Grant ASHP

[Mike_scotland]

Hey group,

 

My builder has been telling me for months of our build he is purchasing us a vailliant or daiken heat pump.... now this morning he has said its going to be a Grant aerona or something....(fiest i heard)  has anyone heard of this manufacturer? 

[JohnMo]

Heard of them, if you look on eBay there is one going quite cheap , not sure if it matches what you need.

[ProDave]

Grant were traditionally a respected make of oil fired boilers who relatively recently have branched into ASHP's and hybrid boilers.

[Mike_scotland]

15 minutes ago, ProDave said:

Grant were traditionally a respected make of oil fired boilers who relatively recently have branched into ASHP's and hybrid boilers.

Do we know much about them? 

[ReedRichards]

Grant is a UK manufacturer; they gave me a quote when I was looking for heat pump in 2020.  They were also the favoured choice of two Scottish companies that (over?) sell heat pumps with teams of fitters to do the installation.  Possibly Grant heat pumps are not terribly sophisticated because oil boilers are not terribly sophisticated.  They also make aluminium radiators (of which I have two).

[Mike_scotland]

14 minutes ago, ReedRichards said:

Grant is a UK manufacturer; they gave me a quote when I was looking for heat pump in 2020.  They were also the favoured choice of two Scottish companies that (over?) sell heat pumps with teams of fitters to do the installation.  Possibly Grant heat pumps are not terribly sophisticated because oil boilers are not terribly sophisticated.  They also make aluminium radiators (of which I have two).

Did you go with them if bot why and who did you go with

[SteamyTea]

They have been discussed on here quite a bit.

Do a search for them. I think one person has had one for quite a few years.

[Mike_scotland]

Are all heat pumps the same? Like a diaken 13kw be same as a nibe 13kw per say

[Kevm]

Here is some info about Grant ASHPs from a user on another forum.  I've just cut and pasted it so no guarantees...

 

 

I was in exactly the same situation 3 months ago - lead times on the Ecodan cylinders were out to 12 weeks and we couldn't wait.  So we went with the Grant 13kW. House is about half the size of yours, radiators, TRVs, oil boiler, Cambridgeshire.

The installer recommended the 10kW Grant but I went for the 13kW as it's double fan and supposedly quieter (and the actual spec sheet says they are respectively 10.5kW and 11.4kW at 55C, which is more realistic since we have radiators - so the 13kW isn't actually massively more powerful, although the flow rates are higher).  It remains to be seen how it copes in spring and autumn when only a little heat is required, but in winter it seems to be coping fine.

Now, the Grant heat pump seems to be a good unit.  It's made in Japan by a company called Chofu Seisakusho Co. Ltd - Grant buy them from a European distributor and rebrand them. From what I've seen of the unit and the documentation it seems to be good build quality.  I've been curating some documentation here - the Chofu installation manual, service manual, etc and marketing information from other countries.

The problem is that Grant is really an oil boiler company, and they want a heat pump to behave like a boiler, which it isn't.  My install is absolutely by the Grant book, the problem is that Grant took the perfectly good English installation instructions from Chofu, deleted lots of stuff (it should do cooling, which they don't admit to.  I enabled the cooling button, but can't really test it in winter), and added a relay box to interface it to UK on/off boiler controls.

The trouble is that on/off thermostats aren't good for heat pumps - my installer provided a Honeywell Lyric controller which does TPI.  TPI is a way that, by default, it looks at every 10 minute period and decides how much the boiler should be on. Result is that it turns the boiler on for say 3 minutes, then off for 7 minutes, repeatedly throughout the day.  You can set that back to 20 minutes, but can't turn off TPI. This is terrible for heat pump efficiency. With some great help from a heating engineer who installs these, we managed to reverse engineer the Modbus protocol, which is a way of logging data from the heat pump, and I'm now logging this into Home Assistant.  That shows me how spiky things are:

I have, just today, figured out how to revert to the Chofu room controller (ie cutting out the Honeywell and using the heat pump's own room thermostat) and am doing some experiments as to what difference it makes. Removing the Honeywell out of the loop completely is going to require some minor rewiring of pumps and valves, but I have just tried things temporarily as a test for now.  I should get a better feel over the coming days.

We also have some noise issues which might be being caused by TPI's constant switching on and off, or might be something else (there was terrible noise to begin with, because there was loads of air in the system). The heat pump is currently mounted next to the kitchen, so about a metre from the kettle with a window adjacent, which means it is audible inside. A family member is very noise sensitive so the contingency plan is to move it to the bottom of the garden, if my tinkering can't improve matters.  From measurement the noise is in spec, but there are certain points in the spinup curve where it buzzes (another thing to investigate).

