Dormitory and living area zone valves?

[ericmark]

I can understand the idea of splitting the heating between the two areas of the house, with a timer (programmer) selecting between the two, however I can’t understand how the anti-cycle wall thermostat is deployed when splitting the output of the boiler?

Assuming no electronic TRV heads as if they were fitted then zone valves would not be required, so I would assume some way the micro switches in the zone valves will need to switch between two wall thermostats in a way where you never have both connected at the same time, as you can’t as far as I am aware fit two modulating thermostats.

I see Orange (Com) White (N/C) and Grey (N/O) wires which seem to be volt free, and integral by-pass valves built into the motorised valve, and many circuit diagrams showing how they were used before the modulating boiler and thermostat were common place. I see adverts for auxiliary switches so may be it needs these to work with two heating zones.

However the terrier i30 TRV head is just £17 and motorised valve double that and requires extra pipe work so house would need to be over 3 bedroom to ever be worth using motorised valves to split between dormitory and living area, and it would also be hard to change use of single room, be it an office upstairs or bedroom downstairs, and it would also impact on wall thermostats.

I am at the moment looking at moving, I realise valves could be energised at all times and use electronic TRV head instead, but this would I assume mean a wiring change to the wall thermostat/s.

And although central heating does not NEED a wall thermostat, without it then the user needs to decide when to turn off the system to prevent cycling, and whole idea of zone valves is automation, one could also turn radiators off/on so rather pointless unless automated.

 

[SimonH2]

The "classic" way of using multiple zones is to have a thermostat for each zone. The output of the thermostat powers the motor in that zone's valve and nothing else - assuming S-Plan (Y-Plan is a bit more complicated but doesn't do multiple heating zones). When the valve opens, the microswitch inside closes and connects the orange and grey wires together. Parallel all the microswitches (so connect all the oranges together, and all the greys together, and connect these across the demand terminals for the boiler.
Result: when any zone valve is open, boiler runs; when all are closed, boiler shuts down.

You can have as many zones as you want - traditionally the heating coil in the DHW cylinder is a zone of it's own. I heard tell that the bungalow up the road from us back in the 70's had some custom work in it (it was built after our house) - specifically a zone valve and wall stat for each room. That was majorly complex for it's day. And effectively, that is now replicated by these electronic TRV heads that radio back to a control box to signal when heat is required and the boiler needs to run.

Now, reading your description, you clearly have something a bit more than just a standard 2 port zone valve. To start with you have a white wire as well which is not standard, and an internal bypass valve.
One issue with S-Plan is that (especially if the pump is boiler controlled and has run-on) you can have a situation where all the zone valves are shut and the pump is then dead-headed. So a bypass is needed so that the pump can still pump round the boiler when all the zones are shut.

 

[ericmark]

The "classic" way of using multiple zones is to have a thermostat for each zone. The output of the thermostat powers the motor in that zone's valve and nothing else - assuming S-Plan (Y-Plan is a bit more complicated but doesn't do multiple heating zones). When the valve opens, the microswitch inside closes and connects the orange and grey wires together. Parallel all the microswitches (so connect all the oranges together, and all the greys together, and connect these across the demand terminals for the boiler.
Result: when any zone valve is open, boiler runs; when all are closed, boiler shuts down.

You can have as many zones as you want - traditionally the heating coil in the DHW cylinder is a zone of it's own. I heard tell that the bungalow up the road from us back in the 70's had some custom work in it (it was built after our house) - specifically a zone valve and wall stat for each room. That was majorly complex for it's day. And effectively, that is now replicated by these electronic TRV heads that radio back to a control box to signal when heat is required and the boiler needs to run.

Now, reading your description, you clearly have something a bit more than just a standard 2 port zone valve. To start with you have a white wire as well which is not standard, and an internal bypass valve.
One issue with S-Plan is that (especially if the pump is boiler controlled and has run-on) you can have a situation where all the zone valves are shut and the pump is then dead-headed. So a bypass is needed so that the pump can still pump round the boiler when all the zones are shut.

Pre-modulating boiler what you describe would be great, however with a modulating boiler there are two way to control the modulation as I understand it, one temperature of return water, and two connection to the boiler's bus. As far as I am aware you can't parallel up multi modulating thermostats, and if you switch the boiler off/on with a mark/space ratio to control output it is very wasteful.

However without water flow a boiler can't know how to either modulate or once fully modulated and using mark/space ratio what is required, so it without a thermostat will fire up every so often to test what is required, to prevent that we use on/off wall thermostats traditionally in a cool room down stairs with no outside door or alternative heating.

