Nest boiler running, but schedule is off.

[ericmark]

This morning I could hear something, on getting dressed and hunting found boiler running, just at that point it switched off, however the schedule for domestic hot water is set Monday, Wednesday, Friday and Sunday to run 7 am to 7:30 am and the wall thermostat set to 16°C and it is reporting 19°C so there is no reason I can see why the boiler should run.

When the boiler is running for hot water on the wall thermostat there is a little rain dropped shaped icon that comes on in orange, I did not see this on the thermostat, and I thing it also goes orange when central heating is called for, so scratching my head as to why boiler was running.

Any ideas why Nest would switch on boiler without reporting it had switched on boiler? History for central heating shows not used in last 7 days, there is no history for DHW.

 

[ericmark]

In the end I found Nest thermostat help UK, they seem to think it is the system trying to learn how much in advance it needs to run heating to get room to new temperature on temperature change, and they got me to disable functions which they think will cure it, however seems odd to me that it runs a boiler but does not record it is running it on any software. History over last 10 days says it has not run, they say it is something called far sight, but all I can see is it has burnt oil it did not need to burn, and heated a house already too hot.

 

[aptsys]

It'll have done it to heat the hot water tank for a longer period. If you set the DHW for short periods of time and sparse intervals you'll find it firing up the boiler a lot more regularly.
There's a setting somewhere for it and is what the orange droplet was signifying.

 

[ericmark]

There was no orange water droplet, that was my point, it thermostat and software said it was not heating the DHW, but the heat link was clearly powering the boiler, one could hear the relay clicking in and out as power turned off/on, it was as if the heat link was connected to a different thermostat.

Today after following instructions and switching off the hot water scheduled it does not switch on at the programmed times.

 

[ericmark]

Reading other forums and it seems I am not on my own, one person seemed to think it was antibacterial mode that switches water on if dormant to combat legionnaires? I have noted if set to run 1/2 hour per day, then does exactly that, but where I set to miss a day, then on that day it randomly switches on, however switch the schedule off, and it does not fire up, so not sure what is going on.

There seems at the moment to be three options.
1) Switch off schedule and select boost every other day.
2) Set the schedule to ½ hour every day, with no days missed.
3) Leave it as it is and see if it settles down.

Had I got a tank thermostat there would be no problem, however there is no easy route to run wires, and only in summer months is there a problem, when central heating is running one can't turn DHW off, so always heated in winter, and to lift floor panels, and remove false ceiling to run cables for a thermostat for summer months only seems a bit OTT.

 

[ericmark]

Think I have found it.

How the Nest thermostat helps prevent Legionella bacteria
Legionnaires’ disease is a potentially fatal type of pneumonia that’s contracted by inhaling water droplets that contain Legionella bacteria. The 3rd gen Google Nest Thermostat’s Bacteria Prevention feature works with both On/Off hot water systems and OpenTherm hot water system boilers. To help prevent bacterial growth, it will heat your hot water tank even if your home is in Away mode.

Legionella bacteria can develop in water that has been exposed to impurities like rust, algae and limescale, in temperatures between 20 and 45 °C. The bacteria are dormant below 20 °C and do not survive above 60 °C (Source: HSE UK).

Bacteria Prevention is an exclusive feature of 3rd gen Nest Learning Thermostats. Bacteria Prevention mode will activate if your domestic water hasn’t been heated for at least 2 consecutive hours in the last 48 hours. This can happen if there is a gap of more than 48 hours in your hot water heating schedule or if you are away from home for longer than 48 hours. For instance, if you have a second home or holiday home and only need hot water for weekends, you can create a hot water schedule for Saturday and Sunday, and the Bacteria Prevention mode will automatically heat the hot water tank during the week.

Your Nest thermostat will let you know Bacteria Prevention mode is running by showing you a water droplet inside of a circle

on the temperature screen.

Note: The Bacteria Prevention icon

(water drop with circle) is different than the hot water boost icon

(no circle). To learn about these or any other icons that appear on your thermostat screen, visit our article about what you'll see on your Nest thermostat.

This does explain what I was getting, would have been nice if it was included in the manual that came with the thermostat.

 

[winston1]

Think I have found it.

This does explain what I was getting, would have been nice if it was included in the manual that came with the thermostat.

I thought no one read manuals!

 

[ericmark]

I thought no one read manuals!

You are in some ways right, there is so much which clearly does not relate to what one is doing, one tends to ignore much of what they say, the Nest manual has 6 wiring diagrams, and the wiring diagram I have used does not match any in the manual. But when it comes to setting software, it was very sparse, it says the Nest thermostat will switch on and take you through the Nest set up.

However it comes up with names which one does not always know what they mean, OK I know what a combi is, and I know what OpenTherm is, however what is a system boiler, and what is an other boiler? When I went through the set up I ended up with no option to select hot water, on returning I tried "Other" and got the hot water. I then went into the PC and set the schedule again nothing worked, seemed I had to enable schedule on the thermostat for it to work, and what is far sight?

The whole set up is full of jargon, so one needs to be able to work out what each thing does, however I twice went onto the help web sight, and the first time they aborted the question answer thing and phoned me, however neither time did they say "This is suppose to happen, it is to stop legionnaire, if you want you can turn it off this is how you do it." they had me running up and down stairs listening to relays click. And turning off the schedule which would not help a bit.

 

[aptsys]

Think I have found it.

This does explain what I was getting, would have been nice if it was included in the manual that came with the thermostat.

Yes, this is exactly what I was talking about.

 

[Mack66]

This morning I could hear something, on getting dressed and hunting found boiler running, just at that point it switched off, however the schedule for domestic hot water is set Monday, Wednesday, Friday and Sunday to run 7 am to 7:30 am and the wall thermostat set to 16°C and it is reporting 19°C so there is no reason I can see why the boiler should run.

When the boiler is running for hot water on the wall thermostat there is a little rain dropped shaped icon that comes on in orange, I did not see this on the thermostat, and I thing it also goes orange when central heating is called for, so scratching my head as to why boiler was running.

Any ideas why Nest would switch on boiler without reporting it had switched on boiler? History for central heating shows not used in last 7 days, there is no history for DHW.

1.Press your thermostat ring to bring up the Quick View menu 2.Select Settings . 3. Select Equipment and Continue. 4. Choose Bacteria Prevention. 5. Turn Bacteria Prevention on or off. Note: You can only switch Bacteria Prevention on or off from the thermostat. This option isn’t available in the app.

 

[Mack66]

Think I have found it.

This does explain what I was getting, would have been nice if it was included in the manual that came with the thermostat.

1.Press your thermostat ring to bring up the Quick View menu 2.Select Settings . 3. Select Equipment and Continue. 4. Choose Bacteria Prevention. 5. Turn Bacteria Prevention on or off. Note: You can only switch Bacteria Prevention on or off from the thermostat. This option isn’t available in the app.

 

[davelx]

You have replied to a four year old post -- twice!

 

[ericmark]

I have now turned it off, the Nest Gen 3 was really a useless thermostat, it did not do as it claimed.

However not bad enough to change it, it does allow control with two wires between thermostat and the base plus charging, even if it will not connect to the Energenie TRV heads.