Going Green isn’t easy

[Sam Vimes]

This debate seems to be going around in circles and getting a little personal.

I'll not lock it yet but my summary is....

Heat pump related equipment is good for some and not others. Just because of one or two of your own experiences, good or bad, does not mean the technology is bad or good in general.

 

[Oscarmax]

We are fortunate our 2 bedroom bungalow was built in 2017, over a 12 hour period in the current cold weather we lose 3 degrees C, this morning to heat up from 19 degrees C back up to 22 degrees C just our 1 hour hour.

When we refurbish the kitchen we will change the Ideal combi to a Bosch and the tumble dryer (which is every other day 365 days a year) to an AEG 9 kg heat pump dyer (as there are no heating element run it off peak rate overnight)

 

[GUMPY]

Would be interesting to know how hard the boiler is running to do that. On our system, gas boiler with weather compensation, it takes about an hour per degree to heat the house from 16 to 18.5* on these cold mornings. However it's a 15kW boiler but apart from when it's heating the hot water when it gets to 11kW (flow temp 80deg) it rarely runs above 5kW due to the lower flow temperature (40-55 Deg C) for the heating.

I'm still experimenting to find the most economical way of running it, so far it seems to be maintaining an even temperature all day, even if we are out, rather than heating and cooling the house.



* Thermostat/timer is in the hall which is a 1-2 degrees colder than the rest of the living area.

 

[otherclive]

We are fortunate our 2 bedroom bungalow was built in 2017, over a 12 hour period in the current cold weather we lose 3 degrees C, this morning to heat up from 19 degrees C back up to 22 degrees C just our 1 hour hour.

When we refurbish the kitchen we will change the Ideal combi to a Bosch and the tumble dryer (which is every other day 365 days a year) to an AEG 9 kg heat pump dyer (as there are no heating element run it off peak rate overnight)

That’s similar to our temperature drop overnight last Tuesday until mid day Wednesday and the overnight outside temperature was minus 2 deg C. Post #194 shows the cooling and heating curve.

 

[Dustydog]

Our four year old Vaillant Eco gas boiler is A rated allegedly reaching 94% efficiency .

Do you think it is cheaper to keep the house at a low of say 15 degs C overnight warming it up to say 19 degs when occupied?
Or let the temperature drop with the weather and then warm up?

 

[otherclive]

Our four year old Vaillant Eco gas boiler is A rated allegedly reaching 94% efficiency .

Do you think it is cheaper to keep the house at a low of say 15 degs C overnight warming it up to say 19 degs when occupied?
Or let the temperature drop with the weather and then warm up?

That’s a difficult one to answer. We tend to just let it drop overnight as the boiler turns off at 2130. It’s scheduled time to come on is 0730 but generally we have it turned off for heating and on for 2 hours for hot water. Putting it on generally around 1300. If the external temperature is forecast to be low we will set it at 17 deg C in order for the inside temperature not to drop further. But last Wednesday it did not come on until mid day as we were going out all morning and had set it at 15 deg c but it never dropped quite that low.

We are away all this coming week and the boiler will be off as there’s no frost forecast. Before we leave to return home I will switch it on using Hive so we will have warmth and hot water for when we arrive home.

 

[GUMPY]

Boiler efficiency figures are almost never achieved in real life. The figures are calculated when the boiler would be at maximum condensing mode. This happens when the flow temperature is below 55degC most boilers are set up by the installers to run at DT50* this means that the flow temperature is above 65degC so no condensing happens at all and the efficiency goes down dramatically.

* DT50 means there is a 50deg difference between flow temperature and the desired room temperature. Radiators are normally sized for this temperature difference, running lower DT means using bigger radiators.


The system here is set to vary the flow temperature depending on the outside temperature, the colder it is outside the higher the flow temp and radiator temperature.

Even at 0deg outside the house here only loses about 3 Deg overnight. I'm looking at setting the overnight temperature up a degree or two (it's 16deg at present) to see how much or little it uses compared to raising the temperature by 3deg every morning.

 

[GUMPY]

It’s scheduled time to come on is 0730 but generally we have it turned off for heating and on for 2 hours for hot water.

Because I use variable flow temperature I have both heating and hot water on first thing. This means flow temp is 80deg whilst the hot water is on dropping to 50deg once the HW stat switches off. This boosts the heating effect of the radiators hopefully causing the house to heat up quicker.
However it's still early days tuning this system.

 

[otherclive]

Boiler efficiency figures are almost never achieved in real life. The figures are calculated when the boiler would be at maximum condensing mode. This happens when the flow temperature is below 55degC most boilers are set up by the installers to run at DT50* this means that the flow temperature is above 65degC so no condensing happens at all and the efficiency goes down dramatically.

* DT50 means there is a 50deg difference between flow temperature and the desired room temperature. Radiators are normally sized for this temperature difference, running lower DT means using bigger radiators.


The system here is set to vary the flow temperature depending on the outside temperature, the colder it is outside the higher the flow temp and radiator temperature.

Even at 0deg outside the house here only loses about 3 Deg overnight. I'm looking at setting the overnight temperature up a degree or two (it's 16deg at present) to see how much or little it uses compared to raising the temperature by 3deg every morning.

Thanks, I never knew that aspect of a condensing boiler. Bit of a well shrouded secret in the trade. So once our house is up to temperature it might be more economical to wind the boiler heating water temperature lower, so it’s running longer but at lower output and at higher efficiency.