Combi Boiler problem

[semps]

We've been in our current house for nearly 2 years now. When we moved in we had a problem with our boiler (an ariston sx20 mffice). The air pressure switch was replaced and all has been fine till last week, when the boiler would not start up.

Neither the hot water or central heating would work, so we called out our local experts. They came out and diagnosed the problem as a faulty control box, and one was duley ordered. They returned and fitted the new box, but whilst watching the installation noticed that the boiler was not starting up.

He emptied the pressure from the system and fiddled with the pump. He then repressurised the system and suddenly it powered into life. He left it going for a while and then turned it back off to retest. Upon trying to restart, the boiler was dead again. Eventually he got it going and I voiced my concerns about the boiler not restarting, he said it needed time to run since it had been off for a week. (the time from their initial visit to diagnose, and the return to fit the part)and wouldbe fine. I have come back to it today after it has been running for 30 odd hrs, and adjust the timing on the clock.

The CH turned itself off, and upon trying to get it going again, the boiler is once again dead. Really fed up now, and have no CH or HW and will probably have to wait till end of next week for them to come out again.

Sorry for the long post, but wondered if anybody had any ideas?

Cheers

 

[DP]

I am surprised you have written the post yet you are unaware what is wrong.

It is not the pcb that should have been changed but establishing if the pump was operating. Suspect pump faulty

 

[weargas]

long standing problem on the sx 20 is the primary flow switch which is the diaphragm and microswitch type. first, as DP said check the pump. if the pump is running look at the flow switch (just to the right and slightly above the pump) there's a clear cover on the microswitch (swivel it round to see it) does the pin come out fully and operate the microswitch?

if it doesn't it could be a few things

1. the pump is running but hasn't the power to push the pin all the way up
2. the flow switch diaphragm is split/stretched
3. the small copper tubes feeding the flow switch are blocked/restricted
4. main heat exchanger blocked (this results in ch working fine but no hw)
5. blockage where the right hand pipe from the main heat exchagner connects to the manifold that's attached to the diverter valve. The angle on this connection and the fact that a thermostat phial is partially blocking the path of the water makes these prone to blocking.

order in which to test
5, 3, 2, 1, 4

if you're gonna attempt this yourself change the fibre washers in the connections you break and clean any old washers from the flange ends fully, they're murder for getting watertight.

 

[weargas]

It is not the pcb that should have been changed but establishing if the pump was operating.

its amazing the amount of engineers who don't test appliances fully before jumping in and changing parts that a boiler probably didn't need (at the customers expense). have you come across much of this DP?

 

[semps]

I suspected that he had mis diagnosed when he fitted the new control box and it still did'nt work..... I'm just not confident in doing this work myself, so I guess I'm just gona have to force them to come out and fix it again and make sure that its in fully working order.

I was just glad that he had fixed the boiler initially. Thanks for the replies anyway, looks like I'll just have to wrap up warm and wait

Just as a reply to waegas, the boiler is completely dead (the power light is on and thats it!) no fan or no noise from the pump.

 

[semps]

JUst had a closer inspection and although the pump is'nt working when the boiler is turned on, it's still incredibly hot to touch even though the voiler has been off for 12 hours.

 

[weargas]

semps
i would switch off the electricity supply to the boiler if the pump's hot.
if you're not confident of doing the work yourself well done for not attempting it.
i know it could be more expense initially but ringing mts(ariston) and getting one of their recommended engineers to take a look at it may mean less expense in the long run. don't pay people who clearly aren't that experienced on that model boiler, they'll probably just keep changing parts until it works (at your expense)

it does sound like it's the pump though.

their number is
(01494) 539579

 

[semps]

Yeah, I agree. When its turned on the pump gets hot but does'nt run. Really annoyed that I've spend quite a lot of money on a prt that it does'nt look like i needed...

I've had a look inside and have a liitle more confidence than I thought, but will still get someone out (although I feel that the company that I called out should be made to fix it!).

DP, thanks for the response, yes I did feel that it may have been the pump, but the engineer explained it as a loose connection in the pump, and at the end of the day, he is supposed to be the expert, so I believed him

 

[semps]

OK,

I've turned the pump manually, with everything turned off. Refilled the system, and turned on. It powered up straight away. At least we have heat and HW now .....

Looks like a new pump then

 

[semps]

Ok now I am confused...

Had a look on HRPC and the pump I need (this one?)

ARIS 570590 PUMP GOLD 50V
SX 20 EUROCOMBI,379975

Retail Price
(Excluding VAT and quantity discounts) £104.64

I have had a look on Screwfix and what looks like the same pump here

is only £32

Any ideas? and how easy is a pump to fit?

 

[weargas]

the screwfix pump has different diameter connections to the eurocombi pump.

 

[semps]

thats damn annoying then big difference in price

I take it you've come across this problem before then (could'nt find details on the connection on either site)

Forgot to say that its a Wilo Gold V pump attached at the moment

Can you buy an adapter for the screwfix pump, or is there a cheaper supplier for the pump I need? Sorry for all questions, but getting fed up of being ripped off

 

[weargas]

pumps have removeable heads. there is a possibility that you can buy the cheaper pump and replace only the head (2 allen bolts) you will need to know the specs of the existing pump and the replacement.

BE WARNED
slight differences may result in the new pump head not being compatible with the old casting. if you're gonna try it be prepared to have bought a pump for nowt.

 

[semps]

Fair enough worth a thought though

Gonna get the company that came out before, and demand they get it sorted, cant do any harm.

Thanks for your help

 

[DP]

Weargas,part change without foundation is a common problem. Las week repaired a Vokera Flowmatic that had been fitted with a new fan, pump and PCB. It was the flow switch that was causing the problem!!!