Away temperature on thermostat, keep it warm or cold?

ProTofik

I just converted from old inefficient oil burner with no thermostat or timer to a brand new gas combi boiler with Google Nest thermostat.

I think I have done all I could to get the most out of it. I insulated my attic (300mm), readjusted all doors and windows (from 2014, double glazed), replaced all extractor fan vents etc, bled radiators, balanced the system for 10C drop etc...

Anyway, my thermostat has 'Away' feature, which tracks me using GPS on my phone. When I'm not home, it will switch from my normal temperature of 20C during the day and 17C at night to 'Eco' temperature. My questions is, what should I set the 'Eco' temp to?

I have encountered two conflicting theories.

1. Set 'away' temperature to 10C. It makes no sense to heat up the house when you are away.

2. Set 'away' to something like 15-16C to maintain some level of heat. It takes less energy to then bring it back up to 20C when you're back.

So, what are your thoughts? I was trying to google it myself but I haven't found any scientifically proved answer, just people arguing with one another. 

JGB1955

I would set away temperature to 5 degrees, offering  frost protection. Then use your app to turn the heating on about 6 hours before you return home. If you're only out for the day  the temperature is unlikely to fall  much beow 15 degrees. My comments were based on being away on holiday for 7 days+.

ProTofik

JGB1955 said:

I would set away temperature to 5 degrees, offering  frost protection. Then use your app to turn the heating on about 6 hours before you return home.

Frost protection is another separate feature of google nest. No matter what mode is selected (on/off/away), if the temp drops to 5C it automatically turns heating on.

I guess Away Eco temp is meant to be used when I'm away for anywhere from few hours to maybe 24-48h. If I was to be away more than that I would probably switch heating off completely, leaving just frost protection in place. 

Neil_Jones

do whatever works for you.

Modern boilers have built-in frost protection so if it drops to arctic levels it'll fire up anyway.  To prevent it freezing.  Also modern thermostats usually don't turn "off" as such in the default state, they just drop to the lowest available which is again arctic levels it'll fire up anyway.

If your house heats up quickly its immaterial really what you do, and if you only ever go away in summer it becomes irrelevant, unless you want to come home to a sauna.

ProTofik

The way I think it works is that every house has some level of constant energy (heat) loss. It therefore makes no sense to be pumping energy into the house if it disappears into atmosphere anyway. It heats up pretty quickly now with brand new heating system and all insulation work I did so I think I will go with theory #1. 

QrizB

One minor caution - make sure the room with your fridge-freezer (if you have one) stays warm enough that the appliance still works. Some fridge-freezers are prone to defrosting if the room gets too cold. Yes it sounds crazy:

https://www.ukwhitegoods.co.uk/help/buying-advice/installation-advice/2793-fridges-a-freezers-in-garages-or-outhouses

Reed_Richards

How fast do you travel?  Your house will need time to warm up after your Nest thermostat detects that you are coming home so there could be a race between you and the heating.  The cooler your Away temperature, the longer it will take to re-warm the house.

wittynamegoeshere

I think you should give away every aspect of your movements and privacy to an unaccountable foreign business so they can analyse your lifestyle and target you with adverts for the tat they think you might buy.

We press a button to switch the heating on if it feels cold.  If we're not in the house stays cold.  We have frost protection that switches on at about 7 degrees.

Our kitchen gets down to single-digit temperatures at times.  The fridge always works perfectly.

The theory that it somehow takes less energy to stay warm than to get cold then heat up is a nonsense myth.  If you keep the house warmer while you're not there it will definitely cost more, absolutely no two ways about it.

coffeehound

Check your buildings insurance fineprint - they probably specify that the building needs to be maintained no cooler than 14º while unoccupied.  

clive0510

I leave mine on 10 when I'm away for any length of time.  lets it stay dormant for most of the time, but it will cut in if it really needs it. works fine for me.

Staffordian11

wittynamegoeshere said:

.

Our kitchen gets down to single-digit temperatures at times.  The fridge always works perfectly.

Fridges are fine.

So are freezers.

The issue is certain fridge freezers. If they rely on a single thermostat to control when the compressor kicks in, then that will be in the fridge.

In a *very* cold room, the fridge will remain cold indefinitely without the compressor coming on.

Thus no cooling occurs, so the freezer thaws.