Another thing is that Grant have switched from installing a buffer tank (that we have) to a low loss header.  I'm sure some more plumbing-knowledgeable folks can comment on this, but I know plumbers familiar with the units are not impressed (read the Twitter replies) - I defer to more experienced folks, but seems to be just another thing Grant doing backwards to make it look like a boiler.

One other thing is that the way Grant plumb in the buffer isn't good for doing cooling - it should work, but be less efficient.  Investigating that is for another time of year...

The Honeywell does have the ability to be controlled by an app, the Chofu natively doesn't*. Since I have Modbus up and running on Home Assistant I'm thinking of doing something in that area too, not sure quite what. I gather some of the other heat pump vendors are better in this respect.

* Chofu the company also sells oil boilers and those can have controllers with apps which look very similar to the ASHP controller - maybe they will talk to it? But they would probably be in Japanese...

On the flip side, it works, it heats, the hot water is great.  On a cold January day (daytime maybe 3-5C) we're probably using 30kWh per day for heating, on a warmer one a lot less.

So I think you can get a better outcome if you can avoid some of the installation problems (buffer not LLH, use the room controller or put in a smart thermostat that will run the heat pump for long periods not pulse it), use the heat pump to control the pumps and valves rather than the thermostat.  I understand the price wholesale is quite good, which might be why installers like them.

According to the Grant person on that Twitter thread:

We are more than happy to let installers like yourself install how you want to and to get the best out of the systems they install. In fact we have embraced many more installers with our new offerings which include 3 port direct systems using our controller to maximise efficiency

Just to be clear - you Don’t have to fit the units this way. If you are an experienced engineer and are sizing systems correctly we have no issues with you fitting it to your preferred suitable method.

so it is something they are happy with, but your regular plumbing and heating engineer is going to install it like a boiler, and that's not so good.  It works and all, but it could be better.

Bottom line: would I do it again?  Depends how much money is at stake.  In our case we didn't have a lot of other options (the oil boiler had been condemned a year before and finally expired a few weeks before installation), and I think I probably would. Basically it was a calculated gamble, with various things I didn't know (noise, controls, cooling enablement) but thought were worth the risk, and some within my competence to address. I don't have final answers on those yet, but they are looking promising - I don't think there's any showstoppers.  (In the worst case, moving it will be most work, but we get to rearrange the garden which needs doing anyway). On the other hand it has become a bit of a 'project' - if somebody was offering me an Ecodan for a few hundred quid more I probably would still take it (although it's possible noise etc issues would still apply)

 

[ReedRichards]

7 hours ago, Mike_scotland said:

Did you go with them if not why and who did you go with

 

I thought the companies offering a Grant heat pump were being over-optimistic about savings that this could achieve by comparison with my oil boiler.  Nor did I like their impersonal service using teams of fitters roaming Scotland.  And I wanted more than just a heat pump and radiators, I also wanted to re-route a lot of my heating pipes.  So I went with a contractor that could offer me a personal service, quote for all the work I wanted and was prepared to admit that it was a close-run thing to save on running costs.

 

By the way I see nothing wrong with TPI per se but you have to be able to limit the number of cycles per hour.  I was just helping a relative set up an oil boiler controller with TPI and I set it to 3 cycles per hour because an oil boiler is another type of heater that you don't want to be on for just a few minutes at a time. 

[Mike_scotland]

Soooo im speaking to my builder and his mcs registered contact and there now suggesting a 10kw grant heat pump, i asked for the hear calcs and was told there going by a basic 45w per m2.... this is making me feel a tad uneasy

 

Any advice

[Mike_scotland]

On 06/02/2022 at 14:26, Kevm said:

Here is some info about Grant ASHPs from a user on another forum.  I've just cut and pasted it so no guarantees...

 

 

I was in exactly the same situation 3 months ago - lead times on the Ecodan cylinders were out to 12 weeks and we couldn't wait.  So we went with the Grant 13kW. House is about half the size of yours, radiators, TRVs, oil boiler, Cambridgeshire.

The installer recommended the 10kW Grant but I went for the 13kW as it's double fan and supposedly quieter (and the actual spec sheet says they are respectively 10.5kW and 11.4kW at 55C, which is more realistic since we have radiators - so the 13kW isn't actually massively more powerful, although the flow rates are higher).  It remains to be seen how it copes in spring and autumn when only a little heat is required, but in winter it seems to be coping fine.

Now, the Grant heat pump seems to be a good unit.  It's made in Japan by a company called Chofu Seisakusho Co. Ltd - Grant buy them from a European distributor and rebrand them. From what I've seen of the unit and the documentation it seems to be good build quality.  I've been curating some documentation here - the Chofu installation manual, service manual, etc and marketing information from other countries.

