ariston euro combi mx20
- Thread starter mustang
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primary microswitch is not making because the manifold in front of the diverter is full of **** at the bend where the downpipe/thermostat phial meet
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WHen the pump runs for the HW, does the pin come out of the PRIMARY flow detector a bit? a lot? does it hit the microswitch?
If it moves but not far enough, you could check the primary diaphragm/shaft, but it could well be a tired _pump_. Take the head off the pump and get it running. You should have to try pretty hard to stop it with one finger.
Is it a Wilo? Their capacitors dry up with age. Pump's a bit expensive if it's the type with a long shaft (can you get your fingers behind the rotor with the head off?_
If it moves but not far enough, you could check the primary diaphragm/shaft, but it could well be a tired _pump_. Take the head off the pump and get it running. You should have to try pretty hard to stop it with one finger.
Is it a Wilo? Their capacitors dry up with age. Pump's a bit expensive if it's the type with a long shaft (can you get your fingers behind the rotor with the head off?_
had it all apart, pump seems fine and strong, chtg mode pin hits flow switch and moves easy and makes the contact, turn on tap for hw and pin drops breaking flow switch and just leaving pump running. turn off tap pin rises and htg works fine, this boiler going to end up in bin very soon 
I can't be really specific because there are so many Eurocombis (17 !!), but you have to look carefully at the flow route through the boiler, and where the pressures for the primary flow switch are sensed. There has to be enough flow past those points for the diaphragm to move the pin.
It's "flow" x "flow resistance" = "pressure difference" ( like amps x ohms = volts)
So if the pump is working properly, either the resistance between the sensing points is too LOW (unlikely), or the flow around the whole circuit is too slow because of resistance there being too high.
Ariston are always quick to accuse dirt in the primary side of the secondary h/e , but in the one I took apart last any increase in restriction there INcreased the pressure diff at the flow switch. The problem was that the HW loop resistance was much less than the CH loop, so the pin didn't move enough on HW. SOmeone had swapped a washer on the 2ndry h/e for one with a smaller hole in the middle, which helped, but was only a botch - because the pump was knackd.
As I said it does depend where the pressure is sampled, but if the 2ndry h/e is clean, the only thing to slow the flow is the various waterways - as Weargas suggested, or the main h/e.
SO - assuming you have the book of words or enough patience to work it all out from the castings, you could have a busy weekend!
By the way was it a greeny-goldy Wilo pump with the long shaft as I mentioned?
Good luck - it might be just a flake of scale somewhere critical.
It's "flow" x "flow resistance" = "pressure difference" ( like amps x ohms = volts)
So if the pump is working properly, either the resistance between the sensing points is too LOW (unlikely), or the flow around the whole circuit is too slow because of resistance there being too high.
Ariston are always quick to accuse dirt in the primary side of the secondary h/e , but in the one I took apart last any increase in restriction there INcreased the pressure diff at the flow switch. The problem was that the HW loop resistance was much less than the CH loop, so the pin didn't move enough on HW. SOmeone had swapped a washer on the 2ndry h/e for one with a smaller hole in the middle, which helped, but was only a botch - because the pump was knackd.
As I said it does depend where the pressure is sampled, but if the 2ndry h/e is clean, the only thing to slow the flow is the various waterways - as Weargas suggested, or the main h/e.
SO - assuming you have the book of words or enough patience to work it all out from the castings, you could have a busy weekend!
By the way was it a greeny-goldy Wilo pump with the long shaft as I mentioned?
Good luck - it might be just a flake of scale somewhere critical.
ollski said:
all old pumps? with stuck on fibre washers??
Yes it is a wilo pump and it does have the longer shaft, this problem a challenge between me and the boiler now,its got personal but i'll win, think i'll try another pump as it the only thing inot really leaned out, main h/e seems fine and clear
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