boiler cycling

[mpooley]

I don't claim to have the knowledge of the other guys but the oversized boiler explanation makes sense to me.

Since it is not too cold yet and you do have a very powerful boiler (with some rads turned off), the system will get up to temp very quickly (within 20 mins).

Once the water in the system reaches the desired temp (as specified by the boiler's internal thermostat) the boiler will switch its burner off but leave the pump running in order to keep circulating water around the system. Then, because you have quite a large number of rads still running, the water will cool down pretty quickly. It does not have to cool down too much before the boiler's thermostat triggers and starts it up again.

Given the power of your boiler it will then heat the water up very quickly and the cycle will repeat.

To reasure yourself that all is well, turn the house thermostat down and wait for the system to properly cool down (about an hour). Then turn the thermostat back up and see what the boiler does when the water in the system is cold. If it still cycles during this initial heat-up phase then there may be another issue.

iep

Thanks that is a good explanation of it.

I will try that tomorrow.
I would have hoped that the boiler controls were a bit more sophisticated than just a thermostat on the burner. But it looks like I am wrong. lol

My cct diagrams in the manual dont show any internal thermostat at all so i cant really judge what is going on.

thanks

 

[Agile]

All boilers have to control the output flow temperature.

It could be that you are looking for the word "thermostat" Most boilers nowadays use electronic sensors to monitor temperatures.

So to address the problem the boiler power output needs to be reduced. Unfortunately with your type of boiler thats not so easy. The coarse control is with the nozzle size but in between there is usually a further adjustment allowed by the manufacturer by altering the burner pressure.

But its not just a simple DIY adjustment because if its altered the combustion gases need to be measured to set the parameters to the optimum for the new settings.

One wonders why the question of power output did not come up at the previous annual services.

Over cycling reduces efficiency and you may need to consider if you really want to sacrifice inefficiency for the ability to heat the whole house just for a few days. Remember these heat calculations are based on the worse case of -1° outside. For most of the year the heat output is only 30-40% of the maximum.

Tony

 

[D_Hailsham]

It might be worth considering weather compensation. Grant make the Efficiency Optimizer which does this. It does cost nearly £600, so that may not help.