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Room Thermostats, Zone Valves and ASHP efficiency - what we did

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 As part of our new build's design, the underfloor heating (UFH) was zoned and every room has a room thermostat. Section 8.2 of the Scottish Government's 2022 " Domestic Building Services Compliance Guide for Scotland " states in "Table 25: Recommended minimum standards for control of wet and electric underfloor heating systems" that "Each room should have its own thermostat, sensor or programmable thermostat." and we have exactly that. However, it is generally accepted that zoning is not a good setup to allow an air source heat pump (ASHP) to run efficiently. Zoning restricts how much of the UFH system is used to heat the house. As part of our ASHP installation, we specified two key things: the ASHP should have a controller in the main living area the UFH room thermostats should not be used to control the ASHP and that's what we have. Our Mitsubishi ASHP has a wired Mitsubishi controller in our main living area and the system is configured to ...
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Heat Pumps like a 'Small Delta T'

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Looking these three graphs (today and two hours today) from MELCloud Home, I'm happy that we are running with a maximum Delta T of about 5C. Here's the day (so far) and two hours from when the heating was on  The high temperatures at the start of the day are because the hot water came on for 12 mins late last night.
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Storm Boelo, a power cut and solar generation

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 We lost power at about 4am and our Powerwall 3 is now powering the house. We've turned the heating off and will let the warmth of the house coast and hopefully we'll be warm enough. SSEN think the power is expected back by 8pm tonight, even allowing for the storm. There's a little bit of sun so we're even managing to recharge the battery. Power came back just after 2pm so the folks at SSEN have done a great job. The house temperature dropped to 19C just before noon but then rose again. I think there was a little solar gain. This log from Home Assistant details the time the power went and then returned. All this is possible because we have the Tesla Gateway to go with the Powerwall 3. It allows the system to go into "island mode" and operate independently of the grid. Two key elements needed for Island mode are a gateway with the necessary switching to disconnect the system from the grid live, neutral and ground connections a ground rod to provide a ground con...
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Some Smart Meter Data

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Now that our smart meter communications hub is communicating, the last 30 days of meter data has been downloaded and you can see the effect of our solar panels and battery. Half of September cost us approximately £11 and October to date has cost us £20 Our heating and hot water is provided by our Air Source Heat Pump. These consumption/generation graphs come from the Mitsubishi MELCloud app. I know our energy use is low but I do doubt the COP calculations in these screenshots. A COP over a week of 7.8 seems too good to be true. Nearly all the electricity we've used in September and October has come from our solar panels, often being stored in our batteries. Todate, we've been running our system in "Self Powered" mode minimising the need to draw power from the grid. Solar power is used, in this order, to: power immediate demand recharge the battery export to the grid and we've only imported from the grid when the battery is discharged. In September  and October to ...
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Our smart meter is finally smart

 and sending data to the Smart Data Communications Company and then on to  Octopus who are our electricity supplier. The 420Mhz communications hub has been replaced with a GSM (4G I assume) communications hub which is communicating. Next steps are to get an export MPAN and tariff and then sign up to Octopus agile and their Virtual Power Plant system. It's annoying that it's taken this long and we've missed out on all of this summer's solar export.
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I'm SG Ready. I did not know this. Perhaps it does not matter.

Now that our house is bedded in and everything is operating well, I've been reading some of the specification details and small print. It turns out that both the Tesla Powerwall 3 and our Mitsubishi Ecodan ASHP are "SG Ready". A "Smart Grid" is one that can signal to devices via a "Home Energy Management System" (HEMS) the stats of the grid and if it would be good to reduce load where possible or to increase it. I wonder if this is one of the sources of the "smart meters will let them turn your fridge" stories we seen and causing some people to oppose smart meters. As far as I can tell, smart meters and the Smart Grid signalling are two quite different things. Here is the UK, the Smart Grid does not seem to have much traction. One DNO, UK Power Networks does mention Smart Grid on their website and says "Learn more at our dedicated Smart Grid web-pages." but the "Find out more" button goes to their DSO home page which has n...
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Our COP for September

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is reported at 7.6 which I'm taking with a pinch of salt because I think a COP of 7.6 is exceptional. I'd like to think it's true but the Mitsubishi system's figures don't seem to have a reputation for total accuracy. The export says 46.9kWh of energy was consumed and 353.9kWh of energy was produced (well, pumped) which would make the COP 7.5 which seems very high. I'm expecting a good COP as we have a well insulated new build with full underfloor heating enabling us to run a low flow temperature. Looking at HeatpumpMonitor.org I see there's a 8kW Mitsubishi system in Gloucestershire that's got a heating COP for September of 6.1 and a hot water COP of 3.8. The total COP is 4.9 due to the balance of energy use across heating and hot water. Perhaps our figures are not too far of the mark.
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