Yet another Nest Gen3 Question

[Incipience]

I recently upgraded our aging Channelplus h27xl to a Nest GEN3 - We have Oil Fired Boiler for Rads and Hot Water.

HW works fine, the boiler fires up when Hot Water Turned on at Nest. Boiler Fires Up when CH is also turned on, however, RADS do not heat up unless the Hot Water is on too.

Anyone have any suggestions?

 

[muggles]

How old is the oil boiler? Did it work before you changed?

 

[Incipience]

Not sure of the Age, it is a jet stream 4.

 

[flameport]

RADS do not heat up unless the Hot Water is on too.

Did the old controller have the option of radiators without hot water?

 

[Incipience]

yes, i could time either or both, and boost either or booth. I did not install the previous Controller, simply marked the cables and removed it. It Had CH on and HW on. Transferred those cables to the NEST. CH to 3 and HW to 6 - looped live to 2 and 5. An odd one was that the previous controller also had neutral cable for CH and HW, the neutral were all bridged together. I say odd as I have not seen that before, I have only come across switched lives in a controller.

 

[flameport]

An odd one was that the previous controller also had neutral cable for CH and HW, the neutral were all bridged together.

What happened to those - are they still connected as before?

There are really only two possibilities - either something is not wired as it was before, or some other unrelated fault has occurred at the exact same time.

 

[Incipience]

I assume the previous controller was able to fire the pump, for the heating and operated the gravity hotwater. How, I dont know. There was a jumper for selecting gravity or pumped on the old controller, no such thing I can see on NEST

 

[Johnmdc]

If you change the wires round in terminals 5 and 6, then put a link in between terminals 3 and 4 that will replicate what your old controller did when set to gravity mode.

 

[Incipience]

To Be Clear - Bridge 2 and 6 instead of 2 and 5, and then bridge 3 and 4? Can you explain why this would work. So that I could understand clearly what this is doing. Many Thanks

 

[Echo the husky]

Here's a drawing I did a while back which should help explain.