The problem is that Grant is really an oil boiler company, and they want a heat pump to behave like a boiler, which it isn't.  My install is absolutely by the Grant book, the problem is that Grant took the perfectly good English installation instructions from Chofu, deleted lots of stuff (it should do cooling, which they don't admit to.  I enabled the cooling button, but can't really test it in winter), and added a relay box to interface it to UK on/off boiler controls.

The trouble is that on/off thermostats aren't good for heat pumps - my installer provided a Honeywell Lyric controller which does TPI.  TPI is a way that, by default, it looks at every 10 minute period and decides how much the boiler should be on. Result is that it turns the boiler on for say 3 minutes, then off for 7 minutes, repeatedly throughout the day.  You can set that back to 20 minutes, but can't turn off TPI. This is terrible for heat pump efficiency. With some great help from a heating engineer who installs these, we managed to reverse engineer the Modbus protocol, which is a way of logging data from the heat pump, and I'm now logging this into Home Assistant.  That shows me how spiky things are:

I have, just today, figured out how to revert to the Chofu room controller (ie cutting out the Honeywell and using the heat pump's own room thermostat) and am doing some experiments as to what difference it makes. Removing the Honeywell out of the loop completely is going to require some minor rewiring of pumps and valves, but I have just tried things temporarily as a test for now.  I should get a better feel over the coming days.

We also have some noise issues which might be being caused by TPI's constant switching on and off, or might be something else (there was terrible noise to begin with, because there was loads of air in the system). The heat pump is currently mounted next to the kitchen, so about a metre from the kettle with a window adjacent, which means it is audible inside. A family member is very noise sensitive so the contingency plan is to move it to the bottom of the garden, if my tinkering can't improve matters.  From measurement the noise is in spec, but there are certain points in the spinup curve where it buzzes (another thing to investigate).

Another thing is that Grant have switched from installing a buffer tank (that we have) to a low loss header.  I'm sure some more plumbing-knowledgeable folks can comment on this, but I know plumbers familiar with the units are not impressed (read the Twitter replies) - I defer to more experienced folks, but seems to be just another thing Grant doing backwards to make it look like a boiler.

One other thing is that the way Grant plumb in the buffer isn't good for doing cooling - it should work, but be less efficient.  Investigating that is for another time of year...

The Honeywell does have the ability to be controlled by an app, the Chofu natively doesn't*. Since I have Modbus up and running on Home Assistant I'm thinking of doing something in that area too, not sure quite what. I gather some of the other heat pump vendors are better in this respect.

* Chofu the company also sells oil boilers and those can have controllers with apps which look very similar to the ASHP controller - maybe they will talk to it? But they would probably be in Japanese...

On the flip side, it works, it heats, the hot water is great.  On a cold January day (daytime maybe 3-5C) we're probably using 30kWh per day for heating, on a warmer one a lot less.

So I think you can get a better outcome if you can avoid some of the installation problems (buffer not LLH, use the room controller or put in a smart thermostat that will run the heat pump for long periods not pulse it), use the heat pump to control the pumps and valves rather than the thermostat.  I understand the price wholesale is quite good, which might be why installers like them.

According to the Grant person on that Twitter thread:

We are more than happy to let installers like yourself install how you want to and to get the best out of the systems they install. In fact we have embraced many more installers with our new offerings which include 3 port direct systems using our controller to maximise efficiency

Just to be clear - you Don’t have to fit the units this way. If you are an experienced engineer and are sizing systems correctly we have no issues with you fitting it to your preferred suitable method.

so it is something they are happy with, but your regular plumbing and heating engineer is going to install it like a boiler, and that's not so good.  It works and all, but it could be better.

Bottom line: would I do it again?  Depends how much money is at stake.  In our case we didn't have a lot of other options (the oil boiler had been condemned a year before and finally expired a few weeks before installation), and I think I probably would. Basically it was a calculated gamble, with various things I didn't know (noise, controls, cooling enablement) but thought were worth the risk, and some within my competence to address. I don't have final answers on those yet, but they are looking promising - I don't think there's any showstoppers.  (In the worst case, moving it will be most work, but we get to rearrange the garden which needs doing anyway). On the other hand it has become a bit of a 'project' - if somebody was offering me an Ecodan for a few hundred quid more I probably would still take it (although it's possible noise etc issues would still apply)

 

Did you get proper heat calcs carried out? Im getting told a 10kw will do? 

