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PClem

Hi,

I have a Y Plan system that has worked fine for years but recently developed a strange fault where the hot water on/off is only controlled by the Cylinder thermostat. The HW relay on the programmer is permanently on and although the relay clicks, its output does not change status with the indicator when selected.

System consists of:
Baxi Bermuda 45/4 Electronic Back Boiler
Drayton LP722 Programmer
Honeywell V4073A 3 way valve
Honeywell L641A Cylinder thermostat
Satchwell TLX 2259 Room thermostat

The wiring, following the Honeywell Sundial Y Plan diagram, has been double checked by another electrician and confirmed correct. I have replaced the Programmer, 3 way valve and cylinder thermostat. After replacing the programmer it worked correctly at first but the following day the HW fault had returned and it appears that something in the circuit is damaging the programmer HW relay.

By process of elimination I now suspect the boiler PCB – 237730 but would appreciate any suggestions or advice from those with experience of a similar fault.

Thanks in advance

Pete

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Tony S

Replace the timer.

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Sharpend

Rather than just replacing things have we actually done any testing? 

Have we checked voltages are both correct and at the correct time throughout the system? 

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kerching

Y plan is the work of the devil and all his little 💩

 

Search on here for how it works and why.....don't just expect 230 on /off

 

@ProDave ( I think?) did a very good post on it a while,ago

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ProDave

I am talking to a customer of mine in the Highlands?  I have just such a fault to attend this week, fuse in CU feeding heating keeps blowing.  Of course the first time I went everything tested fine and it worked and the fuse did not blow, so I hope next visit the fault has the grace to show itself.

 

And yes the one I am going to is an old boiler, but I think a Potterton Profile.

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Doc Hudson
6 hours ago, PClem said:

Hi,

I have a Y Plan system that has worked fine for years but recently developed a strange fault where the hot water on/off is only controlled by the Cylinder thermostat. The HW relay on the programmer is permanently on and although the relay clicks, its output does not change status with the indicator when selected.

System consists of:
Baxi Bermuda 45/4 Electronic Back Boiler
Drayton LP722 Programmer
Honeywell V4073A 3 way valve
Honeywell L641A Cylinder thermostat
Satchwell TLX 2259 Room thermostat

The wiring, following the Honeywell Sundial Y Plan diagram, has been double checked by another electrician and confirmed correct. I have replaced the Programmer, 3 way valve and cylinder thermostat. After replacing the programmer it worked correctly at first but the following day the HW fault had returned and it appears that something in the circuit is damaging the programmer HW relay.

By process of elimination I now suspect the boiler PCB – 237730 but would appreciate any suggestions or advice from those with experience of a similar fault.

Thanks in advance

Pete

 

From what I read here you have not actually proved any individual item is working correctly. Just gone through a Swap it and see process. Sounds like you may well have replaced perfectly good working items for no reason at all. Couldn't the electrician who double checked the wiring also have confirm each of the components functionality before you started swapping things? You say you have replaced the 3port valve, is that just the head or the whole body?

 

Doc H.

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