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Running a heat pump

Hi all,

I’ve just had a heat pump (12kw Midea unit) installed. Over the summer I didn’t really do anything, no need for heating and it only did hot water. We have Solar (8.4kw) and batteries (14.2kwh), so it was free to run.

Now we are getting into the winter, the heating is now on and I am interesting in better monitoring and control of the unit. Currently its just controlled via a Nest thermostat.

I would be really grateful for some recommendations on where to start as I want to get things moving before we get into the depths of winter.

Cheers!

Hello @oatspie sounds like a great setup! Have you seen our page on heat pump monitoring here Heat Pump Monitoring - Guide | OpenEnergyMonitor it discusses a number of different options that might be of interest. Does the Midea itself provide any data output options?

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Yes it has a tonne of information on the controller. But I can’t get the information out without manually loading up the screen. Eventually I’d like to build a proper controller as it’s being run from a nest at the moment and that means it’s not being very efficient. Lots of start ups.

I did take a look and I was thinking of going down the pi route. It’s just I haven’t built a system like this, so wanted to check with people before i pull the trigger. My aim would be to use the Pi as a charge controller on my Sofar ME3000SP to control the batteries, control the heat pump, monitor the heat pump and probably as a pi hole on my home network. Which is quite a few jobs!!

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Hi @oatspie,
I am working on controlling several systems and a Raspberry is a good option.
You will find problems to access the equipment that you want to measure and control, so first you have to see how you are going to communicate with them. If these devices use MODBUS, the serial port, relays … This is the essential first step
Once you have the way to communicate you must study what hardware accessories you need in your Raspberri
Regarding the control logic I advise you to use Node-RED and MQTT. The Open Energy Monitor products that use the EmonESP or EmonCMS (emonpi) software integrate MQTT with what you have a great number of possibilities

Excuse my English
I hope I’ve helped

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can you recommend the best place to start. Ideally I don’t want to cut into any pipes yet. But everything is all located in the same place (except the hot water cylinder, which is in the loft).

On the practical side of what to monitor. Its good to draw a rough sketch of the layout. I suggest reading the flow and return pipes from the heat pump and if you have any complexity in the system like a low loss header or mixing valve anywhere, the flow and return to the emitter. Its always worth keeping an eye on the amount of power used when then its not actually heating.

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hi @oatspie , I’m interested in your idea of future Pi-based controller for the Midea HP. I’m planning to integrate the PI-based OEM Heat Pump Monitor with a Midea ASHP next month and while this would only be used for monitoring not control, I’m wondering to what extent to could be extended to handle some additional control tasks if necessary.

I believe the Midea is controlled over modbus so not native to the OEM monitor currently (i believe) but could be enhanced I imagine as its using MBus.

Not to go off-topic but slightly concerned by the issues you’re getting with the Nest (my set-up will also have Nest-controlled zones, illustrated). Are you using the Learning controls or as a simple time programmer and remote control? I might PM you on this if I may…

@thedawnbefore I am getting somewhere with the unit, and i’ve not made any structural changes. Have you found the MSmartlife app isnt working in the view data mode? All I get the query failed, which is quite frustrating.

For the time being I’ve heavily adjusted my weather compensation down to 50 degrees at -4 and 25 degrees at 14 and then I set my nest to heat to 22 degrees. The result is that the thermostat is now constantly calling for heating but the house is being controlled by the weather compensation and is staying between 20-21 degrees at all times. Its not perfect, but until I get the modifications I want doing, this is the route I am sticking with.

As an FYI I am getting heating COPs (not hot water) of 3-4 in this weather. The next step is to lose my zone heating, replace the diverter valve with a high flow rate one, bypass (or lose) the low loss header (as its inefficient) and move to the Midea controller unit away from the thermostat. These should all increase my efficiency.

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Thanks for the heads up. I’ve not installed the ASHP, it arrives next week. It’s interesting to hear your experiences - from what I understand, you would not recommend installing Nest-controlled zone valves as part of a Midea ASHP system given the choice, and, instead, rely on the Midea controller entirely?

At the moment I have zone valves and I am looking to take them out. Everyone is different so I can’t say if it’s better for you or not. My zones are upstairs and downstairs and we don’t really need the upstairs zone now we keep the ASHP running at a low level 24hrs. We can control the bedrooms with TRVs. On the controller I don’t really see why I need the Nest, given the ASHP has a controller - what’s the benefit? All the Nest will do is turn it on and then it’ll run in weather comp. Seems like an extra step.

But I don’t see the need for my low loss header, it’s just adding inefficiency, which adds to my costs. So I’ll be having it bypassed, then I can run the ASHP at a lower temperature.

Thanks @oatspie , I’ve messaged you if that’s OK as I respect I’m going a bit off topic here!