Posted by: @allyfish

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@daveb Hi Dave, weather compensation is a must - and Grant should be enabling it on every MCS install. There's evidence from multiple Grant ASHP users this isn't the case. Here's the Grant installer literature for the Aerona3 ASHP, which you can easily download.

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It's a reduced version of Chofu's own manual, without the sections on cooling as that's not used in the UK, and so it is rather disjointed and awkward to follow as a result. The settings below in section 8.2.2 are what you need to check and adjust. There's only 5 4-digit parameters required to check.

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You need to access INSTALLER LEVEL on the controller to set up weather compensation. Press and hold the 3 buttons highlighted below for 3 seconds:

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Then you'll see the screen clear and: 'INST ----' appear. You're now able to use the - and + buttons as left and right and up/down arrow buttons to enter a 4 digit parameter. First one 2100 (enter 21 on the left, use the + move to the right, enter 00) press the tick and you'll see either a 0 or 1 display. If weather compensation is off you'll see a 0. Use the up/down arrow keys to change the value to 1 and press tick again.

You need to set these parameters to enable weather compensation:

2100 to 1

2102 to your maximum outgoing water temperature, say, 45degC (the higher you set this, the more energy you'll use, every 1degC increase is about a 2.5% increase in electrical input power. You want it as low as possible)

2103 to the minimum outgoing water temperature, 30degC

2104 to the minimum outdoor air temperature corresponding to the maximum outgoing water temperature, I would use 0degC rather than the -4degC default.

2105 to the maximum outdoor ait temperature corresponding to the minimum* outgoing water temperature, 20degC (*typo in Grant literature, they state  maximum, this is incorrect)

Once all is set, scroll through them all to double check, then press and hold the 3 highlighted buttons simultaneously again for 3 seconds to return you to the home screen. You can tweak the weather compensation to your heart's content. If you find the house overheats, lower the minimum outgoing water temperature. If you find it's not getting warm enough, raise the maximum outgoing temperature or the corresponding minimum outdoor ambient temperature at which this is delivered. It's a process of trial and error as every house & heating system responds differently.

 

Hi to All,

And great Info by Allyfish re the Grant controller.

We have a 17kw Grant ashp that was installed 3 years ago. I have found it a constant battle to get head n tail of the system until avisit from EHG.

 

Long story short it was commissioned by Grants and we were overloaded with information and told to leave it alone!! Sound familiar?

I decided I wasn't happy with the performance/astronomical electric bills so I did some investigation and earlier this year I had a visit from a local Elite Heat Geek.

Anyway the ashp is on, Weather Curve set to 35c flow temperature as apparently it was set by Grants to give full flow temperature. I now control our heating just via this controller and leave the thermostats just to look at to see what temperature is and no more. 

 

One thing that I may need is the EHG back, As our Hot water is not that hot. Any ideas how we can check to make sure we are getting the full temperature for hot water. 

 

Kind Regards

RB

 

 

 

Posted by: @allyfish

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One thing that I may need is the EHG back, As our Hot water is not that hot. Any ideas how we can check to make sure we are getting the full temperature for hot water. 

Hi @roamingbull. Another Grant unit 'commissioned' without WC enabled? There's definitely a pattern here. Grant are still coming out of the dark ages a little, and the 'we know best' don't touch mentality that has prevailed from some ASHP suppliers. The person who knows best how to set the heating up is the homeowner. The Chofu controller is not a very friendly user interface, but Grant are now partnering with Homely. Hooray!

The maximum hot water temperature is set by parameter 4130 in SERV service level access. It's defaulted to 55degC by Grant, but is adjustable up to 60degC. I've raised mine, the DHW supply at 60degC will charge a 250 litre tank in 1hour to 55degC whereas before as set to 55degC, the cylinder would never reach much above 51 or 52degC within an hour.

Service level is a bit of a faff to access, first you go into INST installer level, pressing and holding highlighted buttons above for 3s, then enter 9999 and press tick. A value of 0 appears, scroll this up to 738 and press tick. That gets you into SERV level. 738 is a not-so-secret access to service level, since Grant publish it! Now enter parameter 4130 and tick to check the value. Chances are its at 55degC. You can raise it up to 60degC in 1degC steps using the up and down arrows. 60degC is within the capabilities of the Chofu/Grant unit.

