Honeywell T6620B Wiring

[stoatgobbler]

I have recently installed a Honeywell t6620B room Stat(replacing a very old stat) Since doing this a switched fuse to the programmer blows every time the heating is activated (ie set to 21 degrees)
I am wondering if the Stat is\wired correctly. 3 wires that are connected to it are : red, black and green/yellow.
I have read some posts that say not to use the neutral wire on a digital stat. Is this correct?
someone Please can someone tell me the correct wiring for this stat?
thanks

 

[namsag]

Is your stat the digital display one . If so you just use live in live out to connections A and B no earth or neutral.
Ifg its the mechanical one then live in is 1 live out is 3 and neutral is 2.

Dont think because you have a red ,black and green/yellow that these equate to live neutral earth , you have to test to see which one is live in and live out etc

 

[stoatgobbler]

Thanks,
Yes it is digital, previous one was a manual dial.
I dont have a tester so will have to call on an electrician. The stat displays the temperatures ok. I have all three \wires connected at the moment. Would that cause the fuse to blow?

 

[namsag]

Because you have connected a wire that should not be connected , can you remember if your earth wire was connected to an earth on old stat.

How have you connected 3 wires as terminal C has a blank above it

 

[stoatgobbler]

Not sure if eath was wired in old stat. Attached pic of wiring. Sory about poor quality

 

[londonboy]

remove that earth and stick in small connector block, as said above I thought there was only two connections on these stats, A and B. I think (off memory) move the black to the terminal where the earth is at the moment.
Also the black should have brown/red sleeving on to indicate live conductor.

 

[stoatgobbler]

thanks,
Would this currrent wiring cause the switched fuse to blow?

 

[londonboy]

Yes, because your probably shoving 240v down an earth wire!

 

[stoatgobbler]

not sure if im brave enough to do that. may have to wait for an electrician!!!

 

[londonboy]

If you were brave enough to install in the 1st place then you should be able to remove and swap two cables!

 

[johnfox]

put your old thermostat back on.then get a qualfied person in to correctly fit digital stat.

 

[D_Hailsham]

Many old stats had three terminals: Live, Switched Live and Neutral. It was common for these to be wired using two core plus earth cable with the red used for live, black for neutral and the earth for the switched live.

Putting the red wire into the A terminal will be OK, but it would be guessing to know which wire should go into the B terminal (C is not used).

If you can remember how the old stat was wired and which make/model stat it was, the correct wiring can be given to you.