Ideal Isar

[DP]

I have a possible defect on an Ideal Isar. Rads are heating when there is no CH demand

The boiler, after a HW demand stays in ‘d’ mode with burners fired for some 20 seconds. While have not established if rads are heating up during HW demand (diverter passing), but hope to establish if this is the case at next visit. Rads are certainly hot when HW is demanded.

Called technical to be told it is the cold water flowing across the thermistor that results in burner staying on and display showing ‘d’. Could not get a positive answer whether it was primary or secondary water. Am I wrong to assume ‘d’ would only be displayed while a tap is running. Can understand pump overrun could result in rads getting hot, but am at a loss (unless preheat is a feature) why the burner stays on well after the HW demand is satisfied.

Can someone enlighten me on operate sequence of this boiler please

 

[scatmanjohn]

I would be suprised if it was not the diverter.

The d is displayed during hot water demand and also whilst in pre heat.

As far as i know the preheat can not be turned off.

I have had 4/5 with this very fault.

 

[corgiman]

as scats says the preheat cannae be turned off

also a slightly drippy tap can cause the pre heat to come on loads

 

[gas4you]

Isar can be 'stuck' on hw mode through a dripping tap.

Try turning off the cold inlet valve under the boiler. If boiler goes to C or 0 then a hot water drip or leak is your problem.

Isar's are VERY prone to diverter valve problems though, quite easy to change but watch the alignment of the rubber gasket

 

[DP]

Thanks guys

 

[gas4you]

Just read you're op again. You have now confused me. Firstly you state rads heating when no c/h demand, then you say 'have not established rads are getting hot on hw demand'

Certainly sounds like diverter fault.

Boiler should be showing '0' with no heat or hot water demand. 'C' with heating demand, 'D' with hw demand, 't' with plate heat exchanger pre heat demand.

Boiler will over run after demand has finished with white neon flashing. neon flashing quickly is ignition cycle, constant is burner alight.

Hope this helps

 

[DP]

What I meant to say was, have not established if radiators are getting hot during HW demand or at the end of the demand, but hot they do get.

Above replies certainly help. Will return to the boiler to attack the diverter.

Will post findings.

Thanks for replies.