Posted by: @sirpatchuk1980

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@allyfish 
This is the type of KW usage that I need to be achieving!

Are you able to help me and explain how your thermostat/heating works.

We have a Honeywell Evo Home third party controller and, from reading this, it appears this is wrong.

What do I need to do in order to get my Grant ASHP running likes yours?  

Thanks

Hello @sirpatchuk1980, welcome. Lots of useful info on here on how to maximise efficiency of ASHPs, especially retrofits. First things first, a bit of info about your ASHP set-up. Grant installs are not the most efficient, and they do seem to fit 3rd party central heating and hot water timers and thermostats onto their systems, seems to be more out of habit of doing this on their fired boiler product ranges. No-one within Grant seems to have considered whether it's a good idea. Also, their ASHPs are made by Chofu in Japan, good proven units and well built, but with THE most complicated remote controller ever created!

So, what's your install? Grant model? Emitters- radiator, underfloor, both? Low Loss Header/Volumiser? Design heating temperature? Climate Compensation enabled? Emitter control, TEV's, mixer valves, smart wireless TEVs? House floor area and calculated heating load?

Main issues with my Grant install was three things:

1. Using a HIVE thermostat in the lounge to control the heating. It was cycling the ASHP on an off far too often.

2. Grant didn't enable the climate compensation at the Chofu ASHP controller, so it was continually trying to achieve 50degC design flow temperature.

3. Low loss header not balanced, too much primary (ASHP) flow compared to secondary (radiator) side.

Enabling climate compensation, and lowering the design flow temperature (after experimenting) to 42degC max at 0degC outdoor temperature has helped efficiency. Using climate compensation to control heat in rooms rather than TRVs. TRVs are set to prevent overheating, but usually on all the time. Some HIVE smart TRVs provide zone control in rooms I don't heat weekdays or weekends. Low loss header was balanced by lowering the ASHP pump flow dip switch settings to match the secondary side flow. Main HIVE thermostat is set to 24degC, higher than I want the house, so as to be continually calling for heating when heating is on. I heat for 15hrs a day, but switch off rather than set back at night. Again, to stop the ASHP compressor cycling in set back. It's cheaper to switch off overnight for 7hrs, even though the first two hours in the morning are quite high energy consumption as the whole system has to get back up to temperature. Hot water is boosted once a day 1-2pm when the outdoor air temperature is highest and the impact of loss of heating to the house is least. Lots of small tweaks that, in combination, make a big difference.

Hi, thanks.

We have a Grant 17KW with Honeywell Evo Home.
We had it installed in May 2022.  UFH downstairs and radiators upstairs.  Ultimately our UFH does not work as it has the wrong installation was done (spreader plates over wooden suspended floor).  It was never heating up and using too much electric.  We are going to get radiators retro fitted downstairs this year.  
So we are currently living with radiators working ok upstairs and our UFH turned off downstairs as it is not fir for purpose.  Therefore, I know whatever I am doing now is no real test until I get downstairs working.

However, knowing what I know now I am thinking is Honeywell Evo home the correct thing?  Should I have zones?

I am slightly confused about having the thermostats set to call for heat all the time and that makes is a more efficient/economical system... how?

Currently we have our radiators set in each zone to 16 or 18, depending on whether we are in our not and the ASHP kicks in as appropriate....

All the rooms upstairs have their own zone and have their own thermostatic valve head
https://plumbingsuppliesdirect.co.uk/honeywell-evohome-hr92uk-radiator-controller/
Four bedrooms, bathroom, ensuite and hallway.

Weather compensation is on and set between 35 and 45 (0 to 20 degrees)

We mainly out during the day Mon-Fri and home first thing, evenings and weekends.  
I need to understand what to so and how to run the ASHP effectively.....

Thanks for your help.

@sirpatchuk1980 I had EvoHome in my last house, a great (if expensive!) setup that did work on my gas boiler.

I would not use it on my heat pump though - even if it is one that is "heat pump ready". These are the model where the bdr91 (boiler relay) have the little embossed house symbol in one of the corners.

The EvoHome and other 3rd party controls work by demanding heat for about 15 / 20 minutes, then stopping demand for 20 / 40 minutes before repeating the process. Your heat pump can not work effectively like this, it will run at near full bore (~4kW) at initial start-up to get the flow temperature up before starting to calm down to an efficient state just as the EvoHome says 'turn off'. Then the system cools and it has to start from scratch when the EvoHome says 'turn on'.

If you are chewing through electric and noticing your house is not really warm etc. then personally I would remove each of the EvoHome TRV heads from your radiators, go to the EvoHome control panel (which should be the thermostat for one zone in your house) and turn the temperature on this up to 25°C permanent. That system is then calling for heat 24/7 and is essentially redundant.

