Nest not reaching temperature when slightly warmer outside

[Samvdv]

Hello,

Since about a month I've had the nest thermostat installed. For the biggest part ot's worked very well. We have had freezing temperatures outside, but when we asked the thermostat for a certain temperature inside it would quickly reach it. The last few days however it has heated up outside (to about 10°C) and for some reason we are often only getting 18-19 °C when we are asking for 21°C or more. This causes it to be quite cold inside. The boiler seems to only slightly heat up, whereas I used to see it heating up untill more than 50°C now if I look for a while I usually don't see it going any higher than 30°C. Does some setting need to be adjusted on the thermostat for it to heat to the desired temperatures? 

Thanks in advance for any tips/help.

Best regards,

Sam

[zoeuvre]

Hi Samvdv, 

Uh-oh! I'm sorry to hear that you're experiencing a decrease in heating performance from your Nest Thermostat, especially during milder outdoor temperatures. Do you have a heat pump system? If so, AUX heat is a second source of heat that comes with some heat pump systems. Heat pumps are the main source of heat most of the time, but they aren't effective when it's very cold outside. Your system can use AUX heat to help keep you comfortable in harsh weather or help change the temperature in your home quickly. Heat pumps are very effective compared to most other heating systems, but they take longer to heat your home the colder it gets outside. So heat pumps are sometimes paired with powerful AUX heat, which is more expensive, but can heat your home quicker. AUX heat can turn on when it's too cold outside, or your heat pump needs to defrost. Learn more here in the heat pump balance article. 

Keep us posted. We're happy to help.

Best,

Zoe