@mjw321

There is quite a bit there Mark. I have a more modern Samsung unit with a different controller. 

The diameter of the UFH pipes might be a problem. Do you know what flow temperature you are running at with them? Are you using weather compensation (Water Law) or a fixed flow temperature. 

What diameter pipes are running from the outside unit to the cylinder? 

Im not sure how much of a problem the power washer damage is. 

There is other stuff but that will do for now. 

So a few additional questions.

How do you operate the heating system, do you leave on all the time?

Do you have on timed program for heating the house?

Do you operate upstairs differently from downstairs?

What flow temperature do you run at or is the temperature dependent on outside temp, if so tell us your current flow temp and outside temp?

You say you have an unvented, assume this is a typo, as the cylinder says vented?

Posted by: @mjw321

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• UFH - seems very expensive and I wonder about the width of the pipe (I had a specialist firm booked to install, they let me down and as it was just before xmas I made what I believe was a very bad decision to trust the plumber working with the decorators - is this UFH system fundamentally unsuitable for ASHP or is optimisation possible?
• Main controller in airing cupboard and use of remote stats which impose on/off behaviour - should I aim for control solely by main unit (repositioned)?
• Main controller seems very basic compared to what I've read from others on here - suggestions welcome here
• Subsidiary pumps for both up- and downstairs systems - removed these? (incl flow control on UFH system)
• traditional valves (visible in pics of indoor install)- replace with valves optimised for flow?
• restricted flow rate due to narrow gauge pipe as described above - would like to understand priority of doing this
• damage to outdoor unit from pressure washer - how much inefficiency is this causing and can I replace damaged parts?

Lastly (I think) - I live in a very hard water area in SE England and suspect lack of maintenance of pipework throughout property (built ~1960) - should I consider a water softening solution at source of the property and a descaling procedure?
Any advice from the many helpful experts here would be greatly appreciated - a good friend is a plumber and would be keen to be involved in any suggested remediations.

Its difficult to comment with certainty based on relatively little information (and impossible for you to be comprehensive) however, in the same order

UFH is a good match to ASHP because it operates at low flow temperatures.  However as you also have radiators upstairs there will likely (unless they are sized for UFH flow temperatures) determine the FT you can operate at.

Remote stats imposing on/off behaviour is the worst possible way to operate.  Fundamentally ASHPs should be driven by weather compensation, ie the flow temperature should be adjusted (by the main controller) according to the outside temperature, so that with the ASHP operated 24*7 the heat loss from the house is just balanced by the heat emitted from the radiators.  Can you please check if weather compensation is enabled and what the parameters are.  If weather compensation isnt operating, what flow temperature is the heat pump set to?   Samsung call weather compensation 'water law'.  Remote stats should be viewed as temperature limiters not temperature controllers, ie set a couple of degrees above the target temperature.  Some 'clever' remote stats need to be excluded entirely as they attempt to pwm modulate the HP output, which is even worse than a traditional bimetalic on-off job!  Please post the make and model of your remote stats

Samsung main controller is a bit basic but adequate if you are prepared to take the time to adjust the WC curve.  The principal omission is some sort of auto adaption  - a feature which takes the basic weather compensation curve and tweaks it based on measurement.  With Samsung you need to do this manually over a period of time.  The Third party heat pump controller, hoemly, can do this, integrates with Samsung and has a good reputation.  However its not necessary.

Only one pump should be necessary, however see next point  Do you have any kind of heat exchanger or buffer tank between outdoor unit and emitters

3m of narrow gauge pipe probably shouldn't be a problem.  If it is the effect would be to restrict throughput which you only notice when its very cold.  However it may be what you have subsidiary pumps.  Its unlikely materially to affect efficiency

Not sure what the damage is so cant comment on this

An unvented DHW system is (normally) a mains system, do you mean vented.  If the gledhill tank shown in the picture is it then it should be big enough that it can feed the shower and you can dispense with the triton.  Please confirm make and model of DHW tank

I can see at least 3 valves when I would expect only 1 diverter valve or two shut off valves, do you know what they do or have a system diagram?

If weather compensation (water law) is not enabled thats probably the first change you should make, together with adjustments so that its WC controlling the system not on/off stats.

Fundamentally the best Heat pump systems are the simplest.  Heat pump directly connected to emitters with a diverter valve for DHW, operated 24*7 with the emitters open and weather compensation adjusted so that, at all outdoor temperatures, the system operates at lowest possible flow temperature consistent with keeping the house at the desired temperature.  No on/off switching, no zoning.  This is a direct consequence of the underlying thermodynamics.

