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Grant Aerona3 10kW – A few questions

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(@biagg)
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Hi, I've recently installed a ASHP system via the ECO gov Grant. The installer has installed a 10kw Grant aerona3 with 5 new radiators and 2 radiators with the fans (kitchen and bathroom) I know almost nothing about heating systems but have been reading through this forum the last few days regarding Grant aerona's and their system and have a few questions regarding my system. 

 

Surprisingly the installers turned weather compensation on (which I've noticed doesn't happen on most GRANT aeronas installs) 

I've changed some of the other values:

WC / 2100: 1 

Max outgoing water temp / 2102 : 45degC

Min water temp / 2103 : 35degC

Min OAT / 2104 : 0degC (was -7degC)

Max OAT / 2105 : 20degC

I've only just changed these settings and will see how I get on, I know every system is different but would anyone change anything? we usually hardly have the heating on for more than 2-3 hours a day when we had oil even in winter. So having the heating on all day for efficiency is very weird for us. 

As far as I am aware, having WC on overrides the thermostat settings is this correct? I've changed the thermostat to 25degC I've attached a picture of the thermostat below.  

Screenshot 2024 01 29 122933

I also have this box in the systems closet, do i need to change the heating settings from ON to another settings for Grants WC to take control or is this right?

Screenshot 2024 01 29 122940

 Lastly on Grants main system box, where does the system take the temperature from? Should my thermostat downstairs (first picture) be the same as grants box upstairs in the systems cupboard (last picture) ?

Screenshot 1

 

Thanks for any help people might be able to give me, I'm not savvy with the vocab of heating systems yet, and apologies for any grammar or punctuation errors it's not my strong suit.

 

 


   
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MikeFl
(@mikefl)
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Hi, welcome to the forum!

To answer your questions in order:

"having WC on overrides the thermostat settings is this correct? I've changed the thermostat to 25degC"

WC doesn't override the thermostat settings; the heating will be 'on' and trying to reach your target, whatever that may be, but the idea of WC is to have it set so it just replaces the heat lost by the house, to maintain your desired temperature.

For example, say you want your house at 22C.

Imagine it's currently at 22C, and the OAT is 21C. At this point, based on your settings the HP won't do anything, even if the room thermostats are asking for heat. In this case your house is likely to stay around 22C.

If the OAT is 15C then your house will cool slowly, the room stat demands heat, and your HP will deliver water around 38C; this will cause the house to heat up, slowly.

If the OAT was 0C, then your house will cool rapidly, the room stat demands heat,  and your HP will deliver water at 45C; hopefully heating your house quicker.

However, suppose in this last case, with the water arriving at 45C to your house it carries on heating ... going to 22C, 23C, 24C, ... way beyond what you want. This would show that water at 45C for an OAT of 0C is too high - you're not just replacing the lost heat, but adding to the house temp. This would indicate to you to adjust the 45C (2102 parameter) down a little, until you reach the scenario where an OAT of 0C leads to the house just maintaining your 22C target.

The 25C on your room thermostat just acts as a 'backstop' to ensure your house never just carries on heating (i.e. in the case above, once 25C is reached, the room stat stops demanding heat and the HP turns off).

Hope this is clear ... it takes a while to get used to. BTW, your settings look about right. Certainly a good starting point.

And yes, it is weird to have the heating on all the time, but once you're around your desired temp the HP should run at its lowest setting, consuming about 600-700W which is very little for an entire house. 

 

"I also have this box in the systems closet, do i need to change the heating settings from ON to another settings for Grants WC to take control or is this right?"

I think this is a standard dual channel controller. You should leave the CH 'on' all the time, using WC to control things (as above); and I assume the DHW 'timed' is a setting to heat the HW once or twice a day for an hour? A HP can only heat one thing at a time, so it's either DHW or CH, but not both, so check when DHW is on, the HW cylinder is getting the heat, not the CH.

 

"Lastly on Grants main system box, where does the system take the temperature from? Should my thermostat downstairs (first picture) be the same as grants box upstairs in the systems cupboard (last picture)"

- the top value (24c) is the temperature where the Grant controller is. In a better world, you'd be using this to set your target temperature, but the way Grants are installed, this temperature setting is ignored, so you can forget about it. The room stat (first pic) is what is setting the target temperature.

 

Grant Aerona 3 10kW


   
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(@biagg)
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Topic starter  

@mikefl Thanks Mike that explanation clicked in my head, while waiting for a reply and after changing the settings I was starting to bake as the house was getting to the 25C I had set the thermostat to. From what I understand now I should adjust the 45C (2102) to a lower temp (say 40C) keep my thermostat at 25C and see if the house gets to reasonable temp and not boils me alive? 

Hopefully I have that sort of right.

I understand currently that my system will be running 24/hr depending on the temperature outside if I use WC. Would it be possible for me to use timings on the dual channel controller to control my CH to turn it off between say 11pm and 4am? Currently I have set the Water to turn on between 12 noon and 2pm, but we shall see if this works tomorrow as it was betwwen 4-7am and 6-8pm. 

 

Thanks for the help.


