help needed please

[Dougie212]

Hi there...

I hope someone is able to help, it's needed urgently......

I have an old Valliant Combi boiler with a British gas EMT2 timer fitted and a room thermostat downstairs.

The room thermostat dated to the 60's so I brought a Honeywell T6360 to replace it. When I took the old one off I found a red,black and earth cable, and a single red on it's own. I was advised..(hmm) to firstly try wiring the thermostat without using the single red. I did this but the boiler wouldn't fire up. I was then advised (hmm) to simply connect the 2 red wires together. This had the desired effect the boiler sprung to life... however when I lowered the thermostat past the switching point the trip switch clicked.

When I turned the power back on I found that the boiler wouldn't fire up again. There is a light on the timer and I can hear the clock mechanism working. I have since put the old thermostat back on and still the boiler wont fire up.

I have now been advised, by someone else!!.. that I dont really need the thermostat as the house is only small and needs to be cranked up to make any difference anyway, so does anyone know first of all how I would I remove the thermostat from the circuit?? Does anyone know how they are wired into this timer..??

The other thing I need to know is is there a fuse in the timer or boiler that will have blown when the power tripped?? There is obviously power getting to the timer as the mech and light is still working, it just doesn't seem to be getting out the other side...

Your help in this is very much appreciated.!!

Dougie

 

[flameport]

The thermostat you have got requires a permanent live and permanent neutral. The 3rd terminal is a switched live which is what controls the boiler.

The wires you have MAY be a live, switched live and neutral. However they could just as easily be some other arrangement. You will need to identify the wires before anything else.
Randomly connecting them could damage other parts of the system.

Whoever told you that a room theremostat is not needed is a fool.
Without it, you can expect the house to get excessively hot and stay that way. You can also look forward to a massive gas bill.

 

[Space cat]

however when I lowered the thermostat past the switching point the trip switch clicked.

How did you connect the wires to the thermostat? It sounds very much like you were using the wrong terminals, maybe from the outset. The neutral wire MUST go on the correct terminal, namely the one that DOESN'T connect to either side of the internal switch. (I don't have a picture of your thermostat in front of me right now.)

If you had neutral on one of the switch terminals and live feed from the timer on the other, turning down the thermostat would close its switch and short out the supply. The resulting heavy current would trip the breaker - which is what happened - but it is also likely to have damaged the timer switch --

Randomly connecting them could damage other parts of the system.

You'll probably need a new timer.

 

[ericmark]

As the others have said you need to identify the neutral.

As to need for thermostat where all radiators are fitted with thermostatic radiator valves and you have a modern boiler of condensation type often there is an electronic system which is designed as an anti-cycle device which measures the time it takes for hot water to return and if over set time then increases cycle time and if under decreases cycle time.

If you are using one of these modern boilers then the thermostat is really only to turn off system in Summer.

But on older boilers the software does not exist and even with thermostatic valves on every radiator the boiler will cycle on regular basis around 20 minutes or less and it would be both costly and tend to warm the house from the warm pipes.