help with heating fault

[LPC82]

Hello I have a Glowworm boiler and a fully pumped system on a Y plan with a Tower mid position valve

The fault is as follows

When the programmer is switched to heating the boiler fires and the heating reaches temp etc..
When the programmer is switched to hot water the boiler does nothing
If when the heating is on I also put the hot water on the boiler goes out and stys out until hot water is switched to off

So far I have checked that there is 240v going into the programmer and 240v coming out of the programmer on HOT WATER ON if the cylinder stat is turned up
If I turn the cylinder stat down there is still 240v at HOT WATER ON and nothing on the grey wire ( hot water off I think ? )

I thought that it looked liked faulty cylinder stat so replaced that but the fault is as before
Whats the next step ? Programmer or actuator ? anything else ?

Many thanks for any help

 

[gas4you]

You need to check for 240V on the orange wire out of the actuator in all modes.

 

[LPC82]

Hello mate thanks for the reply

In heating - Orange, grey and white have 240v
In hot water - None have 240v ( on the valve )
If on both - None have 240v ( even when h/w stat is turned down/satisfied )

 

[ollski]

Which wires are you measuring across to determine no voltage?

 

[LPC82]

Hello mate

neutral to Orange
neutral to white
neutral to grey

Is that correct ?

Its seems very odd to me ( I have a very basic understanding of whats goes on but I'm baffled )

 

[LPC82]

Any other ideas / tests much appreciated ??

Many thanks

 

[twgas]

I think you've probably got a wiring fault, check wiring diagram, this may help

http://www.tlc-direct.co.uk/Technical/DataSheets/Horstmann/Pics.pdf

 

[LPC82]

Hello

Does sound unlikely to be the programmer or actuator then ?
Nothing has been altered on the wiring side of things ? In fact we've never really had any problems with the system at all ! If it is not going to be the programmer or actuator should I call an electrician to check the cable runs or a heating engineer ?

Many thanks all advice appreciated

 

[AlanE]

Check, with DHW only, if you have 240v on common of cylinder stat. You should then have 240v on the call for heat terminal when heat required and 240 volts on the satisfied when not.

If you have 240 on the call terminal you should then have 240v on orange when in hotwater only situation.

Remember the power to boiler etc comes from the cylinder stat when DHW only or DHW+CH is being called for and from 3 port valve with CH only demands.

 

[LPC82]

I see !

So i'm getting 240v up to the cylinder stat but nothing back on the orange
I replaced the cylinder stat and had no joy ( although I did get the satisfied and calling wires the wrong way round which tripped the consumer unit ? )
So it now looks like there is a break in the cable ? Hmm I think I'll contact an electrician then

Cheers

 

[D_Hailsham]

So i'm getting 240v up to the cylinder stat but nothing back on the orange. I replaced the cylinder stat and had no joy ( although I did get the satisfied and calling wires the wrong way round which tripped the consumer unit ? ) So it now looks like there is a break in the cable ? Hmm I think I'll contact an electrician then

Forget about the orange wire. The only reason it appears to have any voltage on it in HW only or HW and CH, is because it is connected to the same terminal as the HW Call. Disconnect the orange wire and measure the voltage on the orange wire by itself. You will find that it only has 240v when CH only is on.

It is all explained in How a Mid position Valve Works

If your meter can measure resistance, use it to check the cable from the HW stat to the wiring centre. (Turn of power and disconnect one end first - but try not to trip the consumer unit when you reconnect ). This will verify if that lead has any breaks.

 

[D_Hailsham]

In heating - Orange, grey and white have 240v -Correct
In hot water - None have 240v ( on the valve ) - Correct
If on both - None have 240v ( even when h/w stat is turned down/satisfied ) - Wrong - the white should have 240V

The white gets its supply from the CH thermostat, so you need to check that.

Can you check that the valve is the correct way round: Port A to Radiators; Port B to HW cylinder?