Would I benefit from range rating my boiler?

[Pearly King]

I have large house, 6 beds, 3 reception, 3 showers: Vaillant ecotec plus 37 kW, 16 rads, 3 towel rails and hot water tank. Mostly just my wife and I and we "shut down" parts of the house, unless family visit, and run 8 rads, 2 towel rails and hot water tank.
Based on what I have read it seems that I would reduce boiler recycling and improve efficiency if I changed the boiler power rating from auto to, say, 20kw.
Does that sound right?

 

[Last Plumber]

The boiler will modulate down to around 20% of the max anyway and that will be as low as it will go.
It will do that automatically. If you know the output if those rads you use and the output of the cylinder coil (badge on side normally) you could set it to the higher of the two if you like. It could reduce cycling whilst things get up to temperature.

What is the reason this came to mind?
Is the system balanced?
Have you tried reducing temp in rooms you do not use instead of turning them off, to see which way is more efficient.
Cold rooms increase heat loss from heated rooms next to them and increase the heat required into the heated room if that makes sense. Each property is different and should be taken on its own merits of course.

 

[Pearlyking]

The boiler will modulate down to around 20% of the max anyway and that will be as low as it will go.
It will do that automatically. If you know the output if those rads you use and the output of the cylinder coil (badge on side normally) you could set it to the higher of the two if you like. It could reduce cycling whilst things get up to temperature.

What is the reason this came to mind?
Is the system balanced?
Have you tried reducing temp in rooms you do not use instead of turning them off, to see which way is more efficient.
Cold rooms increase heat loss from heated rooms next to them and increase the heat required into the heated room if that makes sense. Each property is different and should be taken on its own merits of course.

Thanks for replying.
Like lots of others, given current gas prices, I was exploring ways to ensure that my system was running as economically/efficiently as possible.
I started by trying to balance the system but the first 6 rads I tried, all the lockshield valves leaked when trying to adjust them. I haven't found a way to fix them (please see my other post on Faringdon lockshield valves leaking), so I started to look at reducing the power of the boiler.
I haven't tried your suggestion of setting unused rooms at a low temperature rather than turning them off completely. I take your point about heat loss from cold to warm areas, I need to consider that.
It sounds like my best bet is several days of trial and error and see what the effects are
Thanks again.

 

[John.g]

If the heating demand is lower than the minimum output then the boiler will cycle anyway, range rating will (only) delay that process when heating up the system water as well, from cold.
Where it may help is in getting the boiler to refire successfully first time after recycling even though it won't reduce the 55% to 65% firing rate required by Vaillants for ignition and the 60 secs until the controls allow the boiler to modulate.

 

[Pearly King]

The boiler will modulate down to around 20% of the max anyway and that will be as low as it will go.
It will do that automatically. If you know the output if those rads you use and the output of the cylinder coil (badge on side normally) you could set it to the higher of the two if you like. It could reduce cycling whilst things get up to temperature.

What is the reason this came to mind?
Is the system balanced?
Have you tried reducing temp in rooms you do not use instead of turning them off, to see which way is more efficient.
Cold rooms increase heat loss from heated rooms next to them and increase the heat required into the heated room if that makes sense. Each property is different and should be taken on its own merits of course.

Thank you for the advice.
I thought I had replied to you earlier today, but it is not showing up, so this may appear twice.
I started to look at this to ensure that my system was running as economically/efficiently as possible, as so many people are given the energy prices. I started by trying to balance the system. However, I had to abandon that as for the first 6 rads I tried the lockshield valve leaked when I adjusted it. The valves are brass with a threaded plug insert that is adjusted with an allen key.(Please see my other post "Faringdon lockshield Valve leaking" for more details and photos) I have searched high and low to see how to fix them but without success. That is when I turned to looking at the boiler power setting. I haven't tried setting the unused rooms trv to a low setting, I will give that a go. I take your point about heat loss from cold to warm areas. It looks like I have several days of trial and error to see what effects
Thanks again.

 

[Pearly King]

If the heating demand is lower than the minimum output then the boiler will cycle anyway, range rating will (only) delay that process when heating up the system water as well, from cold.
Where it may help is in getting the boiler to refire successfully first time after recycling even though it won't reduce the 55% to 65% firing rate required by Vaillants for ignition and the 60 secs until the controls allow the boiler to modulate.

Thanks for the information. I'll experiment a bit and se what results I get.

 

[Last Plumber]

Thank you for the advice.
I thought I had replied to you earlier today, but it is not showing up, so this may appear twice.
I started to look at this to ensure that my system was running as economically/efficiently as possible, as so many people are given the energy prices. I started by trying to balance the system. However, I had to abandon that as for the first 6 rads I tried the lockshield valve leaked when I adjusted it. The valves are brass with a threaded plug insert that is adjusted with an allen key.(Please see my other post "Faringdon lockshield Valve leaking" for more details and photos) I have searched high and low to see how to fix them but without success. That is when I turned to looking at the boiler power setting. I haven't tried setting the unused rooms trv to a low setting, I will give that a go. I take your point about heat loss from cold to warm areas. It looks like I have several days of trial and error to see what effects
Thanks again.

Best advice I can give you is to look into the sensocomfort control for Vaillant. Pick the one that deals with your number of zones and a water tank.
It will give weather compensation to the boiler and that will only allow the boiler to heat the rads to the required amount to match the heat loss from the building. The heat curve needs to be set in but your installer will do that. Mine is range rated down with these controls, they work well.

 

[Pearly King]

Best advice I can give you is to look into the sensocomfort control for Vaillant. Pick the one that deals with your number of zones and a water tank.
It will give weather compensation to the boiler and that will only allow the boiler to heat the rads to the required amount to match the heat loss from the building. The heat curve needs to be set in but your installer will do that. Mine is range rated down with these controls, they work well.

Many thanks. I'll look into that.