On the face of it a simple question, but bear with me
I had a new boiler fitted in January, a Worcester Bosch 27i LPG Compact System boiler, this load modulates and can be weather compensated.
I noticed immediately that when set at the 60C (1st indent on the knob) point to allow maximum condensing it could not heat the contents of the hot water tank. The 20 year old previous boiler had no trouble with this when set to a 60C flow temp.
I was advised to try the 2nd indent (75C) and this improved matters but it really didn't work properly until set to maximum.
The boiler manual and the sales literature state that weather compensation is not possible with system boilers, but faced with the prospect of next to no condensing in my new boiler, I did a lot of research and was able to apply weather compensation, get it to work properly AND still heat the water.
I did this by using the hot water on demand signal from the tank controls to put a resistor in parallel with the compensation sensor. This dummies the boiler into thinking that the outside temperature is very cold, it therefore runs at maximum temperature until hot water demand is fulfilled and then compensated service is resumed. This works well
The disadvantage of this is that the central heating also runs at maximum boiler temperature until the central heating demand is satisfied, resulting in a large thermal overshoot in the house.
Here's the question (AT LAST! they all cried)
Given all the above, might it be cheaper to use the immersion heater, controlled by my existing timer via a suitable contactor, and just use the boiler for weather compensated central heating? The immersion would after all, just be heating the tank, not the pipe work and over heating the house.
Does anyone have any experience of making this comparison, or any learned sources I could look up?
Thanks in anticipation, Goffy.
I had a new boiler fitted in January, a Worcester Bosch 27i LPG Compact System boiler, this load modulates and can be weather compensated.
I noticed immediately that when set at the 60C (1st indent on the knob) point to allow maximum condensing it could not heat the contents of the hot water tank. The 20 year old previous boiler had no trouble with this when set to a 60C flow temp.
I was advised to try the 2nd indent (75C) and this improved matters but it really didn't work properly until set to maximum.
The boiler manual and the sales literature state that weather compensation is not possible with system boilers, but faced with the prospect of next to no condensing in my new boiler, I did a lot of research and was able to apply weather compensation, get it to work properly AND still heat the water.
I did this by using the hot water on demand signal from the tank controls to put a resistor in parallel with the compensation sensor. This dummies the boiler into thinking that the outside temperature is very cold, it therefore runs at maximum temperature until hot water demand is fulfilled and then compensated service is resumed. This works well
The disadvantage of this is that the central heating also runs at maximum boiler temperature until the central heating demand is satisfied, resulting in a large thermal overshoot in the house.
Here's the question (AT LAST! they all cried)
Given all the above, might it be cheaper to use the immersion heater, controlled by my existing timer via a suitable contactor, and just use the boiler for weather compensated central heating? The immersion would after all, just be heating the tank, not the pipe work and over heating the house.
Does anyone have any experience of making this comparison, or any learned sources I could look up?
Thanks in anticipation, Goffy.