Are you heating in June?  Or is it in cooling mode?  Are the sensors on external pipework or inside the unit?

Yes, probably it does matter, depending on the rest of your system.  If you have a heat exchanger, it's likely using it the wrong way around, which will cost around 5degC, dropping efficiency by around 10%.  If you have radiators, there should be a magnetic trap before the heatexchanger - it will be less effective at protecting the complex heat exchanging structure from black crud if it is "after" it.

The refrigerant side of the ASHP plate heat exchanger is a condenser, superheated refrigerant gas in at the top, lower pressure sub-cooled liquid out at the other bottom. It is always piped counter flow to the return (RWT) and leaving (LWT) water side connections. So that means ASHP connections are usually return in at the bottom and flow out at the top.

The flow on the water side could be piped wrong, Samsungs don't have a built in primary circulating pump. Some knuckle scraping installer could have crossed the house side primary flow and return water connections. In heating, your LWT will always be higher than your RWT.

Surprised the ASHP sensors don't register RWT > LWT and throw an error code 'incorrect flow direction' when in heating mode, but Samsung might assume, not unreasonably, no installer would be that stupid and therefore no error code is required for this. Ah, how little they know about UK installation standards!!....

Thanks for the replies! The Samsung unit has the sensors built into it and yes it would make sense for the system to raise a fault code once it sees the return temp higher than the flow! Perhaps newer units would do this! 10% efficiency loss is 10% higher bills so I will get it changed. I don’t believe there is a filter either so when I swap pipes around I will put a filter on flow to stop any dirt that’s in the system going into heat pump. The system was poorly commissioned, stats were controlling wrong zones too but that was a simple fix by swapping over valve actuators. - there’s probably a good business in the making to go around optimising poorly installed heat pump systems 😂

Posted by: @clongwill

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 - there’s probably a good business in the making to go around optimising poorly installed heat pump systems 😂

I am seriously considering having @heacool or a Heat Geek engineer to come and have a look at my recently commissioned install.

Posted by: @clongwill

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there’s probably a good business in the making to go around optimising poorly installed heat pump systems 😂

There sure is, but it's not the most rewarding work going round sorting out other folks' cock-ups. If there's one thing I've learned on my domestic ASHP journey over the last 1 year, and my 30+ year journey in building services; inefficiency is due to poor design and control. An A2W ASHP will do what it's designed to do, capture heat from the outside air and transfer it to a secondary medium. It'll perform reliably as per it's rated capacity and published performance data. But from the unit water connections, the variables are in the hands of the system designer and installer. How much of that heat gets transmitted into the heated space, and how efficiently, can vary enormously. The ASHP gets the blame as that's the bit the customer assumes 'doesn't work'. Almost always the ASHP isn't the problem.

In your case, it looks like the installers didn't even get the water connections to the ASHP right, so I would get an independent expert report prepared and it will be money well spent. If it's new build under NHBC, and major issues are identified, have you any redress with the developer? Have neighbours got similar systems with identical issues?

@allyfish Surely if the water circuit was plumbed incorrectly and water was pumped the wrong way, the flow switch in the heat pump would not be activated and the heat pump would be prevented from starting?

@iaack hi again. The flow sensor is external on the system hot water cylinder on Samsung Gen6, not internal to the monobloc, so it's possible to have correct flow at the cylinder but reversed flow and return connections at the ASHP. Monoblocs with internal primary pump and flow monitoring can't have reverse flow. I think you can with the Samsung because these items are external. Given the standard and quality of some new build installs, it's quite possible!