   
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MikeFl
(@mikefl)
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It depends a little on what the current OAT is. You're basically lowing the WC line to generate less heat, so you could lower either end, or both ends. Generally people leave the 0C/45C end adjustment for when it's freezing outside and the house isn't warming enough; adjusting 2103 might be the way to go, but judge it based on if you're currently closer to the 0C or 20C end of the line (if you picture it that way). Or reduce both ends by the same amount, and you lower the line, but keep the slope the same. This really is a "one size doesn't fit all" thing.

Yes - for overnight rather than having 25C as your backstop, have a reasonable setback temperature between 11pm and 4am. I'd have a lower temp target rather than off, simply because if a cold night dropped the house to say 15C it would take several hours to get back to a reasonable temperature the next day. e.g. if you like your house at 22C, a nighttime temp of 20C might be a good starting point and see how you get on, lowering further if you feel it's too warm.

HW heating will use a higher LWT than for CH (it's fixed at 55C I think) so you want to run HW heating during the warmest part of the day, whenever that may be - early afternoon usually favoured. Modern HW cylinders are very well insulated so water should stay hot for a long time. My cylinder needs only 30-60 mins a day for a full 24 hours heat but will depend on demand, obviously. 

 

(to correct my first reply, the LWT would be 32.5C for an OAT of 15C with your initial parameter values)

Grant Aerona 3 10kW


   
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(@biagg)
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@mikefl Thanks, I will fiddle around with the settings over the next few weeks at home and find a sweet spot, Then hopefully wait for Homely to be released to get a better read on things.

 

One last thing from my understanding from reading around is usually to have all the TRV's on my radiators fully open because a HP works more efficiently with an open circuit? We have quite a large house for just the two of us and usually only the office (we both WFH) bedroom and kitchen. All the other rooms were turned down to a 1-2 and the rooms we used were fully open at 5. I guess this would just be another trial and error and see how it effects the efficiency of the HP and costs?

 

Overall I'm actually surprised how well the installers did and how cost effective its been for the last week or so since installation. I'm in W Scotland and it's still pretty chilly here but has kept the house warm (so far)

This post was modified 4 months ago by Biagg

   
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MikeFl
(@mikefl)
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For adjusting the overall system I'd leave everything open - you want to adjust things for when there's full demand on the system. Use TRVs to reduce heat in rooms rarely used. There's an argument for whether it's more efficient to have all rooms at one temperature - clearly there will be heat loss to an adjoining room at 15C which will be greater than if it were at 20C, but each home and home usage is different. It's what works for you. Certainly the strategy of making small adjustments and giving them a few days to settle in, is wise. Heat pumps are made for 'low and slow' heating, so nothing should change rapidly.

Glad you seem to have a decent system. West Scotland will give it a good workout.

Grant Aerona 3 10kW


   
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(@derek-m)
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Posted by: @biagg

@mikefl Thanks, I will fiddle around with the settings over the next few weeks at home and find a sweet spot, Then hopefully wait for Homely to be released to get a better read on things.

 

One last thing from my understanding from reading around is usually to have all the TRV's on my radiators fully open because a HP works more efficiently with an open circuit? We have quite a large house for just the two of us and usually only the office (we both WFH) bedroom and kitchen. All the other rooms were turned down to a 1-2 and the rooms we used were fully open at 5. I guess this would just be another trial and error and see how it effects the efficiency of the HP and costs?

 

Overall I'm actually surprised how well the installers did and how cost effective its been for the last week or so since installation. I'm in W Scotland and it's still pretty chilly here but has kept the house warm (so far)

Just to add to the advice given  by MikeFl.

The objective is to match the Weather Compensation (WC) curve as closely as possible to the heat loss of your home, such that it maintains the Indoor Air Temperature (IAT) at approximately the desired value. This can be a lengthy process, involving making a slight adjustment and then monitoring the result over probably a day or so.

As the weather gets milder you will find that the heat pump starts switching on and off (cycling), and unless this becomes 6 or more times each hour (short cycling), it is normal operation.

 


   
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(@allyfish)
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Welcome @biagg from a fellow Grant 10kW Aerona owner.

The key with the Aerona is to have all radiators and thermostats constantly calling for heat and then adjust the weather compensation max and min flow temperatures and corresponding external ambient temperatures to get it to balance. The balance is when the heat being lost by your house is being matched by the heat being emitted into it. It's a process of trial and error, every house is different, but you've got your head round the Grant controller and parameters you need. Use TRVs simply as overheat protection devices - set them higher than you want the room. That way, if sunlight is streaming into a south facing room, the TRV will close down to avoid the room cooking.

It's counter-intuitive for anyone who used to have a fired boiler and the heating on early morning, evening, giving a massive boost of heating to quickly warm the house, and the heating off with the house cooling down at all other times. 'Saw tooth' heating control rather than flat line heating control. We have a compromise where we switch off at 9pm and back on at 5am (4am when it gets really cold). It works for us, and is cheaper than having the heating on 24/7, and more importantly keeps my wife happy.

