!I assumed that because water to feed the copper cylinder came from a header tank it was...
Replies
2
Views
245
plumberhelp!
plumberhelp!
W
I've had someone round and I have the answer. It was the pump overrun stat, it's broken down internally (you can hear it rattle) and was providing...
Replies
27
Views
404
West Country
W
C
Interesting idea when most people at the moment are trying to reduce their heating usage. ....
Replies
5
Views
268
Murdoch
M
Creating content since 2001. Untold Media is a Registered Trademark.

Newest Threads (Please Reply)

Search Forum

Top