Advice on Boiler efficiency

[yiangosliv]

Hi All,

I have a question which i believe mostly professionals would be able to answer. I have an Evohome system which works with two valves, one for HW and one for heating the radiators (with HR92s). My boiler works with LPG (not sure if this is relevant). Does anyone know whether turning on the HW (HW BDR91) while the heating is on (Heating BDR91) is more cost effective compared to turning on the HW when Heating is off. Currently I would like to turn on HW 30-60 mins before i would like to use it (but sometimes during that time the heating is off since the house has already reached a good temperature).

I ve been hearing from "old school" professional that turning on the HW while the heating is on is more cost effective - but in some cases you might use the HW 6-7 hours later and there would be definitely some temperature loss.

[bruce_miranda]

The answer to this question is going to be how cold the HW tank is before the HW cycle and how fast you want it to heat up.

[yiangosliv]

I am living in Cyprus, therefore we have relatively higher temperatures than UK. I am not sure how accurate is the HW strap-on sensor but if the temp indicator on HW kit on EVOHOME hits higher than 30+ based on experience the water is adequate for two persons having a shower. If i dont switch it on at all during the day/night it can show a temp of 18-20. If i switch on the boost (1hour) after that the indicator could show 35-37. I dont think i would need to turn on the HW for more than 1 hour in the morning and an hour in the afternoon.

[bruce_miranda]

Whenever you run the boiler, the created heat has to go somewhere. So you need to decide, it either goes into the tank, the radiators or infact cycle back to the boiler. The more heat you can extract from the water, before it returns back to the boiler to get reheated, the more efficient things get.