Ariston Microsystem 28 RFFI boiler continuely cuts out after 15 secs..........Help!

[mij908]

Hi all, I'm new to the forum and would greatly appreciate your help!

Have an Ariston Microsystem 28 RFFI boiler that continuely cycles as follows: heats up for 15secs then stops for approx. 1 minute etc.. This happens regardless of HW/CH setting. System is currently running quietly at 1.5 Bar.

I see the problem as one of two areas 1. Poor Circulation 2. Faulty Sensors but there could be more??

So far the pump has been replaced (no noticeable change!). All rads have been removed/ flushed and the system has been cleaned with chemical flush (Improvement to rad performance only!).

The next proposed area to investigate are the sensors. There appears to be three Thermostats on this model i) Regulation ii) Overheat iii) Frost

Question: Would you recommend replacing these next? if so, in what order? OR is there another likely candidate for this 15secs cycling?

 

[shorticus]

Re: Ariston Microsystem 28 RFFI boiler continuely cuts out after 15 secs..........Hel

See if we can help, couple of rudimentary questions to begin with, please don't be offended

Are you a the home owner or a gas op?
Is it a Y plan or S plan system, are the MV/MVs functioning correctly i.e. opening when required?
Is the flow pipe from the boiler getting hot?
When the boiler shuts down or cycles do any of the LEDs illuminate?
If the boiler isn't going to lock out then the overheat stat is fine so check the regulation stat, it's an NTC so is easily and quickly checked with a multimeter
If all the above checks out then there may be a problem with the auto by-pass possibly creating a short circuit
Hope this helps

 

[mij908]

Re: Ariston Microsystem 28 RFFI boiler continuely cuts out after 15 secs..........Hel

Shorticus, Thankyou for initial post.

1. I'm the Homeowner /Engineer by trade.
2. System is Y plan. 3 port has recently been replaced and opening when called.
3. Flow from boiler is getting hot.
4. No additional LEDs illuminate. ie. Power ON / CH ON / Reset OFF remain unchanged.
5. Regulation Stat appear to check OK on multimeter for ON/OFFfunction. Max heat setting does increase burner time 35secs with approx. 30 secs OFF (again continuous cycling!).

Is there an easy check on the auto by-pass?

 

[shorticus]

Re: Ariston Microsystem 28 RFFI boiler continuely cuts out after 15 secs..........Hel

what readings did you get across that thermistor, did you measure at different temperatures?
does the cycling happen from cold start?
have you checked burner pressure and gas rate?
the bypass is a link pipe from just under the pump across into the flow goup just behind the prv, see if that pipe get hot from cold start with all rad valves open