@iantelescope this is very interesting but I am at a loss as to what you are trying to prove so please explain 🙂

Posted by: @iantelescope

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Switching and Water Flow rates can be Safely controlled  by the PWM inputs rather than Power Relays!

 

I think you misunderstand regarding the suggestion of using a relay. The relay is to switch the power to the pump on and off not control its speed. You are trying to get a static speed in your secondary pump to achieve the required flow rate around your radiator circuit. The pump needs to be switched on and off by your Samsung controller in order to separate the dependency of the pump from your Honeywell thermostat.

The Samsung controller output is only capable of supplying up to 100W so you need to use a relay to switch the power on and off for a pump that consumes power greater than 100W otherwise it will damage your control board. The pump relay, via this Samsung output, will only be switched on and off in sync with your heat pump compressor etc, which in turn powers your pump on and off, it is not used to produce a pulse train to control the pump speed, merely the electrical power to the rotor.

I am not sure how this secondary PWM pump was controlled before you used your Arduino but I hazard a guess it was running a constant speed when first installed?

If a constant speed configuration is not possible with your PWM pump then you may have to consider a fixed speed pump replacement such as a Wilo pump on which you can manually set the required head pressure and get the desired flow rate.

Regards

@iantelescope

It would have probably been more useful to show the inlet and outlet temperatures on the primary side of the PHE along with the inlet and outlet temperatures on the secondary side. All on the same chart if possible.

Flow rate and DT are inter-related, though it may be useful if I try to explain using voltage (DT), current (flow rate) and variable resistance to represent heat emitters.

Consider a system that has 10 radiators (10 x 10 Ohm resistors) all connected in parallel. If the supply voltage is 10 volts then 1 amp will flow through each resistor, producing a total supply current of 10 amps. The total amount of power being dissipated by the resistors will be V x I, giving 10 x 10 = 100 watts.

If each resistor is now reduced to 5 Ohms, then at a supply voltage of 10 volts, the total supply current would increase to 20 amps, giving a total power dissipation of 200 watts. To keep the power dissipation at 100 watts it would be necessary to reduce the supply voltage from 10 volts to 5 volts.

If the above is now consider in a slightly different way, in that the current (flow rate) is fixed at say 10 amps, but that the resistance is varied to vary the amount of power dissipated, with the volt drop across the resistors indicating the produced DT.

For a power dissipation of  100 watts the produced volt drop would be 10 volts.

For a power dissipation of  50 watts the produced volt drop would be 5 volts.

For a power dissipation of  20 watts the produced volt drop would be 2 volts.

It is probable that your charts are showing that a similar quantity of thermal energy (power) is being dissipated, but by changing the flow rate (current), the DT (volt drop) is being changed.

Changing the flow rate in either the primary or secondary side of the PHE will change the relevant DT.

@derek-m 

For Efficiency , Hot Water Heating DOES NOT NEED the Radiator Motor Water Pump to be AUTOMATICALLY USED.

Many thanks @derek-m

Sensors .....more & More & more!

I am building a permanent  box to increase my DS18B20 Temperature Array to 12   X  DS18B20 and another Arduino . 

I will measure and control the Secondary , Radiator Delta_t ...........in due course.

In limiting the Flow rate , I have greatly increased the Primary Delta_t.

Note that the PWM input to the Grundfoss Motors was used to reduce and control the Flow rates NOT the RELAYS.

Parallel Grundfoss Motor Operation:

For efficiency when Heating Hot Water the Radiator Motor Water Motor SHOULD NOT BE AUTOMATICALLY USED.

Parallel Grundfoss Motor Operation WOULD BRING BOTH PUMPS into operation when ONLY ONE MAY BE REQUIRED!.

Note the different Amplitudes, reflecting the Single or DUAL Motor Operation.

The Thermostat SIGNAL does NOT ALWAYS start  the Compressor OR the Primary Grundfoss Water PUMP.

Thermostat Cycling and Weather Compensation Cycling:

During  a Cold February my Heat Pump Cycle Time is controlled by BOTH Weather Compensation AND my Thermostat.

 The following graphs show the Power , Heat PUMP Output Water Flow Temperature  and Radiator Output Water Flow Temperature  on 7th February 2023.

The 10 Shorter 10 minute "Short Cycling " is here vividly contrasted with the 1 Hour Cycling Time set by the Weather Compensation Thermostat.

My Conclusion is that Weather Compensation is perfectly capable of controlling BOTH THE Primary AND SECONDARY,RADIATOR Grundfoss Motors!.

I further conclude that , in the absence of my Thermostat 20 minute "Cycle Time " my Heat Pump would revert to Weather Compensation.

The Buffer tank Controversy

Given that the Buffer tank appears to provide a Winter "Cycle Time " of one hour, I should Replace the Thermostat with a Simple ON-OFF Thermostat !

Water FLOW RATE Control  

Given the proven operation of the PWM in increasing the Heat Exchanger Delta_t WHY are RELAYS BEING Advocated ?

Case 1 , PWM OR Case 2 , RELAY ??

Why SHOULD I USE CASE 1 , the Pulse Width Modulation , PWM Grundfoss Motor Control to control the Primary Water Flow rate as illustrated in the Installation manual?

Why SHOULD I USE CASE 2 , Relay Control , to control the Primary Water Flow rate , as illustrated in the Installation manual?

PWM proving to be MUCH Simpler & Safer !!

@technogeek and @derek_m

Why , on earth are SAMSUNG,  Still , in the 21st century using RELAYS ??

My Grundfoss Motors can be Switched  OFF AND ON using a PWM Signal :

My Grundfoss motor can return its status:

When used , the PWM Grundfoss motors ,  case 1 in the SAMSUNG Installation Manual the 240ac are permanently ON ( see installation  manual)

Hysteresis:

The PWM signal when operating at 4 khz or 256 us has a  Hysteresis  from  91% , or 233 us to 95% , or 243 us .

Overheating safety limit :

The PWM signal when operating with a signal < 10% , or 25 us ,  is fixed at Maximum Speed ensuring maximum speed during Signal failure.

When Signal noise is between 0 and  10% the Motor is driven at maximum speed cooling the water , and motor.

Feedback:

The PWM Motor returns the Alarm and  motor Status with current consumption. This is NOT currently used by SAMSUNG.

Speed Control Linearity :

The PWM is linear between the OFF Speed , 256 us Pulse width  and the ON Pulse Width of <10 us.

Why , on earth are SAMSUNG,  in the 21st century STILL using RELAYS ??

@technogeek & @derek-m

A Simple ON-OFF No-nonsense  Radio Controlled Thermostat ?

Where Can I Get a Simple ON-OFF  Radio controlled Thermostat ?

Most of the on line Thermostats, on offer,  do not have sufficient Technical Information, being aimed at "simplicity of operation  " , "Looks" , and "simplicity of installation" !