Posted by: @iantelescope

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@johnmo 

Sorry @johnmo , The Renewable Hub cannot accept many standard Linux format files.

I can usually translate them into Jpg ,Pdf et al , but often not .

 

 

@jamespa 

@jamesPa  Should I talk to my Plumber , holding Off until late next week ?

The Buffer Tank , originally installed  "to reduce , or stop  Short Cycling " was later installed "to reduce or prevent Heat Pump fin icing  ". ( Samsung-Dalliium - Engineer )

The Heat Exchanger was installed , by Telford, to "protect the Heat Pump from the user accidentally stopping water flow in the Radiator circuit".

A single water circuit would expose the Heat Pump to potential Water flow failure. (Telford -Engineer)

Posted by: @iantelescope

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@jamespa 

@jamesPa  Should I talk to my Plumber , holding Off until late next week ?

 

Yes

Posted by: @iantelescope

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The Buffer Tank , originally installed  "to reduce , or stop  Short Cycling " was later installed "to reduce or prevent Heat Pump fin icing  ". ( Samsung-Dalliium - Engineer )

Most likely we will suggest it is retained, but replumbed as a two port volumiser in the return, for the purpose of assisting de-icing.

Posted by: @iantelescope

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The Heat Exchanger was installed , by Telford, to "protect the Heat Pump from the user accidentally stopping water flow in the Radiator circuit".

A single water circuit would expose the Heat Pump to potential Water flow failure. (Telford -Engineer)

This is muddle-headed out of date thinking.  Heat pumps must be run with most of the system in circuit, controlled by the weather compensation (water law) curve not on/off thermostats or TRVs.  So the user wont/cant/shouldn't do this.  The heat exchanger reduces efficiency and effectiveness, in your case because of the parallel buffer tank very likely very significantly..

The people mentioned above are conversing in the background and we will have something for you in the next couple of days.  Basically your plan is correct, there may be a few tweaks,

@jamespa 

Plumber:

Many thanks for your advice , it is appreciated, I will try and stop the Plumber until late next week.

Heat Exchanger:

The visiting French Samsung Engineer and the NIC engineer  described, and defended, the Heat Exchanger as a hydraulic barrier allowing heat to be transferred but not water.

The Heat exchanger apparently "allows for different water, and different  flow rates on both Water circuits".

The French Engineer later describing the Heat Exchanger as a "hydraulic isolator" .

Potable Water ??

Some plate heat Exchanger manufacturers have been using Cheaper Stainless Steel on the assumption that the water is "potable"? ( Seigenthaler , Hydronic  Heating systems )

What is potable Water ?

My EAC Heat exchanger was manufactured in Alamabad, India ......................without instruction manual.

Many thanks for your advice !

@iantelescope

Potable water is fit for human consumption, drinking, cooking etc.

@derek-m 

Many thanks derek ...............my Heat Pump output pipe water is definitely NOT fit for human consumption being Black , or dark green !

@iantelescope I attach a proposed revised system diagram and list of tasks/SoW that @derek-m, @johnmo and I suggest, with special thanks to @johnmo who did most of the diagram This assumes that you are now retaining a cylinder not converting to thermino. 

Some of the tuning in the list of tasks will be best done by you over a period of time, eg of WC curve and whether to use timed (batch) heating either end of the season to reduce the inevitable cycling which will occur when the demand is low.

Please feel free to ask any questions/discuss anything in the diagram or on the list.

Hope this helps

Many thanks @johnmo , @jamesPa  and @derek-m

Your help is invaluable!

Your rebuild of my Heat Pump is identical to my own thoughts with a couple of reservations.

Buffer

A buffer in series with the return , although simple on a circuit diagram,  involves  pipes  physically performing U turns , the Buffer being currently positioned to the left of the Water Tank with the pipes currently pointing or traveling  to the right.

I suggested to my Plumber that we remove the entire birds nest of pipes replacing with parallel pipework attached to the kitchen walls. Costly , time consuming ,  but neat and tidy !. From experience, Neat & Tidy is  easier to maintain.

I would like to fit valves on either side of the Buffer with a third valve Shorting the Buffer. This to allow cleaning and reduction in the inevitable Energy losses during Summer. During Spring and autumn the Buffer would be used to reduce short cycling, during winter the buffer would be used to protect against icing .

Again, many thanks .

ian

Posted by: @iantelescope

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I would like to fit valves on either side of the Buffer with a third valve Shorting the Buffer. This to allow cleaning and reduction in the inevitable Energy losses during Summer. During Spring and autumn the Buffer would be used to reduce short cycling, during winter the buffer would be used to protect against icing .

The valves will also enable you to determine if it's actually needed!

Posted by: @iantelescope

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A buffer in series with the return , athough simple on a circuit diagram,  involves  pipes  physically performing U turns , the Buffer being currently positioned to the left of the Water Tank with the pipes currently pointing or traveling  to the right.

I had that on a combi in a kitchen once.  With a bit of careful plumbing it was made to look quite sensible!

Posted by: @iantelescope

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From experience, Neat & Tidy is  easier to maintain.

Agreed!

@jamespa 

I do not understand your suggestion that increasing the Thermostat demand Temperature will have any affect upon the Thermostat Pulse rate, PRF.

A typical graph of Power is shown in :

Where the Cycle time is here 10 minutes:

OR

Where the Cycle time is here 20 minutes.

Notice that the Time between Pulses is fixed by the Thermostat Cycle Time , either 10 or 20 minutes.

The Thermostat Cycle Time is set by the user from a selection of 3 or 6 or 12 cycles per hour.

The Room Temperature is transmitted by the Thermostat by varying the Run Time.

If the Room Temperature increases the Thermostat will reduce the Run Time.

If the Room Temperature reduces the Thermostat will increase the Run Time.

The changes in Run Time are shown here :

The Time between Run Pulses , the Cycle Time is constant.

Therefore, the  continual ON / OFF Switching , initially , and wrongly , thought to be "Short Cycling " will NOT be altered by increasing the Thermostat Temperature.

The Excessive  Motor Wear  will continue independent of  Room Temperature.

Apologies in advance ,I may very well be wrong !

I am assuming that the thermostat is trying to simulate proportional control by on off switching (it can't do true proportional control).  The purpose of this is to avoid overshoot.

So if the actual temperature is far from the target temperature (by which I mean the temperature to which the thermostat is set, not your actual target room temperature) it will presumably switch on full time, otherwise the effect would be unnecessarily to slow down the approach to the target temperature.  Only when the actual temperature gets close (within the 'proportional band') to the target temperature would I expect it to invoke cycling.

This is a known control approach when true proportional control is not available.  I actually experienced this in a chlorine dosing controller for a swimming pool.  The pump was capable of being on or off but the controller simulated proportional control by the same means as your thermostat appears to do.  However once the actual departed from the target by a set amount it reverted to always on.

So assuming your thermostat does the same (we don't know but I can't see a logical alternative) setting the thermostat to well above the actual desired room temp will prevent the cycling.

Just add - I don't believe your cycling is anything to do your thermostat, I believe it's a red herring.

Your current flow path of water from the heat pump is 2 port valve, buffer then HEX and back to the ASHP. The issue, which I believe is going on, is the pressure drop across the HEX is higher than the buffer. So water (or most of it) just takes a short cut and bypasses through buffer straight back to the ASHP. So your return temp goes up too quickly and the heat pump just shuts down.