@mikeavison A secondary pump (like wot I have) might be fitted if there is a Heat Exchanger or a Low Loss Header in the plumbing interposed between the heat pump and the radiators / hot water tank. The debate over the need for a HE or an LLH has been given much coverage in this august organ so I’ll not say more, just that the secondary pump circulates the water in one side of the circuit whilst the heat pump’s primary pump supplies the water from the heat pump as far as the HE or LLH.

Regards, Toodles.

@toodles Hi , thank you for your reply, I definitely will have another word with homely tech support and thanks for your information.I am no heating enengineer but as i understand it if any heating circuit that has a buffer or a low loss header tank it will have a secondary circulating pump, so if the Homely tec guy is correct, they are excluding them selves from at least half of the market, very strange.

@mikeavison Hi, thank you for your reply, sorry for all the questions but I am trying to find out what your homely controls, could you tell me where circulating pump is located.

@potatoman Hi,

The pump pushes hot water around the rad circuit. Homely is wired into the Midea controller. The primary circuit is switched between a heat exchanger (rads) and a cylinder coil.

@mikeavison Thanks for a great picture, it helps me a lot.

I had a midea ASHP installed with homely at the time of installation by Evergreen two winters ago. Exact same setup as @mikeavison shows in his photos, there is a secondary pump for the rads, as Evergreen only installs the system with a plate heat exchanger so you have to have the second pump to drive the rad side loop. As far as I can tell, this is driven by the midea controls, not by homely, so it's a simple case of homely telling the midea unit 'provide heating' and the midea turns on both pumps.

A couple of things to mention about the homely system:

- It's really good! Don't let what I say next put you off, consider it more of a statement on how I had to adapt to using it.

- It isn't for quite a few of the people that inhabit these forums, namely people interested in monitoring and controlling the equipment themselves. I've a scientific background and was really interested in monitoring COP/SCOP and seeing behind the curtain, it took me some time to get used to the fact that this isn't really what homely is intended to do. As has been mentioned earlier, the two things homely does well is 1) take installer / user expertise out of the equation by essentially learning the compensation curve and profile of the house and 2) optimises *not for SCOP* but for cost-to-user. This is by far the most important thing to understand about homely in my opinion. 1) gets you as efficient a system as possible beyond the quality of installation, and 2) then modifies this to account for time-of-use tarrifs.

- The system works as mentioned by combining a small wi-fi connected computer that talks to the HP controls via RS232. This means homely has to reverse engineer whatever the manufacturer is making available on that bus, hence the limited support for different manufacturers. The homely computer also talks to a remote temp and light sensor that you put somewhere you'd normally place a thermostat. The light sensor part is because the unit does take into account solar heating to some extent (i believe based on their literature, it's a black box as far as how this is used). The third component is the app which lets you set your schedules for DHW and heating. 

- The app is very basic, it asks you what you want your DHW temp to be and when, and what temp you want your house to be and when. It's a little clunky as you can't eg: copy/paste schedules, you have to enter each manually for each day. Until recently my main beef with the app was that it didn't report the current DHW tank temp, but it has been updated to report this now, so I'm very happy with it.

- The main feature, that really makes homely worthwhile in my opinion is the time-of-use tarrif integration. It knows I'm on agile, and this works a charm: I've watched it preheat the DHW at the lowest cost point of the day, and it correctly preheats the house (within a user-specified comfort range) ahead of the 4pm price spike and the morning hump to make sure it isn't having to use as much power in the more expensive times. This is completely hands-off, no need to change your heating schedules or DHW usage, homely just does it. It has settings so that if you don't want it to preheat at night for cooler sleepers it'll avoid this (but obviously that comes with a slight increase in cost as it'll heat at times that are more expensive).

- The app has a 'holiday mode' that lets you tell it when you're away. It'll disable DHW and setback to 14C by default, though I tend to put it a little lower than this. It will preheat the house in time for your return, and usually starts the day before so it keeps the HP running slowly rather than blasting 55C rad temps an hour before you're in the door again.

