ariston combi sx20

[kam12an]

I have a problem- ariston sx20 and a trigger happy plumber...
Basically primary flow switch pin working with CH on but not with dhw alone.
So Plumber attends and says switch not working correctly as pin not rising fully (although it seemed to be to me -(the untrained eye!))
So he replaced the pin + spring etc.
Now the pin not rising at all - neither for dhw or CH!
So he decided to just bypass the entire mechanism and stick the two ends of the microswitch together.

Yes it works fine (no rising of pin but hot water!!)

Q1 - So what am i getting my self in to??

I did mention the pump and the small kinked pipes from the flow switch as two possibilities as stated on this forum in the past .
I have replaced diverter valve in past (thank you ezyparts for ****ing my plumber off as i got the valve for £50 less than what he wanted to charge me for!!)

He says pump fine cause if it was not i would be getting trouble with CH not heating up right or overheat on dhw and CH.
So has offered to come back and clean pipes out... to see if the problem is grime that has now shifted further round.

Q2 - He told me the "stuff to clean the system with cost £65" - seems steep - is this correct and if not can anyone direct me to where it can be brought cheaper?

Q3 - If cleaning the system does not work (makes sense that it should.. but if it does not...) then should i get pump replaced or should i bite the bullet and change the boiler?
(£1200 ish for total work)

 

[Tibbot]

So he decided to just bypass the entire mechanism and stick the two ends of the microswitch together.

This is potentially dangerous and probably illegal but it's about the only level of tradesman you can expect. This is because, as you've described, when there's an opportunity to undercut, you halt proceedings whilst sourcing parts yourself. It is of course your entitlement to carry on as you wish, however reptutable outfits who can solve your problems first hand are unlikely to serve you in this way.

 

[bengasman]

Changing the spring and pin is unlikely to solve it.
What probably needs changing is the membrane. If nothing moves at all, he probably stuck the springs in the wrong place.
The pump is not the problem.
Plumber sounds like a cowboy.

Solution: ditch him and get a decent RGI to do the job; anyone that did the above is not going to get you a good replacement either. Nor is anyone else for 1300 quid supply and fit.

 

[Gasguru]

The problem could be several things...so start with the easiest first.

Take off the pump head and check the torque of the impeller....sometimes the capacitor has reduced in value sufficient to effect the torque.

Often the fibre washers at each connection can result in a buildup of crud reducing flow and reducing the pressure differential to operate the microswitch.

IMHO there is normally nothing wrong with the differential pressure assembly...the problem lies elsewhere.