folder.
Device | ID | Notes |
---|---|---|
1g | FEDA88A08188E083 | Borrowed as eye-level sensor placed near room geometric centre. |
4o | 819C99B4B9BD84BB | In sheltered porch outside. |
5s | E091B7DC8FEDC7A9 | Removed from radiator to prevent temperature regulation, but within ~10cm of normal location. |
t (h) | e (kWh) | Time (UTC) | Gas (m^3) | Notes |
---|---|---|---|---|
00.0 | 08:31Z | XXX5.622 | pre | |
0.0 | 00.0 | 08:52Z | XXX5.622 | start |
2.6 | 05.6 | 11:27Z | XXX6.127 | ~2.2kW |
5.5 | 10.4 | 14:22Z | XXX6.560 | |
6.4 | 11.6 | 15:18Z | XXX6.664 | |
7.2 | 13.0 | 16:05Z | XXX6.791 | end, mean 1.8kW |
Looking at the shape of the graph suggests that the effective thermal capacitance of the room surfaces and contents is ~0.1kWh/K.
That nominally puts a limit on the speed of response of temperature to the radiator going on, very crudely 4K/h (4°C/h). This is in line with my expectations I think.
I may try to refine this crude estimate, eg with another testing run, and/or by estimating the capactance of key elements such as the plasterboard inboard of the aerogel IWI and the mass of materials in the room.
Maximum power consumption from gas mains ~2.2kW for 5s radiator. Given likely 80% efficiency of boiler, heat delivery maybe maximum ~1.8kW.
In fact, given the radiator characteristics and δT (flow-to-room), mean heat power to the room was likely a little under 400W, for ~2.7kWh total. That implies a ~20% overall efficiency from gas in to heat out, nowhere near even the SEDBUK ~80%!
My 24kW boiler is massively oversized for even whole-house peak demand, and so running modulated to minimum and then cycling is bound to be less good. This demonstates that correct system sizing is important!
, after several days on my own and the rest of the family away... Mean outside temperatures were in the single digits and there was some snow! Mean internal temperatures got down to about 13.5°C. All the Radbots (except the hallway, on frost) were calling for heat. The boiler in DHW-only mode was roundly ignoring them, as intended.
To avoid (justified) complaints from returning family, I put the heating on briefly (ie switched the boiler from DHW only to DHW+CH) at 12:32Z with gas at XXX6.731m^3.
By 12:43Z the boiler flame was out for the first time (ie the heating was limited by power delivery via pipework and radiator, and circuit thermal capacitance.
At 12:57Z gas was XXX7.171m^3, ie ~5kWh consumed.
At 13:54Z gas was XXX7.442m^3, ie ~7.7kWh consumed, and I put the boiler back to DHW only. The estimated mean internal temperature was now ~17°C.
No complaints from returnees a little later, in fact at least one window was opened!
In both cases the rest of the family went to visit my partner's father, who is on his own, and whom we are in a coronavirus "bubble" with.