Then on the Grant controller make sure that weather compensation is enabled and configured correctly as per your own property's heat loss design document - for example max flow temp of 45° at -4 outside and minimum flow temp of 20° at +16° outside. Get hold of the installer document from the Grant website to figure out how to get to the controller configuration menus.

Then walk away and leave the system alone. It'll take a fair few hours to pump heat into your house and bring it to a constant temperature.

After a fair few hours (say more than 6 hours, maybe a day depending on how cold the house is Vs outside) your heat pump should have settled into a constant running rate of (say) between 1.2kW and 1.5kW.

At this point ask yourself are you feeling comfortable / too hot / too cold?

If comfortable, great, you are lucky and configured the system as near as damnit just right on the first attempt.

If cold, adjust the weather compensation settings. Say maximum flow temperature up a couple of degrees leaving outside temperature the same.

If hot, adjust the weather compensation maximum flow temperature down a degree or two. Leave other settings as is.

It may take a few days of tweaking to get 'just right'. And very likely you will need to revisit the settings as we come back to the cold weather later in the year. Just make notes of the parameters as they are now - so you have a baseline - and what you changed them to and when so you can refer back.

There is no one size fits all configuration. It has taken me a couple of months to get 'nearly there'. I cannot get my own system anymore efficient until I replace radiators and that will not happen until spring when the heating gets turned off, then I will have to revisit all my settings again.

Posted by: @sirpatchuk1980

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It was never heating up and using too much electric.

Was this a zone on the EvoHome system or just had water flowing when one of the zones was calling for heat?

If you can get the heat pump running 24/7 on weather compensation without EvoHome turning it off then you *may* find the ufh is actually ok.

Posted by: @sirpatchuk1980

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I am slightly confused about having the thermostats set to call for heat all the time and that makes is a more efficient/economical system... how?

Currently we have our radiators set in each zone to 16 or 18, depending on whether we are in our not and the ASHP kicks in as appropriate....

It is more efficient in the long run as you want the flow temperature to be as low as possible while keeping the house warm, with the heat pump running as long as possible to output at that low flow temperature. On weather compensation you don't want any external controls interfering, let the heat pump make the decisions. That way the heat pump will dial back its compressor as low as it can do while maintaining a steady for temperature at a given outside temperature, minimising electricity consumption.

Rather than running hard to try and get for temperature up to say 50° and likely never being able to reach such a temperature before EvoHome turns it off it worse, because it is running hard it goes into defrost, cooling the water it has just tried hard to heat, running hard again to try and get up to temperature, defrosting again.... Vicious cycle ...

You don't want an ASHP kicking in as appropriate - ideally it runs 24/7, it chooses when to run the compressor itself based on outside temperature and flow/return temperatures, and it outputs enough heat to tick over and make up for the heat that is leaking out of your house naturally.

Posted by: @aceshigh

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Posted by: @sirpatchuk1980

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It was never heating up and using too much electric.

Was this a zone on the EvoHome system or just had water flowing when one of the zones was calling for heat?

 

If you can get the heat pump running 24/7 on weather compensation without EvoHome turning it off then you *may* find the ufh is actually ok.

The only thing that I would add is to balance your radiators and UFH, so that you are getting the correct amount of heat energy to each room, to replace the heat being lost, at the desired temperature for that particular room.

@aceshigh Thanks.

shall I get normal trvs for the radiators?

And I’ll keep the evo home setup… just make one zone downstairs?

@aceshigh 

should I get the evo home disconnected altogether then and just use the grant white box?

the Honeywell controller has cycle rates which minimum is three per hour 

@sirpatchuk1980 (sorry @aceshigh) just chipping in. Looks like your Grant controller is hidden away with some of the pipework and system components. If the external 3rd party thermostat is disconnected, the in-built room temperature thermostat in the Grant controller is enabled. Might be best to leave the Honeywell controller, but use it as an overheat protection thermostat, by setting it to, say, 25degC whenever you want heating energised. That's all I did with my HIVE. The Honeywell has some control on cycles per hour, the HIVE is useless with nothing that can be adjusted such as hysteresis or cycle rate. You can lave TRVs and 3rd party thermostats in the system, just set them such that they provide overheat protection. Use climatic control + radiator balancing for space heating control.

@allyfish is it best to have more or less cycles then?

@sirpatchuk1980 ASHPs work best when continuously running. Less wear and tear and better efficiency. The outdoor unit has in built stop/start cycle protection, with a minimum off period before restarting. But when it's cycling on and off under the demand of a room thermostat its never under stable control.

@allyfish 

that’s where I am worried that the Honeywell I have has the cycle rate set to 3 per hour and that’s the minimum. It doesn’t appear you can override this. Hence disconnecting it?