I agree with GrahamF about the Smart Controller manual. Some of it has confused the hell out of me especially around temperature correction and even hysteresis. With our old GSHP the hysteresis behaved as I expected: if there is a 47c target then raise the temp above it and when the temp falls some degrees below it then kick in the heating. However, our DHW does not hit the target of 47 at all but cycles somewhat below it (with 6c hysteresis):

I have manually had to reduce the target the last few days for the central heating to get a look in. 
I will reduce the DHW schedule to a few hours in the morning and afternoon but I cannot understand the mechanism which switches off the compressor when the DHW hits around 45.5c.

Our controller certainly has no input for temperature sensor on Circuit 1. Econet24 just shows it the same as Heat Pump Actual Temp. Currently the three circuits are set to fixed temp but I am going to try weather compensation as that certainly worked well on the GSHP. (It was an IVT with some REGO controller. Much, much simpler than the Grant Smart Controller.)

Thanks again,

Gerald.

According to the Smart Controller Installer and Operating Instructions table in Section 7.14.1

''DECREASING FIXED WATER TEMPERATURE' applies only to non-weather compensated circuits.  Therefore it does not apply to us.

Section 7.14.2 for Weather Compensated Circuits is confusing.  I think it is meant to apply a setback to the flow temperature during Night Mode.

It says:

During a scheduled night/unoccupied time period, the water flow temperature will be reduced by the configured value 
‘DECREASE WATER TEMPERATURE’ set during system setup or in the circuit settings.

However, confusingly then it goes on to say something that seems to contradict Room Temperature Correction below.

...With a Thermostat...

If ‘THERMOSTATIC PUMP BLOCKADE’ is not enabled, once the target air temperature is achieved the smart controller will use decrease the flow temperature target by the ‘DECREASE WATER TEMPERATURE’ value, which is set correctly will maintain the target air temperature. Refer to 7.3.1.3 for recommended setback values based on heat emitters for the circuit.

Room Temperature Correction

Target temperature with correction = Target air temperature of the thermostat assigned to the circuit minus Current temperature of the thermostat assigned to the circuit x Room temperature correction.

By default, the Room temperature correction value is 4.0, and the value range is 0 - 10.

It is necessary to find appropriate value of the Room temperature correction. The higher the coefficient, the greater the correction of target circuit temperature. If the setting is “0”, the target circuit temperature is not corrected. Note: setting a value of the room temperature coefficient too high may cause cyclical fluctuations of the room temperature.

Bottom line, I think you should use Decrease Water Temperature for Night Time set back and Room Temperature Correction to add some room influence to the flow temperature.  But I could be wrong!

Graham

On the bright side, I've got a COP of 6 so far 

that’s pretty impressive. I cannot remember many pumps beating that..

Again, really don't know how accurate this is! 

I'm unsure if there's inhibitor, I can double check but they seemed to know what they were doing. There's the mag filter and 2 new expansion vessels and one valve I believe 

Econet24 up and running, I've spent way too long looking at it already

Single zone, and yes running 24/7 

For now I've got a single DHW run overnight, I know this isn't the most efficient time but it's when my electricity is cheapest. So far it has held up just fine

Good advice on the lock-shield valves, I think I slightly oversized my living room radiator so I will try to balance them all

Here is how it has been running so far, I've had it set to quiet mode (level 2) which seems to limit the compressor/fan - although I've noticed the limited fan speed caused more defrosts overnight, so I've actually set a schedule on the quiet mode so that it turns off overnight during my off-peak electricity rates and hopefully needs to defrost less often. I still can't hear it inside when it's not on a quiet mode and it's not a problem for the neighbours either, but it is quite loud if you stand near it!

For Circuit 1 (the only circuit) I've disabled Thermostat pump blockade. Having that on seemed to make it behave like a traditional thermostat, where once temperature was met the system would shut off entirely until it falls below the hysteresis value. The only issue is that even when the pump is on standby (compressor & fan both off) the pump continues to run at about 11L/min, effectively cooling the radiators sooner... I don't see any way to stop this behaviour. 

I'm also not entirely confident on what effect Decreasing fixed water temperature and Room temperature correction settings have when the pump blockade is disabled. If you, or anyone else, has knowledge here I'd love to hear it. Sometimes the unit goes into standby for 30 min when I'm not sure it needs to, like earlier this evening:

Ignore the low DHW temperature above... the thermostat is at the bottom of the cylinder and it didn't do a DWH cycle last night because I set the hysteresis too high. Despite being over a day since last reheat, it was still plenty hot enough for a shower! 

I have changed the default fans speeds for idle/min/max to 25/30/100 (this is the lowest you can set idle/min without the setting being reverted). I don't know why, but minimum is 50% by default which was giving me a higher flow rate than I needed 

@batpred I think its own COP rating is probably being a little generous, I'm relying on its own power consumption values which I don't know the accuracy of. It's also April so a favourable month overall for heat pumps. 

that’s pretty impressive. I cannot remember many pumps beating that..

Our standard query, inspired on @jamespa is along these lines " We only want a simple system with weather compensation and a thermostat. We do not want any buffer (2 port volumiser acceptable) and no external heat exchanger between ODU (outdoor unit) and emitters, for max efficiency ".

