britony combi 80 DHW heats CH ?

[chris 666]

hi
Im looking for some advice on a britony combi 80. When the hot water tap is turned on the radiators warm up and the hot water system stays cold now according to the fault finding page in the installation manual this fault is down to the 3 way valve? Which has now been changed but fault is still the same any ideas anybody all advice gratefully received.

Many Thanks Chris

 

[meldrew's_mate]

Chris, if my memory serves me you have an electrically operated diverter valve actuated by a stepper motor. By cycling the power OFF-ON it will perform a sort of self test by driving one way, then the next. If it's quiet you should be able to hear this. That should eliminate a valve fault. You should still check this valve for scale/debris as this can lodge in it and render it stuck, though my experience has been that it tends to stick in the DHW position.

If you definitely can't detect the valve driving suspect the PCB, although if you have the old valve and re-connect it to the cable temporarily (and it drives!) you can pretty much discount the PCB.

Don't suppose the two flowswitch cables have been inadvertantly transposed? They share the same connectors as each other, though the wires have different colours - refer to the wiring schedule on the casing/in the book.

 

[chris 666]

cheers meldrew's_mate

All connections in right place

cant hear motor move but will try old 1 see if i can see it move

dont suppose you know the switching voltage from pcb at the moment can only detect 0.4 of a volt going to 3 way.


thanks again chris

 

[Agile]

I think its a stepper motor!

Plug in the old one loose and see if it moves.

I assume the plate heat exchanger is not blocked?

Tony

 

[chris 666]

hi

The old 3 way valve does not operate when plugged in loose,looked down the housing with torch to check?

cheers chris

 

[chrishutt]

The old 3 way valve does not operate

Which proves that (a) the voltage to move valve is not being received from PCB or (b) that old diverter valve is faulty.

 

[chris 666]

hi everybody
yes thats right chris so i could really do with an indepth circuit diagram .The one with the boiler is pretty basic so im going to ring chaff et technical helpline in the morning see if they can give me some output voltages to 3 way.If not suicide is always an options anyway thanks for your advice gratefully received any further advice please feel free.

 

[chrishutt]

Voltage to diverter valve should be as follows (during operation only) - terminal 3 (white wire) to terminal 6 (yellow wire) - 15 volts AC. terminal 3 to terminal 5 (orange wire) - 24 volts AC. If you're not getting these voltages you need to change the control board.

If you want a detailed look at the workings of this boiler, go to partsarena and select Baxi (yes, Baxi) and then Genesis. You can then view the fault finding and spare parts details for the Baxi Genesis, which is virtually identical to the Chaffoteaux Britony Combi. The Baxi instructions are much better than the Chaffoteaux ones.

 

[chris 666]

Thanks chris
this information is most useful so i can check pcb out and check for voltages stated (i originally come from an electronic background)

many thanks chris


Will let you know either way cheers

 

[Agile]

This is the kind of fault that I like! One that needs logic to deduce the cause!

One think that I would find reasuring is if you can put a diverter valve into the DHW position and fit it to confirm that when the diverter is correctly set for DHW that the boiler will indeed operate on DHW OK.

It does so far sound like a PCB fault. The pcbs are fiddly with questionable interconnections!

Chris666, one annoying aspect of working with boilers is that the actual circuit diagrams of the various pcbs are just not available. They seem to be a closely guarded secret!

Tony Glazier

 

[chris 666]

hi tony

Could you explain this in a bit more detail

One thing that I would find reasuring is if you can put a diverter valve into the DHW position and fit it to confirm that when the diverter is correctly set for DHW that the boiler will indeed operate on DHW OK.


Cheers chris

The only worrying point is the lack of voltage to the 3 way when tested showing 0.4v with a 10%-/+ i.e 0.35 to 0.45

 

[Agile]

Not sure how to explain it in more detail!

The diverter presumably "rests" in the CH position.

What I would like to see you do is to to get it into the DHW position externally by pulsing the winding or whatever and then to fit in into the boiler to confirm that the boiler will then operate correctly in the DHW mode.

I dont know exactly how these motors work. Perhaps by applying DC to one winding and then pulsing the other? Perhaps reversing one of the polarities to get the movement in the other direction?

All of this kind of information is unavailable to us in relation to boilers!

Tony

 

[chris 666]

The diverter presumably "rests" in the CH position.

hi tony yes it does i will give it a try tommorow and will post outcome on forum


many thanks chris

 

[chris 666]

hi everybody
im getting 14v on the yellow wire and 0.2v on the orange wire not 24v? does this point to pcb?

cheers chris

 

[chris 666]

Hi everybody
Boiler now working orange wire had broken down tested voltage at board voltage correct checked voltage at 3 way 0.2v replaced wire HOT WATER YIPPEE... or words to that affect A BIG THANK YOU TO EVERYONE who gave me advice.

THE OLD 3 WAY STILL DIDNT MOVE EVEN WITH NEW WIRE ON SO MUST HAVE BEEN BROKE MAYBE THAT CAUSED WIRE FAILURE???

Anyway many thanks again couldnt have done it without you

chris