Enclosure or longer piping run for split ASHP system

[markocosic]

2 hours ago, JamesPa said:

Can you clarify a bit the rationale.  My simple physics says that the refrigerant line post compression must be hotter than the water flow temp so thermal losses are greater, but I must be missing something otherwise what's the point of splits?

 

Smaller pipe smaller losses.

 

The liquid line will be 1/4" OD (6.35 mm) for say a 5 kW unit. Teeny tiny vs say 22 mm for the equivalent in water with a 5 degC deltaT.

 

The liquid<>gas phase change transfers massively more heat than simply heating/cooling in the liquid state.

 

 

 

 

Also a piece of pish to route pipework vs hulking great water pipes and the associated insulation.

 

Also no concerns with regards freezing. You'll find that cold country installs prefer all the water to be kept inside the house; with only the refrigerant that can't freeze outside the house.

 

Monoblocs are for only for convenience (not needing to make high pressure gas tight joints with clean pipe) and toxicity/flammability/explosive limits/refrigerant leaks (can't use masses of propane inside a building, but you can pipe water around inside; can't avoid HFC leaks inside a building, but you can pipe water around inside)

[JamesPa]

2 hours ago, markocosic said:

 

Smaller pipe smaller losses.

 

The liquid line will be 1/4" OD (6.35 mm) for say a 5 kW unit. Teeny tiny vs say 22 mm for the equivalent in water with a 5 degC deltaT.

 

The liquid<>gas phase change transfers massively more heat than simply heating/cooling in the liquid state.

 

 

 

 

Also a piece of pish to route pipework vs hulking great water pipes and the associated insulation.

 

Also no concerns with regards freezing. You'll find that cold country installs prefer all the water to be kept inside the house; with only the refrigerant that can't freeze outside the house.

 

Monoblocs are for only for convenience (not needing to make high pressure gas tight joints with clean pipe) and toxicity/flammability/explosive limits/refrigerant leaks (can't use masses of propane inside a building, but you can pipe water around inside; can't avoid HFC leaks inside a building, but you can pipe water around inside)

Thanks, that's helpful..  Are there, so far as you know, any actual figures for loss eg per metre.  I completely understand the practical arguments but obviously the numbers do matter.  I calculated 300W penalty for 20m of well insulated water line, that's not insignificant.  It would be good to know what the same length of refrigerant line does.

[Jonshine]

This would also be useful for me to know, either way, because even if we don't move the Heat Pump, there are still some 7m of refrigerant piping outside and if moving that inside will generate a meaningful efficiency improvement (and be allowed), then that's something we could do under either option.

 

Just to clarify, our Samsung unit was installed at the tail end of 2021, so it's not that old. Insulating the interior water pipes definitely made a difference to the noise and that would've been the case under any system. It's partly just a circumstance of getting used to a different set of night noises - we're certainly not bothered by it anymore.

 

Does anyone know what the market-leading ASHP unit is in terms of quietness? We're happy to consider the 'real' number from using a quiet mode with a more powerful unit (although of course the full sound power must be used in the MCS calculation). Our current unit is a 12kW, but spends most of it's time in quiet mode so I think it's actually managing with a bit more than 9kW.

[JamesPa]

3 hours ago, JamesPa said:

Thanks, that's helpful..  Are there, so far as you know, any actual figures for loss eg per metre.  I completely understand the practical arguments but obviously the numbers do matter.  I calculated 300W penalty for 20m of well insulated water line, that's not insignificant.  It would be good to know what the same length of refrigerant line does.

 

6 hours ago, markocosic said:

Smaller pipe smaller losses.

 

The liquid line will be 1/4" OD (6.35 mm) for say a 5 kW unit. Teeny tiny vs say 22 mm for the equivalent in water with a 5 degC deltaT.

Ok, so attempting to answer my own question, engineering toolbox https://www.engineeringtoolbox.com/heat-loss-insulated-pipes-d_1151.html

gives loss curves for insulated metal pipes.  If we assume 5/8":3/8" which seems quite common, and say 10-20mm insulation, again quite common, the loss at a delta T of say 40  is around 10W/m.  That's not insignificant over a 20m length (X2 for out and back).

 

If these assumptions are even faintly correct then you need a lot more insulation than the standard provided to achieve negligible loss, which makes it a lot less easy to handle.  Have I gone wrong somewhere?

[JamesPa]

3 hours ago, Jonshine said:

Does anyone know what the market-leading ASHP unit is in terms of quietness?

Vaillant quote about 54dB(A) for their R290 models, but they specify it's at A7W55.  I haven't found a 'maximum'.  LG quote 60 but then say it might be up to 64.  Many others just quote a figure.  All this makes me doubt whether the manufacturers are quoting on a like for like basis and/or whether the number in the spec sheet is the number required for the MCS calculation.  

 

I have a feeling ochsner might be the absolute quietest, they do horizontal fans in a bulky split at silly prices so I looked at them briefly then discounted 

[sharpener]

18 minutes ago, JamesPa said:

Vaillant quote about 54dB(A) for their R290 models, but they specify it's at A7W55. 

 

Been looking at this. That's for the single fan models. The Arotherm + 12kW is 60. Have just been quoted for a Stiebel Eltron 25 which is about the same output but only 54 or 55 dB so only needs a partial screen.

