Vokera 20-80 RS Flowmatic hot water problem

[Beno76]

Evening, I had a problem with the boiler last week when we had heating, but no hot water. I changed the divertor valve and the diaphragm and then had hot water and heating !!
However have just realised that this works when the boiler is on constant. When in summer mode I get no hot water, I have watched the pin coming out and engaging the micro switch to start the hot water when the tap is turned on, but the boiler doesn't kick in and no hot water. If I push the micro switch myself with a screwdriver and get someone to turn the tap on, I then get hot water !!!! How can this be ? Doesn't make sense

 

[DP]

Did you vent the white vessel
If you did, and no difference, change the pump

 

[Beno76]

Hi, are you talking about the cylindrical DHW heat exchanger ?
to note that I drained the system, swapped the parts out and re pressurised the system etc. But did not vent a white vessel, would that make a difference ? still not sure how the boiler kicks on when I engage the micro switch but doesn't when the diverter valve engages it !! doesn't make sense, surely it should work on the diverter valve too ?

 

[ianmcd]

There is a vent point on the top of the calorifier or what you call a white vessel you need to crack that open air will come out then water , when the water comes out close the valve , top up the pressure and you might be good to go , there is another problem that sometimes happens with these and you will not be able to sort this yourself , but if you have not bled the calorifier then it is most likely that

 

[DP]

I always thought it was good manners to thank people who have rendered assistance. Perhaps my thoughts are out dated.

 

[DP]

Thank you
The three way diverter services easily but end user replacement, like you have done, for whole unit is better

When drawing hot water, the diverter primes the system for hot water and activates the microswitch that runs the pump and prepares electrical circuit

Movement of primary water operates the microswitch to the left of gas valve. If the white vessel is not evacuated of air, the plunger/ spindle in not drawn in to start the burner sequence. One of the issues with this fine boiler ( now about 25 years of age), the plunger left of gas valve sticks in in the retracted position. Burner fires and if water pressure zero, melt components in the combustion chamber

 

[Beno76]

Right !! Just to explain the situation at present which I trust might go some way to reasoning why my manners may have not been promptly posted DP.
After just moving house with my partner being ill, I am working a 50 plus hour a week job with a 100 mile
Daily commute whilst also trying to look after our 4 children and ferry them around for school etc and everything else that goes on in life, whilst also laying under a boiler trying to fix it !!! Sorry in my haste to get everything done and desperation to get this fixed without the standard " your boiler is 20 years old mate, we can't do anything with it other than throw it in a skip " and charged £3000 to replace it ! My apologies for not being prompt with the little thanks icon !! To note after venting he white heat exchange the boiler still doesn't kick in on the divertor valve engaging the micro switch. It still only kicks in when I engage he micro switch with a screw driver or something.
Thanks for the assistanc and pointers so far !

 

[Agile]

What you are saying seems illogical.

The boiler does not know if the switch is being operated by the diaphragm unit or a screwdriver.

I would suggest that you test the switch electrically and see if it is really being operated by the diverter valve pin.

Then there is the other illogical point. If the white heat exchanger is mostly full of air then the HW coil inside is not going to receive heat from the boiler circulating water.

These are quite old now but a very few are still operating. I must be one of the very few who will agree to go to repair them.

Tony

 

[rules&rulers]

Make sure the grub screws have been tightened so the diverter valve is fixed firmly to the diaphragm housing.
Vent the white vessel during drawing off hot water,beware live electrics.
Is the dhw micro switch housing perfectly aligned,fixed firmly,not bent away from the actuating pin.
Trying to think of more reasons
How far does the pin travel out ?.in mm.
Is there any additional metal washers fitted where the micro switch housing bolts onto the actuation pin shaft.
Is the pin in the extension shaft (the pin that hits the micro switch arm) free to move,not bent.did you change this shaft.
These are a very sturdy mechanical old fashioned combi boiler so no need to change it,although there is another diaphragm operated pin (which if sticks when running at 0 pressure or pump failure will result in your boiler melting,cannot give advice as its safety related but your annual service/safety inspection this would have been checked for correct operation thats why we have appliances serviced/safety checked).

