ASHP Samsung gen6 help needed

[loxian]

I have a new build property with a 12kw Samsung heat pump installed. The installer has fitted the system and left us with nothing - no user manual, no hand-over information, nothing! Without Google and YouTube I wouldn't even have the passcode to access the control panel.

Being a new build, the house is extremely well insulated and actually needs very little heat, yet our electricity usage is eye-wateringly high. Even now in late May when the heating hasn't even been switched on for several weeks, the heat pump is using an average of 15kwh per day just providing hot water. Surely this can't be right? Even when we have been away for a weekend and there has been no hot water used at all the usage remains around 14kwh per day. I really need a bit of help from someone who knows these systems as I have tried everything I can think of. ANY suggestions at all would be very gratefully received as I feel I have been left high and dry.

Lox.

[JohnMo]

It sounds like the the cylinder set point is too high.  So the heat pump runs to max temperature stops and restarts and keeps doing this. Your set point should be say around 48. 

 

What temp are you trying to achieve in the cylinder and from the cylinder nameplate it should state the coil size. 

 

So can you confirm cylinder set point, and coil size?

[JamesPa]

10 hours ago, loxian said:

I have a new build property with a 12kw Samsung heat pump installed. The installer has fitted the system and left us with nothing - no user manual, no hand-over information, nothing! Without Google and YouTube I wouldn't even have the passcode to access the control panel.

Being a new build, the house is extremely well insulated and actually needs very little heat

In addition to the comment by @JohnMo, the text quoted above says a lot.  It sounds like your system is way oversized (at a guess it should probably be about half the size) and will likely therefore be cycling badly and/or deploying the 'compressor bypass trick' described elsewhere by @markocosic, which potentially kills CoP.  It might be worth contacting the developer and making a complaint, but they will doubtless have a wealth of spurious pseudo-arguments to put you off because, lets face it, elements of the construction industry are pretty naff.

 

Its now summer so its going to be difficult to do anything experimental about the heating until later in the year, but some info might help and in the mean time sorting out whats happening with DHW is the thing to do.  Thus I suggest you

 

1. answer @JohnMo s questions 

2. answer the following - roughly how much DHW do you use per day.  Do you have several people who take a daily power shower or is your use more modest.  14kWh/day at a COP of say 2 (which is low) would indicate a usage of about 800l/day, 6 times the national average per-person consumption of water (hot + cold).

3. find out from your controller (1) what flow temp is set for Central heating and (2) whether weather compensation (which Samsung call 'water law') is enabled, tell us

4. tell us a bit more about your house (floor area, construction)

5. complain to the developer.  Not leaving you with instructions is inexcusable, and the high usage suggests it might have been badly set up/specified 

 

That's at least a start but fundamentally it sounds like your developer has done a bad job of this aspect of the house, and if that's the case probably also other aspects.  Situation normal then, sadly!

[loxian]

I don't know where to find the cylinder set point, although I suspect you are right. I have no user manual so I am largely working blind.

I have two cylinders- a 60 litre tank connected directly to the HP external unit which feeds a 210 litre DHW cylinder, UFH and radiator circuit. DHW is set at 42 Celsius which seems comfortable.

The 60 litre tank seems hot - well above 42 degrees but I can't work out how to control the temperature.

I have checked the control panel usage stats; While electricity consumption is around 14kwh most days, the figure for generation is much lower, as low as 1.8kwh some days.

Forgive me if I'm coming across as a complete noob, but I want to fully understand how the system works and this is a very steep learning curve. 

I have attached photos of the cylinder labels

[loxian]

Daily water usage is not high. We are a family of 4. I would estimate we use 200-250 litres of hot water per day max. Certainly not the 800+ litres the energy consumption would suggest!

Flow temp for CH is set at around 40 for both UFH and upstairs rads, although heating has been unused for several weeks now, only using DHW .

The house is a 4 bed bungalow (probably larger than average room size). Highly insulated new build, thermal glass etc. UFH downstairs, radiators upstairs although we found we rarely needed the radiators, even in the coldest months as rising heat from downstairs warms the bedrooms nicely.

[JamesPa]

1 hour ago, loxian said:

I have two cylinders- a 60 litre tank connected directly to the HP external unit

How many connections to this?  2, 3 or 4?

 

Do you have/can you create a diagram of how it's all plumbed together.  

Edited May 29, 2023 by JamesPa

[crispy_wafer]

Wonder if this 60l tank is some kind of buffer tank?  Does it have it's own immersion?

[JamesPa]

1 minute ago, crispy_wafer said:

Wonder if this 60l tank is some kind of buffer tank?  Does it have it's own immersion?

That's what I'm thinking, but without a system diagram it's complete guesswork.  A lot of energy is apparently going somewhere 

Edited May 29, 2023 by JamesPa

[JamesPa]

1 hour ago, loxian said:

I have checked the control panel usage stats; While electricity consumption is around 14kwh most days, the figure for generation is much lower, as low as 1.8kwh some days.

That sounds all wrong.  Photo please showing this.

[loxian]

I have done a bit more digging and tried to work out what is going where.

As far as I can work out, a pump circulates water from the 60 litre buffer tank through the heat pump. There is then another circuit taking water from the 60 litre buffer tank, splitting three ways with three valves controlling UFH, radiators and DHW. There is another pump in this circuit but there is no obvious sign that it is functioning. It is exactly the same type of pump as the first one but whereas the first pump lights up with a digital display, the second pump stays dark.

I wonder if perhaps this pump could be the source of my issues...

[JamesPa]

13 hours ago, loxian said:

I have done a bit more digging and tried to work out what is going where.

