Evohome - fine tuning controls

[Midori]

I have a Vaillant heat only boiler controlled by an Evohome, installed one month ago and all working perfectly. The Vaillant, when asked provide heat, controls the burner, pump, pump overrun time, minimum burner cycle time, etc. I have three zone valves, and their auxilliary contacts in parallel signal the boiler to provide heat when any valve is fully open. The three zone valves are switched open/shut by three BDR91 relays individually bound to the Evohome and receiving signals from A) internal temperature sensor, B) a remote room temperature sensor Y7RF, and C) a HW cylinder temperature sensor and transmitter ATF500. The Evohome User Guide is not very detailed and I am searching for clarification on some of the System settings.

Minimum On Time: If set to 5 mins what does this control and how will it interact with each of my three BRD91 relays?

Cycle Rate: If set to 6/hr (10 mins), is this the minimum time any of my three BRD91 relays can cycle On to OFF and back ON again?

HWS Valve close delay: If this delays HWS zone valve closing by holding ON my BRD91 relay then boiler will continue provide heat. Since boiler prolongs pump running when firing ceases the should I set this to 0 mins and leave Vaillant to continue pump overrun function?

The HW Cylinder sensor ATF500 has an adjustable differential which is understandable, however the room temperature sensor Y7RF has no mention of differential anywhere. How does Evohome System settings cause the BRD91 relay associated with room temperature sensor Y7RF to cycle on/off. In the old days room thermostats would have an anticipation heater to cycle the heating on/off according to load. How is it done with my Evohome system?

[HenGus]

I am sure that Honeywell will be along soon. Most of the issues that you have raised have been discussed previously on this forum. It is also worth looking at the training package for Evohome installers:

http://youlearn.honeywelluk.com/courses

[paulockenden]

Looks to me from your description that you don't have a boiler relay, only relays on the valves. In which case you shouldn't be seeing those "minimum on time" and "cycle rate" settings.

Either your Evohome system has been configured incorrectly or I've misunderstood your setup.

P.

[top brake]

I have a Vaillant heat only boiler controlled by an Evohome, installed one month ago and all working perfectly. The Vaillant, when asked provide heat, controls the burner, pump, pump overrun time, minimum burner cycle time, etc. I have three zone valves, and their auxilliary contacts in parallel signal the boiler to provide heat when any valve is fully open. The three zone valves are switched open/shut by three BDR91 relays individually bound to the Evohome and receiving signals from A) internal temperature sensor, B) a remote room temperature sensor Y7RF, and C) a HW cylinder temperature sensor and transmitter ATF500. The Evohome User Guide is not very detailed and I am searching for clarification on some of the System settings.

Minimum On Time: If set to 5 mins what does this control and how will it interact with each of my three BRD91 relays?

Cycle Rate: If set to 6/hr (10 mins), is this the minimum time any of my three BRD91 relays can cycle On to OFF and back ON again?

HWS Valve close delay: If this delays HWS zone valve closing by holding ON my BRD91 relay then boiler will continue provide heat. Since boiler prolongs pump running when firing ceases the should I set this to 0 mins and leave Vaillant to continue pump overrun function?

The HW Cylinder sensor ATF500 has an adjustable differential which is understandable, however the room temperature sensor Y7RF has no mention of differential anywhere. How does Evohome System settings cause the BRD91 relay associated with room temperature sensor Y7RF to cycle on/off. In the old days room thermostats would have an anticipation heater to cycle the heating on/off according to load. How is it done with my Evohome system?

as Paul has already noted it sounds like you have no boiler relay (the BDR91 that came in the box with the evohome)

How is your system wired up to call for heat from the boiler?

some pics would be really helpful

[Midori]

Thanks for above thoughts and feedback as follows:-
@HenGus: Yes I completed that course when I first got the kit.
@paulockenden: Yes you are correct, there is no single boiler relay as such. There are the equivalent of 3 boiler relays in parallel. The temperature sensors signal the relays, which open/shut the Honeywell zone valves, and the aux contacts on the Honeywell valves tell the boiler when the valve is fully open. I was guided thru set up by http://theevohomeshop.co.uk
@top brake: The wiring: I have three Honeywell zone valves, and their auxilliary contacts are wired in parallel so any one can signal the boiler to provide heat ( when a valve is fully open). The three Honeywell zone valves are switched open/shut by three BDR91 relays. Each of the three BDR relays is controlled by its related thermostat (as Fig 9 of Installation Guide).

I mentioned all is working fine, and the system configuration is catered for in evohome installation guides which I fully understand being an H&V engineer. Nevertheless, it is common knowledge that pumped hot water radiator heating systems have a large thermal delay when controlled by a room thermostat. The evohome and room temperature sensors replaced my Satchwell thermostats which had anticipation heaters in them. It's like P+I+D control where the sensor foresees a rising temperature and switches off to avoid wasting heat and avoiding temperature overswing. The on/off time ratio therefore becomes proportional to the actual load and the room temperature stays stable.
Put another way to Mr Honeywell, if room temperature sensor Y7RF had a switching differential to switch zone valve on and off, where is it mentioned in the paperwork and what is the differential value and adjustment?

[top brake]

Thanks

So what you need to do to optimise your system is delete all bindings and factory reset

Get another BDR91 and wire it directly to the boiler. Disconnect orange wires from zone valves.

