Incompetent Installers , incompetent regulation Do I need a MIM-B19N?


Its clear that you not been well served by your heat pump installation, but I’m intrigued by your comment that your electricity bill has increased by 33%. An average household (without an EV) should expect to see their electricity bill increase by roughly 100% on installing an ASHP. Obviously compensated for by having a 100% reduction in gas bill (assuming no other gas appliances).

I say this because an average home uses 3000kWh of electricity and 12,000kWh of gas. So if your heat pump is operating with a CoP of about 3.5, and you boiler was about 85% efficient, you would need about 3000kWh of electricity - i.e. double.

So maybe if your house isn’t warm enough, its simply because your heat pump is undersized (as you’ve indicated) and nothing more problematic than that? You might overcome that with direct electric booster of about 2kW, which isn’t ideal, but would only operate on the coldest days.


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Hi Glyn, Tim,Christian,Trystan,

I have been pondering How to express the operation of the Field bits 2091 options 1,2,3 and 4.
on Samsung Heat Pumps.

The Samsung manuals were written in Korean and then translated by an Machine , probably a PC , into several other languages.

Calling a compensation COMP Status BIT Run

The Samsung Heat Pump uses TWO Thermostats when operating in Weather Compensation mode.

  1. An External Room thermostat, my thermostat is a Honeywell Home Thermostat, for example.

This room thermostat is true, i.e. asking for COMP operation when

Room_Thermostat COMP_operation is TRUE when Room Temperature is Less than the Set Temperature

ROOM_COMP_DEMAND = (Room_Temp < Set_Temp)

  1. The WATER LAW Thermostat comparing the Flow water Temperature with the Value +/- 5 C displayed on the lcd screen of the Samsung Heat Pump.

This Water Law thermostat is true, i.e. asking for COMP operation when

Outside _Temperature is less than the Water_Law _Temperature set on the LCD display.

WATER_LAW_COMP_DEMAND =( Outside_Temp < LCD Display Temperature)

With Address 2091 using options 2,3 or 4 The following Truth table can be drawn up from experiment!

( Room_Temp < Set_Temp ) ( Outside_Temp < Water_Law_Temp ) COMP_DEMAND
0 0 0
1 0 0
0 1 0
1 1 1

This is a classic AND Condition with the TWO Thermostats ANDED together before demanding the Heat Pump Status bit COMP be TRUE.

I hope this clarifies the operation of the Samsung Heat Pump , in Weather Compensation Mode .

As I say, LOGIC is here the ONLY way to describe the ACTUAL operation of the Heat Pump in Weather Compensation mode.

The Korean " Translated explanation" is unintelligible!


Sorry, I made several typos in the previous version. [Deleted for clarity - Moderator (RW)]

Hi Rachel,

My December 22 Energy bill is 247% larger than my December 21 Energy bill.

My Energy cost has risen by 180 % from Dec 21 to Dec22.

I expected to pay my bill of Dec 21 x 1.8 .

I actually paid a bill 247% larger

My suspected increase due the installation of the Heat pump in July 2022 is therefore (247/ 180) X 100 = 37%

I know it is fatal to compare year on year …but this increase has now been suspected over three months.

I also compared the Energy usage in Dec 22 and subtracted the Electricity usage for Dec21 giving me the approximate energy that would have been produced by my former Gas boiler.

Dividing the Gas Consumption for Dec21 by the Energy that would have been produced in Dec22 gives a measure of the Overall efficiency .

The Overall efficiency ~~~~~ Cop ~ 2.2 for Nov,Dec, and Jan 2022.

Samsung quotes the actual efficiency of a Heat Pump operating at -4 C as 1.97 !.

I therefore suspect that I have a REAL COP of circa 2.2 !

I also suspect that the Heat pump has increased my bills by 37% !


Hi Ian,

Apologies if I misunderstood your OP, but it did say your electricity bill had increased 319% and your rate had gone up by 175%, so overall I interpreted that as a rise of about x1.8 in actual usage, which given that you aren’t getting a warm house seems about right.

