drayton combistat RTS8

[suffolklad]

hi all i fitted the above room stat to my worcester 28si been working for last two weeks but lately ive noticed hearing like arcing sound from stat for a little while as it switches ,i didnt notice it when it was first fitted . its wired correctly using 0.75 flex , 3 wire connection as per instructions . i took stat case off to look what happens and i could see little arcs as the switch tried to seperate . QUESTION IS SHOULD THIS HAPPEN. i am thinking that perhaps this is not good for the boiler if its not switching correctly, is their a set time that it should take for it to switch?. any help most welcome paul

 

[D_Hailsham]

No it should not be arcing.

Are you sure you have wired it up correctly? The instructions are here if you have lost them:

http://www.invensyscontrolseurope.c...6A-4E3F-A026-625C98E429AE/0/D512CombiStat.pdf

There are different connections depending on the current drawn; but the top diagram is the usual one

What sort of cable are you using? I trust you are not using twin + earth.

The correct cable is three core plus earth, even if you do not use the earth.

 

[suffolklad]

so why mustnt you use twin and earth flex ? surely ok if wires are taped correctly an earth is not needed anyway. it was ok for first week or two its when the stat is set at 20 more than anything its as if the switch doesnt want to seperate very quick . if i turn it to a point near 20 it does it

 

[D_Hailsham]

so why mustnt you use twin and earth flex ? surely ok if wires are taped correctly an earth is not needed anyway.

In your initial post you said:

its wired correctly using 0.75 flex , 3 wire connection as per instructions

I took this to mean that you were using all three wires. This would mean that you would have to use the earth lead as the switched live to the boiler. This is very bad practice as anyone not knowing what you had done would automatically assume that this was the earth wire

From what you now say you are only using two wires: live to the thermostat(?red or brown and switched live to the boiler (?black or blue)

If you look at the wiring diagram the thermostat needs three wires: Live, Neutral and Switched live. The correct way of doing this is to use a three core cable or a three core + earth, even if you do not use the earth.

it was ok for first week or two its when the stat is set at 20 more than anything its as if the switch doesnt want to seperate very quick . if i turn it to a point near 20 it does it

Check and double check your wiring. Are you using the correct terminals? See the instructions at the URL in my earlier post.