Potterton Profile 60e Air Pressure Switch Faulty

[Razoo]

Hi Roger,

No problem re. APS Part No. - thanks for your input.

[geoff]

In message , Razoo writes

I just knew you were going to say that

Something told me

So the problem can absolutely be tied down to lack of differential pressure at the diaphragm

Profile 60 fans can drop off in power, but its not very common. On the Netaheat (the Profile's predecessor), there is a bulkhead connector with a fine hole in it (to avoid wind affecting the pressure at the APS. Check if your boiler has one. If it does, this can get crudded up and prevent the APS from seeing the correct pressure

Other things which can cause problems are (as someone else said) a blockage in the flue, clogged heat exchanger fins, lack of integrity of the case seal (you might not have noticed that rusty hole)

If you are sure you have checked all of these, then if you ring tomorrow between 9 and 10 am, and ask for John, he's worked on profiles and such for about 2000 years on the gas board and there is very little he doesn't know about profiles. After 10, he should be off doing a delivery run. I should be there after about 10am

01923 229224

If you do think its the fan I do an exchange one for £45 ++

[Tommy]

On 6 Oct, 11:37, "Razoo" wrote: Last question first!!

Relying on memory here, the aps is below the combustion chamber within the grey plasic boiler housing & the aps tubes connect to metal pipes with 1 pipe travelling up to the fan where it is connected to it with another white rubber tube. Clear the metal tube & also especially the plastic venturi connecting the tube to the fan.....only if gas-safe registered though.

Are you sure you connected the wires to the correct terminals?

By change state do you mean the ignition sequence begins? if yes Does the burner light? if no its your gas valve

forget that

Yes but not likely

[geoff]

Aah a 'kin feral fitter

so why the stupid reply regarding the OH reset ?

Aha - we is in agreement

The APS is purely a membrane which moves under the action of the differential pressure caused by the fan. This membrane moves a microswitch from the NC to the NO position

that's it

[Razoo]

I just knew that would be the outcome. I guess we both have a close affinity with Mr Sod and his Law ;-)

Yes, it can.

Well, I have now found the fault, and it is the fan.

I took the fan out and ran it on the bench. I could then see it had a tendency to run seemingly well for a short while, and then hesitate slightly, before picking up again. I guess in reality the fan was running significantly slower than its normal operating speed, resulting in reduced airflow (and consequently the lack of differential pressure across the APS).

I stripped the fan down and found that the armature sleeve bearings were dry and binding, especially the front bearing.

It's a Sifan fan (Model: 409583) with spherical, self-aligning sleeve bearings bedded in Permawick. The Permawick has completely dried out.

If the bearings had been fitted with the more common oil-soaked felts, I could have had the fan up an running again in no time. But getting hold of some Permawick quickly - now there's a challenge! I guess I might be making up some felt pads tonight.

Thanks, that's kind of you to offer this service.

That's a reasonable price. The price I've been quoted for a new fan spoils the look of £100.

I intend to have another go at the fan bearings tonight. I'll report back.

[Razoo]

The APS is located where you say. The two metal APS tubes travel up the inside left of the boiler casing, and protrude into the intake air plenum. Both metal tubes are then connected by flexible silicone rubber tubes to two metal stub tubes protruding from the exhaust flue elbow.

There's no direct 'tube to fan' connection (see above).

Absolutely! The boiler runs fine if I manually operate the APS.

No, I mean that the APS microswitch contacts operated by the APS diaphragm change over (the NC contact opens and the NO contact closes).

It turns out that the fan is faulty (partially seized armature sleeve bearings, causing the fan to run slow).

[Razoo]

Turned what down?