Descaling of the water supply system is nothing much to do with the heat pump.  However the water in the system itself needs to be treated or better still adjusted to VDI2035

Hope that helps to get you started in addition to the above, if you reply to the questions others have asked and I have put in bold some further things can be confirmed; others will doubtless chip in further. 

@johnmo yes correct (just dropped that in there to see who wasn't paying attention!) - thanks for spotting. Vented HW system so miserable hot water pressure...

@jamespa Many thanks for all this info - really appreciate it!

I'll go through all points tomorrow as I'm off to bed now but re the descaling question; my thinking was that over many years - scale buildup in the pipes would impede the flow. That's logical right?

Will feed back shortly - thanks again 👍  

@johnmo 

How do you operate the heating system, do you leave on all the time?

Not exactly all the time, but I tighten up the difference in min night time temp i.e. it's only slightly lower than daytime (~1 degree). Stats seems to cause constant on/off behaviour though

Do you have on timed program for heating the house?

See above

Do you operate upstairs differently from downstairs?

Slightly coller temp on the stat upstairs, based on fact that loft insulation is good and the heat rises

What flow temperature do you run at or is the temperature dependent on outside temp, if so tell us your current flow temp and outside temp?

Need to check this...

You say you have an unvented, assume this is a typo, as the cylinder says vented?

Posted by: @mjw321

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- scale buildup in the pipes would impede the flow. That's logical right?

Yes, but only in the pipes between the cylinder and the taps, not the heating pipes (unless you change the heating water regularly).  This will impede DHW flow but, as its vented, the first port of call to improve matters is to go unvented.

@bontwoody 

According to Samsung instrument panel, the "Supply water temperature to the load" (that's the samsung manual description - I'm assuming that's the flow temp) is currently 43.3C - I cannot adjust this temp on the unit with the current system config - will provide more details of that in a separate reply.

I also cannot put the system in Water Law mode, which is my current main concern, so I'm currently running on a fixed temp...

Re the diameter of the pipes from the outside unit - they appear to be 24mm (measured by eye with tape measure)

Hi @jamespa (and FYI @bontwoody as it relates to your other reply),

Thanks again for any help you can offer here - it really is appreciated!, Answers to you bold points from yesterday below - seems like my top issue is that I cannot set the system to operate in Water Law mode at all....

Can you please check if weather compensation is enabled and what the parameters are.  If weather compensation isnt operating, what flow temperature is the heat pump set to? 

Water law is not enabled and I cannot seem to enable it. Manual says I should be able to using the space mode selector, but that button doesn't work on mine (I get the flashing finger icon which means it's not an available function).

Snippet from the manual about this suggest this gets disabled if an 'external room thermostat' is connected 

This evening I tried disconnecting both the stats (upstairs rads and downstairs UFH) wiring completely from the panel - this made no difference. I still could not select the Water Law mode.

Any suggestions here? I could arrange for a plumber to be here if someone was able to advise on what he needed to do? Otherwise it seems that I need a specialist in this system to come out (I'm in SE England, between London and Reading).

It's looking like my system is set up incorrectly and cannot be operated efficiently... 

Please post the make and model of your remote stats

Both are Drayton Digistats - I've attached pics here of the remote controllers and the units wired to the samsung controller

Do you have any kind of heat exchanger or buffer tank between outdoor unit and emitters

I don't believe so - everything is shown in the pics I added to my original post

 Please confirm make and model of DHW tank

Its a Gledhill open vented cylinder - Barcode lookup doesn't return any result. I managed to get a pick of the label on the side (attached pic) which indicates its the ASL 180 Heatpump Openvented

I can see at least 3 valves when I would expect only 1 diverter valve or two shut off valves, do you know what they do or have a system diagram?

This one is beyond me I'm afraid - I can ask my friend (a plumber but no real knowledge of ASHP systems) to help with this.

Descaling of the water supply system is nothing much to do with the heat pump.  However the water in the system itself needs to be treated or better still adjusted to VDI2035

I know it's had some treatment (glycol I think?)

Thanks for the response.

So far as I can tell the thermostats are pure on/off not 'smart' which is a good thing

Lack of WC will be a prime contributor to inefficient operation.  Certainly more recent Samsung heat pumps can combine wc and an external thermostat (or the internal sensor), however I don't know about older models.  I suspect this is down to the control unit not the condenser unit itself.  Can you upload your whole manual, the answer will likely be in some of the field setting values (installer mode).  I could find it for another model but better to find it for your model and you will probably have to set a combination of values.  Can you also upload a photo of the display.

Hi @jamespa,

I've attached the whole manual 

and also a pic of my control unit display here

Thanks,

Mark