Cant turn off heating on a Worcester Greenstar

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Peter Lowthian

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Hi all
Im having a problem with my boiler as i cant turn the heating off (unless i turn the dial to frost mode).
I have removed the RX1 from the back plate and i have 240v on Ns and Ls and i also have 240v on Lr which if i'm right should be 0v and only 240v when the RX1 sends the 240v to the boiler via this connection.
As it looks like Lr is constantly 240v will this keep the heating on. Can anyone help me out here on what else i can check out before calling the Cavalry.?
Thanks for any help it appreciated.
 
Is it a new boiler and do you have a room stat fitted I'm assuming the link has been removed usually a grey spade connector
 
Any particular Greenstar model? There's about 50 to choose from so if you can give us a clue we might be able to help
 
Hi thanks for the reply its a Greenstar 24i Junior. It is conected to a Danfoss RX1 and a wireless connection to a TP5000 RF Si.
The problem i,m having is that the boiler wont turn off, its been fitted for years and working great until recently.
It does not have a hard wired thermostat so that cant be the problem.
I think the boiler has an internal issue as i get mains voltage on Lr even when the Danfoss RX1 has been removed.
thanks again for your help in this.
 
Peter Lowthian said:
I have removed the RX1 from the back plate and i have 240v on Ns and Ls and i also have 240v on Lr which if i'm right should be 0v and only 240v when the RX1 sends the 240v to the boiler via this connection.
Click to expand...

That is correct, Ls (Live supply) should be 'live' permanently. Lr (Live return) on the other hand, should only be 'live' when the controls 'call for heat'.

Peter Lowthian said:
i get mains voltage on Lr even when the Danfoss RX1 has been removed.
Click to expand...

So, are you saying that the heating stays 'on' when Lr doesn't have any electrical connection made to it?
 
yes that's exactly right , i have removed the RX! from the wall leaving just the back plate with the wiring connections and Lr has a mains voltage on it , which i why i think i have a boiler fault (short circuit on the boiler pcb )
 
If i'm right the RX1 should apply 240v to Lr when heating is required. It should not be on the back plate when the RX1 has been removed.
 
Something is definitely wrong it shouldn't work without a connection to Lr.
Peter Lowthian said:
If i'm right the RX1 should apply 240v to Lr when heating is required. It should not be on the back plate when the RX1 has been removed.
Click to expand...

In theory, yes and especially so if it used to work and the wiring hasn't been touched. However, I would be inclined to remove the wire from Lr as a final test, just in case it's connected to something somewhere else (ie not the RX1).

Do you have any connections to the remote frost stat terminals FS and FR?
 
Im not sure its in a friends house and i have only checked Ls Ns and Lr and dont know where or how to check the remote frost stat can you advise me on this.
You could be right as if it was internal to the boiler Lr would become live when activated creating the scenerio i have now.
Thanks for you help.
 
An external frost stat overrides all other controls to operate the boiler when the ambient temperature in the area where they are located falls low enough to pose a risk of freezing. They are not usually fitted to most installations, only those where the boiler, or another part of the system are in an unheated garage, outbuilding or exposed location. Some frost stats have a limited low range, but some are capable of 20 degrees plus. So if one was fitted, and had been inadvertently turned up, or was faulty, that could create the problem you describe.

If a frost stat is fitted it should have been wired to terminals FS and FR. As Lr and FR both have the same function, (ie operating the boiler) it is quite possible that FR is linked to Lr internally.

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Hi thanks for the info ill have another look at it tomorrow and see if one has been fitted ,
I wouldnt have thought so because the boiler has been installed in a bedroom cupboard.
Ill let you know how i get on, once again thanks for your help.
 
Looks like ill have to leave it to the experts as the boiler cover is part of the combustion chamber and needs to be tested after removal / replacement. Not a DIY job as i thought. Thanks again.
 
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