Room Thermostat Problem!

[diyclogger]

Hi All

Im a first time poster who's looking for some help after scratching my head trying to work out what the hell I've done wrong!!

So....Ive installed a new room thermostat - a Siemens Rev100 - and wired it (I believe) correctly - its a 2-wire unit, so red to L and yellow to L1.

Ive also had a new Honeywell ST9400 programmer installed recently and all was fine until the new room thermostat went in....now I cant get EITHER to switch the central heating on. Hot water from the Honeywell is fine, but heating isnt....can someone try and unpick this for me and tell me where Ive gone wrong? It seems as though the room stat has affected the programmers capability of turning on the heating....even if I take the batteries out of the room stat!!

 

[diyclogger]

Too add to this - I can get the 'flame' to come on the room stat but it doesnt seem to be calling for heat correctly as the boiler isnt flaring up....might it be a wiring problem after all?

 

[D_Hailsham]

What do the other ends of the red and yellow wires, connected to the Rev100, connect to?

 

[diyclogger]

I can tell you how they were connected in my old stat (a honeywell T6360B) - Earth to Earth, Blue to 2, Yellow to 3, Nothing in 4, Red to 1. Ive taped/blocked the Blue and Earth.

 

[picasso]

check the dipswitches are in the correct positions.

 

[diyclogger]

PIDs are in the 'self-learning' mode.

 

[picasso]

is the red that is connected to L in the rev100 connected to 4 in the honeywell programmer?

 

[diyclogger]

let me check...

 

[diyclogger]

its yellow in 4 and red in 3.....do I need to change over the wiring in the stat?

 

[D_Hailsham]

its yellow in 4 and red in 3.....do I need to change over the wiring in the stat?

But 4 is CH ON and 3 is HW ON! Are you sure they are the same yellow and red wires? You can tell because they should be within the same cable at both ends.

Do you have a HW cylinder, one or two motorized valves and a wiring centre (junction box) into which everything connects?

Do you have a multi-meter - and know how to use it?

 

[bengasman]

Sounds like you have wired them up in parallel, in stead of in series. With a heat only boiler, all the elements should be connected directly to the wiring centre, but it can work the way you have it; just a bit of a botch.

 

[diyclogger]

The full story is that I had a qualified sparky fit the honeywell, and clever ol' me thought that it was an easy job to just replace the stat - Im ok on electrical basics and didnt expect a stat to be much different than a socket or switch

I really couldnt tell you any more than what Ive posted already....I think theres a lesson in here somewhere

I assume that he wired up the Honeywell to work with my old 3-wire stat, and with me changing it to a 2-wire digi one Ive screwed it up somewhere along the line and got its knickers in a twist??

 

[D_Hailsham]

Many electricians do not know anything about wiring boilers and their controls; two- and three-way light switches are the limit of their knowledge.

If the original thermostat had been wired correctly, changing to the new one would have been easy and just as you did it. But a mistake has been made (not by you), which has to be sorted.

I asked if the red and yellow wires are in the same cable at each end. I really meant to say are they within one or two cables at each end.

Edit: In other words, how do you know they are the same red and yellow wires?

I asked if you had a multimeter (or even a neon mains tester). Any chance of an answer?

 

[diyclogger]

Both ends are a single grey cable with red yellow blue and earth. I can get a meter on it tonight. I don't actually know it's the same cable or not.....

 

[bengasman]

If you are convinced you can do a safe job yourself, just stick the switch wires of the stat in series with the switch wires or the thermostat. Job done.