As far as I can work out, a pump circulates water from the 60 litre buffer tank through the heat pump. There is then another circuit taking water from the 60 litre buffer tank, splitting three ways with three valves controlling UFH, radiators and DHW. There is another pump in this circuit but there is no obvious sign that it is functioning. It is exactly the same type of pump as the first one but whereas the first pump lights up with a digital display, the second pump stays dark.

I wonder if perhaps this pump could be the source of my issues...

OK its basically a small buffer tank which will thus have zero stratification.  This will increase your consumption by 10-15%, even assuming that the secondary pump (the one in the CH/DHW loop) is working.  If the secondary pump isn't working you wont get much heat to your emitters but you will still waste lots of energy.

 

Without considerable further work its not going to be easy to diagnose fully, I suspect you have multiple problems.  But the pump and the buffer tank are a good starting point.

[loxian]

Ok, finally got to the bottom of this. When there is demand for DHW the HP is heating the 60L buffer tank but water is not circulating through the hot water tank as the circulation pump only activates when there is demand from UFH or radiators. As a consequence, in the summer when the heating is off, the DHW cylinder is literally only heated by thermal conduction along the copper pipe!! (Unless the booster heater is enabled - in which case the cylinder is heated entirely by the emersion heater).

After speaking to an engineer from Samsung, it turns out that they do specify the use of a buffer cylinder in order to ensure sufficient flow volume through the heat pump but, crucially, they specify a T-connection from the heat pump directly to the DHW cylinder bypassing the buffer cylinder. The installer had never fitted this, meaning that DHW only functions when either the UFH or radiators are on. This explains entirely why our electricity usage was static at about 15KWh per day just for hot water, even when no hot water had been used. There was a constant demand for DHW throughout the day (and night) which was never able to be satisfied. The HP just short-cycles as the buffer cylinder is at max temperature yet the DHW cylinder never reaches temperature.

[JamesPa]

On 01/06/2023 at 22:11, loxian said:

Ok, finally got to the bottom of this. When there is demand for DHW the HP is heating the 60L buffer tank but water is not circulating through the hot water tank as the circulation pump only activates when there is demand from UFH or radiators. As a consequence, in the summer when the heating is off, the DHW cylinder is literally only heated by thermal conduction along the copper pipe!! (Unless the booster heater is enabled - in which case the cylinder is heated entirely by the emersion heater).

After speaking to an engineer from Samsung, it turns out that they do specify the use of a buffer cylinder in order to ensure sufficient flow volume through the heat pump but, crucially, they specify a T-connection from the heat pump directly to the DHW cylinder bypassing the buffer cylinder. The installer had never fitted this, meaning that DHW only functions when either the UFH or radiators are on. This explains entirely why our electricity usage was static at about 15KWh per day just for hot water, even when no hot water had been used. There was a constant demand for DHW throughout the day (and night) which was never able to be satisfied. The HP just short-cycles as the buffer cylinder is at max temperature yet the DHW cylinder never reaches temperature.

Well that's that one sorted at least, but I'm curious whether there is a diverter valve or not and if so where this fits.  Might be worth checking this too.

 

Also you should be aware that your tiny 4 port buffer tank will certainly be costing you a 10-15 percent increase in consumption during the heating season.  There are more intelligent ways to increase system volume if that's the only objective, namely a 2 port buffer and ditch the second pump.  However without a full system diagram, making changes could have unexpected knock on effects so it would be inadvisable without getting in someone who knows what they are doing.

[JohnMo]

On 01/06/2023 at 22:11, loxian said:

they specify a T-connection from the heat pump directly to the DHW cylinder bypassing the buffer cylinder

That T connection should be a 3 way diverter valve. So when there is a DHW call for heat, the heat pump sends a voltage to move the valve from CH to DHW. The buffer as you say should be downstream of the 3 way valve on the CH side. 

[JamesPa]

26 minutes ago, JohnMo said:

That T connection should be a 3 way diverter valve. So when there is a DHW call for heat, the heat pump sends a voltage to move the valve from CH to DHW. The buffer as you say should be downstream of the 3 way valve on the CH side. 

That's what I thought too (and still think), but was wondering if they were relying on the impedance of the ch pump when off to do the same thing.  

[JamesPa]

1 minute ago, JamesPa said:

That's what I thought too (and still think), but was wondering if they were relying on the impedance of the ch pump when off to do the same thing.  

Scrub that thought, it could too easily result in water at ch flow temp being pumped through the dhw cylinder thus cooling it down.  It must surely be a diverter valve.

[loxian]

On 03/06/2023 at 08:47, JohnMo said:

That T connection should be a 3 way diverter valve. So when there is a DHW call for heat, the heat pump sends a voltage to move the valve from CH to DHW. The buffer as you say should be downstream of the 3 way valve on the CH side. 

Absolutely right. That is how it is shown in the installation manual under application examples. The engineer has been in and added a T from the HP to DHW so that we can at least now use DHW without having to have the UFH on - our spare bedroom was like a sauna! - but it's still wrong. There is no 3-way valve fitted so the HP still heats the 60L buffer tank but with absolutely no output from the tank when only DHW is in use! The buffer cylinder is now being heated literally just so it can cool down again! Seriously, does anyone know a good heating engineer around Lincolnshire? I need someone who knows what they are doing to come and take a look and finally get all these issues resolved.

[JohnMo]

Just need a plumber who isn't short of a brain cell or two.

 

You need either a 3 port diverter (not a mid point valve) to suit the piping size you have, or an alternative is 2 off, 2 port valves, one normally open the other normally closed.  The normally open one is used on the central heating side the other on the cylinder side.  You should have a power signal coming from ASHP that gives power the diverter valve when you have a call for cylinder heat.