Can't bind HR92s

[paulockenden]

Surely normal practice is something like this:

12863787.jpg

So if all of the rad valves are closed there's no flow on that circuit.

Why would you have a bypass loop on a radiator circuit? The bypass should be the other side of the motorised valves?

Or am I being daft?

P.

[MrB]

Shows 2 layouts. The 2 pipe ends in a 'dead-end' as you stated.
The 1 pipe keeps going...

http://www.home-heating-systems-and-...pe-system.html

Not you being daft - you were correct in what you said then - me being upside-down... -- has just made me think about a problem the blokes doing our new heating system atm are working on.... hmmm...

[paulockenden]

As the link says, I think you'd only have the one-pipe configuration on a gravity fed system.

I think the confusion probably comes from referring to the circuit as a 'loop'. It isn't really.

P.

[MrB]

Paul,
Yep - a section of the old system being replaced was a single pipe - good job it's going..

And now everything is clearly understood about the Evohome setup etc.... Confusion does come from relating to old systems and what a full Evohome system can really do. Your thinking gets coloured by "what is" when it should be that you simply ignore what exists.

So the solution (now) is :
+ HW - wireless from HW Tank sensor to Controller, which in turn manages a BDR91 that operates the HW 2-way valve.
+ All 2-way valves are wired to the new Boiler to give a Heat Request signal.
+ Boiler manages Ciruclation Pump On/Off/Overrun.
+ 2 CH pipe "runs" because our pipe distances are too long and a single run looses heat at the distant radiators. These 2 are Upstairs and Downstairs {you can have as many as you want actually}
+ Every radiator has a HR92 TRV linked to the Evohome Controller - very important point.
+ Each CH pipe run has it's own 2-Way Valve, which I now understand were installed by 'habit' and only 1 is really necessary because unless a single HR92 on the individual pipe run is open there is no hot water flowing through that CH pipe run. As the two 2-way valves have already been installed they will simply be wired in parallel to the same Heating BDR91 Relay, which is managed by the Evohome Controller. This is being done because of the way the new pipework and valves have been installed and remember the Boiler is being fired from the Zone Valves being open. So both CH 2-way valves will be opened simultaneously, but no water will flow beyond the 2-way valve unless at least 1 of the HR92 TRVs on that run is open. So that's efficient.

So, as the extra CH 2-way valve is already installed it will remain just in case it's useful in the future. Of course, hindsight, and what I wrote above about ignore existing, means in reality it's totally redundant.

The only point still to be answered is whether it's best to have the 2-way valves fire the boiler or the EvoHome Controller because of short cycling as I've seen mentioned. If Plan A creates a problem then I'll change it over to Plan B and have the Evohome fire the boiler instead.

[Jon T]

Thanks MrB ! It's nice to know you guys appreciate my frustration - Fingers crossed the Honeywell developers are listening.
2 outstanding thoughts on my side.
1. If I managed to get the system working successfully for 3 upstair zones (while also running hot water and downstairs). Why won't it work for 4, 5 or more? Was I simply lucky in stumbling across a loophole or is there a piece of firmware code that says, "if quantity of zone valves is greater than 3 flip-out and annoy Jon T". What is the barrier? Limited wi-fi channels or? I'm guessing development to cover my problem would not require a great deal.
2. Does anyone think the addition of the Evohome Thermostat for the downstairs circuit will work?
I'm happy to make small compromises but anymore and the installer will be ripping out the Evohome and re-instating my old "Boost, Boost, Boost" button system.

[paulockenden]

As with MrB, if you have hr92s on all of your rads, and/or hcc80rs on any underfloor heating then you really don't need all of those zone valves. Do you?

[Jon T]

Hi Paul, yes having HR92's on all my rads is one but VERY expensive solution. I only have 3 motorised valves but tricking the Evohome onto thinking I have 5 is working. I just wish it would accept more 'virtual' zone valves. If you or anyone is interested to know how I did this I could explain later. Some of you will be able to work it out from my previous posts.

[paulockenden]

If you have a big 'zones' without any hr92s I guess you could control them from an hcc80r. It's meant for underfloor heating, of course, but I can't see why you couldn't use it to control your zone valves.

Don't think you'd get the same degree of comfort or control as you would with rad valves throughout though.

I know a load of hr92s isn't cheap, but if you're saving 30-40% on your heating bills how long would it take to pay for them?

[Fen Tiger]

Jon, I agree with Paul. It seem to me that if you use Evohome to simply control big zones it's kind of missing the point. You might as well use Hive, Nest or some other intelligent controller. I accept in your case that 35 rads @ £50ea requires deep pockets but its the ability to apply heat to a single rad while the rest of the house sits at a low temperature that sets Evohome apart IMO

[paulockenden]

35 rads - is your name Liz Windsor?