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

Hi Ian,

From a quick look back it looks like your high flow temp issue occurred 7 days ago, along with the time which it started this morning being out with your normal schedules, this suggests to me that it may be trying to attempt a weekly legionella cycle? What temp is your DHW normally set to and do you know if it was much hotter out the tap this morning?

Did you get anywhere with arranging a visit from a Samsung engineer? If you’re struggling getting this arranged through your installer then you may have more luck going to Samsung direct and explaining your issue.

I agree that monitoring equipment would be the way forward, with at least temperature probes and CTs both connected to an emonBase/ emonTx. I have a combination of sensors in pockets and sensors strapped to the pipes and don’t find them to be vastly different in readings, the pocket sensors will be more accurate but are more expensive. Ideally you would have a heat meter to accurately measure the COP, but this can get quite pricey


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Hi William,

I have been considering the Modbus module , MIM-B15N since the beginning.

The Diagnostic t1 within the Outdoor unit , shows the Status registers.

Can I, however, read the status registers on an active, running system?

My ideal system would use RS485/Modbus Power , Energy, & Temperature sensors along with the RS485/Modbus Status register within the outdoor unit.

A long line of RS485 sensors!


Hi Colin,

I have also become convinced that the Over-temperature problem is caused by the Hot Water cycle.
The problem is that the Legionella Temperature is set for 60C for a maximum time of 1 hour.

As I speak the Heat Pump is still stuck in Heating the Hot Water from the outdoor unit in my garden.
The Hot Water temperature is above the set , demanded, temperature of 50 C but the Heat Pump is still stuck in supplying electricity to the Hot Water system!

I have now forced the Hot water Temperature down to 45 C , and, mercifully ,the Hot Water cycling has stopped!! Return to sanity!

This may not be legionella misfiring it could be the standard Hot Water system not stopping at the upper tank Temperature temperature. The Hot water Tank Temperature sensor?

Many thanks Colin , you have made me experiment and think!

Let me investigate,


What your graph says is that the HP flow temperature is 55 degrees, not that the hot water temperature is 50 degrees. The sensor in the tank could be reading 50 degrees, so the HP thinks the tank still needs more heat. Can you access the temperature as read by the sensor? Could you graph that against the HP flow temperature?


Hi Trystan,

Again many thanks for the information.

Getting an Engineer has proven to be another nightmare.

I asked the original companies who quoted for the installation to quote for repairs or upgrade.

One company quoted a price “without Warranty” or a price of £5k with warranty. The company demanded £96 for their advice. No thanks. .

A second company, wanted to entirely remove not only the Heat Pump but the pipes and the Radiators, saying that the radiators and pipes were too small. An excellent company but no. !^K is too much.

The third company proclaimed that “i Was to blame for choosing these cowboys”.
The Engineer of the third company had two groups of letters after his name, pretending to hold Learned Society membership. The Learned societies turned out to “City & Guilds”. Again , no thanks.

I am in no doubt that the only people who can fix this are Samsung and Telford.

I have twice been promised a visit from Samsung, but, my Installer described the Samsung bill for travelling from Wigan for three days as “ludicrous”.

As to the problem with the Heat Pump It looks like the Hot Water was called , increased the water temperature but failed to stop reaching 65 C without protest.
It looks like the Hot Water thermostat this time.

My previous problems with the Weather compensation, were also probably caused by the air Temperature Thermistor. The Weather compensation seen to rise and fall unexpectedly.

A case of too many thermistors!

Many thanks for your help. I am getting tired, after 8 months of heat pumps.


I don’t think you can get the elec consumption - but you can get a bunch of other stuff including things like compressor frequency or similar data. See this thread. I have some other renovation jobs to focus on this week (thermal solar, and waste water heat recovery for the shower) but will get back to the modbus stuff soon after.

Hi Simon,

The Hot Water temperature was above 52 C , the Hot water system , with a maximum temperature set to 50 C ,should have stopped demanding energy from the heat pump.

The High Flow temperature shown on the graphs does not show the actual Flow temperature of 65 C.
My K type sensor is only fitted across the pipe not the water within the pipe.

I forced the System out of Hot Water pumping by lowering the Hot Water Temperature to 46 C.

The Heat Pump then returned to normal…


hi William,

Many thanks.

i stand corrected.

I missed Tim’s excellent e-mail on using the Modbus adaptor.


What’s the capacity of your heat pump and diameter of the pipes? Your annual consumption figures sound like a 5kW heat pump and heat loss? but Im not sure if that’s correct/established? I’d expect 22mm primary pipework at 5kW, I think Samsung may even recommend 28mm for part of the primary pipework even down to 5kW, but 22mm should be plenty (mine is all 22mm primaries for a 5kW heat pump, radiator connections all T off with 15mm pipes, all copper).

I would try contacting Samsung directly. I know Mitsubishi will send an engineer out if there is a suspected equipment fault (I dont think this is charged for - but I may be wrong about that).