For interest, this is my monthly gas and electric use for the last 12 years. In 2016 I got an EV and in Apr 22 I installed the ASHP. The blue line exludes my EV usage, but includes the ASHP usage. (Green is my PV generation). As you can see my electricity use (excluding my EV) was three times as high in December 2022 as in December 2021. But that’s what I’d expect - my average annual CoP I’m expecting to be a little over 4, but in the month of December my CoP was about 3.0.

If you are really having issues with defrost and insufficient volume, then replacing the heat exchanger with a low loss header might achieve both your goals of higher volume available for defrost and avoiding the exchanger delta-T problem. But none of that will give you a warm house on the coldest days if the heatpump is undersized.

Incidently, if you have any towel radiators (or other suitable vertical radiators) on your circuit, you could put up to about 600W of direct heating into those fairly cheaply (maybe controlled with a Shelly device or similar) as a quick fix to get more heat into the circuit.


Hi Rachel,

I got to say your presentation is excellent!.

I have been concerned about the Definition of COP.

COP on my Samsung is currently measured as the Ratio of the Energy Generated divided by the Energy consumed.

The Energy Generated and the Energy consumed are displayed on the Screen of my Samsung Heat Pump.

My Official COP is about 3.4.

However, the energy generated has to go through a heat exchanger , two pumps , two filters and a labyrinth of pipes .

My Real COP should measure the losses following the Heat Pump output.

Measuring the actual energy generated would require the installation of a SonTex Heat meter.

In the interim I have estimated ( guessed ) the Real COP by comparing the Energy consumption before the Heat Pump was installed with that a year ago.

This is what my best guess is of the Real COP

The 4th month is here December 2022 with the estimated COP circa 1.95 in minimum temperatures of -4 C between 4am and 8 am .

my Heat pump was originally "designed " and estimated for an 8Kw Heat pump.
Because of Covid, the Heat pump was not available and was replaced with a six Kw heat pump and finally a five Kw heat pump described that it “would be sufficient” by my installer.

With the reduced power during temperatures about -4 C the power would reduce to 4.35 Kw ( Samsung’s figures ).

Finally, The Heat Exchanger and the additional filters and pipes reduced the output power to 3.7 Kw.

My Electricity consumption is shown in the following



Hi Ian,

It might be worth plotting your historical gas use as kWh/degree day as this will normalise it somewhat to ambient temperature and may allow you to make a better comparison (I use a base of 15.5C - i.e. my house doesn’t need heating if the ambient is above 15.5) - I use about 6-7kWh / degree day and it’s not changed much beween boiler and ASHP (I thought it might increase a bit becuase the ASHP keeps the house warm all day, but it’s barely noticeable.) (Apologies also for strnge scales - trying to keep everything on one chart!, but the Cop is effectively expressed as an efficiency on the right scale).

The heat meter (EmonPi heat) was a bit hit and miss befor January, so I’m using the ASHP system data to record CoP, but despite that, my 2022 heat input is roughly in alignment with 2020/21 and with gas use over both past winters shown when you consider degree days.

You can download degree days for your area from: Degree Days For Free - Stark


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Hi all
The problem is you cannot compare month on month a year apart for energy use unless all anomalies were equal. Also all cop figures given in manuals are generated in perfect setups. The best we can hope for is to try and replicate those figures in our own systems, a heat loss calculation if done correctly will give you a great starting point but every system that I have ever sized and installed has had to be tweaked to optimise efficiency and running costs. The tolerances on heatpump settings are so small compared to a gas/oil boiler that if they are out then the consequences have such a dramatic on the system and user.

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Hi Mike,

I am , by now , all to well aware that ALL of my measurements are subject to intense objections from my “installer”.

I agree, I cannot compare year with year …But in the absence of both Electrical Power meters to measure the input , and the even more significant absence of a water Temp/Flow rate Power meter on the output I have no other alternative.

My Installer has NOT fitted the promised input Electrical power meters .

My Installer has NOT fitted the promised output Water Flow power meter ( SonTex 789 ) .

I have used a home-made Input power meter with a Chinese Data logger to get what information I can.

I will have to pay £250 to get a SonTex 789.