Good luck,

 

[Beno76]

Hi Tony, I know it seems illogical ! I spent most of last night watching it and seeing if i could work out why and how ! but I have taken the cover of the boiler off and watch the pin on the diverter valve engage the microswitch, heard it click 3 times and then do nothing. I have then used a screw driver to engage the microswitch, heard it click 2 times and then fire up and deliver hot water to the tap when it is turned on !!! it really doesn't make any sense at all. I loosened the screw at the top of the white heat exchanger and a little air came out before water then came out so guessing that there isn't an air lock or build up of air in there. It just doesn't make sense ! if the switch is being engaged by the screw driver or by the divertor valve it should have the same end result surely ? hot water at the tap. I am not a plumber but logically it isn't right !getting a bit frustrated !!

Hi DP, So this could be an issue that requires a registered engineer on the gas side now ? I'm not sure I understand fully, but wouldn't the microswitch work if the diverter pushed it out just the same as when I push it out with a screw driver ?

Hi Creamcrackers, the diverter valve is tight against the manifold, I double and triple checked everything on putting it on and have checked since. I have drained the heat exchange tank of air until water came out. I replaced the whole diverter valve, body and all the insides purchased a genuine part, the microswitch is mounted in the same position as it was previously before replacing the valve, I can measure the distance the pin comes out when I get home and confirm, but I have watched it numerous times come out and does engage the switch and can hear the switch click. At the end of the diverter valve there is an extension where the pin comes out of, shouldn't this be tightened up against the body of the diverter valve ? I would assume it would leak otherwise, the old diverter valve was tight against the body on this bit.

All in all, Im very confused at why the micro switch works when I push it but not when the diverter valve does !! just doesn't add up !!!!!!

Thanks for all of the guidance so far !! much appreciated.

 

[rules&rulers]

If the pin hits the arm to activate the micro switches (3 micro switches in that housing ) and only fires when manually pressed,maybe not enough pin pressure/travel to make all 3 switches make/break for summer operation.
How good is the flow of water to the hot taps ?.
That extension shaft needs to be tight against the front of the dirverter.No washers are req on the extension shaft.
Maybe turn off the boiler make electrically safe,use finger to pull back switch lever(where you previously used a screwdriver,the screwdriver could be making it fire up as more pressure is applied or at a different angle to the pin) and listen for 3 positive clicks,you need 3 clicks for the boiler to work or remove the housing and look at the 3 micro sw contact points turn different angles all contacts should be the same height,use small screwdriver to press each contact point,should be a positive click on all of them.

 

[ianmcd]

What you are saying seems illogical.

The boiler does not know if the switch is being operated by the diaphragm unit or a screwdriver.

I would suggest that you test the switch electrically and see if it is really being operated by the diverter valve pin.

Then there is the other illogical point. If the white heat exchanger is mostly full of air then the HW coil inside is not going to receive heat from the boiler circulating water.

These are quite old now but a very few are still operating. I must be one of the very few who will agree to go to repair them.

Tony

you are at it again , I repair and service these on a weekly basis, I know what is wrong with it but you do not and OP will not be able to repair this if he has bled the Calorifier, and for the record neither would you be able to sort it

 

[Steelmasons]

. I must be one of the very few who will agree to go to repair them.

I was installing the 20/80 flowmatic before you even thought about leaving the BBC for a career change in boiler repairs.
How do you know that you are one of the very few that carrys out repairs on these boilers?....you don't would be the correct answer...
Once again you perch yourself on that imaginary pedestal of yours.........you even had the audacity to suggest in the closed part of the forum that you use compressed air when draining a cylinder..

 

[Beno76]

Ummm, not sure about the last few comments !? Have I missed something ?
Steelmasons, can you offer any advice ? To note that the boiler works fine in constant mode !? I'm confused by this !
Thanks

 

[Beno76]

Ianmcd, any advice or solutions to this ?
Thanks