@iantelescope 

That's some 'say hello and introduce yourself' post!

It's also a travesty how the industry has treated you.  I wish you luck.

@iantelescope I had a remarkably similar experience (though I am happy with the heat pump itself).  I ended up taking my installer to court but Travis Perkins bankrupted them through the courts at the same time so no money received.  There seems to be some right cowboys out with toothless tigers watching overt them.

Obviously (as this thread proves) system design, installation and commissioning are massive factors in getting a usable heating system. 

Are there any current market ASHP manufacturers or models that people would just absolutely recommend people avoid? (e.g. wouldn't meet their stated performance even in an ideal install / notoriously prone to failure)

E.g. There appear to be lots of posts on here with issues on Ecodan systems. Is the kit itself good/fine just issues down to the installers and complication of getting where you want to be with the controller? 

(I'll be honest I had one desktop quote that recommended an Ecodan and I was put off by two main things 1) the installers desire to use the associated preplumbed cylinder with separate plate heat exchanger and extra pumps 2) marketing material / videos based more on a marketable face / fluff pieces / generally selling the idea of an ASHP rather than this ASHP) Trying to gauge if I was unfairly dismissive

Also I've seen articles (on here and elsewhere) advocating a LLH/Buffer/superfluous pumps free installation philosophy where 'you just let the HP controller to do its thing'. Am I correct in thinking pretty much all current models are inverter HP's in so far as the compressor speeds been varied (not on / off)? But not all having variable pump speeds? If anyone has a link to a good list of fully variable ASHP's that would be much appreciated. 

I am about to order a Vaillant but Mitsubishi Ecodan was on my short list and I would have been equally confident if that had been the best match.  There are plenty of posts here and elesewhere from people satisfied with their ecodans. Furthermore they publish lots of technical detail, unlike some, and also unlike some they will answer technical questions when you ask them rather than fobbing you off with 'ask your installer' or simply ignoring you.

Installer desire to use preplumbed cylinder and add in lots of extraneous parts is common.  Pre-plumbed cylinders allow them to use cheap labour to put it together, and the extraneous parts whilst sometimes necessary are more likely backside covering.  Find another installer. 

So far as I am aware all heat pumps from major manufacturers now modulate, but its not always easy to come by figures.  When they are quoted they often quote modulation ratio at a given temperature, which is not the interesting number.  The interesting number is the max output at OAT = -2 (or whatever your design OAT is) vs the min output at OAT = say 12.  3:1 is doable, some manage only 2:1.  beware that several manufacturers, particularly those who apparently do lots of models, actually produce rather fewer hardware variants and simply software limit the max output.  This of course has a negative effect on modulation ratio (which they try to hide) because the minimum output for the lowest in the otherwise equal models is the same as the minimum output for the highest in the otherwise equal models.  

Because of limited modulation range heat pumps should not be oversized (there is actually some evidence that slightly undersizing them is preferable).  Again installers try to get round this by adding buffers, which allows them to be sloppy with sizing and well oversize.  Its probably the case that the installer who quotes the pump with the smallest output and fewest add on parts is the one of the better ones, because they have (probably) thought about it.

@declan90

Now in my 14th month in trying to get my Samsung 5kw heat pump working I am still faced with a constant cycle time of 10.5 mins no matter the load.

My heat pump was "designed" for a 6 kW Heat pump with my "installer" installing a 5 kW Heat Pump.

My Samsung Compressor motor is frequency modulated to control the Heat Power.

My Samsung is attached to a Telford tank fitted with a Heat exchanger " to protect the Heat Pump from variations in the Radiator circuit" , Two Pulse width Modulated Motors "to control the Water Flow rate"  and a 50 litre Buffer " to increase the cycle time"..

Despite all of the above .....my heat pump still "short cycles" with a constant  cycle time of 10.5 mins, independently of the load.

I would advise anyone buying such a system to ask the installer "how many of these systems have you installed?" . My "installer" lied to me saying that he had personally installed six such systems!

Given the total incompetence displayed by my "installer" I should have installed the Heat Pump myself.

Be very careful ............many "installers" are incompetent...........

Do it yourself!

ian 

What is your calculated house heat loss?

If its low, then it would be very likely that the pump was sized for DHW not space heating.  In this circumstance then, when its doing space heating (which is the majority of the time), it is absolutely inevitable that it will cycle, the only variable you can play with is the cycle period.

I suspect that 10.5min is the 'minimum cycle time' which the installer has chosen to give maximum comfort.  You could try turning this setting up. 

Some more info would help us point you in the right direction.

@jamespa Thank you for the thorough reply, glad to hear they are a serious contender. They certainly seem to be a frequently installed model. Scrolling through its always easiest for the 'problems' to jump out, and I am trying to keep my mind open to the fact there will be a good proportion of users finding this forum to help improve or optimise installs already completed.

Your point about the temperatures is a good one. I certainly would like to think whatever we chose to install has the grunt to manage -5C (can't be dealing with the extended family moaning its too cold at xmas!), but run nice and efficiently into those shoulder months before the heating is off. 

(again the pessimist in me) I do struggle taking manufacturer's quoted SCOP values at face value (I need to do a bit more research as to how these are weighted) as I am anticipating its in the 5-15C ambient range where you're really getting good COP figures to balance out those achieved closer to 0C or design OAT. Much prefer it when a nice range of figures is quoted for COP's at different flow and OAT as it makes me feel (rightly or wrongly) like I can gauge performance a bit better that way

You need the detailed data book to get COP and max output at various flow temps and OATs and this is often quite comprehensive. 

Most manufacturers (including Mitsubishi) publish one, the problem is finding it.  Frequently the same document also gives the min output.  Mitsubishi's is called 'Ecodan_ATW_Databook_R32' and if you google that you will find it.  It takes a bit of intelligent guesswork to find other manufacturers equivalents, some make it easy to find on their website others (eg Daikin) appear deliberately to restrict the information that they will give to end customers.

Thanks, I'll check it out. 

You mentioned you went with the Vaillant in the end as best fit. What criteria was this based on (out of interest)? 

@declan90 Physical size, appearance, noise spec and output, plus finding a contractor who would do the install at a sensible price, were, in the end, the dominant factors.  The models I considered all had a SCOP which was good enough at my target flow temp of 45C.  Output is just enough, but that's OK as far as I am concerned, if I need a a bit of supplementary heating when it gets below the design temp, I will light up the log burner.