Rebind system using guided configuration

Add boiler relay

Bind the three zones as 'zone valve' type.


Now you can adjust the cycle rate and minimum run times. This optimises the TPI (PI) control. There is no proportional band adjustment it is hard coded at 1.5 degC

Hope this helps? Happy to discuss during working hours on 07814910642

[Midori]

Thanks

So what you need to do to optimise your system is delete all bindings and factory reset

Get another BDR91 and wire it directly to the boiler. Disconnect orange wires from zone valves.

Rebind system using guided configuration

Add boiler relay

Bind the three zones as 'zone valve' type.

Now you can adjust the cycle rate and minimum run times. This optimises the TPI (PI) control. There is no proportional band adjustment it is hard coded at 1.5 degC

Hope this helps? Happy to discuss during working hours on 07814910642

Thanks again,

I am understanding to stop my 2 heating zone relays/valves opening and shutting in periods anywhere down to as short an 60 seconds, I have to use a boiler relay configuration. The EVO can only apply "MIN ON TIME" to that single relay for the boiler. This then leaves the zone relays/valves to chomp away on & off for short periods, but without consequence on my boiler ignition circuit.

So I will unbind all devices and end up with the following config:
Cycle Rate = 6 (10 mins / hr)
Min On Time = 5 mins

System Devices
- Boiler Control = RELAY (this is the new relay4)
- HWS = enabled (this is existing relay1)

Zone Configuration
Upstairs:-
- Htg Type = zone valve (this is existing relay2)
- Temp Sensor = remote sensor (this is Y87RF)
- RF Binding = devices bound

Downstairs:-
- Htg Type = zone valve (this is existing relay3)
- Temp Sensor = Evo Touch sensor *** note below
- RF Binding = devices bound


System Summary
- HWS = hot water only valve
- Upstairs = Zone Valve
- Downstairs = zone valve - EVO touch sensor *** note below

Fail safe = disabled
Optimise = disabled

*** if I replace "EVO touch sensor" to "Remote Sensor" by adding a new Y87RF in "co" mode, do I need to unbind internal EVOcontroller stat somehow or is this done during EVO reset?

[top brake]

You have understood correctly.

Regarding settings what fuel is you boiler? If gas I would leave it in default 6 cycles and 1 minute.

Factory reset the evohome and follow guided configuration to create the zones as you have planned

Thanks again,

I am understanding to stop my 2 heating zone relays/valves opening and shutting in periods anywhere down to as short an 60 seconds, I have to use a boiler relay configuration. The EVO can only apply "MIN ON TIME" to that single relay for the boiler. This then leaves the zone relays/valves to chomp away on & off for short periods, but without consequence on my boiler ignition circuit.

So I will unbind all devices and end up with the following config:
Cycle Rate = 6 (10 mins / hr)
Min On Time = 5 mins

System Devices
- Boiler Control = RELAY (this is the new relay4)
- HWS = enabled (this is existing relay1)

Zone Configuration
Upstairs:-
- Htg Type = zone valve (this is existing relay2)
- Temp Sensor = remote sensor (this is Y87RF)
- RF Binding = devices bound

Downstairs:-
- Htg Type = zone valve (this is existing relay3)
- Temp Sensor = Evo Touch sensor *** note below
- RF Binding = devices bound


System Summary
- HWS = hot water only valve
- Upstairs = Zone Valve
- Downstairs = zone valve - EVO touch sensor *** note below

Fail safe = disabled
Optimise = disabled

*** if I replace "EVO touch sensor" to "Remote Sensor" by adding a new Y87RF in "co" mode, do I need to unbind internal EVOcontroller stat somehow or is this done during EVO reset?

[Midori]

My boiler (Vaillant 418) is gas fired heat only open vent type. Burner start-up sequence to confirm electrics, pump running, fan pressure correct and open gas valve takes around 50 seconds. So when the Evohome relays open and close for one minute or so, my boiler gets abused real bad. There is no time for the burner to do its work and, even though there is a water pump run on period, the water is not heated anyway, the pump runs 100% thru bypass because zone valves are closed, and the rads stay cold of course. So every 10 Evotherm cycle minutes my burner gets abused and the rads get colder. I have to solve it or buy another manufacture's control product.

If you are saying the default EVO cycle is 6/hr (10 mins), that is what I have set (see above). I dissagree the MIN ON TIME (1 to 5) set at 1 minute is correct. Not only will it knacker my boiller, but also wear out the motorised valves earlier, after intial warm up, and the rads will get colder and colder each cycle. And it is a waste of gas! Perhaps I misunderstand Honeywell's purpose for Min On Time set 1 minute. Is it to pulse elecronic radiator valves (not fitted in my case) whilst the pump and boiler stays running?

[Midori]

*** if I replace "EVO touch sensor" to "Remote Sensor" by adding a new Y87RF in "co" mode, do I need to unbind internal EVOcontroller stat somehow or is this done during EVO reset?

And I wonder about how this internal sensor self binds. To bind a remote sensor (Y87RF) we have to be aware that "co" not "bo" mode has to be preselected during binding process. When EVO binds in the internal sensor how does if konw it is functioning in "co" mode and not "bo" mode ?