Hi there, I had the exact same error on my Midea system last year and once I had cleared the inline filter (mine was outside just behind the unit) it was fine. I made sure that it was checked on the annual service and it has been fine.

@paul436 - thanks, that would appear to confirm what i thought.

Many thanks. That sounds promising and gives me a little hope...does anyone have a picture of it, or where I can find it? Installation manual does not help here...

@iwolf - on my installation there are two flexible connectors connecting the heat pump flow and return to the fixed pipework where it passes through the wall into the house. About half way along one of those flexible connectors, I presume the return, there is what looks like a normal quarter turn ball valve but it is modified to hold the filter. On the bottom of the valve, on the opposite side to the handle, there is a large nut. Unscrew that to access the filter, which you then pull out of the body of the valve. Turn off the heat pump (I do that at the main distribution board) and close the valve (1/4 turn) before undoing the nut.

Unbelievable, but after your advice the technician came by, cleaned the filter and since then the heat pump has been running as it should.

Is there any experience of what is more efficient? Set the temperature using the weather curve, or manually using a timer?

This would allow me to reduce the temperature for example between 11pm and 5am. In my opinion, it consumes too much power at night with the weather curve (including strange peaks...last night 0 o'clock of 10kw) without me needing the heat. 

Posted by: @iwolf

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Unbelievable, but after your advice the technician came by, cleaned the filter and since then the heat pump has been running as it should.

Is there any experience of what is more efficient? Set the temperature using the weather curve, or manually using a timer?

This would allow me to reduce the temperature for example between 11pm and 5am. In my opinion, it consumes too much power at night with the weather curve (including strange peaks...last night 0 o'clock of 10kw) without me needing the heat. 

Generally the best advice is to set your weather curve as low as it will go without the house getting too cool. 

Then, once you have done this and are sure it's working well over a range of temperatures, if you want it slightly cooler at night by all means turn the heat pump off for a few hours (or down if your controller is capable) but not so much that you need to turn up the weather curve to recover in time.

That said I think it's fair to say that there are some 'setback' observations we don't understand, but the above is the best at present unless you have a very low loss house or some other edge case.

Not sure what a 10kW peak is, it's more than 32A so unlikely to be possible without tripping the breaker, are you sure this is correct?

Posted by: @iwolf

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Unbelievable, but after your advice the technician came by, cleaned the filter and since then the heat pump has been running as it should.

Is there any experience of what is more efficient? Set the temperature using the weather curve, or manually using a timer?

This would allow me to reduce the temperature for example between 11pm and 5am. In my opinion, it consumes too much power at night with the weather curve (including strange peaks...last night 0 o'clock of 10kw) without me needing the heat. 

Generally best advice is to set the weather curve as low as possible consistent with the house reaching temperature.   This should be done with TRVs fully open or set a couple of degrees above target if you have them.

Once that is working well over a range of outdoor temperatures you can turn off ( or down if your controller supports it) for a few hours if you want it cooler overnight but not so much that you have to turn up the weather curve in order for it to recover in time.

That said there are some things about 'setback' which are not yet well understood in all house types but ti think it fair to say that the above is generally best advice at present unless you have an 'edge' case such as a very low loss house or very oversized heat pump.

10kW is more than 32A and so would lijely trip your breaker, unless you are running 3 phase.  Do you mean that and for how long was it drawing a high power?

Posted by: @iwolf

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Is there any experience of what is more efficient? Set the temperature using the weather curve, or manually using a timer?

This would allow me to reduce the temperature for example between 11pm and 5am.

It is not either or, you can use both weather compensation and a timer.

In my case, I have a fully open system (all TRVs always fully open, rads balanced via lockshield valves), room stat set to a high temp that will never be reached eg 26 degrees (which means the heating is always on) and a weather compensation curve tweaked such that most of the time my house is at 19 degrees or thereabouts, thereabouts because weather factors can and do cause fluctuations. In this state, it runs continuously in weather compensation mode. To turn the heating off say when summer arrives, I set the room stat to a low temp eg 10 degrees, which means the heating is always off. The important thing to grasp is the room stat is not being used as a thermostat to control temperature, it is instead simply and only an on/off switch. The temperature control comes from the weather compensation curve.

Like many, I think it is likely that I can save a few bob by having an overnight setback. This apparently simple idea is shot through with complexities, so much so that despite many a long and winding thread discussing the matter, we still don't have a definitive answer, the problem being the theory (in essence, the conservation of energy, you can't make or destroy energy, you can only transform it from one form to anther) doesn't sit well with empirical observation, with the former suggesting that the latter over-estimates the savings. The complexity comes from the fact we don't really understand how especially older buildings heat up and cool down, because the fabric becomes a sort of heat battery that can and does absorb and discharge heat energy. As if that is not enough, further complexity comes from the fact no two days are exactly the same. Ideally, to compare setback running to no setback running, we need periods in which everything (especially outside air temp and weather conditions), is identical, apart from the presence or absence of a setback. Unfortunately Mother Nature does not oblige on these things, though as time goes by, and I collect more data, I may get to the point where I have periods where the conditions are almost identical, and useful valid comparisons can be made.    

With the complexity, which is why it is so hard to give a definitive answer on how much can be saved, out of the way, back to using weather compensation and a timer. Let's say I want that overnight setback to run from 2100 to 0300. To do this, I leave the weather compensation (and everything else in the Midea wired controller) untouched, and just set a program on my room stat (you need one with a timer, obvs) that sets back the desired room temp from 19 degrees to 16 degrees between 2100 and 0300. Because my building cools slowly, this effectively turns off the the heat pump between 2100 and 0300, with the 16 degrees there just in case for some reason (I don't think in practice it has ever happened) the room temp falls below 16 degrees. I have this limit because if the building does cool down a lot, my heat pump takes forever to warm it up again. This is also why the setback runs from 2100 to 0300 rather than 11pm to 5am, it gives the heat pump longer to recover before I get up in the morning.

