Potterton Performa 24 - Central heating diaphragm

[kvfilms]

Hi,

I have replaced the hot water diaphragm, using the instructions below:

"Isolate boiler electrics, remove dhw flow switch, isolate cold inlet under boiler,open a hot tap to remove any residual water pressure...."

worked a treat, now I need to change the central heating diaphragm, my question is, do I need to do anything else/ different to avoid mass water spillage when I remove the Central Heating Pressure Differential Valve to get to the diaphragm, like release the pressure in the CH system? or are the instructions above the same?

Thanks in advance

 

[Gasguru]

Why do you want to replace the CH diaphragm.

it's actually used to detect primary circuit flow during BOTH CH and DHW operation.

The pin failing to rise is rarely due to the diaphragm failing.

 

[kvfilms]

Why do you want to replace the CH diaphragm.

it's actually used to detect primary circuit flow during BOTH CH and DHW operation.

The pin failing to rise is rarely due to the diaphragm failing.

because when the boiler is on the heating runs as well as the hot water and can only be turned off if I switch the power off.

I changed the DHW diaphragm because that pushrod was sticking, that is now working fine, but the pushrod on the CH only lowers when the power is cut. I explained problem to boiler spares trader, he was of the mind that the CH diaphram was most likely damaged.

 

[Agile]

Perhaps the trader just wanted you to buy something?

Your pump proving diaphragm is working just fine!

The diverter valve manifold is jammed either fully or partially!

Tony

 

[kvfilms]

What might be jammed? looking at the manual there isn't any moving parts to fail, only diaphragms, springs and pushrods.

 

[Gasguru]

No, it's likely to be the DHW microswitch at the front of the diverter...you should feel the lever click as you operate....they often fail resulting in the boiler firing up constantly.

 

[Agile]

I changed the DHW diaphragm because that pushrod was sticking, that is now working fine, but the pushrod on the CH only lowers when the power is cut. I explained problem to boiler spares trader, he was of the mind that the CH diaphram was most likely damaged.

If the pushrod is resting in and extends when DHW is taken then the switch itself might be faulty as Geoff suggests.

Feeling the lever there should be a click which brings on the boiler.

Tony

 

[kvfilms]

ahhh, the CH microswitch on the top clicks normally, but the microswitch on the DHW does not click. I had a look at it, and because it is different design to the CH microswitch, I assumed it wasn't meant to click.... so could be HW microswitch on front?

 

[Gasguru]

Yes, very common failure.

 

[kvfilms]

Yes, very common failure.

Great. I've ordered... Microswitch Assy 248067, but as with all the suppliers I looked at it differs slightly from the one I have. Part numbers match, but mine has three cables running into it, and they're not the crimped on like the microswitch on top, which two of the three cables do I attach? There's Black, Blue and Brown.

Thanks for you help!

 

[Gasguru]

That's the wrong switch...you want 248207...it comes with a jungle of wiring If you're good with a soldering iron just cut the switch wires and join...finish off with heatshrink. It's quicker and you don't risk the pcb playing up afterwards with iffy solder pads etc.

 

[kvfilms]

That's the wrong switch...you want 248207...it comes with a jungle of wiring If you're good with a soldering iron just cut the switch wires and join...finish off with heatshrink. It's quicker and you don't risk the pcb playing up afterwards with iffy solder pads etc.

Opps lol are you saying its easier to cut n solder or order the right part? I followed cables to pcb, lost them in a jungle of other cables. Im not bad with a soldering iron. If I cut n solder wires, which 2 of the 3 wires do I need to solder to new microswitch?

 

[Gasguru]

No you need the switch with the wiring harness.

But to save faffing around with the harness for me it's easier to cut and solder the new switch wiring onto the old harness.

 

[kvfilms]

Ok, but the new switch only has two male connectors to solder to, but on the wiring loom there's three different coloured wires, how do you turn three into two? There's blue, Black and brown.

 

[Gasguru]

248207 has 3 wires, cut them and join to the existing harness.

http://www.boilerparts.co.uk/Uploads/BAXI/248207.jpg


You can't use the microswitch with the lugs on it.