- Minor quibbles: I wish the app gave you some more info to geek out on, like COP/SCOP, how many kW of heating / DHW you used over the last days / weeks and maybe graphs of temperature inside vs outside to explore, but again, we're not the target audience. During pricing plunges it'd be fun if even if you didn't need the DHW it was cheeky and topped off or fully heated your tank. When I'm on vacation if I get a negative price alert I'll boost the DHW to 55C from the app because I'd might as well kill some legionella and get paid for it.

The time-of-use aware mode is 25GBP/year, but after the installation cost if you use it in 'dumb' or no-TOU mode it's free. It has saved me I conservatively estimate about a hundred pounds over the last year in electricity bill, so I'm more than happy to pay that 25GBP for the TOU option.

Think Homely is a balancing act and really depends on a few things. TOU tariff is one, and not be able or wanting to take the time and set up things like WC. If you don't have a complex TOU tariff like agile, not sure i would bother.

Next winter will be my second heating season with the heat pump and it was only a couple of weeks ago, I got it running as it should (getting the compressor start/stop hysterisis correctly set). Tried every running method out there the first year. But this time it will be zero controls - other than WC curve. A temp gauge effectively to let me know if the curve needs tweaking.

My only control will DHW and a switch for cooling and heating change over. One circulation pump inside the ASHP.  Then left to get on with it.

Will also be flushing out all the glycol, using demineralised water to reduce pump losses and generally improve efficiency all round. No defrost valve either, not sure it's really required. Have battery and back up geny.

@starkers I had the Homely controller fitted as soon as it was available for my Daikin ASHP and Evergreen/Homely had written some code in to work with a secondary pump that feeds from the LLH to the rads. I have the controller set up for Cosy now as previously it was set to the Agile tariff. I have explained to their technical team that the TOU element is less important as I have Powerwall storage. I think that come the autumn, when it would be time to cough up if I wish to continue with their ‘+’ service, I’ll then speak to them again as I don’t think I need the extras at all.

Regarding the schedule setting, I have suggested improvements with copy and paste or whatever and they made a note to include this in the future. I also requested a few minor graphics tweaks for the visually impaired such as myself and that is being taken on board too.

I have had long discussions with the techies about the TOU and anticipatory  tweaks that Homely adopts ‘on the fly’ so to speak. I had found that the system tended to warm up at times (to make the most of TOU dips in energy costs) beyond what I really required [about 1.5 - 2 degrees above set level] Another factor for me was that our node is in our living room that faces North East, meanwhile the back rooms experience solar gain and we had a peak temperature spike mid afternoon. About that time, a techie explained that there was an option in the temperature tolerance to tighten the control to 1.0 degrees C (this was a recent improvement I think that I had not seen and had had ours set to 2 degrees C until then).

I am unaware of the light sensing element, is this part of the node or an add-on please? Altogether I am very pleased with the controller and yes, if you don’t care to know what is going on in heat pump land - then just trust it to do the job for you!

The Homely Technical Support granted me access to the installers app and using this, I can check the performance (COP but not SCOP, the history only allows about a fortnight or so and I have requested that they might increase the history memory but I haven’t heard any more on this yet. Now they have released ‘Connect’ as a full blown app for installers to monitor their installations they may have improved this. I will have to contact them and see if I can also use ‘Connect’ on my system for my own delectation!

Regards, Toodles.

Posted by: @johnmo

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Think Homely is a balancing act and really depends on a few things. TOU tariff is one, and not be able or wanting to take the time and set up things like WC. If you don't have a complex TOU tariff like agile, not sure i would bother.

I mostly agree, in that if you don't have a TOU tarrif and are sufficiently knowledgeable/willing to spend the time on it you can probably get the same or better performance from your ASHP as homely does, but I think we are in the minority in this forum- most homeowners will be coming over from condensing boilers that are much simpler and more forgiving, and most installers are still going to be pretty inexperienced when it comes to both configuring units and educating users on what they might want to fiddle with. Homely removes that part of the equation entirely which I think is a huge benefit to the average user. Since I like to know how the sausage is made, I'd also wonder if it was worth it without the TOU aspect but since I use that it's also nice to not worry if I'm squeezing every last drop of COP out of the unit because that's no longer the target metric to optimise.

