Posted by: @derek-m

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Posted by: @jamespa

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Posted by: @iantelescope

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I use, and intellectually understand, .......................but I, and quite a few others , do not like!

I guess that's where homely comes in.  @toodles has summarised why he has it.

Unfortunately the Samsung heat pump controller lacks (or did lack - it may have changed since I studied their manual) auto adaption.  Thus it relies on the installer or homeowner to set up WC correctly.  The first is challenging to say the least  unless the installer revisits during the season, which few will.  The second is very unlikely with the average homeowner.  Basically its a 'fail' in most of real world, which is probably why homely saw Samsung as one of several good targets.  Maybe Samsung's principal market has different user/installer characteristics.

I think that balancing the heat emitters is probably more difficult than setting the WC curve, the important aspect is not to try to rush either.

As a starting point, the warmer weather end of the WC curve could be set for a LWT of 25C at an OAT of 20C, then dependent upon the heat loss calculation data, the cold weather end could be set at something like 45C at an OAT of -5C.

The above should provide a reasonable IAT, which should then be monitored for a period of time. If the IAT is deemed to be too high, then lower the 45C value slightly and monitor again. Repeat the process over days, or even weeks, until you are happy with the results.

 

Agree on all counts.

However you will surely also agree that this is not a realistic process for the average installer or the average householder.

This alone, or the consequences thereof, probably account for a significant proportion of the complaints against heat pump installs, and the reason that many plumbers won't touch low temperature heating, preferring instead the 'established' route of whacking up ft (gas oil or heat pump), ignoring balancing and WC, and letting trvs 'sort it out', albeit at the expense both of comfort and efficiency.

It's difficult not to concede that the latter approach does have some attraction, however poor it is in terms of efficiency (and comfort).

@jamespa &derek-m

Water Law

I have regularly changed the Water Law curves for winter.

Winter:

The Top left ordinate with  Zero Offset from the Weather Compensation panel is set to -5 C.

The Top left co-ordinate with  Zero Offset from the Weather Compensation panel is set to +45 C.

The Center ordinate with  Zero Offset from the Weather Compensation panel is set to +15 C.

The Center co-ordinate with  Zero Offset from the Weather Compensation panel is set to +35 C.

The Right hand  ordinate with  Zero Offset from the Weather Compensation panel is set to +30 C.

The Center co-ordinate with  Zero Offset from the Weather Compensation panel is set to +35 C.

These figures being supplied by Samsung in a You Tube video for Scotland.

Six field parameters have to be set ...........correctly set.

Summer:

The Top left ordinate with  Zero Offset from the Weather Compensation panel is set to -5 C.

The Top left co-ordinate with  Zero Offset from the Weather Compensation panel is set to +40 C.

The Center ordinate with  Zero Offset from the Weather Compensation panel is set to +15 C.

The Center co-ordinate with  Zero Offset from the Weather Compensation panel is set to +30 C.

The Right hand  ordinate with  Zero Offset from the Weather Compensation panel is set to +30 C.

The Center co-ordinate with  Zero Offset from the Weather Compensation panel is set to +30 C.

Six field parameters have to be set ...........correctly set.

I use the Offset into the Water Law graph screen to adjust the Water Law Offset +/- 5 C .

to set the indoor temperature.

Violent reaction from my then Installer:

Seeing my notes scribbled in the operators manual, my Installer , and an accompanying NIC Engineer exclaimed ( expletive deleted )

that I was forbidden to change these parameters .

These parameters should, apparently ONLY be adjusted by experts!

Aye , that will be right !

Leave a reply

I can't recall how the Samsung water law adjustment works, but will look it up later.  I think we have established that you should ignore your installer.

It's absolute nonsense to talk of water law 'fie Scotland' the water law will depend on the design flow temperature and outdoor temperature and the type of emitter (ufh Vs radiators).  Whilst the design OAT might be the same across Scotland, the design ft will differ from instal to instal.

Can you advise what your 

design flow temperature 

Design outdoor temperature 

and emitter type is.  

I will then try to explain further using your figures as an example, which should also provide a sense check on your settings.

