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Help! Nest - Dual zone - Opentherm!

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The instructions talk about the hot water stat binding to the controller first, then binding the BDR91 which will be the control.

I imagine the opentherm bridge will open up control to the boiler to the communicator... As otherwise the boiler would be wired both ways.

Can anyone confirm?
 
I would imagine you would bind the cylinder stat then a bdr91 which will go on a diverter valve of some description.
This would then switch the valve via the bdr91 and fire up the boiler via the Opentherm Bridge.
 
Good point... The wiring diagram points to the boiler and 2 way going to a junction box, so didn't know if the boiler would have any control over the 2 way what so ever.

That does make sense though and explains why there's a separate wiring spec just for a 2 way...
 
So... where I am with this. I am going to be wiring the system to my Y plan circuit this weekend - to get it up and running and learning - it also means a partial disabling once the opentherm system goes in, so less work to do later.

My question is this though - I can see in the instructions that it can be applied to a Y plan system with no HR92's - i can also see an ideal Honeywell circuit with a 2 way valve for the HW and nothing on the CH piping, whilst using HR92's (which aren't on the Y plan diagram).

I presume given the wiring of the 3 way diverter goes into the boiler and HW relays - that when binded, the commuinicator will take signal from any of the HR92's and then switch the boiler on and point the 3 way in the right direction... but I don't want to disable everything before finding that out.

My pump and 3 way is currently upstairs in the middle of the house, the boiler and stat are downstairs - so i am pretty much going have to go back to basics, setting a new junction box in both locations - utilising the existing embedded wiring joining both locations - so it won't be simple putting it back together once stripped

Thanks in advance :)
 
Update! I'm fully wired up and the system is working. So far it's only been a day but I am highly impressed. Just need to refine the schedule to suit our comings and goings.

I have replaced one of the heads for our en suite with a manual one for now as I don't have a relief valve fitted... Set this at 2 out of 5, so hopefully that will protect it until the new system goes in.

Thanks for everyone's help on this, notably Rob and Shaun... Thanks chaps
 
It soon learns the rooms, at first mine all overshot the temps, now it knows when to switch off to hit the target. For the living room set to go off at 20:00 it is turning off around 19:00 now.
When it has the rooms up to temp the boiler is still cycling a bit but the flow is only around 32c.
Maybe when the whole house is falling for heat it will not cycle at all.
 
That's interesting... Is it possible given the age of my boiler that it won't have the capability beyond on and off? It is 31 years old

Have you got both optimize options set I gather? I've set the start up option for 1 hour prior
 
Not yet.... That's on the new system which will be fitted at the start of next year. I've a few jobs to do yet... Including sorting the electrics, clearing space and shifting things for the new cylinder etc...

This is the original 1986 boiler and open vented cylinder. Not doing bad considering
 
1animal1 said:
Not yet.. That's on the new system which will be fitted at the start of next year. I've a few jobs to do yet... Including sorting the electrics, clearing space and shifting things for the new cylinder etc...

This is the original 1986 boiler and open vented cylinder. Not doing bad considering
Click to expand...

Yeah that probably won't modulate, but you should be able to adjust the flow temperature manually.
 
I apologise for being late responding on the thread. However Drayton have released a good system this week. Just mentioning it as it gives other people reading the thread another option to look at. Should they wish.
 
Slightly old thread resurrection!

I wanted to come back to you all and say thank you for all the guidance on this project. It was finally completed in July - I am absolutely blown away with the results. Definitely worth all the hassle - huge shout out to my heating engineer who took the Atag course especially for my requirements due to the Viessman not working properly with Opentherm.

PureGas Services on Instagram: “First @atagheating boiler fitted as requested by customer #hvac #copper #plumber #gasengineer #puregas”
 
Thanks for coming back

Everything looks great except my opinion few snagging points

D1 is too long
D2 is too shot
(Unvented safety vent d1 is the distance to the tundish 600 mm max, d2 is from the tundish to the first bend 300mm min)

Condense doesn't look likes it's falling might be the pics

Are the pipes now insulated?
 
Thanks Shaun!

There is a very slight drop on the condense... The other areas, D1 and D2, are you saying the tundish should have been mounted further up?

Is this the end of the world type deal where i need to get him back?

I might have impacted this as needed this area to be compact, as a fridge lives next to this area, pushed up (but not touching).

Thanks

Tim
 
Correct and if it every discharges it could overflow due to the bend being too close, I'm very surprised he's done it as it's regulations

D2 is the most important one

Hope you don't mind
 
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