SOLVED! - Central heating only comes on if hot water is set to on

[stem]

looking at the plan stem sent of wiring i'm just missing cable going from terminal 7 to HW off on programmer... am i right? surely that's not all it needs?

Quite likely. The 'hot water off' connection is provided to tell the motorised valve to wind fully across to the heating only position. You definitely need it with a three port valve.

The 'hot water off' connection should go to the grey wire of the motorised valve.

 

[flameport]

Its british gas who keep telling me parts cant be purchased anymore

BG persons either get a big fat bonus for selling new boilers to people or may be required to sell a certain number of them. Perhaps both.
They might be tempted to make up stories about all kinds of things to get a sale.

and its off the charts in effeciency...well its G Rated anyhow

Obviously it will use more gas than a new one - but even if it saved you 30% on your annual gas bill, how much is that in money terms per year, and how long before you cover the cost of the new boiler? And after however many years that it, what state is the 'new' boiler going to be in?

Also consider that people may have had new boilers installed and claim vast savings - but those savings are not entirely due to the boiler, since replacing the controls (thermostat etc.) also has a big effect.

 

[oakc]

BG persons either get a big fat bonus for selling new boilers to people or may be required to sell a certain number of them. Perhaps both.
They might be tempted to make up stories about all kinds of things to get a sale.


Obviously it will use more gas than a new one - but even if it saved you 30% on your annual gas bill, how much is that in money terms per year, and how long before you cover the cost of the new boiler? And after however many years that it, what state is the 'new' boiler going to be in?

Also consider that people may have had new boilers installed and claim vast savings - but those savings are not entirely due to the boiler, since replacing the controls (thermostat etc.) also has a big effect.

thanks flameport! nice to be reassured!
_________________________________

thanks for all your replies - tado support have finally just got back to me and said they have changed the interface remotely and just testing it, it now appears to be working independently boiler fires up when turning thermostat up and stops when turning down with water off and boiler fires up when water is turn on and central heating is off and i'm assuming boths calling when both turned on (don't know how to test that exactly).... how the heck is that possible!?! i'm not convinced... surely if cabling is not there for hw off, it can't work....i'll keep an eye on it lol

 

[stem]

The 'Hot water off' comes from two separate places.

1. Programmer selected hot water set to 'off' and also
2. Cylinder thermostat satisfied (ie the hot water doesn't require heating)

If the hot water 'not required' signal is present from the hot water cylinder thermostat, it will work, but only when the programmer is set to hot water 'on'. When the hot water is set 'off' it wouldn't

 

[oakc]

but it does appear to be working.... i'm not entirely convinced though....although i'm wondering them making "changes to the interface settings" whether when i set programmer to central heating on and hot water off it's actually just calling for both (appearing to work with hot water set to off)

reason i'm skeptical is original wiring setup - central heating only wasn't possible purely because the programmer didn't have that capability... the switch master 400... although the original wiring for that didn't match the diagram on the back of the programmer... that said it should of had one wire to Heating on terminal, one wire to hot water on and one wire to heating off but it only cable wiring to HW ON and CH ON (no heating off/CH OFF) but that worked with hot water only... don't understand how now but it did.

so as it stands cabling in the programmer/extension kit whatever you want to call it i have N|L|HW ON|CH ON, nothing in the terminals for HW OFF and CH OFF.

 

[stem]

OK, if the original programmer didn't have the facility for the hot water off, then that would be why the wire is absent.

Try this sequence.

1. Start with the central heating set 'off' and hot water 'on' (make sure the cylinder thermostat is up so that the boiler actually starts to heat the hot water cylinder)
2. Switch the hot water to 'off'
3. Now switch 'on' the heating only (make sure the room thermostat is up, so that the boiler should start to heat the radiators)

Is the heating running now? (I would be expecting it not to operate at this point)

BTW, you shouldn't have anything in the CH OFF that's not required. The HW Off is a 'foible' of the three port valve.

 

[oakc]

OK, if the original programmer didn't have the facility for the hot water off, then that would be why the wire is absent.

Try this sequence.

1. Start with the central heating set 'off' and hot water 'on' (make sure the cylinder thermostat is up so that the boiler actually starts to heat the hot water cylinder)
2. Switch the hot water to 'off'
3. Now switch 'on' the heating only (make sure the room thermostat is up, so that the boiler should start to heat the radiators)

Is the heating running now? (I would be expecting it not to operate at this point)

BTW, you shouldn't have anything in the CH OFF that's not required. The HW Off is a 'foible' of the three port valve.

is it definitely a 3 port valve i have then? as the was questioned at start of this thread that system can't work independently without some plumbing work done?

and you are right the heating only doesn't work when water is switched off... when tado support change the interface i thought it was working because heating worked when hot water was set to off but in fact all it was doing was calling both as the hot water pipe to the tank got hot too (i'd waited for it to cool down) and i also confirmed this because i turned both the central heating off and the hot water off - waited for the boiler to fire down then turned the hot water thermostat up high and the boiler fired even with the CH and HW OFF set to off on programmer. so i've change the interface back from R02 to R01

anyway....now it works as it originally did, CH only comes on when HW is set to ON. i'm going to post what wires i've got in each terminal and where from and go from there...

 

[jackthom]

As stem said earlier, it's likely all you need now is a wire from the Tado HW OFF to the terminal where the 3-port valve Grey wire is connected in the wiring centre.

 

[oakc]

Awesome - tado came with wire so will use that - will be tomorrow now before i try but i will still post wiring here just incase to double check before i do it...

Thats for all your help so far lads, learnt alot

 

[stem]

is it definitely a 3 port valve i have then?

Yes you do. And because it has three ports (in / out to heating / out to hot water) that is where the term 'Y' in 'Y Plan' comes from

and you are right the heating only doesn't work when water is switched off...

So you know what you have to do...

 

[oakc]

Yes you do. And because it has three ports (in / out to heating / out to hot water) that is where the term 'Y' in 'Y Plan' comes from


So you know what you have to do...

.....aaaaaaaaannnnnnddddd it's working!!!! yay! thanks so much everyone especially you stem! connected cable to T1 (HW OFF) in Tado extension kit to the T10 being used by yellow cable for hot cylinder stat and grey cable from mid actuator valve and hey presto!

 

[stem]

Excellent! and well done, particularly as you spotted that the wire was missing yourself. Thanks for the update, it can help others that may stumble across this thread searching for help with a similar problem.

 

[oakc]

but i wouldn't of spotted it if you hadn't pointed me in the right and been so persistent - yes hopefully this thread could now be useful to others in the future