boilers

naf123

Hi

What is more cost effective for a very modern boiler

• a boiler that turns on, stays on for 20 mins and then turns off till an hour later. Temperature is obviously not consistent but boiler only fired once in that time period.
  
• A boiler that turns on and off several times to maintain the temperature - but it fired several times in the same time period

I guess the real question is, does the actual firing of the boiler use up more gas as it fired several times?

Think subconsciously in the past with old style bulbs always thought it costs more money to turn on/off the light regularly than to leave it on as the initial switch on use lots of power!

JohnB47

naf123 wrote: »

Hi

What is more cost effective for a very modern boiler

• a boiler that turns on, stays on for 20 mins and then turns off till an hour later. Temperature is obviously not consistent but boiler only fired once in that time period.
  
• A boiler that turns on and off several times to maintain the temperature - but it fired several times in the same time period

I guess the real question is, does the actual firing of the boiler use up more gas as it fired several times?

Think subconsciously in the past with old style bulbs always thought it costs more money to turn on/off the light regularly than to leave it on as the initial switch on use lots of power!

I'm no expert but option one seems more efficient in my opinion. A boiler is more efficient when running at full temperature, so coming on and off quickly will waste energy.

Option one seems more normal to me anyway - to get option two I would need my boilers CH temperature turned way down and having low temperature water flowing through the rads is inefficient too (they work best at high temperatures).

Just my DIYer opinion

nofoollikeold

Condensing boiler are at their most efficient when the temperature of the circulating water as it returns to the boiler is 55 degrees Celsius or cooler, as above this temperature the condensing function doesn't work (broadly speaking).

To achieve a 55 degree return temperature, it is normal to size the radiators so that each one has a temperature drop across it (from flow to return) of 20 degrees. This mandates a flow temperature of 75 degrees, say 78 degrees for the water as it exits the boiler.

Because the radiator's average temperature (75 - ((75 -55) / 2)) = 65 degrees is lower than for a non-condensing system (about 70 degrees), the radiators need to be larger (at least in terms of heat loss) to achieve the same room temperature.

Most modern boilers are modulating boilers. This means that they reduce the amount of gas they burn to achieve the required heat output, rather than running full blast and then turning off. By doing so it easier to ensure the return temperature is at the condensing point.

Radiators are no more or less efficient at high or low temperatures. Higher radiator temperatures will heat a room up quicker, but will of course burn more fuel for a shorter period. Radiators need to be sized to give off the amount of heat required to maintain a desired room temperature for the range of external conditions for the room.

stator

In other words, if the boiler is modern and the system is balanced professionally: don't worry about it.