This is what installers that are particularly interested in Grant included: 

Here is my list, some of which is also covered above:

1. I am assuming you have inhibitor in the system and a magnetic filter.
2. Hopefully, you have a new expansion vessel and valve.  If not, make sure that it is not leaking.
3. I had a Shelly Pro EM-50 installed in my consumer unit, so that I could monitor how much power the heat pump is using.
4. Hopefully, you have the Econet24 phone app up and running.
5. Schedule the heating to run 24 hours per day.  If you have zones, run all of them all the time.
6. Schedule the hot water to run in 1 hour slots 2-3 times per day.  Don’t leave it on all the time, because the heat pump cannot run heating and hot water at the same time.  DHW Priority should be set to Yes (check), so you don’t want it to interrupt the heating which reduces efficiency.
7. Start with all your TRVs wide open.  Adjust lock shield valves to balance temperatures across rooms.
8. Your flow temperature looks a bit high to me, but time will tell.  Weather compensation:
   • Assuming you want the indoor temperature to be at 20C, for an outdoor temperature of 20C, set the flow temperature to 20C.  This means it is neither cooling nor heating when it is 20C.  From memory, this is Shift = 0.
   • Your design document should tell you the target flow temperature when it is about -3C outside.  Suppose it is 45C, then adjust the heating curve so that the flow temperature is 45C for an external temperature of -3C.
   • In cold weather, Heating Curve is more significant.  In warm weather, Shift makes more difference.
   • Check the data history for each 24 hour period.  You are aiming to minimise the number of compressor starts and stops, which you can see from the compressor frequency and outlet/inlet temperatures.
   • Initially, adjust the heating curve, but don’t adjust Shift.  Make small changes and then leave it to settle for 24 hours.

I hope this helps.

Now it is running constantly and my house is being kept bang on 19c (my desired temperature)

Well thats a win for starters.  Enjoy!  You may need tweak the WC settings during the height of the next season, but until then you cant really do so.

By setting the following settings

Circuit 1 Regulation mode to Weather
Circuit 1 Decrease water temperature to 3c
Circuit 1 Room temperature correction to 0
Circuit 1 Thermostat pump blockade to off

The system will continue to operate even when the thermostat is satisfied using the weather curve, but will reduce flow temperature by 3c until the thermostat drops below the hysteresis threshold (which is set to 0.3c)

I am not an expert on Grant controls so like you I rely on the manual (plus the fact I have read about 10+ manuals from different heat pumps and you soon get to realise that they are doing more or less the same thing just subtly different ways and with different terminology).

With that caveat I believe you are correct!

My only question regarding the settings is it possible to have the flow rate be reduced a little bit via software? I can see on the econet24 graphs the flow rate seems to change dynamically, but I'm sitting between 3-4c delta T at the minute and I believe it would be a little better with a slightly lower flow rate to get a delta T of 5? 

Unless you are getting excess noise then dont bother.  There is no harm in having a DT lower than 5, in fact it will slightly increase efficiency because it means you can operate at a slightly lower flow temperature for the same average emitter temperature.  In any case you should expect DT5 only when its operating at design load (ie its very cold outside).

Hope that helps!

I've been reading the manual and tinkering with some settings. What I'm going to state might not be 100% correct so anyone who is familiar with this controller please correct me if I'm mistaken

I have a single, open loop circuit with a thermostat (in a sensible location) and outdoor temperature sensor

By setting the following settings

Circuit 1 Regulation mode to Weather
Circuit 1 Decrease water temperature to 3c
Circuit 1 Room temperature correction to 0
Circuit 1 Thermostat pump blockade to off

The system will continue to operate even when the thermostat is satisfied using the weather curve, but will reduce flow temperature by 3c until the thermostat drops below the hysteresis threshold (which is set to 0.3c)

Prior to these changes the thermostat was 'in control' and the system ran for roughly 2 hours then shut off for another 2 hours. Now it is running constantly and my house is being kept bang on 19c (my desired temperature). To be fair to my installer he did have most of this setup but I went and mucked around as a learning experience.

My only question regarding the settings is it possible to have the flow rate be reduced a little bit via software? I can see on the econet24 graphs the flow rate seems to change dynamically, but I'm sitting between 3-4c delta T at the minute and I believe it would be a little better with a slightly lower flow rate to get a delta T of 5? 

Should the pipes inside the plant room (cupboard) be insulated? They're currently exposed and my 250L DHW cylinder seems to be dropping around 0.3c per hour without use

Should the immersion heater be connected to the controller rather than just being something I can manually turn on if the heat pump is not working for whatever reason? By having no immersion heater set in the controller, the option for a legionnaire cycle is not there (despite it being an R290 ASHP)

Hot pipes connected to the cylinder should be insulated for at least 1m from the cylinder.  0.3 C/hr is 87W, what is the cylinder loss spec, this doesn't feel far out.

A legionella cycle should be possible and if it's not the system has not been wired correctly.  It depends on the heat pump whether or not this requires the immersion (and thus a power control by the heat pump).   My vaillant doesn't, legionella is done by the heat pump itself, so the immersion is standalone.  Others use the immersion for the legionella cycle so normally need to be connected back to the heat pump.  Grant do funny things though so it maybe that they supply a separate timer to be located by the dhw tank.  You would need to ask the installers how legionella cycle is controlled.

Is polyethylene foam pipe insulation sufficient when inside trunking? Exposed insulation is of a different type

I can't comment authoritatively on this, can't see why not provided the inside of the ducting stays dry.