That in a nut shell is how I run a setback using weather compensation and a timer, and such a setback should work 'out of the box'. In a recent two week trial period, one week with setback, one week without, I probably saved about 5% when running with a setback.

All that said, I have made the heat pump a bit more responsive by adding an auto-adapt script. This does something the out of the box Midea controls can't do, it tweaks the weather compensation curve (WCC)when the actual indoor air temp (IAT) deviates by more than one degree from the desired IAT. by upping the WCC a bit when the house is too cold, and lowering it when the house is too warm. This means there is a recovery boost after the setback, which mores I use more energy during the recovery boost that I would have used had I not had a setback, and that extra energy use eats into the savings made during the setback. The auto-adapt script runs on a mini PC connected to the wired controller using something called modbus, a cousin of the USB connections that we are all very familiar with. The fact I, an amateur in these things, have managed to do it means that it is not beyond the capabilities of any well-motivated but otherwise ordinary heat pump owner. I have posted much of the detail on how to set this up (and also monitor your system) in this thread, and one day before too long I hope to complete the write up.      

I really don't see the point of using a weather curve when an indoor thermostat is available. A heat pump that adjusts according to a set indoor temperature, automatically takes into account outside temperature. Let alone, that the outside sensor is highly unreliable.

Posted by: @tasos

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I really don't see the point of using a weather curve when an indoor thermostat is available. A heat pump that adjusts according to a set indoor temperature, automatically takes into account outside temperature. Let alone, that the outside sensor is highly unreliable.

Weather compensation is really important for heat pumps and, correctly adjusted, will save you between 10-20% (or in some circumstances more) in running costs.  This comes directly from the underlying thermodynamics so is pretty much inevitable.  It also makes for more comfortable houses because the emitters are 'on' more or less constantly at the lowest possible temperature required to heat the room, rather than cycling on and off at a much higher temperature.  This reduces thermal gradients both across the room and with time.  

Weather compensation has the same effect with boilers.  The saving in money isn't as much (~ 10%) but the comfort improvements are the same and many boilers feature it.  However we are, unfortunately, somewhat backward in the UK when it comes to these things so tend not to use it for boilers, unlike some countries in mainland Europe that have a better developed heating industry and where it is mandated by their equivalent of building regs.  If you have a heat pump, turn off WC at your peril.  If you have a boiler either turn on WC (if the boiler has it and the system is suitable) or turn the flow temperature down as low as possible consistent with the house getting sufficiently warm.  That will give you best comfort and best efficiency.

You really need to experience 'low temperature' heating to appreciate how much better it is just from the PoV of comfort.  I turned my boiler flow temperature down a couple of years ago from the 75 that the installer had set it at to 50/55.  Result - a much more comfortable house and lower bills (because it now condenses).  Unfortunately it doesn't have WC so cant implement that, but my heat pump, which does, is being installed as I write this.

As @cathoderay says you don't have to be completely purist, there are tweaks, but the basic message to enable WC with heat pumps (and, if you can, with boilers) is sound.

@jamespa Modern heat pumps are inverter driven. A room thermostat will not turn the pump on and off, but regulates it evenly around the set point. This is the benefit of inverters. Also a room thermostat relates directly to the desired indoor temperature, so you don't have to experiment with weather curves. These are remnants of the past, before inverters were used.

Posted by: @tasos

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@jamespa Modern heat pumps are inverter driven.

True, but that neither circumvents the thermodynamics not the comfort factors described above.

Posted by: @tasos

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room thermostat will not turn the pump on and off, but regulates it evenly around the set point. This is the benefit of inverters. 

That depends on the thermostat.  If it is an external thermostat then, unless it interfaces to the HP BUS in an appropriate fashion, it can ONLY turn it on or off or alternatively attempt to apply PWM (essentially turning on and off but relatively fast - which is even worse).  Only a thermostat specifically designed for heat pumps and which is compatible with the model of heat pump you have will do the job that needs to be done, which is to adjust the flow temperature.  The only such thermostats currently on the market in the UK are Passiv and Homely (neither of which are really thermostats in the traditional sense). 

The internal room temperature sensor that comes with the heat pump will of course do something sensible, provided it is correctly set up during commissioning, but only when used with weather compensation or 'adaptive' mode (see below) which itself is simply a refinement of weather compensation. 

Posted by: @tasos

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weather curves ...These are remnants of the past, before inverters were used.

Thats simply not the case.  Inverters are there to modulate down the heat pump so it can match its output to the demand on the heat pump.  Weather compensation ensures that the radiator output is matched to the house demand and the heat pump is operating at its optimum point given the house loss.  Two separate functions for two separate purposes.

Posted by: @tasos

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so you don't have to experiment with weather curves

Some, but only some, heat pumps, feature an adaptive mode (terminology differs according to manufacturer ) which automatically tweaks a basic weather curve (which must be input) very slowly as it learns the house behaviour (which responds very slowly).  Homely also does this.  But the underlying principle remains weather compensation and what the heat pump adaptive mode is still doing is to adjust the flow temperature largely according to outside air temperature.  However adaptive mode does mean you dont have to manually fiddle with weather curves, because the unit does it for you.