See page 46 section 9.6 of the Chofu installation manual for details.

PS: Silly question: when do you generate hot water with the ASHP? Force of habit for many heating engineers and homeowners is to do this very early morning, or overnight, perhaps before the heating kicks in. If you have a low overnight electricity tariff fair dos. If you don't, or have battery storage you can utilise, then schedule it early afternoon 1pm, when the outdoor air temperature is highest. Least chance of a defrost cycle mid-charge and highest outdoor air temperature for highest coefficient of performance.

@allyfish 

You do really have a handle on the Grant set up. Honest it drives me up the wall. TBH more so my wife as I'm out of the country and I'm always asking the wife for an update of temperatures etc :0))

The EHG was great and proof will be in the pudding this winter re consumption and comfort levels.

Great quote on heating the water as we do indeed heat throughout the night but are not on any special overnight tarrif!! So will reschedule once back home.

All I want is a system as per Grants instructions that I do indeed leave alone and not have to think about but it still feels like a never ending process and probably the reason ashp's get bad press. I see light at the end of the tunnel though with ours. Well fingers crossed I do.

Like I stated we have ours on a weather curve now that we just control on the 2102 as what information you gave earlier. Not sure on the other information in your post as I can't check atm.

Technically all I can tell you is that we have a 300m2 new build internal of an old building. Concrete floors UFH throughout including upstairs. 150mm insulation in the floors, walls and roof. Maybe more as plaster board was backed with insulation if I remeber rightly.

Any other things we could do to optimise our system? FYI I don't have it to set back on the heatmiser thermostats but just more or less they are just to see the tempratures.    

@roamingbull it's a lot of faff and trial and error. Partly that's because Grant install dumb systems with no intelligence and rather clunky external thermostats and timers for DHW and CH. it's very much obsolete technology and on/off controls from Y and S plan heating circuits.

That will all change with Homely and go a long way to improving efficiencies. Simple is best, and Grant could get rid of the low loss headers & secondary pumps for simple one zone home heating systems. They're robbing a little thermal efficiency and adding running costs, for very questionable technical benefit.

My ASHP was woeful this morning in the cold & damp frosty morning snap we're having, we switch it off 9pm and back on a 5:30am, which isn't very good as it takes an age to warm through from cold first thing in such weather, but we prefer the house cooler overnight and the Grant lacks a set back function. You can only do that on an external or the built in thermostat, but that starts to cycle the compressor on and off which isn't efficient. We've got wet rads and it's a retrofit system, so when it's not going into defrost it does warm up and respond pretty quickly. We probably would keep the unit on 24/7 at a lower supply temperature with UFH.

@allyfish 

Yes ours is on 24/7 now and see how we get on over the winter as per EHG information. By just adjusting the weather comp, like you state basic controls. TBH I'm not bothered regarding too much tech as I just want an easy system to live with.

There was only electric and no gas at the property so thought ashp was the way forward. We got full RHI just at the time so that is I think 400 quid per quarter.

Just out of interest I guess increasing the water temp from 55c to 60c will obviously cost more to heat the water? And I think you stated at 55c we will only get 51/52c?

Posted by: @roamingbull

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Just out of interest I guess increasing the water temp from 55c to 60c will obviously cost more to heat the water? And I think you stated at 55c we will only get 51/52c?

We were off mains gas and on oil, so wanted to get rid as the oil boiler was life expired. No regrets about going all-renewable, solar PV+battery and ASHP, but quite a learning curve.

You'll not get much warmer than 52degC water temperature when the ASHP is supplying at 55degC. The ASHP supplies a coil which transfers heat into the cylinder water, a rule of thumb is the supply water to the heat exchanger needs to be about 5degC warmer than the water in the cylinder to get efficient heat transfer. So supplying water at 60degC will raise your cylinder temperature to 55degC reasonably quickly. It'll cost a bit more in energy and electricity but not a massive difference. For average family hot water consumption the energy needed for your daily hot water is a small percentage of that needed for space heating.

