Boiler will not fire up for hot water

[littlebarney]

I have a Potterton FF80 Fanned Balance Flue Gas Fired Boiler, about 10 years old. Although the boiler will fire up when Central Heating is called for, it will not fire up when Hot Water is called for.

The Drayton ZA5/679-2 (22mm) two port Zone Valve opens but the bolier will not fire up. The Zone Valve Casing feels quite hot whilst the water is cold, or cool. The Servo Motor must be working as the valve opens. Is there any other changeable parts in the Zone Valve which could be producing the heat and/or preventing the boiler to fire up?

 

[Tibbot]

With the CH on, try operating the manual override lever on the HW valve. Heat should pass to cyl coil to give you HW until you can identify fault and replace either head or valve as necessary.

 

[littlebarney]

Many thanks but I am already doing this so that I can at least get hot water when CH is called for. Trouble is the house soon gets up to temperature during this mild weather in the south.

 

[leytonjc]

hi mate, i would say that its definitely your zone valve, it sounds like the valve is opening but not quite reaching the micro switch, you could try removing the head (actuator) from the valve body and check if the boiler fires, although the earlier drayton valves were made with a fixed head so make sure theres a small black button on the opposite side to the little open or closed indicator.

 

[45yearsagasman]

It will be a failed micro switch preventing the boiler from firing on hot water.
The powerheads just unclip and are easily replaced. You may be able to get a switch from, say Maplin, but its better to just replace the head.

 

[littlebarney]

Many thanks, I will check it out. Is the micro switch a changeable part?

 

[leytonjc]

does your valve have a removable head?

 

[littlebarney]

Not sure, I have only ever removed the cover and changed the Servo Motor on the CH Valve. Not sure if anything else could be removed, I will check tomorrow.

 

[littlebarney]

For those who answered my query I am sorry to say I have wasted your time. I was given incorrect information. The Zone Valve is infact a "Honeywell 4043H" but the problem is as stated.

 

[Agile]

I dont think much of the advice would have been any different and some obviously assumed a Honeywell valve anyway.

The Honeywell valves are easier to work with so thats good news for you.

Tony

 

[leytonjc]

if its a honeywell valve remove the cover from the actuator head, underneath the synchron motor you will see an arm, put the dhw on and make sure the arm pushes the button on the microswitch, you should here the microswitch make, if the arm does not reach the microswitch theres a few things you can do to fix the problem.

 

[littlebarney]

Hi Leytonjc, Thanks for your advice. Advanced information is always better than going in blind. If the arm does not reach the microswitch, what else can be done to fix the problem.

 

[leytonjc]

switch off the power at the spur or plug, remove the actuator from the valve body by unscrewing the two domed type screws, then gently manually open and close the valve with a small adjustable spanner until you can use your finger and thumb to open and close it.

 

[littlebarney]

Many Thanks.