ravenheat csi85a causing grief

[alpha50]

we have a ravenheat csi85a with intermittent fault, it can work for days & then not do for days!
whenever HW or CH is called for boiler will fire up for a few seconds & then the burner goes out, the pump still runs, sometimes the burner doesn't ignite at all while again the pump still runs, its had a new HW thermistor which made no difference, am thinking APS? any other ideas?

 

[Agile]

Only last November you had an Ideal Sprint !!!

Now four months later you have a CSI 85a which has already had a new sensor.

Since it is within its warrantee period then why dont you call the installer or the Manufacturer and get them to attend under the warrantee?

Tony

 

[Slugbabydotcom]

Seeing as it affect the ch as well I would have tried the CH thermistor before the HW especially seeing as they go at a ratio of about 20 ch - 1 dhw

 

[alpha50]

ok thanks slug, i'll try that, is the APS worth looking at?

hi agile/Tony, neither the sprint or the ravenheat are actually mine, I was a BG engineer many many moons ago, but with extended families & so on I'm still expected to 'fix' everything that gas passes through, but I'm a bit out of touch

 

[Slugbabydotcom]

Sort the ch thermistor out first. It a very common fault and gives you a level playing field for not much money. Resistance should be between 500 and 20k ohms. IIRC about 7k at room temp and 9k if you stick it under your armpit = roughly 37ºC.
Try your old HW thermistor ... Theres probably nothing wrong with it.
On the earlier type CSI's with 2 fuses on the pcb, if you take the ch thermistor off and then put it back on it will fire up somewhere along the line.
APS is further down the list of things to check after fan, flue and venturi and tube/s.
Honeywell metal variety of APS tend to be sticky

 

[alpha50]

cheers again mate, can't get at it till weekend now but will try what you said