Energy History how?

[ericmark]

It looks really good, but my boiler cycles, and how much it cycles depends on what the TRV heads are doing, there is no link from boiler to Nest thermostat to tell the thermostat when the boiler is running, I am not sure with Gas boilers and OpenTherm what the boiler tells the thermostat, but with my oil boiler how can the thermostat have any idea as to how long the boiler runs for?

 

[Gasguru]

It's all garbage....
According to OVOs graphs we are using 100x the gas as we did in the summer. Now in the summer it's around £12 a month for hot water only...our annual bill is less than £1200.
Reading the meter directly or looking at your oil bill is the only way to get accurate readings.

 

[ericmark]

I expect the chart is how long the thermostat had switched on the boiler for? But all boilers cycle or modulate or both, and if see correct then I would think the wall thermostat should be switched on most of the day, if it is, then clearly the TRV's are doing a good job controlling each room, if the active time that thermostat is on for is low, then either poorly set, or warm day, the longer the heating is on for in winter, then better the control settings are.

Very simple, if boiler not running, the TRV can do what it likes, but it will not heat room.

 

[Terrywookfit]

It is a fancy programmable stat . It will only be on if it is programmed and below the set temp.
If the boiler and pump are off , The TRV will do fook all. It is only fitted to prevent overheating areas.

 

[ericmark]

The TRV I think can be linked using IFTTT to the socket and so switch on the AC even when boiler not running, or of course an oil filled radiator, although I have never really tried to link using IFTTT protocol. I do however in the summer look at the TRV current reading to decide if to manually turn on AC before return. So my TRV does do some thing without the boiler running, and some thermostats can link to TRV and so TRV can turn on thermostat, mine should have worked other way around, the wall thermostat should tell the TRV what to do, but did not work very well so disabled it.

However the energy supplied by the boiler in may case depends on how long it runs for, not how long it is switched on for, and with modulating boilers even when running, the output varies, so that chart has no relationship with energy, "Activation History" would be correct, but it is not "Energy History" when using off/on control, I don't know if "Energy History" when using OpenTherm, but energy does not use hours as a unit of measurement, or does it?

I would expect from my School days that Energy is measured in Joules, and work in Watts i.e. Joule per second, However I see bills with kWh marked on them and it seems the second in Watts and the hour in kWh cancel each other out, so 60 x 60 = 360 so there are 360 Joules in a Watt/Hour. This is the metric system so we have 360 Joules in a Watt/Hour and 4.2 Joules in a calorie, so much easier the metric system I am told your don't have 32 poundals in a pound or 32 pounds in a Slug you have 980 Newtons in a Kilogram. And a circle is divided into 3.14159 bits instead of 360. Not sure where 10 comes into it?

It just seems it is all done to make it harder to work out what is going on. When I was a lad having one's head in the clouds was considered bad, now they tell us it's stored in the cloud as if it is something good. I have heard it being said raining cats and dogs, but ones and zeros is something new.

 

[Terrywookfit]

Do you have an Evohome type of setup,??

 

[ericmark]

I wish, Nest Gen 3 and Energenie TRV heads and eQ-3 TRV heads.

 

[jonm01]

I expect the chart is how long the thermostat had switched on the boiler for? But all boilers cycle or modulate or both, and if see correct then I would think the wall thermostat should be switched on most of the day, if it is, then clearly the TRV's are doing a good job controlling each room, if the active time that thermostat is on for is low, then either poorly set, or warm day, the longer the heating is on for in winter, then better the control settings are.

Very simple, if boiler not running, the TRV can do what it likes, but it will not heat room.

I thought the idea was the roomstat would provide the main temperature control Eric ? If its on most of the day, doesn't that mean the boiler is running just to heat pipework if the TRVs have closed? Would it not be more economical to allow the roomstat to cycle the boiler on and off?

 

[ericmark]

It would mean the boiler would cycle off/on, boilers should have anti-hysteresis software, basic idea is, if when boiler switches on water returns hot in so many seconds, then off time is increased, and if cold off time decreased, so as long as the by-pass valve is close to boiler, the boiler will auto increase times between trying to circulate hot water.

But clearly it can never switch fully off, as there is nothing to switch it back on again, but also while the boiler is controlling the cycling it turns back on at fully modulated, where if an outside the boiler device turns it off, it turns back on with no modulation. In my case oil so boiler does not modulate, but with gas one needs to be careful not to select a thermostat that uses mark/space control to stop the hysteresis as this would cause the boiler not to modulate.

The Nest instead of using mark/space with on/off control uses algorithms to work out the over shoot so it can turn off just once, however that does depend on conditions changing slowly, if some thing happens fast, for example doors left open, it can't work out the change, so these algorithms do not work as they should, add to that a TRV head with it's own anti-hysteresis software, and to be frank the wall thermostat does not stand a chance. Well maybe a chance if connected to boiler with OpenTherm, but not simple on/off.

So there are two methods, TRV tells some hub what is required, or a wall thermostat works the TRV or other zone valve, and you have a wall thermostat in every room or group of rooms, and the thermostats talk to each other. So with EPH thermostats one is the master, rest are slaves, and the master using opentherm tells boiler output required, and the slaves open and close the zone valves and tell the master if open or closed.

But it seems either/or not both, either home split into zones using zone valves or home split into zones using TRV heads, these seems to be no domestic system to combine both.

I looked at the Ivector fan assisted radiators, they seem perfect at first glance, same radiator heats and cools, and it circulates the air using a fan and the output is controlled by the fan speed, there is no TRV or lock shield valve, hot or cold water is circulated, however one would need all radiators in series not parallel and the building management system costs an arm and a leg. Unless in series the boiler would not know when to modulate and the water may not circulate through all radiators.

So the whole system is a compromise. And how we compromise depends on the home and how the home is used. With a modulating boiler it can be circulating water all day at 6 kW output, so as any TRV opens that room is heated, but with a non modulating boiler it turns off/on, and if off, the TRV can do what it likes, room will not heat.

So as the room cools, the TRV keeps opening a little more, I can hear the motors run, as it inches open a little more every few minutes, but it takes around 8 minutes from fully open to fully closed, with a modulated boiler where the water is not that hot that is not a problem, but with non modulating the boiler kicks in, the radiators heats to maximum then the TRV closes by which time it has over shot and the room over heats. With a modulating boiler the lock shield valve can be trimmed to stop over shooting, but not so easy with non modulating.

So as soon as a TRV realises it needs to open, it also needs to tell the boiler to start, the TRV broad casts the info required, my computer can easy see when the boiler needs to fire up if target is above current boiler need to run, however although my computer knows, Nest Gen 3 does not, so boiler does not fire up, my computer can also tell Nest to switch on but it seems it needs a manual intervention to read one bit of info and send to to the other device, they simply don't talk to each other in a way which can control the heating, it is like a Frenchman and an Englishman who can't work together without a bilingual foreman.

I am sure some one can write a computer program to link them, Energenie uses IFTTT not sure about Nest, both Energenie and Nest can be controlled with the Nest Mini, so there is no reason why they should not work together, except no one has marketed that bilingual foreman to do it with.