New heat pump Grant R290 - hot water advice

GSV3MiaC · 31 October 2025 14:58

Ah, an input from Grant technical folks which I will repeat here in case it is of use to anyone (and on the offchance it may be correct ). I inquired about the ‘setpoint temp correction’ parameter in the heat source setup options, and was told:

“The Set point temp correction is relating to a correction temperature to prevent overheating of a space. If you set this to for instance 2°c it will decrease your target flow temperature by this amount to try to help prevent the space overheating. This is more of a trial and error parameter where small changes make a big difference, my advice would be to leave it where it is if your heating is working okay.”

Not sure that makes sense, when we already have the ‘circuit temp correction’ (which increases target flow temp above the WC calculated value), plus WC curve shift options (which can go either way). It must only apply under some circumstance I haven’t figured, or have some effect beyond just winding the LWT target down a bit (which it doesn’t seem to, when I change it).

Maybe it only applies when pump blockade is off, and the room stat says ‘satisfied’, so this correction is applied as well as the reduction coefficient related to how far over/under you are? I have pump blockade on, so wouldn’t see it.

Durruti · 6 November 2025 08:59

Hey Dave,

So connecting up to the local econet api on Home Assistant I see the same pattern of oscillation over a 4 min cycle.

The image above is with a limiter of 70 on maximum pump speed. If I reset to default (no limiter/100) then I get the following.

Below is the same period on my heatpumpmonitor dashboard

Econet300 shows a range from 5l/m to 20l/m

My flow meter shows range of 12.1l/m to 23l/m but both show the same oscillation. I’m going to reinstate the pump limiter now as the 10l/m instant ramping up is very loud and will cause unnecessary wear on the pump.
@glyn.hudson do you have a technical support contact at Grant, I’m reluctant to go through my installer and bother him with what seems like an issue with the new firmware rather than commissioning.

MrW · 11 December 2025 15:55

Sorry to resurrect this and slightly change topic, but I’m wondering Matt (as you are the only person I’m aware of that has the newest firmware) are you able to fiddle with some settings and see if they work? I think you need the new firmware for them:

These ones are in service parameters (0000 password), all in “Main heat source”:

Purge power (think just lets you set a pump speed in % for manual purging)
Manual defrost (why not)
Reboot the unit

And these in service parameters (1234 password), all in “41 Heat Pump Settings”:

I think you’re already playing around with the pump speed so i guess you can change that.

I’m most interested in the fan speed settings

LeeNuss · 22 December 2025 09:28

Hey Matt, I had this pump speed oscillation issue as well and had someone from Grant around (due to a different issue but chatted about the pump speed as well). He said the pump speed oscillation comes from a protection mechanism. If the flow rate is too low while the compressor is running the pump will run at 100% for 2 minutes before dropping down to its normal PWM regulation/speed again.
This scenario can come up if e.g. your system is too restricted to reach the minimum flow rate at your minimum pump speed setting.
To fix the oscillation issue you need to find the sweet spot for this setting to be as low as possible while still reaching the minimum flow rate (I unfortunately forgot what the minimum for this is)

MrW · 23 January 2026 16:33

I rang Grant up, apparently the fan speed functionality isn’t available yet, seems like they are testing internally and then they’ll make it available. The person I spoke to said you wouldn’t need a firmware update on the ASHP itself, not really sure what the actual case is as you had yours upgraded Matt and I had heard previously that the purge function wouldn’t work until the actual ASHP firmware was upgraded, so who knows.

I did figure (from my own testing) that the fan speed when not on silent goes to 650rpm when below 5c ambient temp as measured on the ASHP itself, I wondered if the fan speed was more of a function of things like coil or suction temp but it lines up perfectly - as soon as outside temp drops below 5 the fan goes to 650, and when it gets back up to 5 it drops back to 500, so I assume the various H FAN SPEED settings are for fan speeds in normal mode at various ambient temp conditions. Will be great to get these - aware lowering fan speed would result in more defrosts but i dunno, 650 is very loud IMO

micks_address · 12 February 2026 14:54

hi folks, im looking at the grant 9kw r290 with a potential install date of early May. I’m curious about the hot water settings. Im sure my installer will know. We have a high gain joule hot water cylinder already. For water heating - we plan to heat the water during cheaper electricity rates at 2am. During the day then when the temp drops in the cylinder from usage with showers etc.. is there a setting on the Grant to bring the hot water back to a certain temp based on a the temp drop? For example lets say we heat to 50 degrees, can it trigger hot water heating if the temp in the middle of the tank drops to 40 based on temp sensor?

