Posted by: @ajbevster

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@jamespa once again thank you for the advice last week. I'm keen to move away from the evo thermostat and receiver. Can I just disconnect the receiver from the heat pump (isolating everything) and i assume it will then work purely on wc? I'm tempted to buy the halo air for future tweaking but struggling to see it's major value other than looking pretty and slightly easier to adjust temp inside property.

Is your unit the R290 or the R32 model

I dont know the specific wiring of the Ideal heat pumps but I think what you say is very probably the case.  The R32 manual suggests that either the Halo or a call for heat (normally from a thermostat) is needed.  I havent yet looked at the R290 manual.  Thus in either case need to do one of

1. Change an installer setting to tell it that there is no external thermostat

2. Wire together the contacts to which the thermostat is currently connected on the heat pump/wiring centre so that there is a continual call for heat

Otherwise the heat pump will be expecting a call for heat but wont get it.

The latter is more or less bound to work unless they have done something really weird (unlikely) and can be simulated first of all (to check) by setting the thermostat as high as it will go.

Halo looks quite nice but as you say no obvious major value add unless it produces statistics or enables operation from the internet (if that is useful to you).  

@jamespa I went for the ideal halo air controller as I can sell on the evohome to cover costs. Wiring is very straight forward pretty much straight swap apart from a couple of wires moving in control box. 

Last question, do I need to have the control box on my landing or shall I leave it in the loft as I will be able to control the majority of the heat pumps settings from the halo air....

In two minds. 

Last, last question, what is the most efficient way to run the hot water heating system...continually top up or heat twice a day? 

Posted by: @ajbevster

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Last question, do I need to have the control box on my landing or shall I leave it in the loft as I will be able to control the majority of the heat pumps settings from the halo air....

If the halo has an inbuilt temp sensor (which I imagine it does, but check) then you can leave the control unit in the loft.

Posted by: @ajbevster

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Last, last question, what is the most efficient way to run the hot water heating system...continually top up or heat twice a day? 

The latter, or even once per day if you have enough capacity in your DHW tank.  There is probably not a lot of difference however!

@grahamh I took the plunge and git the ideal halo air controller. My current settings are w/c 0.8 with 50% room influence. Only challenge I'm finding is how much to have the controller impact the wc. It's a 10kw logic monobloc and cycling between 1-2 an hour. Flow rate runs about 28l/m. Target temp is 22c (wife likes it warm) with setback at 20c overnight. Hot water set at 46c. Does anyone understand how the halo impacts the wc as I know it's intuitive...I just don't understand how it works together. Maybe I should set room influence lower whilst the system settles and I find the right wc. 

The flow and return always seem a little too similar...currently 36 to 33 return. 

Basically, what in asking is, for the most efficiently run ashp what settings should u be looking for with a 10kw pump? What should target flow rate be, flow temp and return temp. How many cycles should I be aiming for over 24 hours. Is there anything else I'm missing? 

• @jamespa any advice on best setting for hot water...like schedule 2 hours long? Everything the halo air says is to leave the hot water demand on constant for most efficient running but it doesn't feel right...we will never use the 300ltr hot water plus 72ltr buffer. Plus I thought that's what the buffer was for so you didn't have to constantly keep the tank hot water high...I feel like I'm nearly there but not quite getting the best out the system. Should I just go for pure weather comp with scheduled hot water and see how it goes? Kwh averaging 50 a day but has been as low as 30. What's funny is the heat pump says its only using 21kwh a day but I know our normal use is around 10, so any idea where the remaining 20kwh might be being used? 

Personally I would start with pure WC and hot water scheduled once or twice per day  1-2 hrs depending on your consumption.  If you schedule once per day you might need to adjust the dhw hysterisis down from the default to make sure it always reheats.

Once that's working well you can tweak, or not as you choose.  I'm running on pure WC and dhw once per day for 1.5 hrs (hysterisis 3C) but we don't use my dhw.

As to consumption, where do the various figures you quote come from?  I assume your meter and your heat pump.  To answer the question suggest you plot over a couple of weeks to give more insight, then it might be possible to tell.  Spot readings are almost impossible to interpret due to various sources of noise.

What's funny is the heat pump says its only using 21kwh a day but I know our normal use is around 10, so any idea where the remaining 20kwh might be being used?

I have a Logic Air 4kW heat pump and the CoP numbers reported are a work of fiction. It has been installed since November and the Halo Air is reporting a SCOP of 9.87. The main controller unit reports a different figure (though still wrong AFAICT). I complained to an Ideal engineer when he visited and he fobbed me off saying that all manufacturers' reporting is like that. I have installed my own custom monitoring now to get sensible data out of it.

The flow and return always seem a little too similar...currently 36 to 33 return.

What should target flow rate be, flow temp and return temp.

The manual says that the design flow rate for the 10kW model is 28.7 l/m so it sounds like your flow rate is correct. The heat pump uses a fixed flow rate which means the heat pump will control the difference between flow and return temp by modulating the compressor. If the difference gets too small, it will turn off the compressor for a bit. I wouldn't worry about these numbers too much, just tweak the w/c curve until it is achieving your desired temperature.

How many cycles should I be aiming for over 24 hours.

There are two kinds of cycles:

1) The room temperature exceeds some threshold and stops the heating demand. With the Halo Air controller, I think the limit is the set point + 1 degree. This limit only exists if you have room influence enabled. If you set the w/c curve correctly this kind of cycling should never or rarely happen.

2) There is still a heating demand from the controller but the compressor turns off because the flow temp is too close to the return temp because it can't modulate low enough. This kind of cycling depends on how well sized the heat pump is to your house and I don't think there is too much you can do about it. The Ideal engineer told me that up to 3 cycles per hour is acceptable in his opinion.

Is there anything else I'm missing?

If you have an idea of how much heat in kWh your house needs, you could try to estimate whether your heat pump electricity usage is in the right ballpark.

@jamespa so I've tweaked to heat once a day during the midday as we have solar and only tend to use hot water later on in the day. My only issue I'm finding is the system doesn't seem to recognise the correct hot water temperature. Whenever I look at the hot water temp it is normally completely off. See attached. It's meant to be set for 46c but ranges from reading 24 to 60.....could the dhw thermistor be connected in the wrong place?

I know it's not 35 c as it's really hot out the tap

Also, I made sure the hot water is on schedule between 11 and 3 pm and it still seems to come on....any ideas why? Something must be orlveriding the settings... 

Posted by: @ajbevster

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..could the dhw thermistor be connected in the wrong place?

Yes, or not properly pushed into the pocket on the side of the cylinder.

@jamespa does this look right?

Think I'm going to have to get someone else out to check it all...

@ajbevster 

If it's fully pushed in yes, better if it also had some tape over the hole to ensure that circulating air didn't cool down the sensor.

You could take it out and test it!  There maybe a loose connection somewhere.