[Kevm]

It's not me; I just C&P from another forum. The guy in question was going for RHI so he would have had a full heat loss calculation done

[Ommm]

Haven't been on here for a while, but that's my text cut and pasted from above.

 

Full heat loss was done, came to about 5kW if I remember, which i was a bit dubious about. I did the calcs myself and it came to 8kW.  So I think 10kW would have handled it. But the 10kW Grant is 3dB noisier than the 13kW and noise was a critical factor in our install. Also, we have to have the house dead silent at night so we have to start the ASHP from cold in the morning (we don't turn it off but setback to maybe 13C at night time so it only kicks in when it's really cold) - the 13kW should in theory be able to warm it up faster, although it's no gas boiler.  Probably take a hit for efficiency but it modulates down (by default) based on return temperature, so if the emitters can't emit it won't consume so much power ('normal' electrical power is about 3.5kW when it's on (eg in DHW mode), going down to about 1.5kW based on return temp and weather compensation).  The price delta wasn't very much and am generally happy with that choice.

 

TPI is a problem because it takes the first maybe few minutes of 'on' time spinning up, only for TPI to then tell it to turn off again a minute or two later.  Which makes it noisy and maybe interferes with the modulation.  On the Lyric the best I can set it to is 20 minute TPI periods, which is better than the defaults but still not ideal.

 

I'm happy with it as a unit; it works; I'm happy with the efficiency; it is generally configurable if in not the most user friendly way; the way it has been installed could be better. Which is partly the fault of the 'it's a boiler' mindset rather than a problem with the unit itself.

[ReedRichards]

2 hours ago, Ommm said:

...the 13kW should in theory be able to warm it up faster...

I'm not convinced that is significantly true.  Once the water reaches its set temperature the speed with which the building warms up is entirely down to the heat emitters, the radiators and/or UFH.  In my case this takes about 15 minutes from cold; I might be able to shave 5 minutes off that with a bigger heat pump but what's 5 minutes?  Whilst the building is much colder than usual then delta T will be a bit higher than usual but with a nighttime set-back it probably won't be more than 20% so I suppose you could size your heat pump 20% higher than you think you need.  After you have reached temperature if you want a building that warns up more quickly you oversize the heat emitters (radiators) and/or you set the water temperature higher than it would be in its steady state.  The former would make your heating system more prone to cycling and the latter would hit your efficiency.  And the latter you could only do if you have Load Compensation or you intervene manually.     

[PhilC]

Researching grant Aerona as part of renovation, looking at that Chofu document the COP is different (4.30) on the 12XU ( I presume the 13kw grant unit). The grant lists this as COP 5.25 with the same air/water temp. The MCS site shows the SCOP listed in the grant document. At 5.4 SCOP the Aerona seems ahead of the field if I am understanding that right, but if the Chofu document is correct then its average to slightly subpar for the R32 based ASHP. Looking at the MCS test certification process it looks like they take evidence from the supplier rather than conduct tests themselves. I am misunderstanding something here or could the MCS details be wrong?

 

I am hoping to use the system for some amount of cooling in the summer so would be interested Kevm how that would be best achieved in your view. Had a bit of a research on buffers/volumisers/LLH. If I have a large open loop in the system (probably ground livingroom+open plan kitchen area ~60m2) then would i not necessarily need one? Even if I have other controlled loops. As this is largest ground floor central space, its unlikely it would not need heating/cooling if the system was running.

[Ommm]

I don't know the details, but I think the test conditions and hence the COP are different in each jurisdiction. MCS is the UK test cycle, but eg New Zealand has a different test cycle and the datasheet for that may come out with slightly different numbers.  I think that's why the unit is 13kW in the UK and 12kW in New Zealand.  For example the SCOP may differ if the test cycle has a different number of degree days, which it's highly likely to do given a different climate.

 

I can't really answer your question on cooling, but AIUI you can get away without a buffer if you can match input and output heat flow.  If you do the heating design right, that's possible.  But you'd need to ensure that also applies for cooling.  I would worry for cooling with UFH that all your cold is going to sit next to the floor (a bit like a convection oven upside down - hot air at the ceiling, cold pumped in at the floor), which would reduce the cold flux out of the water loop.  The risk is that without a buffer there's nowhere for the cold generated by the heat pump to go, so all it can do is turn off (otherwise it'll freeze), which causes short cycling which is inefficient. With a buffer you have more volume in the system and, while it'll cycle, the cycling will be less frequent. 

 

If you were to have ceiling fans I suspect that would help with air mixing, like a fan oven.

 

That's just my guess though, I'm only an amateur - happy to be corrected by somebody who knows better than I.

[ProDave]

I finally have just a little to add to this thread.