Both of these issues sound like either control setting, circulation pump control or temperature sensor issues. A samsung engineer should be able to get to the bottom of the right configuration for your system.

Could you clarify as well your radiator TRV settings? How do you use the radiator TRV’s? are they all off apart from used rooms? or all on a low level e.g 1-2 or all on max? How many radiators do you have and what kind are they? single or double panel? If you do have time could you list all the radiators in your house, with dimensions and type and how you use those radiators e.g TRV off, TRV 1-2 / max etc?

Hi Tristan and Tim,

Have a look at the excellent text from the MCS about Volumising tanks.

What is your pipe volume ?

Does your system Oscillate, if so, what is the Amplitude and period of the Oscillations?

Can I see examples from other users about Cycling or Oscillations on the power or the Flow Water Temperature ?

Can you keep a database of examples of Cycling ?

Currently, I have switched out the Volumising tank on my Samsung.

The power shows the Oscillations in Power during the evening of 1 Feb .

The Energy on 1 Feb shows the energy consumed during these oscillations.

My Volumising tank was switched off , the Period of the Oscillations therefore shows the effect of a circa 6 litre pipe volume .

Does anyone else see this behaviour?

I will now try again and change one variable each day.

Now I will put the 50 LTR Volumising taking the volume to 56 Litres.


Trystan and Tim?

My Volumising tank was installed in parallel across the Flow and return of the Heat Pump out after the Three way valve!

this parallel fitting of the Volumising tank is supported by Kensa

How do I pipe up a buffer tank?

new buffer layoutYou must install the buffer tank between the flow and return of the heating system only.

The flow is the first tee connection after the 3 port diverter valve. The return from the buffer must be the last tee into the heating return before it joins the return from the cylinder.

The MCS however says that the Buffer should be fitted in SERIES !.

Where should the Volumiser be fitted into my system?

Should volumising tanks be fitted in SERIES or in Parallel across the Heat Pump Output and return?


On our HP, the DHW and Heating have two settings to control when the pump starts and stops. So there is a temperature differential, i.e. when to start and a stop temperature difference. On the DHW side of ours this is set to 0 but it’s set to 2 for the Heating, so when heating the pump will overrun the set point by 2 degrees. Does the Samsung have similar settings and if so could this be the reason for the overrun?

The other reason as @TrystanLea pointed out could be a sensor issue. We had this problem initially. The sensor for the DHW had a bad connection, so the HP was getting a bad reading. The sensors for ours are PT1000s, so any additional resistance from a bad connection gives a false reading.

What was happening due to this, was that the HP thought the DHW wasn’t up to the set point, so kept running until it reached it’s maximum which is around 65 degrees, throw an error, stop for a while and then repeat.


I cant quite see that picture clearly but that’s likely a system without a heat exchanger. It is indeed normal for a buffer or low loss header to be installed in parallel in systems without heat exchangers. The buffer is effectively providing the equivalent (hydraulic separation) function as the heat exchanger is on your system. To have both seems strange to me…? a volumiser in series with the heat exchanger would make sense as it would reduce cycling in the event that the secondary side of the heat exchanger is not loaded. You should however seek advice of a professional heating engineer, Im just an enthusiast householder really when it comes to heating system design giving my 2 cents from what I’ve learnt so far.

Hi Ian,

The Samsung config and documentation is VERY confusing. It might as well be in Latin. I have been extremely careful when changing those settings. You may want to share ALL the settings within that section for DHW. I can compare with mine.


Here is what my Samsung 16kW - via a massive external heat exchanger with the Indirect Hot Water Tank - does

Hi Trystan and Tim,

My Heat Exchanger was fitted by Telford the Hot water tank maker “to isolate the Heat Pump from Pressure and flow rate changes on the Radiators”.

My Volumising tank was calculated for size by Samsung and installed by my then “Installer”.

When my “installer” arrived to install the volumiser they did not know where to install the Volumising tank, the “designer” having been fired four weeks before!

The “installer” was shown both the Kensa and the MCS documentation , finally positioning the Buffer "between point after the 3 way valve and the Flow return, as per Kensa…

If seeking to smooth the power supply on an Amplifier, a 10000 Uf capacitor would be fitted across the power supply.

The 10000 uf capacitor would consume, and store, more energy.

The Buffer is consuming , and storing , more energy!.


Correct, that is what we mean by hydraulic separation. A heat exchanger is typically fitted to allow glycol to be used in the primary circuit for freeze protection and water only (+inhibitor or other protection) in the secondary water that goes around your radiators. I’ve just given Telford technical a quick call and they dont seem to understand either why the buffer is in parallel and agree that a series connection would make more sense (they dont typically install a buffer or volumiser alongside a heat exchanger - at least with more recent samsung models where defrost energy is extracted from the hot water cylinder rather than the space heating system).

I think the buffer is only one factor of several that need looking at with your system. The controls and what is happening on the radiator side may be of greater importance… I asked about your radiators above, could you clarify what you are doing on the radiator side?