lizzie

Heat recovery efficiency

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My MVHR is working well now it has finally been properly set up.  The last couple of months house is staying at +/- 22 degrees day and night with no UFH input.  All good.

 

I have been on my own here for a few days (and nights) and noticed that the temp of the house has dropped a bit.  Just me and woofer here not creating a lot of heat on my own, not much cooking, just one shower a day etc.  Is low occupancy (1) in a reasonable size (200sqm single storey) a factor in this?  Not enough heat to recover?

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We've noticed the same thing over the past few days, as we've had a sustained period of fairly low temperature.  Here the outside temperature hasn't risen above 16°C for about four days now, and has been down around 10°C to 12°C overnight.  That has pulled the house temperature down slowly, to the point where our UFH came on the night before last (it's set to come on at 21°C).  The house climbed back up to about 22°C and is sitting close to that now, some 24 hours or so since the heating last fired up.

 

I find our house takes a couple of days to react to a sustained drop in outside temperature, and then takes half a day to warm up when the heating comes on after having been off for a long time.  Ideally I'd like to have the controls linked to the weather forecast (if it was always accurate) so that the heating could come on several hours before a predicted period of sustained cool weather.  Not that easy to do, although I believe that @TerryE has been working on doing this, with his home brew control system.  If there was a reliable off-the-shelf predictive controller I think I'd seriously consider fitting one, but I'm not sure there is at the moment.

 

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What you experience @lizzie is fairly normal. Have the woofer (and maybe yourself) run around the house for 10-20 minutes to create some extra heat. Or throw a party 🙂

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1 minute ago, BotusBuild said:

What you experience @lizzie is fairly normal. Have the woofer (and maybe yourself) run around the house for 10-20 minutes to create some extra heat. Or throw a party 🙂

Party sounds good!

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2 hours ago, JSHarris said:

Ideally I'd like to have the controls linked to the weather forecast (if it was always accurate) so that the heating could come on several hours before a predicted period of sustained cool weather. 

 

While weather forecasting is still not perfect, gross estimates about upcoming air temperature are usually reasonably reliable. You don't need to know whether it's going to be exactly 10 or 12 degrees - just knowing that it's going to be (for example) a lot cooler for a few days starting tomorrow is probably sufficient to get you 80% of the way there for predictive heating. It may be more complicated if you have a lot of solar gain I suppose - it might be cool air temps but lots of sun, for example. Not an issue I have to contend with in our house, with its relatively low solar gain!

 

That said, our house temp has dropped below 20 degrees in the last couple of days. It's still comfortable enough that I can't be bothered turning the heating back on. 

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18 minutes ago, jack said:

That said, our house temp has dropped below 20 degrees in the last couple of days. It's still comfortable enough that I can't be bothered turning the heating back on. 

 

Mine too. 18.8 currently. I am finding that ok so like you haven’t turned the heating back on. In the winter I find that too cool. No idea why! 🤔

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22 minutes ago, newhome said:

 

Mine too. 18.8 currently. I am finding that ok so like you haven’t turned the heating back on. In the winter I find that too cool. No idea why! 🤔

Mine is back at 22 today....cleaner been this morning so plenty of activity to get the heat up!

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28 minutes ago, newhome said:

 

Mine too. 18.8 currently. I am finding that ok so like you haven’t turned the heating back on. In the winter I find that too cool. No idea why! 🤔

 

I'm convinced there's a bit of subconscious influence at work when it comes to whether or not we feel cool.  21°C indoors when it's dark, grey and wet outside feels too cool.  the same temperature indoors when it's bright and sunny feels fine.  We've noticed that this effect is far more pronounced in the early evening, for some reason.  I guess we must sense the change in light level for the time of day and that somehow recalibrates how we feel temperature.

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There’s also reason for optimism I guess as the mind knows that temperature is likely to go up rather than down in summer, but in the winter without a heat source it will only go lower. That said the weather is grim here today. We have the start of what the SE has had over the last couple of days. 

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23 minutes ago, JSHarris said:

I'm convinced there's a bit of subconscious influence at work when it comes to whether or not we feel cool.  21°C indoors when it's dark, grey and wet outside feels too cool.  the same temperature indoors when it's bright and sunny feels fine.  We've noticed that this effect is far more pronounced in the early evening, for some reason.  I guess we must sense the change in light level for the time of day and that somehow recalibrates how we feel temperature.

 

Your body temperature starts falling in the evenings - that probably has an effect:

 

1610729614_Bodytemp.thumb.JPG.08d628b97847e56c7b56bd0830925894.JPG

 

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4 hours ago, JSHarris said:

Ideally I'd like to have the controls linked to the weather forecast

I have wanted something like that for decades.  My cheap weather station is spookily accurate when it comes to predicting cloud cover.  I wish I knew how it did it.  I have looked for the algorithm online but had no luck finding it.

I believe that you can get an API (whatever that is) for the MetOffice data.  May have to look at that sometime.

I was bloody cold this morning, but house was at normal temperatures.  It has brightened up now, so feel a lot warmer.

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Another comparison.

 

We have had unseasonably cool weather for a MONTH now. I doubt the average temperature has been any higher than 10 degrees, it did get to 20 one day, and below 0 one night.

 

But even with no heating we are still maintaining 20 or a little over inside the house, and for the last few nights have slept with the bedroom window open for a bit of a nigh purge to keep the upstairs cooler.

 

Like others have mentioned before, solar gain via the west facing windows in the evening is the most noticable when the clouds have the grace to depart for a short while. We don't get much solar gain on the south elevation because of the trees.

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