There is no reason why we should not have loads of on/off thermostats one for each room so if any room needs heat the boiler will run, and if we used programmable thermostats the times and temperatures could be set to match the electronic TRV heads so the pair both work together, however in real terms a couple of thermostats is all that is required, selecting rooms carefully, this is how this house works, it does go wrong from time to time, main problem is times and day seem to alter on thermostat so they don't match, but it works.

I would guess with motorised valves today the wiring is very different to old days, with a programmer/timer working valve and the valve connecting and disconnecting the thermostat/s from the boiler, so what ever the temperature once valve is closed there is no connection to thermostat/s. This is OK with an off/on thermostat, it would not matter if there are 10 in parallel, but this would not work with a modulating thermostat.

So to use zone valves it would need some computer type device that monitors the modulating thermostats and combines their signals to give a single output to boiler, in essence a central heating PLC. However I have not found one.

Using electronic TRV heads you can get a special thermostat which combines the report of up to 6 heads and then sends info to the boiler, I am lead to understand there is an add on to EvoHome which does that? But not found anything similar for zone valves.

At my age I am against DIY control systems, as although as an electrical engineer I am sure I could build one, I could also get alzheimer's disease or die and then be unable to maintain it. So I am looking for a standard off the shelve way to run the heating once we move to new house. And for some unknown reason new houses seem to be split into zones for dormitory and living areas, I am lead to understand it is some thing to do with building regulations, so how do you control these zones with a modulating boiler?

 

[SimonH2]

One simple way that any sparky with 2 brain cells to rub together should be able to maintain, though dunno about your average plumber, might be ...
Wall stat in each room, and rather than zone valve, use a thermo-hydraulic head on the TRV - actually, just copy the standard setup for zones UFH but instead of a bank of heads on the manifold, they are on the rads. The boiler will still need to modulate itself, but it will only be demanded to run when at least one room is calling for heat. It's still going to be rather on-off for each room - short of just using programmable TRV heads all interlinked to generate boiler demand, I think that's going to be hard to avoid.

 

[ericmark]

I have looked at my existing TRV heads, they report target temperature and current temperature, theory is easy, if this "target below current on any valve" then run that boiler. Note the words if this then that (IFTTT). However I have not worked out how to do that, I would think I would need an Energenie MiHome relay to actually switch the boiler off/on, but all I have found program wise is the ability to pair the TRV heads with Nest, and if connecting to boiler bus then I can see the advantage with Nest, however a Worcester Bosch boiler does not have OpenTherm and you have to use their own thermostat "Wave" but their thermostat will not pair with any TRV head, so it just controls one room, rest of house is pot luck. Hence why at moment just use two wall thermostats in parallel to switch off boiler when no longer required.

However as we have been looking at houses to move to, I have found new houses seem to have zone valves fitted, Normally two thermostats and some sort of timer (programmer) however in the main pointless asking vendor how wired, they don't know, and not the time to do a full survey of the house.

There must be one assumes a standard method to wire zone valves, but although I can find how to wire with non modulating boiler, simple thermostat works zone valve which in turn works boiler, I can't find out how it is wired using a modulating boiler, timer (programmer) will clearly operate valves at set times of the day, but without zone valves you would have a thermostat of some type some where either regulating boiler output or stopping boiler cycling as the weather warms up.

Maybe it is connected to internet weather reports, or a outside sensor, but pointless having a wall thermostat in an area not being heated as zone valve off, so it would one assumes need to select a thermostat depending on which zone is being heated, and a modulating thermostat can't work the zone valve and zone valve work boiler zone valves are either open or closed, so it would need to swap between two thermostats, question is how is this normally done?

 

[SimonH2]

OpenTRV reports valve position amongst other things. I had been pondering a setup where I'd modulate flow temperature based on the widest open valve - perhaps something like "there's a valve above 50%, increase temp; all valves are below 25%, decrease temp". With a store in place, I'd use a mixing valve & thermo-hydraulic actuator to set flow temp. Unfortunately it looks a bit like OpenTRV/Radbot has stalled a bit and they aren't available. It seems they'd completed some reasonably large scale trials in social housing and were planning to have a proper launch - but were advised that it was the wrong time. Not heard much since.
With that in place, there's then scope for controlling the boiler along the lines of "if upper temp sensor below setpoint OR if (lower temp sensor below required CH flow temp +x˚) THEN run boiler". So the boiler only runs if the upper section (hot water provision) needs heat, or if the middle section (where heating is drawn off) isn't hot enough to supply CH requirements.
In the flat there's a simple pocket stat just below the CH supply tapping that runs the boiler - and it seems to work well enough.