The 10kW unit is sometimes a bit sluggish in our house to warm it up first thing, but it wasn't sized with early morning pre-heat in mind, or being switched off overnight. It's also a little undersized for us due to DNO issues with the 13kW Grant unit which meant we could not install it. But the 10kW is a good work horse and for 95% of the heating season is adequately sized. If it does come up short, or spends a day in defrost (Grant units seem to like defrost!) we have a log burner as secondary heating.

You can bump up the Grant Aerona settings to supply water at 60degC to charge your hot water cylinder. You can charge the tank to 55degC that way. By default the Aerona is set to supply hot water at 55degC in HW mode, which will not get your system tank much above 50degC. We find charging once a day to 55degC is more efficient and less disruptive to heating than twice daily to 50degC. HW charge takes 75minutes with a 250l tank.

This post was modified 4 months ago by AllyFish

   
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(@biagg)
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Thanks guys, I've been adjusting and got it to a sweet spot a few days ago, the temperature outside has been about the same all week, so we shall see what happens when there is a cold snap. But its been working great  Until today.

My hot water is set to go from 12-2pm and at around 13:20 my partner noticed water dripping from the kitchen roof. I ran upstairs to the water/immersion tank and water was dripping out the "secondary return" bolt at the top of the tank

Screenshot 2024 02 03 143836

I actually have no clue how to turn off the system, (the handover was crap) someone was supposed to come out to do a final check and explanation but it hasn't happened yet. I switched the cold water off and emptied the hot and cold taps out and that stopped it for now. 

Unfortunately the company that did it aren't open on weekends, so not much use to get a plumber out unless I pay for one myself. (I'll live without heat and water for the weekend)

There's been a constant hissing or water flow coming through the pipes into the tank since the day after it was installed but i assumed this was just part of the system, But I've not touched any of the valves. 

Anyone have any idea what could have caused this? The hot water tap emptied in a few second so i dont think there was much in it. I'm happy to wait until Monday for them to come, but if anyone has any insight would be helpful. I'll add some more pictures of the system.

Thanks (sorry for pic quality)

Screenshot 2024 02 03 144748
Screenshot 2024 02 03 143853
Screenshot 2024 02 03 143843

   
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(@allyfish)
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Oh that's not good. The pressure is regulated in the Grant hot water tank, and it's a mains pressure unvented type system. The brass cap on the tank connection will need removing and making good. It might just tighten up as it is, worth a try, but don't overtighten it and that could damage the threads on the tank. If the tank is drained, better to remove it, apply some white PTFE tape on the threads and reseal it. Important: if your hot water tank is drained out, make sure the electric immersion heater is switched off at the time clock on the tank and/or the power supply switch to the tank. It may be scheduled to come on for an hour a day or an hour a week via the timer - this is usual and provides protection against Legionella. You don't it switching on at all when the tank is empty!


   
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MikeFl
(@mikefl)
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You've possibly had a pressure issue, which could be the hissing sound, or maybe there's been a slow leak on the secondary return valve that's now got worse. There should be several pressure release valves (PRVs) on the pipework, which vent automatically, so in theory everything should be safe.

The HW cylinder is a sealed system - i.e. water can only flow out of it if replacement water can flow into it, so if you've turned off the cold water supply to the HW cylinder it won't let any hot water out. So the tank might still be full of water.

You say you've turned everything off. Does that include the supply to the immersion heater element? You might have that element in use maybe once a week for Legionella protection; it's not powered from the HP, but comes directly from the HW cylinder itself.

Parameter 01 31 shows the HW cylinder water temperature - or it should if you've had the sensor correctly fitted, and parameter 51 07 set to 1 (if it's zero then I think the Grant guesses based on flow temps to the DHW cylinder). I'd check that. Although there ought to be a PRV triggered by heat on the cylinder; again if anything gets too hot or too high pressure they should vent to the outside (you should have a pipe somewhere to the outside, which goes via a tundish, and you'll see water flowing thru that if anything is venting).

 

btw, it looks like your controller is still 'on' (light on top left of the Grant controller is lit - power for this comes from the external unit); so long as your room stats and DHW timer aren't calling for heating that's okay. However, I believe that pressing that button with the light on (at the top left of the controller) for 3 seconds switches off the HP. Well, it's still 'on' (getting power and frost protection etc will still run) but it won't try to do any heating  of house or water, even if it's asked for. 

Grant Aerona 3 10kW


   
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(@biagg)
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Topic starter  

@mikefl @allyfish Thanks for the replys.

 

I have cut off the Cold water, but the loft CW tank will still be full so i assume the HW tank will be full still. 

01 31 is now 10C (I've never checked it before)

51 07 is set to 0

I've noticed the pipe going outside but couldn't tell you if anythings been draining (it isnt now)

image

This is the box i was told to use if i needed to "top up" the heat of the HW tank, I've turned that off.

 

Its probably best with my knowledge as much i want to try,  is to leave it for an engineer on Monday.

But maybe if i stop the CW mains going into the loft CW tank (which feeds the HW tank and my shower)  in theory i should be able to turn the mains back on and use the sink/toilet? 

Edit:(Ignore the last part i think the tank also takes from the mains)

 

Thanks

This post was modified 4 months ago 2 times by Biagg

   
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