Query on Gas Boiler Efficiency

[chrisb2]

I have a Vaillant wall-mounted 418 ECO TECH PLUS Boiler. Can anyone tell me whether it would use more or less gas if run on hot water only 24/7 with the max' temp' controlled by the thermostat on the hot water tank (set at 60C) , or whether less gas would be used if the programmer is set so that the boiler is OFF overnight for a period of 7 hours.
This is assuming there is a constant use and run off of hot water during the day.
Thank you.

 

[D_Hailsham]

Is your hot water cylinder well insulated, i.e a 25mm or more foam jacket fixed to the cylinder, not a loose jacket?

 

[chrisb2]

D_Hailsham,
My hot water cylinder is definitely well insulated, and has at least a 25mm or more foam jacket fixed to the cylinder. Not a loose jacket.

 

[simond]

This is a very complex question to answer, and there are more variables than you have provided answers to.

My suggestion is that by allowing the cylinder to cool slightly over a 7hr period, the boiler would be more likely to be in condensing mode when the heat is topped up. Therefore this may achieve a slight saving over the 24/7 option.

If you want to save gas, I suggest you worry about addressing the 85% problem rather than the 15%.

Space heating is using 85% of your gas and therefore more close temperature control of the rooms you elect to heat, based upon when you are in them, will liberate much bigger energy saving than anything you attempt with respect to Hot Water.

This is why solar hot water looks great until you do the maths. You are only chasing the 15%, and solar will only address 50% of that (eg: on summer days predominantly).

 

[Agile]

Your cylinder itself will lose very little heat over 7 hours.

What will lose more is the pipework!

All the pipework should be well lagged around the cylinder. Thats actually required when a cylinder is changed but few people do it.

Tony

 

[chrisb2]

Thank you Simon and especially you Tony.

Lagging the pipework? I've just checked the pipework near the hot-water-cylinder and none of it is lagged, so will see into that one.

Simon, from what I understand of your reply (many thanks) I am not referring to the CH but only to HW, (CH is off) so if you would like to expand on what u mean if you do not mind.
Thank you.