glowworm 24hxi f 26 fault?

I had f26 fault on my 30hxi boiler. I installed a magnaclean and added some Ds3 cleaner. I ran the domestic hot water. After a good run I cleaned out the impeller on the pump. I found the magnaclean really cleaned out the system. The boiler now runs well and does not modulate as it used to. The pump is quiet and supplies heat to all 16 rads. on a low setting. I have since cleaned out the pump impeller, and the magnaclean often.

Graham
February 2013

I think Carefree has got it the wrong way round. The temp of the water coming out it too much higher than the water going in, e.g. the system assumes it should heat the water say 20 degrees from whatever temp it goes in at but for some reason it is heating the water 40 degrees (I am making these numbers up but you get the idea). I believe this is most likely to be caused by sludge restricting flow to a dribble.

Tomorrow I will try and isolate the boiler and run a power flush and see if that helps...

Alan
March 2011

Graham

Did you get a solution? My problem is exactly yours; F26, knocking noises in the boiler and obviously a lot of sludge in the pipes. But having drained out a lot of muck twice now, the problems seems to be getting worse, not better. Off today to get a replacement thermistor, but have no great hopes this will resolve anything. I'm on an open system with a F & E tank.

IanC

IanC
February 2011

I am puzzled by the answer given. The F26 error indicates that the temperature difference between flow and return is high and exceeding the maximum permitted, consistent with the flow rate being too low as it would be in a system whose flow rate is restricted by a build up of contaminants.

The answer given is stating the opposite, ie., that the flow is too high, which would not be the case with clogged pipework. A high flow rate would, indeed, result in the temperature difference being low, which would be described as Minimum Delta Temperature surely. Or have I completely misunderstood the basic concepts?

I have had F26 code displayed and resorted to several power flushes, with the boiler isolated, in an attempt to fix it. But the chemicals and the flushing seem to have migrated the previously dormant contaminants (sludge) into the boiler and affected its performance in other ways. This includes, serious knocking noises as boiling point is reached within the heat exchanger, instability of the control loop resulting in overshooting of the set-point, not able to set more than a mid-point temperature, etc. The likeliest solution is possibly the replacement of a three year old boiler - not a very satisfactory one - with another make of boiler which is more tolerant of the contaminant risks associated with older systems. But which to choose is the question.

Keeph1
August 2010

From the installation manual
F26 Maximum delta temperature.
Check thermistor on return.
System too restrictive.

In translation, Pump flow rate too high, causing temperature difference between flow and return to be too low.
Possible faults for you to check:
Has the system by-pass been closed down?
Has the pump speed been altered (turned up)?
Possible thermistor fault, remove the leads to the return thermistor, using a multimeter test across the thermistor. 10k ohms at 25 degrees (ambient).

Carefree
July 2010