Potterton netaheat 80e - no hot water

[DNC]

Hi
Hope someone can help - I have a Potterton netaheat 80e and its stopped giving hot water CH is fine even in this weather! We have spent a lot of money on this piece of work over the last few years - Thanks Pimlico plumbers £900 (PCB, Gas valve and air valve) would have been better spent on a new boiler!
The boiler starts when I have it switched to hot water only, but it goes off after 3 mins or so. If I have the central heating on I get hot rads but no hot water.
There is an immersion heater that I have to plug in separately and this works fine - although it gets very hot.
Next to the cistern there are two "flow switches" - silver Honeywell boxes with pipes in and out. I did have one of these replaced a few years ago and that solved a problem - either no hot water or no Ch not sure which...
If as I suspect it is one of these switches how do I test them and how do I know which is CH and which is HW; and could the problem be the tank thermostat instead?

 

[baxpoti]

how do I test them and how do I know which is CH and which is HW?

Put c/h on and see which one gets hot.

You will notice a lever on one end with c/h on is this lever loose?

Now try your hot water. does the lever on the dhw valve go loose?

 

[Agile]

It is most unlikely that the gas valve AND the PCB had failed at the same time. They probably changed the PCB and then found it was not the cure so replaced the gas valve.

If you must call an expensive firm to do your repairs then thats your choice. They do make them totally clear at the outset. Whats not so clear is that many of their staff are not very skilled at boiler repairs. One of their engineers used to give their customer my telephone number when he could not sort it out.

You may find the hot water valve ( with pipes to the heating coil on the cylinder ) is not opening. You may be able to slide the lever and lock it in the open position but this would not normally bring on the boiler so you would need the heating selected and to turn off the rad valves to stop getting overheated.

Tony

 

[DNC]

Thanks for speedy responses.
I have had the water only on this morning and one of the switches is very hot and has a loose lever - move it to the right and it stays there. The other one springs back when i move it

 

[gavinda]

i cant believe how much pp charged you . this sounds like a very easy fault to sort... why not try bg for a fixed price repair. even one of our monkeys should sort this.... for far less.

 

[Agile]

The motor valve lever is loose when it open.

The lever is tight when its closed.

When its tight if it will slowly open when force is applied then its not seized up and can be locked in the open position. It will not normally bring on the boiler itself when manually opened!

Tony

 

[gavinda]

it can be just the synchron motor in the valve is overheating and 'dropping out, or possible the ball in the zone valve is swollen and sticking.

 

[DNC]

OK so i put it back to hot water only and i manualy opened the valve that is tight - but "will slowly open when force is applied" and i am getting the boiler on but with hot rads.

THEN i turned off the rad valves and went to CH and HW and now nothing...

 

[Agile]

You may find the hot water valve ( with pipes to the heating coil on the cylinder ) is not opening. You may be able to slide the lever and lock it in the open position but this would not normally bring on the boiler so you would need the heating selected and to turn off the rad valves to stop getting overheated.

Tony

For everyone's sake please identify which is which and refer to either the CH or the HW valve when you try to tell us something.

Tony

 

[DNC]

Sorry Tony - i am struggling here... here is a drawing of what i can see really hope it helps you to help me...
View media item 12582

 

[baxpoti]

1 is your hot water valve and is open (loose)
2 is the heating valve and is closed (stiff)

The hot water valve is on its way out and will need replacing soon, it is sometimes cost effective to replace both valves at the same time as s0ds law says..........

 

[DNC]

Thanks for the advice i think you might be right - esp about sods law...
So do i only have to drain the cylinder or the whole system?

 

[Agile]

The implication is that if the HW valve is open then the motor and the shaft are working.

If there is any fault then the microswitch inside is failed.

If they are Honeywell then its possible to just replace the head.

Tony

 

[DNC]

OK that makes sense - I have to go to a place called TLC-direct for something else would they have one and what would i ask for "Honeywell flow valve head"?

 

[Agile]

You would normally ask for a head for a Honeywell 4043H two port valve.

HOWEVER there are two types and they are not interchangeable. You need to see if there is a dimple on the top of the cover to show that its the later type. The head is held on with TWO screws and can be changed without draining.

The price of the head may be almost the same as a whole valve at some places so it may be better to buy the whole valve and just change the head.

Tony