New Digital Room Thermostat overriding boiler programmer!

[wrighthere]

Hi

I was wondering if anyone can help? I have just installed a new room thermostat as the old one stopped working. It all works fine, however it ignores the command of the boiler programmer and will simply fire the boiler whenever the temperature drops below what is set even if the programmer is set to off!

The old room thermostat had a 3 wire connection. The new digital thermostat only had a 2 wire connection, so after reading on here i wired in the red and yellow and made the blue safe.

Could this be what the problem is? Did i need a 3 wire thermostat for the programmer to work?

Any help appreciated.

Cheers

 

[Agile]

Firstly, you cannot assume any particular colour wires have been used.

If the red is live and the yellow the SL then the obvious assumption is that it was not working correctly before due to a system wiring fault.

Otherwise I cannot think of anything that you have done which would cause that.

Tony

 

[wrighthere]

Well the thermostat did work once and kicked in when the programmer said it should. It has to be a wiring issue i agree, i was just wondering how to solve it. Maybe the programmer needs to be wired up differently?

 

[wrighthere]

If it helps the programmer is a Honeywell ST699 Programmer,

Here is how its wired at the moment....

Honeywell ST699

• wrighthere
• 16 Oct 2014
• 1

 

[Richardthe3rd]

It depends if you have zone valves or mid-poss valves or not & how your new room thermostat is wired in. More details please.

PS. Great to see an old St699!!!.....

 

[wrighthere]

HI Richard,

....and you can still buy them!!!

I installed a Salus RT300 http://www.salus-tech.com/products/...ostat/_c1_30_digital-display-room-thermostat/

Standard wiring with L and SL. As i said in earlier post it was a 3 wire install but now just two.

From what i can see the wireing is based on Basic System 3, which i guess would make sense?

http://www.free-instruction-manuals.com/pdf/pa_458224.pdf

 

[First-time-buyer]

Edited...x-many


Questions..

With the timer disconnected...does the room stat operate the boiler? I would assume not.

With the timer disconnected, operate the room stat..the boiler should not light. Push the timer back on, i suspect it will light....

 

[Agile]

Have you fitted a new pump lately?

Tony

 

[wrighthere]

First-time-buyer:

I have just tried what you said and it all now works!!! Cant believe it, i take it all just need to reset itself? Great stuff, thank you so much.