Rayburn 480kb cutting out

[oliverfuller]

Hi - a new boy here with a question:

I have a 12 radiator, gravity fed, CH system powered by an oil Rayburn 480KB. This system has always been reliable until this week. Now, after the system has complete the evening on/off cycle, the Rayburn 'trips' off resulting in no switch on next morning. Resetting the little 'push on' switch on the control panel restores the Rayburn to life again. Herself Indoors is not impressed as you can imagine!

Nothing has changed in the system over the last year and all the ancillaries (auto bypass valve, zone vales, etc) appear to be working fine.

Has anyone come across this scenario before please or can anyone suggest a cure/possible suspect component? All help deeply appreciated.

Best wishes
Oliver
Scotland

 

[dontknowitall]

First question is when was it last serviced? To run well, they need a service once a year.

Assuming it is regularly serviced if the problem is ONLY after the evening cycle, my first guess would be the programmer has developed a fault but it could be the high termperature thermostat that's failed, especially if it happens at other times, say weekends when the timings are different.

My guess is it is more likely to be on the hot water side than the heating as you'd probably notice if the radiators were cooler later in the evening. The hot water would be stored and you wouldn't notice this until you'd drawn it off for a bath/shower. Perhaps you could press the button just before bed after using the hot water at night then see if it works in the morning?

You have two burners. One for hot water/heating and the other for the cooker. If you turn the cooker right up does the Rayburn lock out then?

Apologies for a muddled response, but hopefully something there for you to consider.

 

[oliverfuller]

Hi - thanks for the response.

The boiler is serviced every year - last done March 2009. The time switch has two cycles which apply 7 days a week - 4 hours in the morning and 7 hours in the evening. The 'reset' button trips to off after the evening cycle is completed and while the pump is cycling via, I think, the automatic bypass valve - I assume it does this to 'lose' heat?. Resetting the 'reset' button does ensure the boiler fires up properly in the morning. None of this is affected by the cooker side which shuts down some hours before the CH shuts off. Could it be a faulty CH temperature sensor or bypass valve?

Much appreciated,
Oliver

 

[dontknowitall]

My post wasn't too clear (long day!) but then it's an odd problem.

If you set the evening cycle to a shorter period this might cure the problem. I'm beginning to think it's something to do with the clock/programmer at a certain time (at midnight for instance). You could test this by having hot heating in place, then setting the clock to 11:50pm, changing the last time to 12:10am and see what happens. Basically, fool the clock and time settings to try and trigger the lock out event.

If this doesn't trigger anything, the clock/programmer is probably okay so it could be the temperature sensor as you say.

 

[oliverfuller]

Thanks - I'm working on it ;-)

Oliver

 

[swdart]

My 480KB has started doing this as well.
## System: Installed to give hot water on demand for a combined 300ltr indirect tank for hot water and wet UFH system. Therefore the unit time clock is overriden by wiring direct to heat on-demand.
## Symptoms: The fault manifests itself when the reset cuts-out if the oven is running for a period at mk 4 or more. The control panel plate becomes untouchable (this maybe a red herring) due to it being too hot. Until the panel is cool enough to touch the reset continues to hold OFF. So we have a double whammy of having a cooling oven to get hot water.
## Servicing: The sensor was replaced at the second service last year at Xmas. It's annoying because the hot water system runs from 4 am to be ready for all to wake up and immerse themselves in a warm house at 6.30 on. Technical won't help because I'm not the engineer and they will only talk to the engineer whilst he is on site (not very helpful as it is usually an unaccompanied visit). Also I'll be blowed if I am going to pay for another visit before I am confident there is a fix. Hope that is all self-explanatory.

 

[oliverfuller]

I'm surprised Aga/Rayburn technical help won't talk to you but people do have different experiences of that department!

My problem was with over-heating after shut down on the HW/CH side which was resolved by fitting a wall vent (2 actually) to allow air to circulate around the boiler to Automatic Bypass Valve. It occurs to me that a simpler solution would be to arrange for the heating side zone valve to remain open until the system temperature falls sufficiently but this is beyond my abilities to devise!

Can I suggest you arrange a visit with the engineer when you can be there?

Good luck,
Oliver

 

[swdart]

Thanks I think If I understand correctly that implies that the balanced flue is not/was not working correctly?! I may be more concerned now.
As to the engineer: I object to paying by the hour for someone to talk to technical help on my behalf. I will talk with him again (3rd time in 3 months) and see if I can't resolve this. I might also try a different engineer although there are only 3 to choose from in my area. One of those has already said they find 480's too difficult and tend to avoid.

 

[oliverfuller]

If I understand correctly that implies that the balanced flue is not/was not working correctly?!

No - I'm talking about my experience of a post shut-down hot water issue. Not a balanced flu problem.

I object to paying by the hour for someone to talk to technical help on my behalf.

You are not alone in this!

One of those has already said they find 480's too difficult and tend to avoid.

We had a 360KB for years which was a delight - the current 480KB is a hypochondriac by comparison. I wouldn't buy another. Good luck.

Oliver