@jamespa

@jamespa

@iantelescope

OK let's do some basic water law theory.  In theory, at the design outdoor air temperature (OAT), say -10, your house loses the design heat loss (say 10kW), when it is at its design temperature (say 20C).  Your emitters are sized to emit this amount at the design flow temperature (say 45C).  So if your water law is set so that at oat = -10 and the ft =45, your emitter output will balance your house loss exactly when the house temperature (IAT) is 20C and thus the house will stay at this temperature.  This gives you one point on the water law curve.

At a higher OAT your house will lose less heat, in proportion to the IAT-OAT temperature difference (there is a tweak to this which I will come to later).  So for example  at OAT = 0C it will lose 6.66 kW, at OAT 10C it will lose 3.3kW.

Likewise at a different FT your emitters will emit more or less, this time dependent on the difference between FT and IAT.  So, by adjusting the ft and nothing else, the emitter output can be matched to the house loss at any OAT, which is the aim of the water law.

The relationship between emitter output and FT is linear for ufh, but not for radiators.  Radiator output is proportional to (FT-IAT)^1.3.

Samsung, like many other manufacturers, only allow a linear water law.  Fortunately a best fit linear approximation is within about a degree of the true curve, which is probably good enough given the uncertainties.

So in principle the above allows you to work out exactly what the water law should be, and program the four parameters (basically two ft,oat pairs) that Samsung allows you to program (forget for now the offset function which I believe is a red herring). 

There are a couple of tweaks to this.  Your house is fed constantly with heat from other sources such as the people in it, electronics,  cooking etc.  This means that the amount of energy that your heating needs to supply is a bit less than the house loses.  This is frequently taken into account by means of a 'base temperature', the OAT at which heating is no longer necessary to achieve the desired IAT.  In the UK this is generally taken to be 15.5C, but of course in reality it varies from house to house depending on occupancy, intensity of other energy use etc.  This tweak may matter. 

Also, strictly, the emitter output is dependent on the average temperature difference between the emitter and the IAT, which is a bit less than the difference between FT and IAT*.  You can probably ignore this unless of course you have a high temperature drop across the emitters,  or between the output of the heat pump and the emitters.  Your system featured the second I suspect, but hopefully won't once the rework is done. 

Hopefully this gives you the theory to make sense of what you see.

So how to proceed. Firstly I would check that your heat pump is actually set up to use the water law. I am concerned that you have been able to play with the offset, which should only really apply if the unit is not set up to use the water law, and is instead set up to use a fixed FT. I think its all in the 20xx parameters but I cant quite work out the correct values without a unit in front of me, which I don’t have.

Given that you are starting at the beginning of the season, you are best placed to find the H2 parameters (Im using the notation in the user guide). So I would, for now, set the H1 parameters according to the design values.  Then, on a day when the temperature is fairly constant for at least 12, preferably 24 hrs, set some H2 values. Unfortunately this is rare at either end of the season so Id estimate the average temperature over say 6 hrs and adjust H2 accordingly. This is a bit tricky; others may have worked out a better algorithm!  If you can get H2 roughly right at the beginning of the season you are half way there.

Then as it gets really cold, start adjusting the H1 values. Ideally you want a day when its solidly cold all day and about the same temperature at night. These do occur in midwinter.

All the while refer to the theory to help interpret what is happening.  You will need to iterate.  

To help I have attached an excel which sets out the theoretical FT for radiators at various values. To use it, find the row where the FT (in the body) is the design FT at the design OAT. So for example if the design FT/OAT is 45 at -9, you want row 14. Then the figures in the row are the calculated FT at any other OAT for example 23.4 at 16C. These give you some starting points for H1 and H2.

One point to note (the implications of which I don’t yet entirely understand) is that there seems to be a very consistent tendency to specify somewhat higher FTs at the ‘warm’ end. I suspect this is to compensate for the fact that, at the ‘warm’ end, the heat pump will inevitably cycle, so you need a higher FT to enable the emitters to deliver the required energy given that they are emitting only part of the time.

