The Efficient Home Forum

I am setting up an evohome system with 11 zones and hot water.

The existing system is a standard S-plan setup as shown in the installation guide on Page 42.

Most zones have a single radiator (with HR92’s) a couple have multiple radiators (each with HR92’s) . There are also a couple of fan convectors not controlled by evohome, because there is no way to shut off the water flow, if the heating motorized valve is open, there will be water flow through most of the heating system plumbing.

I expected to be able to open the heating motorized valve when any evohome zone requested heat based on each zones individual temperature / time schedule, and the hot water motorized valve to open based on the hot water temperature / time schedule and hot tank sensor.

However none of the setup guides for the various heating controls (pps 18, 20, 21, 22,24,26) seem to match an S plan system.

The 1 promising match (p 22 wireless relay box to control a zone valve) only allows a single evohome zone to control the relay. This mimics the use of a simple wall thermostat controlling the heating motorized valve. Getting better control of the heating motorized valve was a primary reason for getting the evohome system.

If I remove the hot water control from the evohome system, and use a single BDR91 to control the heating motorized valve, then all works very well. BUT since this control believes the BDR91 is a boiler control, when I add the hot water control to evohome, the heating motorized valve opens when there is hot water demand. This is very wasteful in summer and even worse adds more heat to the house in very hot weather.

Can I setup evohome to work properly with an S-plan heating setup with multiple evohome zones controlling the single S-plan motorized valve?

The short answer is no.

evohome was designed for all radiators to be controlled by HR91/HR92 if you use them. There is no 'plan' for evohome... S Plan, S Plan Plus or Y Plan systems are supposed to be modified to evohome's own system schematic in order to work optimally. So in the case of S Plan/S Plan Plus, the heating valve is disconnected and manually left open (or removed if you really want to but this is unnecessary).

As for your kickspace heaters, a straight valve (https://theevohomeshop.co.uk/radiator-v ... aight.html) mounted with a HR91 (https://theevohomeshop.co.uk/honeywell- ... -hr91.html) with a DTS92 or T87RF in the room as a sensor (https://theevohomeshop.co.uk/25-wireless-thermostats) will ensure these work as part of evohome. Done many like this with great success.

OK thanks, rather disappointing, that for the lack of a trivial extra facility in the controller software I have a whole lot more to do.

pootle wrote:OK thanks, rather disappointing, that for the lack of a trivial extra facility in the controller software I have a whole lot more to do.

TBH, all the other multi-zone systems work exactly the same as this and any good evohome installer is aware of this too. If you are self installing, then I appreciate you might not be aware of this, but its quite fundamental to the operation of multi zone systems, as they are the devices that control the flow now, not the motorised zone valves (with exception of the hot water motorised zone valve).

there is a way actually to do that. first you configure the heating as usual, tie first BDR91 to do appliance control, enroll thermostats and radiator controls. Then configure your hot water, use guided setup and choose 2 valves configuration. It will ask you to bind second BDR91 for hot water valve and rebind first BDR91 as the heating valve. then , go to the system devices, appliance control and set it from wireless relay to none. thats it, your 2 zone valves now control hot water and heating just like they used to. i just finished such setup and tested, works like a charm.

AntonB wrote:there is a way actually to do that. first you configure the heating as usual, tie first BDR91 to do appliance control, enroll thermostats and radiator controls. Then configure your hot water, use guided setup and choose 2 valves configuration. It will ask you to bind second BDR91 for hot water valve and rebind first BDR91 as the heating valve. then , go to the system devices, appliance control and set it from wireless relay to none. thats it, your 2 zone valves now control hot water and heating just like they used to. i just finished such setup and tested, works like a charm.

Yes, but the operation is not optimal, as per the hands-on evohome training (if the heating motorised zone valve fails, it leaves a fail point evohome does not know about although all the HR91/HR92's might be calling for heat).

Best way to do this is when you go through the 'STORED HOT WATER CONFIGURATION' in the 'GUIDED CONFIGURATION' menu you pair the CS92A as the sensor and then select 'HOT WATER ONLY VALVE' instead of 'TWO PORT OR THREE PORT VALVES' then bind the hot water valve BDR91 (heating valve is completely disconnected and has no BDR91).

I have stored hot water and zoned heating with HR92's on all radiators. I have a CS92 cylinder stat with a BD91 wireless relay box controlling a zone valve dedicated to the hot water coil in the tank.
My problem is that the hot water BD91 appears to operates the hot water zone valve based only on the CS92 cylinder stat and not in conjunction with the central controller. With all zones and hot water turned off on the central controller and with hot water in the tank the coil in the tank can thermo-syphon and loose heat to radiator pipework.
Is this likely to be a controls problem or system limitation?
Brian.

BJR wrote:I have stored hot water and zoned heating with HR92's on all radiators. I have a CS92 cylinder stat with a BD91 wireless relay box controlling a zone valve dedicated to the hot water coil in the tank.
My problem is that the hot water BD91 appears to operates the hot water zone valve based only on the CS92 cylinder stat and not in conjunction with the central controller. With all zones and hot water turned off on the central controller and with hot water in the tank the coil in the tank can thermo-syphon and loose heat to radiator pipework.
Is this likely to be a controls problem or system limitation?
Brian.

Sounds like you have a problem beyond evohome? Contact a local competent heating installer.

The EVOHOME Shop wrote:The short answer is no.

evohome was designed for all radiators to be controlled by HR91/HR92 if you use them. There is no 'plan' for evohome... S Plan, S Plan Plus or Y Plan systems are supposed to be modified to evohome's own system schematic in order to work optimally. So in the case of S Plan/S Plan Plus, the heating valve is disconnected and manually left open (or removed if you really want to but this is unnecessary).

As for your kickspace heaters, a straight valve (https://theevohomeshop.co.uk/radiator-v ... aight.html) mounted with a HR91 (https://theevohomeshop.co.uk/honeywell- ... -hr91.html) with a DTS92 or T87RF in the room as a sensor (https://theevohomeshop.co.uk/25-wireless-thermostats) will ensure these work as part of evohome. Done many like this with great success.

Sorry if I'm being a bit thick here. If you have a BDR91 on the hot water valve. And a BDR91 on the heating zone valve. Then Evohome will open the Heating zone valve every time hot water is called for. The solution is for the heating zone valve to be fixed open all the time. Isn't it the same thing ? In both scenarios the heating zone valve is open when hot water is called for.

Ben565 wrote:

The EVOHOME Shop wrote:The short answer is no.

evohome was designed for all radiators to be controlled by HR91/HR92 if you use them. There is no 'plan' for evohome... S Plan, S Plan Plus or Y Plan systems are supposed to be modified to evohome's own system schematic in order to work optimally. So in the case of S Plan/S Plan Plus, the heating valve is disconnected and manually left open (or removed if you really want to but this is unnecessary).

As for your kickspace heaters, a straight valve (https://theevohomeshop.co.uk/radiator-v ... aight.html) mounted with a HR91 (https://theevohomeshop.co.uk/honeywell- ... -hr91.html) with a DTS92 or T87RF in the room as a sensor (https://theevohomeshop.co.uk/25-wireless-thermostats) will ensure these work as part of evohome. Done many like this with great success.

Sorry if I'm being a bit thick here. If you have a BDR91 on the hot water valve. And a BDR91 on the heating zone valve. Then Evohome will open the Heating zone valve every time hot water is called for. The solution is for the heating zone valve to be fixed open all the time. Isn't it the same thing ? In both scenarios the heating zone valve is open when hot water is called for.

No you are not being think. But ask yourself what happens when the heating zone valve fails?