ravenheat rsf84et

[jondavis006]

Hi All merry Xmas

i have a fault with my combi boiler ravenheat rsf84et
when i which on the hot tap i goes hot then cold hot then cold
i have looked at the boiler it lights up then switchs off but when it switchs off the left relay flashs a big spark then 20 to 30 seconds later it start all over again

the central heating is fine the radiators stay warm not a problem

if anyone has any ideas please help

Merry Christmas

Jon

 

[Agile]

Although unusual the heat exchanger may be scaled or the DHW sensor may be failing when it gets hot.

A simple check is to connect a 15k resistor in place of the DHW sensor and see if the boiler runs constantly.

It might also be a fan/vent/aps problem but that would need a gas competent person.

Tony

 

[gas4you]

Try the ch thermister it controls the boiler going to overheat, which is what sounds as if is happening in your case. Probably caused by scaled up or blocked on the dhw side.

 

[Slugbabydotcom]

Classic CH thermistor problem for this boiler. Get it changed because it will go anyway and it needs ruling out to get to the bottom of the problem if its anything else. The problem occurs more frequently if the system water is dirty so consider a flush or powerflush if this sensor is badly coated with crud.

In a fault state just unplugging and quickly re-connecting the wire to it confirms it is the fault if it fires up straight away.
Its low voltage and if you can do it without breaking the larger green lug you get a Blue Peter Badge.

A word of warning. Make sure the boiler is cold when you change it if you intend to DIY