The logical response to this is to set the values of H2 (both FT and OAT) according to the table (or experiment) at the maximum OAT where the heat pump will run without cycling (so for example if the maximum OAT at which the heat pump runs without cycling is 10C, I would set H2 to 10, 30 using row 14 as above). Above this OAT the FT will remain at the H2 value, and thus even with cycling it will be sufficient. You will need to experiment and think about what you are seeing, it may be best to use this way to set H2 rather than what I propose above.

I hope that helps. Comments from others on a better algorithm for setting up WC/Water law welcome

*As an aside, with a fixed water pump speed, the temperature drop across the emitters reduces as the ft reduces, which makes the output curve more closely equal to the ^1.3 curve theoretically required for radiators. There is thus an argument that the pwm function should be disabled if you have radiators, and you should instead run at the fixed speed which gives the design deltaT across the radiators (normally 5C) at the design OAT and FT. The counter argument sometimes used is that heat pumps are ‘designed’ for a particular deltaT and are thus less efficient at other values of delta T. This may be correct, but I have not seen any evidence to support this.

@jamesPa

Hi James,

My Renewable Hub has announced that I have run out of space on this topic. Announcing that I only have 5 characters left .

I realize that my posts are far too long!

My System hanging !

respond to this if you can

ian

Posted by: @iantelescope

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@jamesPa

Hi James,

My Renewable Hub has announced that I have run out of space on this topic. Announcing that I only have 5 characters left .

I realize that my posts are far too long!

My System hanging !

respond to this if you can

ian

 

I dont think its you I think a problem has appeared in the system as I am seeing also similar strange things.  I have PMd the editor but has also managed to post a full response about water law, see my immediately previous post.

@jamespa 

Hope You can see this.

I have received your large Post so ......

"jamesPa -> "I am concerned that you have been able to play with the offset, which should only really apply if the unit is not set up to use the water law, and is instead set up to use a fixed FT. I think its all in the 20xx parameters but I cant quite work out the correct values without a unit in front of me, which I don’t have."

I do not understand ......I have always been able to adjust the Offset Temperature.

The Water LAW Thermostat, aka Offset Temperature or Weather compensation Thermostat or Water Law Interlink is recommended by Samsung-Joule , the French Samsung Engineer and a host of others.

Field option 2091/2092/2093 sub options options 2 3, or 4 always bring on the Water Law Thermostat.

I am confused , sorry

Posted by: @iantelescope

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@jamespa 

Hope You can see this.

I have received your large Post so ......

 

"jamesPa -> "I am concerned that you have been able to play with the offset, which should only really apply if the unit is not set up to use the water law, and is instead set up to use a fixed FT. I think its all in the 20xx parameters but I cant quite work out the correct values without a unit in front of me, which I don’t have."

 

I do not understand ......I have always been able to adjust the Offset Temperature.

The Water LAW Thermostat, aka Offset Temperature or Weather compensation Thermostat or Water Law Interlink is recommended by Samsung-Joule , the French Samsung Engineer and a host of others.

Field option 2091/2092/2093 sub options options 2 3, or 4 always bring on the Water Law Thermostat.

 

I am confused , sorry

 

 

 

 

 

 

OK, I have only the manual not the actual unit on front of me so I am having to make some guesses (which may be wrong) how it operates. 

My underlying concern is that the installer has set your unit up to control the IAT using the thermostat NOT the the water law.  You shouldn't need to be playing with the offset if the unit is correctly set up, it should look after itself.

If you can give me some more info it will prove it one way or another:

1. Have you witnessed the flow temperature changing with OAT (without your intervention)?

2. Can you please tell me the current values of all of the 20xx parameters please so I can better understand how it is currently set up.

Posted by: @derek-m

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As a starting point, the warmer weather end of the WC curve could be set for a LWT of 25C at an OAT of 20C,

I would start your water law curve as described above, and the use your design data to set the other end of the curve for colder weather.

The advantage of the approach above is in warmer weather you don't have to touch anything just leave it running. The ASHP will just look after it's self.

How and why? The delta T is generally 5 degs, so if the room is 20 or above the ASHP will not start as the restart permissive as return temp will be too high.