ASHP - Investigations and calculations

[richbee]

The 10kW unit shows "Heat output, minimum/maximum, A7/W35 5.40 to 12.50 kW"
whilst the 12kW shows "Heat output, minimum/maximum, A7/W35 5.40 to 14.00 kW"

That sounds promising - if the minimum output is the same for both units - doesn't it?

There is a detailed Vaillant output chart available AFAIK only on their Czech web site(!) and also this FB group which confirms that the 10kW has identical performance to the 12 except the top two columns of compressor speed or so are missing from the chart. So not a lot to be saved by specifying the 10, I don't even know why they make the two different models, maybe there is some Euro regulation it just squeezes into.

Yes the twin fan Aerotherm plus models require specific planning permission as they are too big for deemed PP.

Thanks - sounds good (apart from the planning part!)

[richbee]

How likely do we think it is that the permitted development relaxations for heatpumps etc will come in sooner rather than later?
Is it worth hanging for a couple of months to avoid the cost & hassle of a planning application?
I don't really think it would be a problem to get it approved, the area where the heat pump will go backs onto the road - just about >1m away, and there is currently a similar sized oil tank sat there

[Moxi]

There was an article about forthcoming relaxation of planning for heat pumps.

https://utilityweek.co.uk/heat-pump-and ... /?amp=true

[Moxi]

https://www.degreedays.net/

[Fintray]

Found this and thought it could be useful for others

https://www.degreedays.net/

Moxi

That's an interesting site Moxi.

[Moxi]

Thanks Fintray,

[Andy]

Moxi,Given your usage is soooo low wouldn't it be cheaper to just have an immersion/direct heating element? There is so little to go wrong and I imagine it would be a lot cheaper to install. You are talking £40 (£27 if using Octopus cheap rate to do night storage heater) of heating a year of direct electricity usage with the figures you are talking about. It's not worth putting in lots of expensive air source unless it's practically free on the grants.

If I turn my heating off then I'll lose 2 degrees in a maybe 3-4 hours in the winter so it's a big difference to how your house performs. For the heat output of radiators at 25ºC. You are looking at the rated output of the radiators at 25º C being .05 to .1 of the rated output at 70C flow. So the radiator 1000mm x 600mm should have about 150W output at 25ºC and about 50W for the smaller ones so that broadly ties in.

You could really do away with the water based radiators and use electric only of some sort. Use night storage as Joe has done and access the spare power from your solar. Or export the power during the day and charge on the cheap at night to get double return.

I only came to post about the degree days To which I was going to mention that it gives an answer of about 27000kWh for my house but based on Aberdeen which is generally quite a few degrees warmer than my place. In reality we probably use closer to 21000kWh out of the radiators. If using Degree days it doesn't take into account solar gain in the property which can count for quite a bit. Also the MCS calculations take quite a pessimistic view on air changes which can be reduced through diligent searching in your house.

[Moxi]

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[AE-NMidlands]

Hi Andy, that’s the heating side, I need to factor in the DHW bearing in mind we have three kids under six and baths and showers is a daily regimen. We may not use much heating but the DHW is a more significant in my head at least.

Moxi

which is where SWMBO and I both get cross! It's OT, but part of the UK's energy transition ought to be realising that we just don't need (can't afford) to use so much energy and other resources, and IMO so-called "personal hygiene" has been fetishised, probably by the soap manufacturers' advertising agencies.
I nearly inherited the papier-mache bath which did me and my siblings as babies, except that it got used for mixing potting compost when it was clear that mum and dad's grandchildren weren't going to need it!

Our kids were "top and tailed" when tiny and bathed once a week, which generally continues to be our pattern now (not the top and tailing, obviously!) Hard dirty outdoor work means that one son does shower daily now, but I'm hoping that the other one doesn't waste water and electricity on the same fashion treadmill. Maybe our hygiene regime (which hasn't been criticised by friends) is why we are happy to have the house so much cooler than other people. (Since we got gas CH we don't have to get dressed under the bedclothes any more - which was normal in both our childhood homes, btw!)

There is a strong feeling that obsessive cleansing is leaving us vulnerable to bugs which our bodies should be happy to live in harmony with, indeed a healthy flora both outside and inside us is being recognised as a good way of stopping malevolent things getting a hold...
(sorry, about that, rant over!)
A

[richbee]

I struggled with the, degree days part of the MCS spreadsheet - as it did not take account of the allocated temperature of your rooms - the heat loss part reduces if you drop from 21 to 18 degrees in any room, but the total annual demand, which is, based on degree days, doesn't change.
Not sure if the link fixes that issue, or if the standardised method based purely on outside temperature is useful as a comparison.?