Thanks,

Mick

Dave_Storey · 12 February 2026 18:39

yes, yes, there is a hysteresis setting, up to 18c, when the Temp drops that amount below setpoint it will reheat, assuming hot water schedule is set on at that time. You have to experiment to find what value works for you. This assumes you have the smart controller, which you should.

Personally I cheat, I have a second temp sensor much higher in the cylinder, and use home assistant to use that to ‘manually’ trigger water reheat. Ideally you will get away with one heat to 50c or whatever in off-peak, but be aware your house temp will drop some during that time, and dhw heating is quite likely to trigger defrost if temp outside is low and humidity high.

glyn.hudson · 13 February 2026 00:38

No, there’s only one tank set-point setting. It’s not possible to have different tank set-point settings at different times of day. However, if the tank is sized correctly, it’s very unlikely you will run out of hot water. On the rare occasion if you do, you can trigger a manual boost.

Dave_Storey · 13 February 2026 07:08

I think you mean ‘not possible’ @glyn.hudson, but that wasn’t what he wanted, he wanted reheat at 40c, back up to 50c, which you can do by setpoint of 50c, hysteresis of 10c. With a setpoint of 50c, You can’t reheat to 40c, but you can reheat when it drops that far.

micks_address · 13 February 2026 08:36

thanks - i used to use home assistant and a clunky nest integration to trigger my gas boiler hot water for 30 mins on the old cylinder. Use to have a 120 litre cylinder but replaced that with a 200 litre heatpump ready high gain cylinder in december (largest we could fit in the space). 4 of us in the house so 4 showers would probably drain that. The home assistant integration is pretty solid for the grant? With nest there was all sorts of messing with tokens and cookies. Our cylinder has two pockets for temp sensors.. one in the lower middle.. which is currently occupied by a old school thermostat.. and a lower down one i think. i have two temp sensor probes from the myenergy eddi and im hopoing to be able to use at least one of those with the heatpump. for it to work on the heatpump controller i’ll need to leave the hot water cycle schedule on more or less all day? it wont kick in then until it needs to so wont use any energy? Glyn i watched your install video re the grant and its great. How are you finding it since installation? Any regrets going for the Grant over say some of the more expensive options? I’m in dublin and our grant has just increased significantly so should cover most of the cost to install. We don’t need a new cylinder and most of our radiators are pretty new and well sized. Semi detached house. Our installer came out to measure and is doing up the project in a i assume heatpunk or some other software. He seems well clued in anyway to the heatpump world.

Dave_Storey · 13 February 2026 12:39

The econet controller has almost everything available thru a local api (as well as web interface to the cloud) and has been (touch wood) rock solid. yes you can use ha and a ‘restful’ call to startdhw boost, set the desired temp, decide how much hotter you want the lwt to be, etc.

I leave dhw off, boost when I want it (50c at night, 45c if I reheat during the day) lwt 5c above in each case. I am well pleased with the Grant, the local accessibility is much better than most, it shows up on your home network and you just read or write if you want to. iIt also modulates well down, and max output is what it claims,or even better, even when defrosting every hour.

Only annoyances with mine, early firmware, it the oil recovery every 3 hours, which ramps the compressor up to 60hz, whatever the outside temp, and no control of water pump speed, and no quiet mode. New firmware is better, I must do the upgrade.

I swapped only one rad, in ensuite. 200 sqM bungalow, 1000ft up, design was 50c flow,at -3.8c ambient, but it actually runs at no more than 45c, even when it hit -5c briefly. Mostly idles at 400w in, 2.5kW out, 34c flow. I have 21kW (at DT50) of rads, so can only support flow temp down to 29c, without the pump cycling off. My dhw tank is 25 year old, copper, vented, 2sqM coil. Works fine, reheat is 45 mins or so.

fwiw,Octopus Energy are now offering the larger Grant Aeronas if they can’t meet the required output with their own ‘cosy’ models, whereas they used to push Daikin. I rate Daikin for aircon, but their a2w systems are, imo, second rate, especially the controls.

