Potterton Kingfisher RSL100 Lockouts

[redconker]

I have a Potterton Kingfisher RSL100 boiler on a sealed system. Over the last couple of days I am getting lock-out errors.

When I reset the system, it can then run again fully through the cycle without issue. At this time of year, I am only using the system for heating water. Around 80% of the time, this is fine.

I understand the lock-out errors can occur if there is a blockage in system, the pump is not working or the thermostat has failed. Since the system heats water most of the time, am i right in being able to dismiss both a pump and blockage issue?

One last thing, on my road the gas main is being replaced. Could there be rubbish in the pipe clogging up the jets?

Any help would be gratefully received,

thanks.

 

[Agile]

I have to guess that you have a Kingfisher MF as I think of it and it has a PCB which controls the operation and a single lock out likht.

This can be operated by a flame failure or overheat.

The boiler does not know where the heat is going so heating hot water makes no difference to any fault situation.

Its possibly but should not have happened that the gas pressure is seriously reduced momentarily during the street works and that is causing flame failure.

Tony

 

[redconker]

Thanks Tony. It is an MF and does have a PCB. Do you think it's likely to be the PCB with a fault?

 

[Agile]

As the PCB is a more expensive part then I would always eliminate the other possibilities first.

I would eliminate overheat by monitoring the flow temperature and if thats normal then I would measure the sensor resistance to see if it matches the value/temperature.

If that was normal then I would examine the pilot flame and sensing electrode and if all that seemed normal I would monitor the detection voltage at the point of tripping. Those aspects are within the area of work of a registered gas engineer though.

The PCB is the last resort when everything else has been checked. They do sometimes fail like that!

Tony

 

[redconker]

Tony,

Thank you very much for the help. I've noticed the following:

1. The pipes coming from the boiler are red hot when the lockout occurs meaning the lockout is as a result of an overheat(?)

2. The lockout occurs during the afternoon cycle when the on-period is longer and the cylinder may contain some residual hot water.


I am therefore guessing (and would like some agreement please) that the fault in either the cylinder thermostat failing to turn off the boiler when the water reaches temperature leading to an overheat or
the thermostat on the boiler it's self has fails.

With non simplistic tools, is there any way to verify which component is at fault please?

Thank you.

 

[Agile]

An experienced person can do a lot without many tools but would have them anyway.

You need to know the pump is working properly ( see FAQ ).

What setting have you put the boiler stat?

What happens when its turned to minimum?

Tony

 

[redconker]

Thanks Tony for the quick response. The pump is whizzing and if I remove the screw, I can see the propeller spinning. If I change the setting (i to iii), the tone of the pump changes and the whole system becomes noiser as more water is pumped around. I'll search around for the FAQs to see if theres any other tests I should do to ensure the pumps working.

The boiler state is set at 50% - the one on the boiler. I don't feel this has much impact when turned up / down but can test more tonight.

thanks.

 

[redconker]

Hi there,

The temp setting runs from 1 to 11. With the boiler set to 4, it overheats / locks out. Does this suggest the internal thermostate is faulty?

thanks.

 

[redconker]

I would really appreciate some help here as I'm coming to the end of things to test.

At this moment I know:

• The boiler flow (to and from) the hotwater cylinder is okay
  The pump works fine
  If I inhibit flow for a very short period and then open, the hot water return heats very quickly showing no blockage
  Hot water will heat but then the boiler locksout - not always to the same temperature
  Based on the diagnostic tests in the kingfisher manual, the boiler behaves as expected - circuits 1 through 6
  Power is getting to the cylinder thermostat
  Even with the water hot, the cylinder feels only warm
  The cylinder thermostat is situated near the bottom of the cylinder and I guess hot water rises
  I have relaced the thermostat on the boiler
  I have not replaced the overheat stat
  the boiler pipework is very hot when it locksout
  If I forget to press reset in the evening, we have no hot water in the morning

Thanks for anything you guys can suggest.

 

[twgas]

I have relaced the thermostat on the boiler

do you mean the thermister (inside boiler case) or potentiometer (bit behind knob)

 

[redconker]

Hi there,

I mean the thermister which goes into the boiler body.

thanks.

 

[bengasman]

Old open vent systems very often suffer from corrosion related blockage. Several indicators that are very easy to find.
Look inside the header tank, if there is muck in the highest part, it is more than a bit likely that there is a lot at the lower parts.
The old magnet against copper pipes trick; even the smallest attraction means there is a lot of corrosion.
Run the heating and check the bottom of the radiators on the lowest floor; if both valve corners are hotter than the middle at the bottom, time for a clean.

 

[redconker]

thanks for the feedback.

The heating system has been converted to a closed system with a pressure vessel. Prior to this work, the system was fully powerflushed.

thanks.

 

[bengasman]

Still worth checking, you'd be surprised how many "powerflush experts" either don't know what they are doing, or can't be bothered doing the hard work. Numerous people just stick the machine on, and leave it running for a few hours.

 

[Agile]

Hi there,

I mean the thermister which goes into the boiler body.

thanks.

When you replaced it did you add thermal transfer paste?

The pump should be set on "2" ! You earlier implied that it was only on "1".

Do you have any motor valves? Could they be jamming?

Its necessary to measure ( or feel ) the flow AND the return at the boiler when its about to overheat !!!

Tony