@iantelescope

Do you have any thermostats or TRV's in your system? Are you using weather compensation control?

Do you have a buffer tank, low loss header or plate heat exchanger within your system?

Posted by: @grahamh

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look i know its not what you want to hear but stop obsessing over the PWM output. Im afraid that most heat pumps dont really have a pwm function at all, they say they do in the book but the unit is not clever enough to control pump speed and inverter compressor speed. its just life. we have to move on. before we had PWM the units worked fine, they will do so now. if you have rapid cycling its not going to be fixed by altering the speed of the waiter through your unit.

Hi Graham,

Believe it or not but I agree with you !

Having looked over the last year at the poor , incompetent , support I have had from my "installer" .

I have to do something to reduce both the cycling and the bills .other than Change the Field parameters , get the PWM system at least working , what can I do?

I cannot replace pipes or tanks either physically or in the face of my  aggressive "Installer".

I appreciate the difficulties involved in measuring actual flow rates and Temperatures within pipes! Difficult but not impossible to overcome.

Every temperature , pressure or flow rate Measurement currently involves inserting sensors into the pipe!......at  Horrific expense!

If PWM pumps to not work properly , surely that is a problem for the Manufacturers. My old Gas boiler worked perfectly for seven years with PWM Motors, why can't Heat Pumps also work properly?

Surely, the computational power of the processors, built into , both the Heat pumps and their controllers, should, be capable or interrogating their environment?

Why do we not have a pc based program to design Heat pump environments ?

The "intuitive " non-numerical approach has surely past it's retirement age!

ian

Posted by: @grahamh

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...most heat pumps dont really have a pwm function at all,

we have to move on. before we had PWM the units worked fine, they will do so now.

In the time it's taken to discuss this matter here, we could've designed a micro-controller with a couple of temperature inputs and a genuine PWM output to a mains pump.

If that would be a useful 'product' to use across a range of heat pumps, then surely it's worthy of consideration.

Posted by: @iantelescope

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The Second PWM Motor will have to be supplied with a home made "Arduino" source.

Yes... even an AT-Tiny85 would be adequate!

I have a solar-thermal controller with a PWM output. I connected it to the most common Grundfos 15/50, making sure that I set its 3-speed dial to 3 (full on).

So with the right design of separate PWM Driver Box, we don't need expensive pumps either.

so I'm a little late to this thread but.. I have a samsung Gen6 16kw self installed. I have a grundfos UPMM 25-95 pump. physically I have a single circulation loop, open to all downstairs rads, upstairs on programmable TRV's. the pump PWM inputs are connected to the PWM terminals on the control PCB.

I haven't put a scope on the PWM (don't have a scope and no need because its working!). The system is behaving exactly as I expected it to. here is compressor frequency against flow rate against outdoor unit power consumption for this morning's heating run:

so as far as I can see, this unit is modulating down the flow rate  in response to lower compressor freq, via PWM signal to the pump.  because thats the only way it can be working in my house.

whether this is ideal for COP or not is another matter (I'm starting to come to the view that these long runs at low compressor output aren't that efficient, but I need more data)... but this discussion seemed to me to start from the premise that the PWM pump control on the samsung G6 doesn't work. I'm certain that it does. at least on mine!

@iancalderbank 

Hi Ian.

Following my trumpeting of my apparent success in correcting the losses in my heat pump I have to admit that the supposed improvement was an illusion!

Could I ask a question?

When working how does your Grundfos motor show that it is under PWM Control?

Is the green LED flashing at 12 HZ indicating External PWM Control.

Is the Green LED flashing at 1 Hz indicating that the Pump is under Manual control?

My "Grundfoss UPM3 FLEX AS" shows no sign that it is actually working despite being fed the correct 12 V PWM Signal .

Oh how I wish I had installed the system myself ...............You do not know the level of incompetence shown by some installers!

iantelescope

@iantelescope the UPMM pump which I have has no status LED's. It "just worked" - once I'd got the cabling correct. I did find that the labelling of GND and SIG was inconsistent on the control PCB versus the manual vs the printing on the inside of the cover. But trial and error approach found the right way round. I presume you've swapped the cables etc?

 the pump I have is specifically mentioned in the control kit install manual (page 22 - see below) and was recommended by my supplier. I have no information about the pump you're using.

Posted by: @iancalderbank

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@iantelescope the UPMM pump which I have has no status LED's. It "just worked" - once I'd got the cabling correct. I did find that the labelling of GND and SIG was inconsistent on the control PCB versus the manual vs the printing on the inside of the cover. But trial and error approach found the right way round. I presume you've swapped the cables etc?

 the pump I have is specifically mentioned in the control kit install manual (page 22 - see below) and was recommended by my supplier. I have no information about the pump you're using.

-- Attachment is not available --

What is the lowest capacity your heat pump can modulate?

@dandee I didn't include output power on the previous graphs just for simplicity as was trying to show the group that flowrate / compressor / power will all modulate properly and PWM control is working...

so here's same graph with output power (calculated by Flow rate x  DT every 30sec). the steady state power output in the latter part of the graph is 3.6-3.8kw with 1.0 - 1.15kw input.

I don't know that there are any published manufacturer modulation numbers. 

@dandee 

Many thanks ......again I am astonished with the information about the SIG and REF inputs.............

specifically , How have you connected the SIG and REF wires ? What Grundfos cable colours are connected to your Sig/REF?

I have no idea about the minimum power rating allowing power control of my 5 kw Samsung but I guess about 25% of the 5 kkw Maximum rating,, circa 1.25 kw.

iantelescope

@iantelescope  page 9 of this

MIDSUMMERWHOLESALE.CO.UK "https://midsummerwholesale.co.uk/pdfs/schematic-book-202302.pdf"

 is quite clear

the SIG and REF terminals on the samsung controller board are connected to the PWM INPUT and REF cables on the pump. check your pump manual for colours. mine are

@iancalderbank 

Hi ian,

In frustration I have connected a Wave generator only to discover that you are right. The Wiring shown in the manuals is wrong the Ref appears to be connected to Blue wire while the PCB Output should be connected to the Brown wire.

I am very much NOT amused with Grundfos , Samsung or whoever is to blame.

Let me now try again.....some luck this time?

ian

@iantelescope

 I wired it first of all following the instructions on the inside of the controller panel. didn't work. double checked everything. stuck a voltmeter on it and that gave me doubts as to which is GND and which is SIG. so I just thought - could it be as simple as they are wrong way round? and they were!

the grundfos pump cable labelling is right.

the naming of the PWM terminals on the samsung controller PCB , I believe is inconsistent (opposite) between the samsung manual and the labels on the inside of the controller panel.

I believe the instructions on the midsummer wholesale diagram are correct, but I only found that diagram after I'd got it working.

good luck.