EDLA11 started to modulate its heat output

Hardware Heatpump
1

For the first time, in the last couple of days it appears that the heat output is actually being modulated! The left part of the graph is what I’ve typically seen, flow target overshot, pause, restart. The right side is new, where the flow has a ripple in it. There is a 50w variance in the input power as this happens.

https://emoncms.org/app/view?name=MyHeatpump&readkey=f2befde7239c2ce2e9db254e66706870

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3-4c is the sweet spot (is anyone else’s that narrow?) where it will actually run low and slow for extended periods of time.

The rather confusing part is the input power was lower yesterday, around 900w at 2pm compared to this morning where its 950w.

I’d love to know what’s caused it to decide it can modulate it’s heat output. Anyone have any ideas?

2

The target flow temperature is higher on the right hand side, which means the emitter output will be higher, and the heat pump can keep running close to the target. When the target is too low, the emitters can’t keep up, forcing the heatpump to cycle.

You might find the minimum flow temperature for your system is around 35°.
See Calculating the optimal weather compensation curve for my topic on this.

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The ripple is peculiar though, and doesn’t match up to Carnot heat formula, and COP is all over the place:

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4

Yeah, it’s weird eh. 24 hours earlier, the flow target was about the same but no ripple that time.

If we ran at 35c as a minimum, the house would overheat easily. 35c corresponds with 1c ambient outside on our WD curve.

Looking back, in the early hours of Feb 2, you can see we were at about that, flow target was 36c. But then we get into defrost territory.

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If your heat pump is too big for the property, then your only options are to cycle on the flow temperature, or cycle on the room thermostat.

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I’ve got Octopus here shortly to discuss the matter of oversizing.

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