Honeywell CM 927/907 and TPI Control - Question?

[arildthegreat]

I have read with interest about the TPI control on my Honeywell stats and note their energy saving features.

I have a wireless CM927 upstairs and a wired CM907 downstairs. How does it work having 2 of them - will the boiler potentially be cycling 2 x 6 = 12 times an hour! Does it matter? Thanks for advice.

 

[twgas]

your stats should control seperate valves so there would be no excessive cycling if all is working correctly.

 

[ianniann]

Two stats, two zones, I assume? No TRVS?

The boiler will be on whenever either of the two stats is calling for heat. Hence it will be off only when both are not calling for heat. Both of your stats will be switching themselves on and off several times per hour and most likely having no effect at all on the boiler.

The one thing you can pretty much guarantee is that the boiler won't be getting switched at twice the TPI rate. More likely it won't get switched at all as one or other stat will be calling for heat most of the time. Or they might get in sync and actually switch the boiler on and off more or less as designed.

TPI, stupid idea to start with and doubly stupid when there are two of them.

 

[ianniann]

your stats should control seperate valves so there would be no excessive cycling if all is working correctly.

Stats controlling valves? So who is controlling the boiler?

 

[twgas]

your stats should control seperate valves so there would be no excessive cycling if all is working correctly.

Stats controlling valves? So who is controlling the boiler?

the valves have end switches which control the boiler - usually.

 

[arildthegreat]

Yes, 2 zones. All rads have TRVs (set to max in rooms with the stats).

I suppose my worry was the constant cycling with 2 stats regularly calling as outlined in the original post.

But then again, they do his for a reason (energy saving??)

...and yes, valves switch off boiler!

 

[D_Hailsham]

I have a wireless CM927 upstairs and a wired CM907 downstairs. How does it work having 2 of them?

Not very well!

The correct way of doing it is to have two CM927, controlling the upstairs and downstairs zone valves, and a third relay box controlling the boiler. One of the CM927s is set to act as the "System Synchroniser" and this one also controls the boiler relay.

You then do not get the problems you suggested.

 

[arildthegreat]

Oh!

Can you expand on what additional kit I'd require and also changes to wiring.

Potterton Profile 80e boiler. 2 x Bosstherm 2 port valves (3 inc HW)

Thanks for replies so far.

 

[hrustray]

arildthegreat, have you found a solution for your configuration?
I have a similarconfig now and also doubt, if my system works efficiently.