Advice on air-source heatpump/thermostat settings?

[MyForest (David Bowen)]

@mjc506

Do you use EmonCMS to run your ASHP, or just to monitor?

At the moment I have a separate Python script to drive the heatpump which I use it to drive the manufacturers web app. The folks on this forum are much better informed in implementing control hardware than me.

Emoncms is acting as a central point for data from the solar panels, weather station and heat pump so the control alogrithm can get what it wants.

When we get a battery and an agile tariff I may move to the Demand Shaper plugin for Emoncms.

@mjc506

Our DHW is also set to run at 06:30 16:30 each day

You might be interested in these experiments I did…

Improve efficiency: Heat the hot water when it's cold

My flow controller has a mode that tells it to heat the hot water if the temperature (measured at the bottom of the tank) drops by 5C. You can extend that all the way to a drop of 15C if you look in the menus. Sadly that means a shower at 20:00 causes the heat pump to kick in when the outside temperature may have dropped. As discussed elsewhere, it’s better to wait for it to be warm outside before you use the heat pump. However, another factor is that the default behaviour means the water in …

Improve efficiency: After heating the domestic hot water pump the radiators for a bit

This tweak is going to look a bit odd. It’s benefit is more pronounced if you are turning the heat pump on and off quite often. Following a burst of heating the hot water in the cylinder the flow temperature will be high. For example, my hot water is set to 42C which gives a flow of 58C when my heat pump has finished. The trick is then to shut off the heating energy but pump the toastie water around the radiators. This doesn’t sound like it’ll do a lot, but it’s one of those “every little hel…

Improve efficiency: Have a big hot water store and delay heating it until it's warm outside

I’ve implemented a multi-stage algorithm to decide if we should heat the hot water. Note that I only have a sensor at the bottom of the tank so as soon as someone showers, the tank appears cold to my code. Tap usage is so small it doesn’t register. If the tank is cold then we heat it up after 10:00. If the tank is warmish (say over 30) then we defer heating it until 12:00 so it’s warmer outside. Even in the Winter that gives us a chance that the solar diverter might top it up a bit. Notably…

Notably, we don’t heat for when the showers are planned because there are four people in the house and showers are very random. In fact sometimes we shower when it’s a good time for the heat pump. For example we’ll shower at 13:00 when the morning sun has heated the tank and we’re creating “space” for the afternoon sun to heat the tank. Also, our tank doesn’t lose much heat so we’re free to leave it full of water.

@borpin

In all cases though, the original controller (UFH/Tank) is still in place (albeit set low so it does not interfere), as the backup! Belt & Braces.

Yep Brian, that’s been a key part of our setup too. The residents know they can just tell it what to do whenever they like if the clever stuff isn’t working for them. That makes them much more willing to let the computer take control most of the time. It’s rare they feel the need to intervene. My control algorithms have gating unit tests which stops them going live if they are going to misbehave.

@mjc506

I dropped the flow temp to its minimum of 23 degrees (at 18degC oat)

It sounds crazy, but I can understand why you’d do that. We found we weren’t emitting enough heat with a room delta that low so the pump would switch off because the return was coming back too warm.

We think of the radiators as “a big warm dog lay in the corner” rather than “a furnace” so if they are only running at 28 Celsius that’s fine.

@mjc506

Average running CoP since midnight has been ~4.5(!) and ASHP energy use has dropped by ~50%. I’m reasonably happy with that

What will it take to make you very happy?

@mjc506

I probably shouldn’t wait until winter bites to start fiddling with the heating haha

It’s not as mad as it sounds. I took the defaults on our system in October and November and only took computer control at the end of November when I had something interesting to work on and some evidence that the defaults we’re working for me.

That bumped us up from the red line to the blue line:

It was warm enough in October that it would have been OK to have been playing with the control then and people wouldn’t have noticed much. You probably want to get the hardware in place by then though.

Good luck.

David