Multi-zone system confusion!

[TriplVing]

I have a multi-zone central heating system in my new home (new to me but 9 years old) in what I believe is an S-plus design and I am struggling to work out why it is working like it is so was hoping someone could shed some light!

The system comprises an unvented cylinder and 2 zones, the upstairs and downstairs. There are three motorised Honeywell zone valves located next to the cylinder. At the moment, if I have the heating off and switch on the hot water, the boiler fires up and the zone valve activates, all good! Similarly, if I turn up the stat downstairs then the boiler receives the demand, the zone valve activates and the rads start to heat. However, the same doesn't happen for the third zone and this is where I'm confused.

If I turn the downstairs stat to off so the first zone is closed and then turn the upstairs stat to on then the stat clicks on but the boiler never fires and the valve makes no noise. However, if I have the downstairs stat on first (so the valve is active) then the upstairs valve activates and deactivates as expected.

I have done a bit of reading and know a common fault on these zone valves is that they don't activate the microswitch that in turn then activates the boiler, however I have had a look at it in operation (took the cover off) and when it works when the downstairs zone is active it definitely operates the microswitch. Similarly I have manually operated the switch and the boiler kicks into life. So the valve works, including its microswitch, it is correctly controlled by its thermostat but only when the downstairs zone is active.

I'm probably missing something obvious but I don't see why the second zone valve will only work when the first is active? Is this mis-wired somewhere do you think or do you think this is by design?

If I can better describe something then please ask as I am most definitely a novice!

 

[Whyme]

has anybody replaced a valve head recently ?

 

[TriplVing]

Don't think so, they all look original to me

 

[glenntaf]

Turn the downstairs and hot water zones off (no demand) and then turn the upstairs zone on and check if the upstairs motorised valve opens. If it does it could suggest a faulty microswitch (had a number of drayton ones go faulty recently) you can prove this by isolating the power, manually opening the valve and then checking for continuity between the grey and orange wires. if you have continuity then i'm afraid something is wired up wrong.

 

[TriplVing]

What i don't understand is why it works perfectly only when zone 1 is activated. If the valve was faulty then i would expect it to malfunction all the time, I'm guessing it's miswired somehow. Unless these valves are somehow able to be put in series so that one can rely on the other but if so that seems to be counterproductive, at the moment i can only use zone 2 when zone 1 is active? That can't be right surely?

 

[jonnyswamp]

Are you getting power to the upstairs stat when downstairs and hw are off

 

[PhoenixServices]

Sounds like it is not wired correctly. Get a heating engineer to rewire correctly or a sparky who can wire heating systems.

 

[chris watkins]

What time controls do you have? (Programer/s)

Reading through you seem to be operating thermostats to bring the zones on but the power to the them normally comes first from the time control.

 

[TriplVing]

Hi, i have a hive multizone system, so a dual channel receiver downstairs that controls the hot water and zone 1 and a single channel receiver upstairs that controls zone 2. The zone 2 receiver operates correctly without zone 1 being active i.e. if you use the stat to turn the heating on, the receiver clicks on and the green light to say the heating should be on comes on but the zone valve doesn't operate unless zone 1 is already active, meaning i can't heat zone 2 without zone 1 first being heated.

The system that hive replaced had exactly the same behaviour, so the problem is with the plumbing not the thermostat and controllers. Clearly the wire from the single channel hive receiver which controls the zone 2 valve works in terms of sending the signal but the zone valve itself doesn't react to the signal unless zone 1 is active, that can't be right can it?

 

[chris watkins]

No, the whole idea of having the upstairs (bedrooms) separately controlled is that it can be off during the times when not in use but downstairs (living areas) are.

Building Regs ask for separate Time & Temperature for each zone.

In saying that it would be unusual to require bed room heating without living areas.

I don't know much about Hive multi zone system but it sounds like you will need the services of a good heating engineer to check out the wiring / controls to confirm what is wrong.

 

[DaveTidy]

Wiring diagram website for honeywell zones (so you can see colours)

 

[TriplVing]

Thanks for all the help everybody! Following through the wiring diagram, I eventually worked out that the single zone (i.e. zone 2) receiver was wired slightly incorrectly for what I wanted. In fairness to British Gas, he just followed how the developers fitted it originally, which technically might not be considered wrong, just depends what you want.

Anyway, the "common" (i.e. pin 3 or secondary live) line in the single channel receiver was wired into the common line from dual channel receiver's circuit, when in reality for it to be independent, you simply link pins 2 and 3 inside the hive single channel (or indeed whatever thermostat you have controlling zones 2, 3 etc.) so pin 3 (the common) is always live rather than the downstairs circuit having to go live first. Only when both are live will the heat request signal be sent by the receiver to the multi-zone valve.

It's all working now, can control all three zones independently of each other, with each sending a demand to the boiler.

So thanks once again for all your help, this makes the hive system much more useful for me!