Posted by: @pash44pump

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@jamespa thank you. The "incentive" for using the original installer is that because they accept that they put in an undersized HP at the outset, they have agreed to replace it with a new HP at their cost (kit and installation). The downside is that they are being prescriptive on what they want to fit so I'm trying to find a reasonable compromise. 

Regards

 

 

Ok given that history they aren't going to risk under sizing.  I made a couple of suggestions above.

Is it really impossible to fit R290, the rules aren't quite as restrictive as some claim

Suggestions noted thank you

Just one more thought.  If you have convenient space for the 20kW cascade and your installer is paying then it possibly isnt a bad option.  Most of time only one will be running, possibly at a slightly better efficiency than would be the case with a single larger unit.  You almost have a spare.  Depends on the plumbing of course but if you have plenty of otherwise unused low grade space and the additional cost is paid for by the installer perhaps this shouldn't be ruled out.  Annual service might be double though so mind that.  

@jamespa it's a difficult decision. I am being offered either 2 x 10kW Clivet in cascade or a 17kW Grant R32 Aerona. I tried to get them to provide a Grant 290 15.5kW which meets the 14kW Heat Loss Estimate. As I said before, they won't put anything in that can't do 14kW at 50C flow and -5C OAT because those were the parameters used in the Heat Loss Estimate and given they undersized first time, they are now covering their behinds to ensure that I hit desired internal temps.

The 290 protective zone restrictions I think mean I don't have enough space for one on current siting.

I have concerns about cascade because I'm not impressed with the competence of the installer and 2 x heat pumps operating together suggests a lot more things to get wrong on the installation. However, I am aware that the operation of the Grant at milder temperatures is going to be less efficient than a lower-rated pump that can probably heat our house to desired temperature (given my estimate is 11-12kW of actual heat loss max at very low OAT) and indeed lower than the cascaded heat pumps. 

I can try and get them to do 2 x smaller Grants maybe, no harm in trying. The Clivet (rebadged Midea) doesn't seem to have the best reputation and the monitoring capabilities of the Midea controller I have are absolutely awful so I don't really want that brand as a replacement. @benson did you get Homely on your recent install because the Clivet controller is still poor?

For anyone who has a cascade, what do I need to ensure if I go down that route in terms of installation and setup, which is different to a single ASHP system?

Regards

Posted by: @pash44pump

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The Clivet (rebadged Midea) doesn't seem to have the best reputation and the monitoring capabilities of the Midea controller I have are absolutely awful so I don't really want that brand as a replacement. @benson did you get Homely on your recent install because the Clivet controller is still poor?

@pash44pump I have yet to come across any Clivet or Midea complaints aside from the control panel side of things. There was one post on here a few weeks back regarding a recent Clivet install and I believe they had installed their new Clivet controls which weren't working properly (that is the thread you are probably remembering as their solution was to install homely). The units themselves are fine.

If I could do it all again for our house though I'd ask why not just Midea as they are essentially the same units and the Mideas seem to be a fair bit cheaper.

If you dislike the midea controls then that is obviously a key element to consider as unless you like the look of homely your options are limited- the in house solutions, whether this be the midea app, or clivet options perhaps aren't great (or at least the latter may have some teething problems it would appear). I have grown to like ours as it has been very easy to connect to home assistant via modbus and create lots of graphs and customise controls, but appreciate most people probably just want a simple app where they set their preferred IAT.

As for homely we've found it better to just run pure weather comp- seems a bit more efficient and heating output is steadier. If you are looking to exploit time of use tariffs then it is worth a look.

@curlykatie did you get sorted with this?