Vaillant Turbomax plus F22 fault 10 mins after HW demand

[PaulTheOnlyOne]

I have an 828E with the above fault. Nothing wrong with the pump or the system pressure.

Start to have a shower and it becomes a cold one after 10mins. F22 error. Repeatable problem.

 

[picasso]

Could be a pressure sensor fault or dirty system water.

 

[PaulTheOnlyOne]

Thanks Picasso. This model does not have a pressure sensor. An economy too far in my opinion.

Over a year ago I fitted a magnetic filter and I cleaned it out at 3 months and then again a couple of weeks ago and the water is clean. At the same time over a year ago I cleaned out the diverter valve (there was not much sludge in it), replaced the electric actuator on the diverter valve as this has microswitches in it, and replaced both temperature sensors either side of the main heat exchanger. For a while the F22 problem went away but returned about 6 weeks ago.

I am wondering if the main heat exchanger is partly blocked or the secondary hot water one? Don't know if this would give the F22 fault. The pump runs on the faster setting and switching to the slower one gives many more F22 errors. Maybe this is a clue and points to a blockage in the hot water primary circuit?

 

[PaulTheOnlyOne]

PS I changed the pump as well a year ago for a recon one. Swapped the two pumps a couple of times. No difference between them.

 

[picasso]

Yes sorry my bad, the pcb moinitors the difference between the ntcs so could be ntc fault .

 

[PaulTheOnlyOne]

Yes. I will change them again but I am puzzled. I will try and match them at 80 deg C as I have several to get a matched pair.

 

[ollski]

Plated heat exchanger i expect, test the temperatures on the inlet and outlet and see what youve got

 

[PaulTheOnlyOne]

Inlet and outlet of the primary or secondary?

 

[Gasguru]

Across the plate. From cold you'll get a significant temperature drop across the plate but once the metal comes up to temp you're looking for a perhaps a 10 to 20 degree drop. Just use your hands for temperature measurement.
BTW there is no such thing as a recon pump....you've been ripped off and bought a polished secondhand pump. Ebays "recon" category is now totally abused. Pump manufacturers don't sell any parts to enable a pump to be refurbed. Occasionally the capacitor value drops sufficiently to reduce torque and they can sometimes be replaced but I very much doubt they get changed.
Check the pump impeller torque, it's very subjective and unless you have tested many pumps it will be difficult for you too fully assess the performance.

 

[PaulTheOnlyOne]

The cold inlet is about 25 deg C and the outlet is at about 40 deg C measured at the heat exchanger. The hot water setting is at 60 deg C.

I used an infra red thermometer so readings are always a bit iffy but I think these are near enough correct.

Re pumps you are right. I think I bought from crooks.

 

[Gasguru]

Chuck that crapy infra red thermometer in the bin. I can guarantee it's giving you false readings unless you've bought one where you can adjust the emmisivity to match the copper pipe.
I very much doubt your cold water is 25 degrees...that would not be safe to drink.

Feel the temperature across the primary side of the plate ie. the pipes that go to the primary heat exchanger.

 

[PaulTheOnlyOne]

Left side much hotter than the right. Changed the emissivity on my IR thermometer (didn't know I could do that so thanks!)

Temp 45 deg in and about 35 out

 

[Gasguru]

The primary flow temperature to the plate should be more like 80 degrees...

 

[PaulTheOnlyOne]

I have the boiler set to 60 deg. I will test again on maximum but this is pointing to the main heat exchanger at the top isn't it?

 

[Gasguru]

No, none of your temps make any sense. This is probably a simple fault but we're going round in circles because you don't understand what the primary and secondary temps should be.