Boiler Won't Stop When Stat Satisfied.

[BlueToBits]

Can anyone please help with this one?
Our boiler often keeps running when the stat is not calling, but not always

Boiler: Worcester Greenstar R25/30 HE combi (standard condensing combi)
Control: Sunvic TLX RFP Radio Freq Programmable Thermostat circa 2006

Receiver power is supplied from boiler terminal Ns (neutral feed ) Ls (live feed) and Lr (Switched live) as per boiler instruction book.
The receiver has a red power light (lit all times) and a green heat call (boiler run) light

1) With everything connected and the stat is NOT calling, there is 130V on the switched live. I suspect this is enough to keep the boiler running.
2) When the switch wire is disconnected at the receiver the voltage at the output terminal disappears but remains on the disconnected (floating) cable and at the boiler's Lr terminal
3) When the same call cable is disconnected at the Lr boiler terminal the voltage disappears everywhere.
The insulation resistance test (500v) on the fully disconnected cable (approx 3 metres of 3 core & E) is over 200Megs between all conductors.

Where is the 130V coming from?

 

[alli]

I remember doing work with a Worchester combi and I pressed the manual overide switch on the front of the boiler to make sure the boiler fired okay, I got sidetracked and left the switch on, I got a real cheesed off phone call saying they had gone through half a tank of oil in a few weeks!

Does your boiler have a frost stat, and if so is it working properly and not sticking on.

Edit: Sorry, just re-read your post. If in 2) when you dissconnect the cable does the boiler stop firing? If it does forget what I wrote. It would sound like a problem with the wireless stat