Boiler anti-cycling mode and thermostat cycling

[tim_s_uk]

I have a Honeywell CM907 programmable thermostat, which cycles the boiler to maintain a steady room temperature. I've recently had the gas boiler replaced with a Vaillant ecoTec 831 plus, which has an anti-cycling mode. I think this is designed to allow the water in the radiators to cool down further between cycles, and so improve efficiency.

It appears to be a trade off between boiler efficiency and maintaining a steady room temperature. Is there more to it?

Honeywell suggest that anti-cycling does not improve boiler efficiency:
http://content.honeywell.com/uk/homes/files/pag101.pdf

I can adjust the anti-cycling period on the boiler, and also set limits on the thermostat cycling so that the boiler will always switch on when the thermostat calls for heat.
Does anyone have information on how these devices should best be configured to work together?

The boiler anti-cycling default is 20 minutes, while the thermostat defaults to 1 minute 'minimum off time' and a maximum of 6 cycles per hour for a gas boiler.

 

[Jeffrey3796]

Sorry to resurrect an old thread, but I have the same question so I thought I'd post here rather than start a new one.

I have a Vaillant ecoTec 832 plus and Honeywell T4R thermostat. The boiler is set to the default 20 minute max anti-cycle time, the target flow temp is 60C which gives an actual anti-cycle time of 6 minutes. The thermostat was initially set to the default 6 cycles per hour.

Initially the room temperature was getting to 1.5C below the set temperature but then never getting any higher. I think the thermostat was turning the boiler off for 1 minute in every 10, but the anti-cycle time meant the boiler was actually off for 6 minutes followed by 4 minutes at the minimum burn, which was not enough to raise the room temperature further.

I improved things a bit by changing the thermostat to 3 cph, so the thermostat is now turning the boiler off for 1 minute in 20 which equates to 6 minutes off due to anti-cycling followed by 5 minutes at minimum burn and then 9 minutes modulated up. The thermostat now reaches the set temperature, but it takes over an hour to raise the final 1.5C.

Is it safe / advisable to reduce the anti-cycle time to the minimum 2 minutes? This would mean the boiler was on for 18 minutes in 20, not much less than the 19 the thermostat expects. I gather the feature is to reduce the amount of cycling, but the thermostat is going to light the boiler once every 20 minutes regardless, so I'm not sure what difference it makes?