To make your system more efficient you need to increase both your zones’ thermostats to above the temperature you want them at (see Heatgeek for more rational). Then put your ashp to weather compensation.

Please tell us all what make you have and someone will know a fair bit about it and help you adjust it.

@judith thanks

The house gets too hot if I do that.

I've already lowered the water temp down to 45°.

I'd like to lose the redundant second stat.

From my profile:

Retired physics teacher 

New Eco4 install 

Samsung 8kW ASHP

Neomitis thermostat & Hive

12x425W solar install

Tesla Powerwall 3 

Posted by: @profzarkov

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The house gets too hot if I do that.

I've already lowered the water temp down to 45°.

If the house gets too hot reduce the flow water temperature further until it doesn't!  Thats the route to max efficiency/lowest cost and max comfort. 

Posted by: @jamespa

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Posted by: @profzarkov

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The house gets too hot if I do that.

I've already lowered the water temp down to 45°.

If the house gets too hot reduce the flow water temperature further until it doesn't!  Thats the route to max efficiency/lowest cost and max comfort. 

Is that the flow temperature (which the heat pump decides) or the target room temperature (which is an input for deciding the flow temperature)? For example, on my Vaillant system I've currently got the target temperature as 19.5C, the actual room temperature at 20C (in the hall which is one of the colder parts of my house - other rooms are warmer) and the flow temperature is currently 26C. If the radiators are big then tepid water is enough to keep the house warm unless it's very cold outside (whereupon the weather compensation should increase the flow temperature to compensate for the increased heat loss). It's taken me a while to appreciate the reality of this heating by tepid water (I already understood the theory), but it works very efficiently (COP of 6 when it's 6C outside). 😀 

Posted by: @johnr

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Is that the flow temperature (which the heat pump decides) or the target room temperature (which is an input for deciding the flow temperature)? 

Flow temperature.  The heat pump decides this based on the outside temperature, the selected Weather Compensation curve, the target room temperature and (when Room Temp Mod is set to 'Active' or 'Expanded') the actual room temperature.  The ideal is for this to be as low as possible which will give max efficiency (because heat pumps operate most efficiently at lower flow temperatures) and max comfort (because this minimises temperature gradients both in time and apace).  This is, incidentally, probably the only time when the thermodynamics of heating works in our favour, so exploit it!

On a Vaillant its especially easy to adjust this optimally, provided you first take the time to understand the principles.  You want to read Section 2.12 of the Sensocomfort manual, which describes how WC works when the Room Temp Mod is set to 'inactive' (which is the 'basic' configuration -  the one to understand first, and quite possibly the one to operate in).

Suggested procedure (which I followed) is this.

• Read section 2.12 and make sure you understand it!
• Set 'Room Temp Mod' to inactive
• Set target room temp to whatever your target room temp is in the 'reference' room (normally your main living room), where your Sensocomfort is
• Turn up TRVs and external thermostats to full (if your reference room is downstairs and your bedrooms upstairs you can leave trvs turned down a bit in bedrooms if needed to make them cool enough) 
• Then adjust the heat curve setting.  Note what it currently is and turn it down until the house is either just right or just too cold.  If the latter turn it up one notch.  make the adjustment infrequently, no more than once a day as you get close to the right value.

Its best done when its reasonably cold, like now!

At this point you have the weather compensation curve adjusted to its optimum value, ie the lowest possible consistent with warming your house. I turned mine down from 1.3, which is the figure that the installer set it at, to 0.8.  This is about 8C difference which is worth about 20% improvement in efficiency.

If you want you can switch room temp mod to active or expanded, and the heat pump will attempt to improve on the control that pure WC gives.  I've had my heat pump 3 weeks (but have been studying them for 2 years plus so reckon I have a good understanding).  I also found that setting room temp mod to 'active' or 'expanded' doesn't improve on 'inactive', optimum comfort and stability is just to run on pure WC!  However this may be house dependent! 

You can alternatively try 'expanded' and 'adaptive heat curve' mode, which is supposed to sort it all out for you.  Personally I prefer to be in control but I might experiment to see if it fine tunes from a setting that is basically right.

Hope that helps.

Hi

Thanks for all the info.

I've adjusted the WC or Water Law as Samsung call it to 

14° -  -2°

32° -  45°

With the water temp reduced from 50 to 45°C.

The Hive stat is set to 19° from 0400 to 2300 with a setback to 17°.

I have no trv's 

My main question was can I ignore the second room stat and wire in the receiver the same as the hive one...?

Posted by: @profzarkov

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Hi

Thanks for all the info.

I've adjusted the WC or Water Law as Samsung call it to 

14° -  -2°

32° -  45°

With the water temp reduced from 50 to 45°C.

The Hive stat is set to 19° from 0400 to 2300 with a setback to 17°.

I have no trv's 

My main question was can I ignore the second room stat and wire in the receiver the same as the hive one...?

Sorry Im getting mixed up whose house is getting too hot and which heat pump they have!

Same principles apply however, the idea is to get the water law/weather compensation as low as possible consistent with the house heating up, and as much as possible run on WC alone not room stats or TRVs.

In your case

• turn the hive (and any other thermostat/controller) up to well above the target room temp.
• Set the high OAT end of the water law curve to say 20C (OAT)/25C (FT).  (or you can use say 15/30 if you want to impose a minimum FT, you may need to experiment when its mild))
• When its cold outside progressively turn down the FT at the low OAT end until either the house is just right or its just too cold, in the latter case turn it up a smidgen, making adjustments infrequently and not more than once per day once it gets close.

This gets you the lowest WC curve consistent with heating your house, which is both the most efficient and the most comfortable.

Once thats done by all means do a night time setback, but keep the target day temp as set on the hive at least a couple of degrees above what you really want so its constantly calling for heat.

Regarding the second room stat, how are it and the hive currently connected.  If both control a zone valve you need to rewire both.  If the Hive controls the call for heat on the Samsung and the second room stat controls a zone valve, you want that zone valve constantly open.  If you post a bit more info about the wiring I or others can advise the easiest way to make it redundant.

I have the hive on one zone and the old Neomitis stat on zone two, they both call for heat and presumably open the appropriate zone valve. I could just ignore the second stat and latch the zone 2 valve open...

But confused by your abbreviations above. How do they relate to the four figures I've quoted?

Posted by: @profzarkov

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I have the hive on one zone and the old Neomitis stat on zone two, they both call for heat and presumably open the appropriate zone valve. I could just ignore the second stat and latch the zone 2 valve open...

Can you confirm the implication that you have two zone valves and a diverter valve (three in total) and are you sure both hive and neomits stats are connected to zone valves not the heat pump call for heat input.

What area of the house is zone 2?

Posted by: @profzarkov

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But confused by your abbreviations above. How do they relate to the four figures I've quoted?

14° -  -2°  

32° -  45

14/32 ( the high outdoor air temperature end of the wc curve) is what I'm suggesting should be 15/30 or 20/25, but 14/32 is probably OK albeit a somewhat higher min flow temp than you probably need when it's 15/16 outside

-2/45 ( the low OAT end of the wc curve) is what you need to adjust when it's cold.  Leave -2 where it is and adjust 45 down until house is just right when all external controls are calling for heat continuously. 

Ok

I've adjusted them to 15/30, -2/43

See how that goes.

There seems to be three valves see pic

I have two wireless receivers. I was going to connect the signal lines together, so when the Hive stat calls for heat it signals both. I'd then switch off the other stat.