Pellet Boiler continually burning and not reaching MAX temperature

[ollielaroo]

Can anyone help here please?


We've had this OPOP pellet boiler for at least 6 years and it's always been running very well.
But the last few weeks it seems to be behaving differently and I don't know why.


Two storey detached house 192sq meters.
UFH and rads upstairs.
OPOP H430 30kw with Woody/Bio-comfort control panel.
Thermostat at top of buffer tank is set at 60 degrees.
Thermostat at bottom of buffer tank is set at 70 degrees.

The pellet boiler used to always ignite automatically when the water in the buffer tank would drop to a certain temperature. It would burn for a couple of hours (or for however long it took to heat the water in the buffer tank) at 100% Power. Then it would stop and not come on again for hours or a day or until the next time the water in the buffer tank needed heating up again.

Now it seems the boiler is heating to about 72 degrees and the Power % is dropping down gradually. It's as if the boiler won't continue to burn on full Power 100% and bring the temperature up to nearly 80 degrees like it used to. The auger is dribbling in small amounts of pellets at intervals just as it used to before, but I can't understand why it won't just bring the temperature up to 80 degrees and stop burning.


Other things I notice:
The pressure gauge on from of the boiler stays up at 3 bar.
The pump between the buffer tank and the pellet boiler also seems to be constantly running not sure if that was always the way.


The only circumstances that have changed:
Recently I had to turn the speed of the pump for the rads in the house down from 3 to 1 to try reduce the hissing sound from the rads. Also we had power cuts from recent storms but never caused issues before.


I've been trying to understand the settings available on the control panel.

I can access the User Setup and the Advanced/Tech Setup but if I try to change any setting it seems to revert back to what it was before - I don't know why.


After cleaning out all the dust from the bottom of the silo and the auger and a delivery of new pellets there is no change. The boiler is still reaching up to 72 or 73 degrees, the auger is still feeing pellets and the Power % is gradually going down. Has anyone seen this scenario before?

Thank you.

 

[SimonG]

Have you not contacted your service guy?

 

[Worcester]

Your boiler should have been serviced annually cleaned regularly and the flue swept twice a year.

Apart from that, you will need to go in and see what the buffer settings are in the boiler, what hysteresis has been set up etc, get it wrong and you'll be trying to set it up forever..

It may be a faulty sensor, if they are PT1000's it's easy to check wether they are working properly - just check the resistance at various (known) temperatures - google for the values (at 0°C = 1000 ohms, at 100°=1385.0 ohms - put it in a saucepan / pour the kettle over it ) or go here RTD Calculator ? Southern Temperature Sensors Ltd

The air settings may need changing on the boiler, the auger rate may need changing as well (depending upon the quality of the pellets) , auger sensor may be faulty - too many possible variables - you need to get a qualified biomass engineer out that knows these boilers.

It is most likely the bottom sensor getting to 70° that is modulating the boiler down. - They don't tend to be switched off by the top sensor - that is used to switch them on (on at 60° at the top, off at 70° at the bottom)

These guys should be able to help you http://robusenergy.co.uk/

 

[missplumb]

there are many many things that could be wrong, have you cleaned the lambda sensor?

 

[ollielaroo]

It seems we have got to the root cause.

Apparently when the pellet boiler and buffer tank were installed the electrician put in a 'Relay' between the buffer tank and the pellet boiler. Of course I know nothing about Relays, what they do and how they work but I believe it has something to do with how the electricity can managed if you have additional pumps for example. Three electrical wires (from the two thermostats on the tank and the pump that circulates water between the tank and the boiler) are connected in to one side of the box on the wall that houses the Relay. From the other side of the box that houses the Relay the wires then go the Bio-comfort control panel (Woody 5.99E) on the front of the pellet boiler. It seems the Relay isn't working anymore, therefore the pellet boiler wasn't aware of what temperature the thermostats were sensing on the tank and as a result the boiler thought it needed to behave as if it didn't have a buffer tank.

As soon as I pulled the Relay out from its box on the wall the pellet boiler could then be governed by the temperature readings from the thermostats on the tank, like it used to do before the Relay malfunctioned. Apparently I just need to buy a new relay for less than €20 and replace the existing one. Even though I've been told the power cuts during the stormy weather some weeks ago shouldn't have affected the Relay it looks like they did in my case.

Many thanks to my brother, the contributors on this forum and Bradley from kbf.ie.

 

[Worcester]

Thanks for the update, good to hear your problem has been solved.