PhilT

could be - the specs say it has "low temperature protection", but that's a very short warming time and it happens every single discharge irrespective of temperature

At around 02:40, with consumption (orange) continuing at a background level, there is an unscheduled light battery charge (blue and red lines) but, bizarrely, in the first 5 minutes, the SOC (purple line) drops from around 17% to ZERO, WITHOUT ANY CORRESPONDING CHANGE IN CONSUMPTION OR OTHER OUTGOING POWER, then gradually goes up to around 6% SOC at around 03:20 at the end of this mysterious little charge cycle

Every time my battery charges and discharges, even though the minimum discharge level is set to 6%, it always overrides that and discharges to zero then recharges to 6%. Anyone know why that happens?

Gas plant efficiency is far worse than theoretical because of renewables fluctuations

if my calcs are correct a 20% glycol mix will reduce efficiency by around 2%. Important for fully informed choices. Water Cp 4.18 Fernox HP-5c @ 20% 4.085 -2.3%

yikes - storms mainly?

Surely it's similar to the English scheme whereby you can apply for the 7500 grant for a self build if it meets certain criteria

Going away soon. For a week's holiday at this time of year, how do people set their heat pump modes, temps and timings, and with what objectives in mind?

Agreed where we are talking about replacing a perfectly good boiler system. But if it's 30+ years old like mine was, and needs a major upgrade anyway, the net cost to me of a new ASHP, DHW tank and bigger rads was no different to a modern upgraded boiler system. That financial equation of course varies enormously from the cheapest (possibly one of the utility companies like Octopus) to the most expensive (premium expert installers such as Heat Geek)

and an oversize heatpump like mine working 10% more efficiently than a smaller one running flat out/less efficiently on freezing cold days will mean 10% less electricity use at the time when the grid may be well over-stretched. I don't understand why people would burden themselves with additional expense and complexity of adding heating elements, boiler hybrid setups etc. when all you need is a bigger heat pump. Imagine a family during the recent freezing cold spell, they all come down with flu or lurgy of some kind (very likely this season). The house temp needs to be increased a couple of degrees all day and night to give them all the chance to get well again. In those circumstances you need a level of headroom similar to what you got from a boiler. This is just one of the many advantages of an oversized heat pump - extension, faster DHW reheat, less defrost recovery issues etc. etc.

Modern scroll compressor / clever software controlled heat pumps just don't suffer the cycling inefficiences of the bad old days. For me there was no difference in installation price between an 8.5 and an 11 so I went for the 11 and glad I did. It is outperforming spec on cold days by a significant margin. Compare 10% inefficiency on a mild day of say 10kWh consumption compared to 10% better efficiency on a cold day of 100kWh consumption. It's unlikely to be worse than break even over the course of the season. That's definitely what the evidence is saying for mine.

why exactly?

why not just get a bigger heat pump

what's the problem with it being a little louder than whisper quiet for relatively tiny periods of time. The compressor on mine after defrost is barely audible, and I'm sure it's no quieter than the Vaillant

To an extent, yes, but maybe not as much as people believe Green levies are 6% of a typical gas bill, 16% of an electricity bill, and 11% of the average dual fuel bill. Climate change levy rate for gas is 0.672 pence per kWh, while the rate for electricity is 0.775 pence per kWh.

I got my info from here https://www.theecoexperts.co.uk/news/green-levy#:~:text=The green levy is a,or should it be scrapped? but as you imply other sources have a different take, whatever, the point is it's on gas

Not sure that's right Green levy = A tax on dual gas and electricity bills that funds environmental and social programs. Climate Change Levy (CCL) = a tax on business energy (gas, oil and electricity) that encourages energy efficiency and reduces gas emissions. Energy (Oil and Gas) Profits Levy (EPL). A 35% tax on the extraordinary profits of oil and gas companies operating in the UK.

out of interest, how do you achieve that?

The speeded up fan whooshing caught me by surprise during the first freezing night after installation. But I can barely hear that inside the house. What kind of walls and windows are those?

It's about right for a commercial installation - mine is the same but it includes a 24 help line and call out, which I have used a few times.

All true and you're preaching to the converted here, but amongst the general public, I worry about the ever increasing and ill informed adverse publicity especially in national media such as The Daily Mail, This Is Money etc. by people like Jeff Prestridge, who should know better. I wrote him a stinking email recently in direct response to one of his most recent articles - he writes such utter rubbish, but there is a serious concern that perception has gone too far already in the wrong direction

Ofgem web site says about the BUS - "the new heat pump or biomass boiler will not have been used prior to commissioning, except in limited circumstances, eg to dry out plasterwork during construction or renovation (for shared ground loops" maybe if it's second hand but hasn't been used🙂 https://www.ofgem.gov.uk/environmental-and-social-schemes/boiler-upgrade-scheme-bus/installers#:~:text=the new heat pump or biomass boiler will not have,system after it is installed

This is how mine works - completely separate from heat pump and controls. I never use it though😬

It's either one mini-split per room (1st photo), each room having an indoor blower and an outdoor heat pump/air con, or (2nd photo) one central heat pump/air con unit feeding however many indoor blowers for all the rooms you need heating. The first option involves an external unit hanging off the outside wall of every room - very unsightly, as well as being more challenging to install and maintain the upstairs units. The second option is neater but involves pipework installation around the house, and then you still need the DHW tank system in addition, so I would be surprised if a 9 room commercial installation is cheaper than a full hydronic system (net of grant) which, if well designed and installed, could be 30-50% more efficient. It's certainly worth a sustained research effort to get as many quotes and as much info as possible. The major energy suppliers such as Octopus are offering very competitive prices for hydronic systems, but their lead time can be very long and their offerings may not be available in certain areas.