dmajwool · 15 February 2026 08:18

This is what is so frustrating : it must be possible for Daikin to issue new control software for existing systems that addresses the limitations and create a much better, more intuitive user interface.

glyn.hudson · 16 February 2026 22:38

Correct, I meant not possible, I’ve updated my post. Thanks

Anything is possible, using something like Home Assistant to do EcoNet REST API calls. The Grant heat pump must be the easiest heat pump to integrate and controll.

glyn.hudson · 16 February 2026 22:42

The SD card upgrade doesn’t change the oil recovery or allow changing the pump speed. Quite mode is a nice way to limit the compressor output. The oil recovery does not seem to adversely effect performance much.

Agree, I would avoid Daikin A2W. Although, the Cosy seems even worse.

Dave_Storey · 17 February 2026 18:55

Grant sent an sdcard for update but it was doa. I used your zip file (thanks) to roll my own, and ug went fine, apart from the aforementioned ahs temp sensor error. Grant really do need to learn sd cards need more than a,paper wrapping and envelope to survive royal mail sorting systems.

Now I just need to see what level of silent will work at what outside temperatures. (Another wrinkle we love, but Granny might struggle with).

Oh, in case you hadn’t spotted it the reported flow rate is now L/min, whereas it used to be 0.1 cuM per hr.

MrW · 17 February 2026 19:28

With the price of sd cards these days maybe they should just send the files via email!

MrW · 17 February 2026 19:29

Has anyone asked about getting a firmware upgrade on the ASHP? I would very much like to be able to use the fan speed settings

Dave_Storey · 17 February 2026 20:07

Would be nicer to do OTA update, many users won’t have the means to turn .zip files into sdhc cards. I had to hunt around for my adapters from raspi days, to confirm the card received was dead, and to burn a new one. Maybe the display doesn’t have enough inbuilt storage for (safe) OTA update though.

Dave_Storey · 21 February 2026 18:51

Just a brief update, I have home assistant automagically setting quiet mode off when LWT (target) is 45c or more (which covers DHW as well as freezing outside), I set it to high silence (40hz etc) when LWT target is 35c or less (summer running .. well today too, actually), and set it to quiet mode ‘low’ when LWT target is in range 38-42 (ish). In the gaps? I just leave it as it - hysteresis, sort of. That seems to work, but I may need to adjust it a bit (well, Home Assistant may need to).

I did think about setting it on time, or ambient, or wind direction, but LWT target seems sanest.

Another aside, I see that the ‘oil recovery ramp up’ every 4 (in my case 3?) hours is also limited to 40hz or 50hz, down from the usual 60hz. One assumes it still does the job, but in that case why not 40hz all the time??

Dave_Storey · 10 March 2026 16:59

Nice lad called Rhys Simmons came (from Shrewsbury) to update the heatpump firmware - took all of 60 seconds after he got the side off. While he was here he had yet another update for the display and controller (now SO24.29 and SO24.24) though not obvious I got any new functions from that.

He was impressed by the install quality, pipework, groundwork, and bricklaying!

The heatpump firmware update now allows water pump standby / low / high settings (as PWM %), though standby won’t go below 25% or low below 30%, so low (2.5kW heatpump output) still runs at 15L/min, down from 21-23 at the previous fixed 50%. Have yet to see if it modulates nicely (or at all).

No drama, all back to running as before. I now have it set at WC 1.1, shift -4, ‘room influence’ (or whatever they call it) x factor of 10 (ie 1c over on the room stat means 10c drop in flow temp). Set to 21c daytime, 22c at night (though to do that you have to reverse day and night, negative setback not allowed!)

However I am fiddling the curve, to use actual weather station ‘feels like’ temperature (which accounts for wind, as well as having a sensibly placed sensor - not on a wall), to use median house temps (from multiple sensors, rather than just the one) and to apply a fixed offset at night - I use the result of MY calculation to adjust the -4 shift to get the circuit1 target where I think it ought be.

Water pump power is down by about 10W, and DT has increased slightly, but is still <3c at low power outputs.

Rhys hinted that more firmware updates for the pump may be on the way, and that OTA update may arrive one day. We can hope .. sending engineer out for a 1 minute job (requiring special equipment) has got to be dumb.