The Samsung , like every other Heat Pump ONLY measures the Energy Generated BY the Heat PUMP and the Energy consumed by the Heat Pump.itself.

With a Temperature Drop from the Heat Pump output pipe to the Principal Radiator of 14 C the Radiator will only produce about 0.3 of it’s 50C rated output.

Radiator power at water temperature of 50 C = 2900 X 0.515 = 1.5 Kw

Radiator power at 31 C = Room_conductance X ( Indoor Temp - Outdoor )temp )
= 78 X ( 21 - (-5) ) = 2.028 Kw

The Radiator is producing 1.5 Kw against a demand of 2.028 Kw .

I KNOW my sums are NOT dead accurate…

.BUT I am painfully aware of the Warnings from my Energy Supplier !



Hi All,

A Samsung engineer has delivered a report covering the "remedial work " required on my Samsung Heat Pump to my “installer”.

My “installer” has not responded and remains completely silent.

I have NOT been permitted to see the report on the required “Remedial work” now some 9 months after the "installation was started.

The Visiting Samsung Engineer did , however , reveal much else about Samsung Heat pumps.

Samsung Heat Pump problems.

1 Pump motor Pulse Width Controls not working.

The Samsung Control box is supplied with a complete Pulse Width Modulated, PWM motor control system.

According to the Samsung engineer the PWM control, described in the Samsung Engineering manuals DOES NOT YET WORK .

Most GAS boilers are now fitted with continuously variable PWM Motor control, why does the Samsung PWM control STILL NOT Work?

Without PWM the Motors may be seen to Violently oscillate , …


A continuous , variable motor control is required to limit the motor bearing wear AND my electricity BILL.!

2 SAMSUNG MANUALS are machine based "translations " are Good to excellent in parts BUT IN OTHER AREAS ARE TOTALLY INADEQUATE.

The visiting SAMSUNG ENGINEER could not , himself, understand the manuals, and has demanded that SAMSUNG issue proper English Language manuals prepared by ENGINEERS !


Weather compensation saves between 7% and 10% on energy bills.

Weather compensation is enabled using Field bits 2091 Options 2, 3 and 4.

The Samsung Engineer Could not explain the difference between Field bit 2091 Options 2, 3 and **
** 4, however, the differences were " thought to be about motor control!.

AGAIN, Clear unambiguous statements must be provided by SAMSUNG.

From observation the Field bit 2091 options 2, 3 and four perform the LOGICAL AND OF THE ROOM THERMOSTAT AND the Water LAW THERMOSTAT.

The Differences between options 2, 3 and Four are that the WATER LAW THERMOSTAT has different HYSTERESIS , with

a) option 2 having NO Hysteresis ,

b) option 3 having 1 C Hysteresis

c) option 4 having 2 C hysteresis.

The OPTIONS 2, 3 and 4 ALSO TRY to limit oscillations by delaying the the Motor switching ON/OFF.


Hi All,

When using Weather Compensation, Samsung Field bits 2091 options 2, 3 or 4 the Heat pump TEMPERATURE is controlled ONLY by the Flow Water SENSOR. .

When the Temperature Sensor setting is switched to “Indoor” the system REMAINS under the control of the Water Sensor !







I am fitting a Sontec 789 Heat meter to my heat pump.

Given that the Sontec is supplied in various flow rates , what flow rate should I select for my Samsung 5Kw Heat Pump which supplies a maximum of 23 l/min? The Sontec 1.5 m^3/hr = 25 l/min or the Sontec 2.5 M^3/hr ?

How do I fit the flying temperature lead into the other ,Warm feed pipe?
The Flying lead has a 10mm brass thread , so how to fit into a pipe?


You should use the QP 2.5 m3/hr Sontex 789 for a 5kW heat pump.
The smaller 1.5 m3/hr would cause significant pressure drop.

There will be a M10 female to 1/2" male included with the heatmeter, you can then use a 1/2" female to 28mm or 22mm compression tee.

We have Sontex heat meters and all the plumbing fittings and MBUS readers etc, in stock, drop us an email if we can help: [email protected]

@glyn.hudson did you manage to see if those sensors are available individually?

