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kirky76

Hi All,

Just moved in to a new house and trying to work out the central heating system which is currently beating me!

System uses a Worcester CDI 30 Boiler which provides instant hot water so no hot water tank. There is a Drayton Digistat wireless thermostat in the hall.

The issue I have is that I can't seem to stop the central heating from getting hot. The only way I can adjust things appears to be by manually adjusting the CH knob on the actual boiler which reduces the temperature of the radiators. If I set the knob to about 3 then the radiators are permanently on, even though the green LED on the Drayton box remains off.

Any pointers greatly appreciated!

Thanks,
Mark
 
push the bottom button on the receiver and the green light should go out and change the batteries
 
Hi Gasmarc,

Thanks for the quick response. I probably didn't explain properly. The Green LED on the receiver isn't on. It only comes on when I manually increase the temperature on the thermostat temperature above the level of the room temperature so I'm assuming that this is all working correctly.

Basically, the radiators are hot when the CH isn't switched on (no green LED). I can reduce the temp of the radiators only by adjusting the radiator thermostats directly or by reducing the temperature knob on the boiler. I will replace the batteries to remove this from the equation but any further thoughts would be appreciated.

Thanks.
 
that is weird ,it is a combi boiler and you are getting heating even though it is not switched on ? is your hot water normal
 
Yep. Hot water seems to be perfectly fine. Have been in the house for a few days and we're getting good hot water.

Getting a little annoying having to adjust the temp directly on the boiler just to stop the house from over-heating! Doesn't make any sense to me. The boiler fires on and off throughout the day, I'm assuming this is due to the boiler being set to pre-heat the water.
 
if you turn the preheat off that may solve the problem, if you switch the boiler off and its cold and the preheat is off the boiler should not come on for heating, there could be an issue with the diverter valve maybe if the heating is coming on with the preheat is switched on
 
It sounds like the diverter valve could be letting by and if the preheat is constantly on demand it will heat the rads up ,if that makes sense
 
is it the greenstar 30cdi or the old one with the grey bottom panel?
 
Hi All,

Thanks for all the replies. The boiler is the 30cdi, not sure if that helps point to the problem?

I'll have a play with the pre-heat and see what happens with the radiators in the mean time. The odd thing, which could be a red herring, is that the temperature of the radiators goes up/down based on the CH temp knob on the boiler. I have to set it to 1 just to stop the house from over heating.

Thanks,
Mark
 
Hi All,

Been doing a bit more troubleshooting on this one and it appears that the issue I have is that the boiler CH is running all the time, i.e. the pump is running even when the green light on the Drayton thermostat receiver is off i.e. thermostat indicates that no CH is required. Suspecting no either a fault with the Drayton receiver or with the wiring/control board on the boiler. Not sure which is the most likely or how to troubleshoot further. Any suggestions?

Many Thanks,
Mark
 
Yeah, kinda what I'm thinking. Just had a quick look around the boiler and the Digistat SCR box to look at the wiring. I'm no expert, but the boiler only appears to be connected on the Ls and Lr terminals, there is nothing on the Ns. Worcester define these as Ls = Thermostat Live Supply, Lr = Thermostat Live Return and Ns = Thermostat Neutral. Would this be normal? How likely is it that the Digistat SCR box is simply broken and is not switching off when the room is up to temp?
 
i suppose its possible that the receiver is stuck in the on position,just check if you are getting voltage on both wires and if so its shot and needs replacing
 
Hey Gasmarc,

Yep. Just done further checking and it would appear that the relay in the SCR is stuck open so just ordered a new one. Thanks for all the help and pointers.

Mark
 
I wonder if the the digistat is connected inside the boiler? Cos the boiler seems to operate independently of the RF Programmable Roomstat.
Sometimes these digistats have to be re-bonded to each other. If you go on the manufacturers web site you can download the procedure.
Can't locate a Hyperlink, but if you Google -
Digistat RF Troubleshooting Procedure

Its made by Drayton Invensys.

You can also get it from Worcester Bosch web site
 
yes they have to be paired with each other also it helps sometimes to change the batteries
 
the boiler only appears to be connected on the Ls and Lr terminals, there is nothing on the Ns.
Presumably the SCR is getting power to the L and N terminals from somewhere else. The Ns boiler terminal is only there for older mechanical thermostats which needed a neutral connection for the anticipator.
 
if there is only 2 wires going to it there cannot be a neutral other wise it would not work unless there is an internal fault on the boiler and if there was the hot water would not work, then again i could be wrong
 
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