Nest Thermostat Query

kev2009

Hi all,

Recently got a Nest Thermostat installed.  I've turned off the auto schedule and have set a manual schedule and temps.

However, I've set it to be at 70 from 7am and the boiler came on at 6:30.... I've been out so set heating to off, when on my way home, set it to heat and it showed it came on and was set to 70, came home said it was 71 so obviously heating had gone off, now it's saying temp is at 76....

Am I using this incorrectly as I'm not sure why the temperature is moving around....

Is it something stupid like the room gets to 70 but then when I'm in the room and have TV on etc it is causing it to go up? Never had this with the old standard thermostat, albeit was in the hall, I've now got the Nest in the living room, not near any heat sources, just on a shelf.

I could understand a degree or 2 increase maybe but this is like 5 or 6 degrees warmer.  Should I set it to be 5 or 6 degrees below the temp I want it to be?

Thanks

Kev

Le_Kirk

kev2009 said:

Hi all,

Recently got a Nest Thermostat installed.  I've turned off the auto schedule and have set a manual schedule and temps.

However, I've set it to be at 70 from 7am and the boiler came on at 6:30.... I've been out so set heating to off, when on my way home, set it to heat and it showed it came on and was set to 70, came home said it was 71 so obviously heating had gone off, now it's saying temp is at 76....

Am I using this incorrectly as I'm not sure why the temperature is moving around....

Is it something stupid like the room gets to 70 but then when I'm in the room and have TV on etc it is causing it to go up? Never had this with the old standard thermostat, albeit was in the hall, I've now got the Nest in the living room, not near any heat sources, just on a shelf.

I could understand a degree or 2 increase maybe but this is like 5 or 6 degrees warmer.  Should I set it to be 5 or 6 degrees below the temp I want it to be?

Do you mean 70 Fahrenheit?   I didn't know we were still using it, anyway equivalent to 21 deg Celsius.  This is likely to be caused by hysteresis.  When the thermostat reaches set point it will cause the boiler to switch off but there is still heat in the radiator and it will continue to heat up the room for a while.  You wouldn't notice it on an old analogue thermostat as it is not an indicator just a switch.  I expect the temperature wold still have been higher than you set, you just wouldn't know.  Set your thermostat to make the room comfortable.  Start by turning it down one degree at a time.

kev2009

Yes, sorry 70 Fahrenheit.  ok, I'll try setting it at a lower temp.

Thanks

Kev

[Deleted User]

Not sure about Nest but I'm fairly sure most modern thermostats have a mode that learns about the overshoot that occurs when the heating is switched off and compensate for it by switch off the heating just before reaching set temperature.

It might be because you've gone to manual mode that this doesn't happen any more, but my non-nest "smart" thermostat auto adjusts for this.

In fairness body heat and TV's etc all contribute slightly to temperature rising, especially in a small room, and the sun shing through the windows. 

Today is a really warm sunny day for October so could well be a factor, I doubt you need heating today if you are trying to save some money.

kev2009

Thanks, have only fitted it a day ago so still getting used to it.  It was 68 degrees it said so I turned heating on and the schedule was set to 70 so it came on and it went off after reaching 70 but the temp rose up to 76.. it's now come down to 74 atm... makes it a bit too warm so just wondering what was happening as old thermostat with programmer I never had this issue.

Thanks

Kev

Neil_Jones

There may be a "pre heat" or "ready by" or similar option.  What this does is dynamically change the schedule so the boiler comes on earlier to be at your set temperature for the start time (so if you set it for 7am and it was a chilly night you may find it came on at 6:20 for example, to get to your temperature for 7am)..  Over time the system learns how long it takes to get to that temperature and so it adapts.

The old-school method just says "start at 7am come what may, get up to 21 degrees (or whatever), and turn off.  Repeat until end time, then stop coming on at all until 6pm."  This bears no resemblance to the ambient temperature at 7am and so if it was borderlline 21 degrees everything would fire up at 7am for five minutes at full blast and then go off again.  The Hive/Nest/smart will go "hey, I'm due to fire up at 7am, but the house is already at 20.5 degrees at 6:50am, its probably not worth firing up.  Let's wait and see if it drops a degree and then I'll give it a blast."

debitcardmayhem

kev2009 said:

Hi all,

Recently got a Nest Thermostat installed.  I've turned off the auto schedule and have set a manual schedule and temps.

