Boiler cycling on and off

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Grant Euroflame 70-90btu outdoor condensing boiler unit (kerosene oil burner) Riello RDB2 Burner:

When my boiler first starts up in the morning it only heats upstairs rads and immersion tank and fair enough once its cold the burner stays on a long time to heat it up to 60-65c , but once its reached temp in the boiler then even though the rads and immersion is still calling for heat the boiler burner keeps going into an on/off cycling mode then (keeping its heat I suppose) and then starts for a while, stops for a while and then starts again soon (so maybe off for a min then on for a minute then off for a minute) I have heard that this cycling on and off is not good for the boiler as it can shorten its life? What does it shorten is it the electrodes and the high voltage transformer because it has to stop and ingnite more than it should, is that what it is? - any ideas how to stop it cycling on and off like this? Thanks
 
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Why only heating upstairs?

Your choice ?

So what do you expect the boiler to do if your system cannot dissipate the boiler's heat output?
 
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Why only heating upstairs?

Your choice ?

So what do you expect the boiler to do if your system cannot dissipate the boiler's heat output?


moved in december house was built in 2008 - it seems zoned heating , got upstairs and an independant downstairs thermostat
 
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So what do you expect the boiler to do if your system cannot dissipate the boiler's heat output?
 
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So what do you expect the boiler to do if your system cannot dissipate the boiler's heat output?

I dont know - thats why I was hoping someone could give me some helpful advice ! how to correct it (if it can be corrected)
 
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Your boiler gives out a fixed maximum power. It does not modulate down.

So once the flow temperature reaches the set value the only thing it can do is turn off the burner!

It is only doing what it is designed to do.

It is sized to meet the heat requirement when it is -1 C outside. Many are over sized though and that particularly causes cycling.

Tony
 
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Your boiler gives out a fixed maximum power. It does not modulate down.

So once the flow temperature reaches the set value the only ting it can do is turn off the burner!

It is only doing what it is designed to do.

It is sized to meet the heat requirement when it is -1 C outside. Many are over sized though and that particularly causes cycling.

Tony

ah right thanks, yes thats my suspicion also that the boiler is oversized there is on 2 Double radiators in the house , 1 in the living room and 1 in the main bedroom - all the other rads are all single and the boiler is 70-90btu (i wouldnt know what jet is in it i.e. whether its setup for 70,80 or 90btu)
 
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If only heating the upstairs rads, check your pump. Heat rises so convection heats upstairs, the pump may not be circulating.
 

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