Hi Glyn,

Many thanks for the information about the Sontex 789 !.

Is your “MODBUS” reader Linux compatible?

Could I use any serial TTY interface to my Linux PC?


Great, looking forward to seeing the results!

Yes, all open source, part of our python based emonhub application:

Documentation here: emonHub user guide — OpenEnergyMonitor 0.0.1 documentation

The Sontex 789 with MBUS output is cheaper / already included and also supported by the same emonhub application.

Here’s the MBUS reader that we supply M-Bus to USB Converter | HeatPump Monitoring - Shop | OpenEnergyMonitor it just comes up as an serial port on linux.

Do you think it might be worthwhile getting an SDM120 Modbus output electric meter at the same time so that you can be sure of the accuracy of your electricity measurement? The SDM120 is Modbus while the Sontex is MBUS (two different protocols).

Are you talking about the compressor motor or the central heating pump here? Inverter driven compressors are obviously important but the benefit of PWM central heating pumps is more minor. I have a fixed speed central heating pump and get great performance, Glyn’s samsung, while technically installed with a PWM central heating pump, it doesnt really make use of it in any significant way. Other Samsung systems with more flow rate than Glyn’s does show more PWM based central heating pump variation.

Did the Samsung engineer have anything to say about the buffer and heat exchanger on your system? If it was my system, I would personally be tempted to try removing those, adding in a bypass valve for safety or ensuring that at least a few of your radiators are always open, perhaps including a volumiser in series. That should leave you with only one central heating pump, but you would want to make sure that the water quality of your system is good and frost protection is considered carefully. This open circuit approach is the way I have my system configured and it seems to work well. Not to say that it will be the best configuration for all applications.

Hi Glyn and Brian,

Many thanks again.

I have contacted several heat meter suppliers .

They recommend the "Sharky 775 for the following reasons.

  1. The Pressure drop across the Sontex 775 is 800 m bar at 1.5 m^3/hr while the pressure drop across the Sharky 775 is 400 m bar at 1.5 M^3 /hr.

  2. The Body of the Sontex 775 is “composite” while the Sharky id metal. The SONTEX breaks more easily.

  3. The Sharky has an extension lead some 1.5 m compared to the Sontex 775 0.8 M . A significant advantage in that the display will appear above my Floor boards!.

  4. The Sharky while marginally more expensive than the Sontex can be powered from 240 Vac mains.


Hello @iantelescope

If you have glycol in your system for freeze protection, sontex is the only brand that allows for glycol calibration. The Sharky 775 calibrated for water at 4187 J/kg.K would measure a heat output that is 4% higher than a Sontex that is calibrated for a 20% glycol water mix with a specific heat of 4020 J/kg.K.

Do you know how much Glycol is in your system?

The Sontex when connected via MBUS is powered via the MBUS connection, which makes it all very convenient from the installation perspective.

Hi Trystan,

I have not been given access to the Samsung Engineers report.

What ever was in the report has caused my “installer” to resume silence.

When on site , I asked the Samsung engineer why my heat pump is fitted with TWO expensive Grundfoss PWM meters and was fitted with the PWM outputs to drive these PWM motors.

Further, I asked why the SAMSUNG manuals specifically describe the control of the “INV” motors connected to terminals B1 and B6 AND the PWM signals PWM SIG and PWM GND.

The SAMSUNG engineer answered by saying that the PWM signal has shown no significant advantage in terms of efficiency, BUT the PWM may significantly reduce the violent oscillations seen on my Power curve. A continuously variable control is preferable to a ON/OFF Mains switch!

The GRUNDFOSS Motor on the secondary , Radiator circuit , is also fitted with PWM control.

The ENGINEER did not answer as to why the Secondary , Radiator Motor is controlled by PWM, BUT , a continuously variable Temperature Room detector replacing the crude THERMOSTAT switch would finally eliminate the remaining sometimes violent oscillations.

I am trying to remove the Heat Exchanger , the 50 l tank and the expansion system from the heat pump.

However, previous attempts to repair/fix the system have previously been met with hostility by my “installer”.