However, I've set it to be at 70 from 7am and the boiler came on at 6:30.... I've been out so set heating to off, when on my way home, set it to heat and it showed it came on and was set to 70, came home said it was 71 so obviously heating had gone off, now it's saying temp is at 76....

Am I using this incorrectly as I'm not sure why the temperature is moving around....

Is it something stupid like the room gets to 70 but then when I'm in the room and have TV on etc it is causing it to go up? Never had this with the old standard thermostat, albeit was in the hall, I've now got the Nest in the living room, not near any heat sources, just on a shelf.

I could understand a degree or 2 increase maybe but this is like 5 or 6 degrees warmer.  Should I set it to be 5 or 6 degrees below the temp I want it to be?

Thanks

Kev

Is your hall thermostat still connected?

moneysaver

Hi,

      On the Nest app there is a setting called true radiant, this lets the Nest adjust heat up time when your boiler fires up depending on weather outside. It might start earlier than set time also it will usually switch off before desired temp & use residual heat to reach temp. I do not like the setting so do not use it, I prefer to just have it switched on at desired time.

If you have only just installed the Nest it will take a few days to learn how long your house takes to heat up. It might be better to put temp to Celsius as you are using Fahrenheit the increments might be more noticable, this could be why you are seeing bigger overshoots.

Moneysaver

kev2009

Thanks, yes, i seen that setting and its on at the moment, I've only turned off the auto schedule as I prefer to have a fixed schedule.  I've also changed to Celsius so will see how it goes.  I've adjusted the start time to 30mins later to help compensate for any pre-heat stage.

Thanks
Kev

[Deleted User]

moneysaver said:

On the Nest app there is a setting called true radiant, this lets the Nest adjust heat up time when your boiler fires up depending on weather outside. It might start earlier than set time also it will usually switch off before desired temp & use residual heat to reach temp. I do not like the setting so do not use it, I prefer to just have it switched on at desired time.

Not sure why you would invest in an expensive Nest thermostat and then turn off all the smart features that you've paid for and more importantly save energy / money.

The true radiant mode means you don't have to worry about what time the heating comes on, you just set it that you want the house to be 19C at 7am when you get out of bed and it works out whether it needs to put the heating on at say 6:30am or 6:50am.

The true radiant mode also understands the overshoot that occurs when the set temperature is reached and will switch of at 18C because it knows the latent heat in the system will take it up to 19C anyway.

Both save energy and still give you exactly the temperature you need when you need it.

kev2009 said:

 I've also changed to Celsius so will see how it goes.  I've adjusted the start time to 30mins later to help compensate for any pre-heat stage.

Instead of thinking of adjusting to compensate for pre-heat, just set the Nest for the temperature you want at the time you want and let it do the rest.

It is different kind of thinking to old school thermostats and timers where you set the timer to put the heating on before you need it, instead you just tell it you want the house to be X temp at X time and let it figure out when to switch it on. Typically you'd set the morning schedule for the exact time you get out of bed, not before as there is no need.

kev2009

Thanks, yes, I've left the true radiant on, only turned off the auto schedule as I want to set that myself.  My concern is the system turning it on and costing more to keep the house at X temperature so I've now set it 30mins later so that it doesn't come on too early.
It's a shame the history part of the Nest thermostat doesn't give you a list of times it came On/Off, instead the little chart where if the items are close together its hard to see the times.

Still getting used to it here.  Keep changing the settings which prob isn't helping the learning part

The big advantage to this system is being able to adjust/turn on when not at home i.e. when on hols, set temp lower BUT if it got real cold, I'd often thing maybe I set it too low but now I can just increase it etc to suit and also ensure is up to normal temperature when I'm returning home

Kev