@allyfish 

just had its first service by Grant into its second year of installation and it has made a difference, really informative and explained everything as he went along to try and demystify some aspects. 

Ours is set up through the garage and he changed some setting in regards to that. Reassuringly said we had a good set up and did a few tweaks ?increased

the fan speed? Reduced the timer on a separate water pump to decrease electricity usage as have long a long run of pipework from the cylinder to the bathrooms and advised to run the water through until warm (water cheaper than electricity...at the moment anyway).

Also advised to heat water for 4 hours a day broken up into 1 hour segments so it doesn't affect the heating too much (although the hive only allows 3 intervals set at 1.3 segments), again that has made a massive difference to the hot water.

Seems to be running more efficiently for now but we've had some sunny days to offset from the pv and not had too challenging cold snaps yet.

Invested in some supafoil and redid all the internal lagging over the summer, even in the long runs in the loft.

Long term looking at the my energi zappi? for the hot water, and dedicating the space in the garage to a proper insulated plant room.

I'm still getting spikes so will have a go at turning the hive thermostat up...although I don't want to overheat as I prefer to be cooler anyway or put a jumper on, although others in my household may disagree! 😀 

I meant to add because there are 2 10kw running side by side he also changed that set up so both would run at the same time rather than one run then call on the other one to supplement so think that has made a diffence.

@allyfish

I have been in touch with Homely and they say that it will be Spring 2024 before anything becomes available for Grant heat pumps.

@dodgyknee Yes, I'm wondering, well, hoping, that the homely interface is retrofittable to the Aerona3. The Aerona3 uses RS485 so fingers crossed. I would anticipate there's quite an efficiency advantage with Homely, especially for taking advantage of predicted weather and adjusting parameters accordingly. It depends on how much sophistication the first gen of Homely/Grant product has. There was a sneak peek on LinkedIn yesterday from Grant, it's pre-launch promotional level stuff, but it does look much more user friendly. Hey, it couldn't really be made harder than the Chofu controller. Graphics are somewhat clunky & amateur however, but nothing a good graphic artist couldn't make better. https://www.linkedin.com/posts/activity-7120060163910160384-kOYS?utm_source=share&utm_medium=member_desktop

@allyfish 

Thank you for all the information. When home May lift the hot water temperature up to see the difference. 
Regarding Homely guess best to get my EHG to carry out any changes regarding this as tbh I don’t have much confidence in Grant. But got a while to wait for this. 

will check the parameters you provided on the previous page too. 
Asked the wife to lift the flow temp to 35c and as we’ve had a frost or two the house is apparently sat at 21.5c. 
tbh a bit too warm for us but the MIL is staying. 
We have a log burner to complement too. 
Don’t have Solar or anything else just the Ashp. 

AllyFish maybe you can help.

So away and told the wife to up the flow temp to 35c last week as it started to cool off/frost outside. Was apparently 21c in the house after a day.

Anyway today she stated that the temps were down to 17.4c in the house and it's double figures outside. WTF is going on any ideas? This is what I find so frustrating with the ashp it seems to be far to much trial and error. 

So frustrating.

@roamingbull You running on weather compensation? If the house is too cold when it's milder and warmer outside you may need to flatten the WC curve a little and increase your minimum flow temperature. Customising the WC is trial and error as every house is different and how your heating responds is influenced by UFH vs rads or combination and how long each day it's switched on for, etc. 24/7 would give chance of the most stable control of course, but I find that's a little too warm for us overnight. Check these parameters for settings, values are the defaults:

2102 Maximum Water Temp °C 45 (default by Grant, set to 35°C for your system?)

2103 Minimum Water Temp °C 30 (don't set too low, for UFH +wet rad combined this is probably about right)

2104 Minimum Ambient Temp °C -4 (I was advised by Grant commissioning engineer to raise this to 0, which works for me)

2105 Maximum Ambient Temp °C 20 (above this value your heating will be disabled)