 

A few weeks ago I wired the heating of a house having a Grant Aerona ASHP.  I believe the one fitted was the 10kW version, though it was not that obvious exactly what power it was.  A few random observations not in any particular order.

 

From a wiring point of view it was easy. Mains power, a 2 core cable to connect the supplied controller, and "call for heat" inputs for heating and hot water.  A wiring centre was provided to connect the motorised valves, thermostats etc together, all pretty well documented.

 

It also came with a "volumiser" that appeared to just be an over sized willis heater with an immersion heater.  I don't quite understand what this brings to the party other than it is a 3kW electric water heater in series with the ASHP that it can turn on when it wants to.  It talks about being an emergency heater?

 

I didn't do the plumbing for this and I am not sure I agree with how it was plumbed, no external pump used by the plumber just relying on the pump inside the ASHP to circulate the water around the UFH and to the HW tank.  But it did appear to work.

 

I did not spend time delving into settings, so it was left running with default parameters. 

 

It heated the 300L DHW tank from stone cold to 50 degrees in 2 hours. By default it gives priority to DHW switching back to UFH when the tank is satisfied.

 

The outdoor unit was both smaller and quieter than I expected, no complaints there.

 

Unlike some other ASHP's it does not have a temperature probe in the HW tank.  It only knows the DHW is satisfied by a conventional cylinder stat opening.

[Ommm]

It can have a thermistor in the DHW tank (and in the buffer tank) - Grant just don't tell you to do that.  You just have to wire it to a couple of pins on the interface board and flip a config setting to enable it.  The key specs according to the service manual are:

 

NTC

Resistance at 25C: 10K +/- 1%

Beta (B25/85) = 3435K +/- 1%

 

I bought a pair of these:

https://www.aliexpress.com/item/32882640194.html

and have 3D printed a widget to mount them in the tank bosses.  I haven't completed the wiring to enable them yet.

 

It can see the return temperature when in DHW mode, which gives it some idea of the DHW temperature without the external stat or sensor.  (the blizzard of superfluous wiring Grant add to it is really confusing IMHO - the ASHP does all of this stuff internally)

 

Previously Grant told you to use a buffer, which made some kind of sense to my untrained ears for hydraulic separation (at some loss of efficiency).  I think your volumiser is purely increasing the amount of water in the circuit, ie no hydraulic separation between ASHP and emitters?  No external heat exchanger? I know some heating engineers weren't very impressed with changing from buffer to LLH.

 

The immersion in the volumiser (or buffer) is an emergency heater which may come as standard - on my buffer it's not wired.  I think that's good: some of the moans about 'ASHPs are so expensive to run' are because the backup heater has kicked in for whatever reason and the householder hasn't noticed.  I would much rather be cold and light a fire on a freak -15C night than have the ASHP inefficiently gobbling electricity.

 

The ASHP does have means to control both a backup heater and an immersion for legionella, but in the standard wiring Grant don't enable those - instead they have a really clunky relay and timer arrangement for the immersion (I'm wiring a better solution for that...)

Edited October 6, 2022 by Ommm

[ProDave]

28 minutes ago, Ommm said:

I think your volumiser is purely increasing the amount of water in the circuit, ie no hydraulic separation between ASHP and emitters?  No external heat exchanger? I know some heating engineers weren't very impressed with changing from buffer to LLH.

I saw the instructions for the volumiser and it could be piped as in this case in series with the ASHP, or a slightly more complex way using ports on the side it could be configured as a low loss header.  The plumber chose the simple way using the top and bottom ports.

 

Yes there are a lot of terminals in the electrical connection panel so lots of extras and options you can configure, but it could end up with a lot of wiring between the ASHP and the house.

[PhilC]

I had a response from MCS saying they wont comment on how the wholesaler determines the COP of a product. But, they did confirm to become MSC certified the product has to be sent to a certification body, in this case the BBA. Its they who list the COP on the database. Your comment on having different COP in different regions makes sense, although the tests are performed with given air and water temperatures (which are the same on the Chofu details), so that still make we scratch my head, would have to dig down into specific testing details to understand. Its seems irrelevant though as long as the BBA is applying testing consistently and results for those products listed is relative, which I don't have any reason to doubt.

 

Thanks for thoughts on volumizer/LLH etc. I've been watching the heat geek vids on utube mostly seems to suggest LLH are not great for efficiency and a lot of installs contain unnecessary stuff. I would like to just throw this issue to a heating engineer but i am dubious i would necessarily get the design that's in my best interest. Also i am looking at KNX and home assistant integration so i will need to understand the control points in enough detail to do that.

Edited October 6, 2022 by PhilC