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I'm new to all this. Am I setting off on the right foot?

IanMK13 · 2023-07-03T16:37:48Z

The annual gas consumption for CH and DHW for my house is around 3000kWh. I'm told this is high. The boiler was replaced ten years ago (by BG and before I bought the property) and was left configured as 24kW output. It is not ageing well. During the heating season, I set-back the temperature to 19degC overnight, although in the depths of winter it will take hours for the house to slowly get back to a comfortable temperature in a morning. The radiators are hot, but perhaps too small, so I suspect that the boiler may be cycling rather than modulating, resulting in high wear and tear. Since I need to be considering boiler replacement, I have started to look at ASHPs. I am trying to be open-minded despite many aspects presently being non-intuitive to me. To characterise my existing system, I have plotted my gas consumption (from my smart meter and converted to kWh) against degree days (derived from my weather station records) for the past year. I was interested to see that peak gas consumption was around 260kWh at a degree-day value of 19 (referred to 15.5degC). This gave me confidence to adjust the boiler output setting down to 12kW. The trend line for my data is defined by y = 12.822x + 13.658. '13.658' would appear to be the kWh energy expended on DHW per day. Is the '12.822' my property's 'heat loss', or something else? I commissioned a (remote) on-line heat loss estimate which came out at 11kW. My own detailed estimate, which erred on the side of pessimism, was 13.8kW. Being relatively new to this branch of engineering, I'd be interested to hear comments from those with experience.

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Air Source Heat Pumps (ASHPs)

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DougMLancs

(@dougmlancs)

Trusted Member Member

Joined: 4 years ago

Posts: 48

08/07/2023 9:13 am

Good spot- I put kW then copied them. I suppose they amalgamated it with J/s

Smart Tech Specialist with Octopus Energy Services (all views my own). 4.4kW PV with 9.5kWh Givenergy battery. 9kW Panasonic Aquarea L ASHP

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IanMK13

(@ianmk13)

Reputable Member Member

Joined: 4 years ago

Posts: 195

Topic starter 08/07/2023 3:19 pm

Thanks, both. I knew that I had to validate getting the energy to the radiators but haven't yet set about analysing it. Presently, the boiler plumbing is 28mm which splits to 22mm for the two CH and DHW valves. There is just over 2m of 22mm before splitting into two primaries, each of which supplies one 'wing' of the L-shaped property. If necessary, it would be relatively straight-forward to replace this section with 28mm when replacing the DHW cylinder. All branches from the primaries are 15mm, transitioning to 10mm for vertical drops in the walls to downstairs radiators. I am confident that there is only one radiator on each 10mm section but I need to investigate what is on each 15mm branch. There are 15 radiators in all and suspect that 12 will need replacing. The Kitchen/Diner has two tall 'Designer' radiators and I suspect that either a 3rd will need adding or the heating supplementing with an A-A heat pump, which would have the additional benefit of providing cooling in the summer months. Given the expense that all this will entail, should I consider a less efficient high temperature heat pump as an option?

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