Posted by: @toodles

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@starkers I had the Homely controller fitted as soon as it was available for my Daikin ASHP and Evergreen/Homely had written some code in to work with a secondary pump that feeds from the LLH to the rads. I have the controller set up for Cosy now as previously it was set to the Agile tariff. I have explained to their technical team that the TOU element is less important as I have Powerwall storage. I think that come the autumn, when it would be time to cough up if I wish to continue with their ‘+’ service, I’ll then speak to them again as I don’t think I need the extras at all.

Interesting- did they make any mention of future provision for optimisation including powerwall/solar? I know they had this in their marketing literature around when I was getting my HP installed. I can imagine it'd be hard to also include specific software integrations for all the different battery designs but worth keeping an eye on.

Posted by: @toodles

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Regarding the schedule setting, I have suggested improvements with copy and paste or whatever and they made a note to include this in the future. I also requested a few minor graphics tweaks for the visually impaired such as myself and that is being taken on board too.

I have had long discussions with the techies about the TOU and anticipatory  tweaks that Homely adopts ‘on the fly’ so to speak. I had found that the system tended to warm up at times (to make the most of TOU dips in energy costs) beyond what I really required [about 1.5 - 2 degrees above set level] Another factor for me was that our node is in our living room that faces North East, meanwhile the back rooms experience solar gain and we had a peak temperature spike mid afternoon. About that time, a techie explained that there was an option in the temperature tolerance to tighten the control to 1.0 degrees C (this was a recent improvement I think that I had not seen and had had ours set to 2 degrees C until then).

Yes- I've been keeping an eye on the house temperature trends using a little bluetooth device beside the homely sensor, and it does overheat the house by a few degrees when it's cheap to anticipate the setpoint you're looking for later. I was happy enough with the default of a couple of degrees because typically I'm not in just before 4pm when it does this. I did consider adjusting down if it got too uncomfortable at night when it was preheating for the morning, but I've not had a problem with it so far.

Posted by: @toodles

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I am unaware of the light sensing element, is this part of the node or an add-on please? Altogether I am very pleased with the controller and yes, if you don’t care to know what is going on in heat pump land - then just trust it to do the job for you!

I think it's on all the nodes, just not widely documented. From here: https://www.homelyenergy.com/introducing-the-homely-temperature-node/

The node can also monitor more than just temperature as it also reports on light intensity. The amount of sunlight that is entering a room can make a difference to the home’s heating needs. The node measures the light intensity and feeds back that data to the Homely Hub.

Posted by: @toodles

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The Homely Technical Support granted me access to the installers app and using this, I can check the performance (COP but not SCOP, the history only allows about a fortnight or so and I have requested that they might increase the history memory but I haven’t heard any more on this yet. Now they have released ‘Connect’ as a full blown app for installers to monitor their installations they may have improved this. I will have to contact them and see if I can also use ‘Connect’ on my system for my own delectation!

Regards, Toodles.

I'm jealous- I asked them once if I could get installer app access to my installation but they didn't seem too keen to give it out. If you know the magic words to get them to agree please share 🙂

@starkers That’s very interesting, I had not known about the light sensing feature - as you say, not widely documented! I suppose it must have a means of sensing wavelength so as not to be influenced by artificial lights; though even then, there are lights emitting at over 5000 Kelvin, 

Regarding access to the installer app, at the time I enquired about purchasing Homely, they were keen to enlist a few users to provide feedback on the development and improvements etc. When I heard about the installer app, I enquired if I could use it - not to tamper but to monitor and learn! Their very laid back rep. said ‘I see no reason why not’. and authorised it for me. So, sorry, I don’t know the magic words I’m afraid. Whether they will allow me access to the all-new shiny ‘Connect’ I don’t know, I’ll have to email them and see how it goes. Regards, Toodles.

Watching a short video that Homely sent with the blurb about their new ‘Connect’ installer’s app, I came across this presentation which may interest anyone wishing to know more about the Homely controller.

Regards, Toodles.

@johnmo 
> Will also be flushing out all the glycol, using demineralised water to reduce pump losses and generally improve efficiency all round. No defrost valve either, not sure it's really required.
For your Heat Pump Warranty to be valid, it's highly likely they require either glycol OR an anti-freeze valve to be fitted. You might be ok to do this, but might invalidate any future warranty claim. Removal of the glycol will improve the water specific heat capacity (i.e. allow the same volume of water to carry more heat).