Vaillant ecoMAX 835/2E

[ed209]

After advise regarding overheating and cutting out, I have removed both the F&R pipes in the boiler and flushed out, no blockage, blown through heat Ex with short length of hose seems clear, checked and cleaned by pass valve, there should be a filler but does not appear to be in there so either it has been removed in the past or broken up in to the system,

These boiler has a modulating pump and that has on occasion stopped and have had overheat but other times its carried on running I would say fast and strong enough to pump but still cut out

Apparently it was getting fault codes but not while I have been present just overheats, cools cycling
Cust cant remember what the codes were

Haven't tested for pump voltage yet going back tomorrow as I concentrated on initially the rubber pipe being blocked on the flow pipe as this was diagnosed as the problem by another engineer

No evidence of magnite being present

I keep thing it must be the pump or PCB not modulating

but would appreciate any advise

Thanks Paul

 

[villa_tom]

What pump had it got on it???

if it's had a replacement pump in the past and someone's just put a grundfos head in it, then this can cause Imtermitant lock out.

It has to have the manufacturers replacement pump on this because the impellers on the grundfos are larger and the pump doesn't always spin correctly.

 

[ed209]

It's the original pump, it has the usual LNE but also another lead going back to the pcb to modulate the pump speed

 

[jonnyswamp]

Had a similar problem with an 837 se (temp fluctuations on dhw) acting for all the world like a blocked hex, turned out to be weak pump
Also, just because you can blow through the hex, doesn't neccessarily mean it isn't partially blocked

 

[ed209]

Customer phoned up this morning heating is working perfectly but still issue with water, I'm still suspecting the pump either the pump being knackered or getting wrong message from the PCB

 

[ed209]

Does anyone know if I was to Disconect the pump modulating wires will the pump still run and if so would it run at max power

 

[ed209]

Agree that blowing through heat exch is not necessary a indication it is not partially blocked but that's the best I can do boiler in loft with a posh bedroom below or I would run power flusher round it as I do to Worcester Ri,s
Done half a dozen of them lately very satisfying when they clear