Heating system eating fuses after thermostat change...

[andybt]

Hi Folks,

I recently replaced a thermostat on my heating system and am having problems getting the right wires on the correct terminals on the new thermostat. My old thermostat was a Honeywell T6360 and has 4 wires. The terminals were:

1. Live - Red Wire
2. Blue Wire
3. Yellow Wire
4. wire - Earth.

From the wiring diagram the blue and Yellow wires go to Neutral. The Yellow wire passes through the "heating load".

I have replaced the above thermostat with a nice shiny new digital one a Drayton 30002. The options for wiring are:

1. Common / Switched live from time control
2. On
3. Off
4. Neutral
5. Earth

I have tried the Red on Common but this is giving me 240V even with the timer off. If I out the yellow wire in the "On" position the system will heat the radiators, but all of the time i.e. even when the timer is off.

The new thermostat has batteries so do I still need the Red "live" wire or can this be capped off, and then which way round should I be looking for the other wires. I turned the timer on to see if I had a voltage between any combination of the other wires but they were al at 0?

Any clues would be appreciated. The thermostat in question runs our upstairs radiators only as downstairs in underfloor heating in a zone system. The thermostat connects to a two port motorised valve.

Andy

 

[twgas]

if you have a permanant live to room stat either programmer faulty or wired wrong.

 

[simond]

Terminal 4 on a T6360 is not earth. It is the CH off terminal.

Please explain what you mean.

With heating electrical work the colour of the wire often leads to presumptions which are found to be incorrect.

 

[andybt]

twgas, sorry not explaining myself too well there!! The wire was no 4 and is the earth wire connected to the earth point. On the Honeywell thermostat terminal 4 is not used.

The thermostat was changed as the radiators were not calling for the boiler to switch on and heat the system. I changed the thermostat first as that seemed the easiest bit!!!

I've reset the programmer and I will see if that has helped at all regarding the live wire. The system has been in for 8 years and working fine up until it started kicking in this week.

Andy

 

[gas4you]

Only the blue wire should go to neutral. The Yellow wire is the switched live return to the motorised valve or boiler/pump.

This is why the fuses are blowing, you have created a dead short by linking these two.

 

[andybt]

Thanks for the quick reply Dave. I'll go and have another go. From your response I can cap off the Yellow wire. ad just have red / blue connected, and the Earth of course!!

Andy

 

[twgas]

I would advise getting in a heating engineer - from your posts and 'I'll try's' - you are clearly not "electrically minded"

 

[gas4you]

Thanks for the quick reply Dave. I'll go and have another go. From your response I can cap off the Yellow wire. ad just have red / blue connected, and the Earth of course!!

Andy

NO.

The red wire will be live in and the yellow wire is usually the switched live out to whatever the stat is contolling.

The blue neutral is used to keep warm the anticipator to give more accurate temperature readings.

I do not know this stat, but I would say that red =1, yellow =2 blue =neutral, earth is earth.

 

[andybt]

Thanks again Dave.I've changed the wiring as you suggested and the boiler fires straight away. I've had a look in the control unit and there is evidence that something has got hot in there so possibly a fault in the controller.

I'll fit another controller and hopefully that will do the trick. If that doesn't work I'll follow twgas's suggestion!

twgas. The "I tried" bit was to show what had already been done before i wrote asking for help.

Andy