 

Installer said the Vaillant wasn't quite big enough which is odd as the difference is very small (and changes sign with flow temp). Not keen on it as the refrigerant is R410a which is already obsolescent, will I be able to get it re-gassed in 5 yrs' time? Been there with car aircon.

 

Want to have R32 at least, pref R290, Viessmann looks another possibility for that. Another installer coming tomorrow, we shall see.

 

 

[JamesPa]

21 minutes ago, sharpener said:

Installer said the Vaillant wasn't quite big enough

Which likely means, given that vaillant specs are conservative, that it's plenty big enough but his stupid MCS calculations which rely on far too much unknown data about the fabric don't say so and/or he makes more markup on the viessmann.

 

Seriously I would check against actual measurements!

 

 

 

[markocosic]

1 hour ago, JamesPa said:

...If we assume 5/8":3/8" which seems quite common, and say 10-20mm insulation, again quite common, the loss at a delta T of say 40  is around 10W/m.  That's not insignificant over a 20m length (X2 for out and back)...

 

If these assumptions are even faintly correct then you need a lot more insulation than the standard provided to achieve negligible loss, which makes it a lot less easy to handle.  Have I gone wrong somewhere?

 

We can debate line sizes and operative temperatures etc but you're not an order of magnitude out.

 

Pipework outdoors is indeed a crap idea. Particularly so in heating applications.

 

 

Look at installs in hot countries, for cooling purposes, and they don't give too much thought. It's mostly to avoid condensation.

 

Look at installs in cold countries, for heating purposes, and they try hard to minimise the external pipe runs. Outdoor unit typically on the other side of the wall to the indoor unit that does refrigerant:water and has the hot water tank in it etc.

 

 

Picking the Armacell range:

 

https://local.armacell.com/fileadmin/cms/singapore/products/en/ArmaflexClass1/202110_PDS_ArmaFlex_Class_1_SG_EN_web.pdf

 

"Standard" for a monobloc would be ~20 mm of Class O Armacell type insulation on pipework between 22/28 mm

 

"Standard" for an air:air split would be ~14 mm on pipework between 6mm and 13 mm OD

 

 

Let's say temperature difference of 40C for a winter condition and bung it into a calculator for exposed pipework:

5.8W/metre for 1/4" and 14 mm insulation (92W loss @ 16m)

https://kalk.pro/en/heating/pipeline-heat-loss-calculator/?ab_a=1&r_a=1&s_a=6.35&t_a=14&u_a=47&v_a=7&w_a=0.04&x_a=0

8W/metre for 1/2" and 14 mm insulation (128W loss @ 16m)

https://kalk.pro/en/heating/pipeline-heat-loss-calculator/?ab_a=1&r_a=1&s_a=12.7&t_a=14&u_a=47&v_a=7&w_a=0.04&x_a=0

9.7W/metre for 22 mm and 20 mm insulation (155W loss @ 16m)

https://kalk.pro/en/heating/pipeline-heat-loss-calculator/?ab_a=1&r_a=1&s_a=22&t_a=20&u_a=47&v_a=7&w_a=0.04&x_a=0

11.3W/metre for 28 mm and 20 mm insulation (180W loss @ 16m)

https://kalk.pro/en/heating/pipeline-heat-loss-calculator/?ab_a=1&r_a=1&s_a=28&t_a=20&u_a=47&v_a=7&w_a=0.04&x_a=0

 

 

For 16 metres (actually 32 metres) of refrigerant size pipe outdoors vs 8 metres (actually 16 metres) of water size pipe there is a difference/uplift but you wouldn't cry too much about it. You also have to offset there not being a heat exchange and circulator pump; fat hoses; antifreeze valves etc all busy dumping more heat on the refrigerant based installation so the uplift would be lesser in reality.

 

When outputs are of the order 10 kW 200W is material but not deal breaking was my point; and with the relative ease with which you can run fridge pipe vs water pipe I'd not give a second thught to spending £0.20 on some longer fridge pipe vs £5k on a hulking great enclosure.

 

 

Can't really comment on noise. The units are very difference in timbre and source of noise. Vaillant monoblocs have silent fans and compressors but stupidly noisy (high pitched whine) inverter drives - must have been designed by a deaf old man using cheap audible frequency components. @Radian could elaborate on switching frequencies for inverters etc.

 

Panasonic A2A compressors are noisy in the rotating frequency sense rather than the inverter drive sense. Midea A2A actually pretty quiet. Need to see a unit running really to decide if it's noisy and objectionably so.

[sharpener]

29 minutes ago, JamesPa said:

Seriously I would check against actual measurements!

 

And he wants to change the cylinder but curiously not any rads (until I queried it). Came as a recommendation from the Vaillant find-an-installer so its a bit of a disservice to them if other things are equal which I think they are, his calcs show 12.5kW which is probably about right and within its capability.

 

Has put Mechanical Ventilation = No even though we have MVHR in all bedrooms, has been told not to allow for it but cannot explain why.

 

At least he is prepared to design for OAT -0.2 as per CIBSE and MCS table and 55C flow (which is odd as the Stiebel Eltron has a poorer CoP at 55 than the Vaillant).

 

Whereas tomorrow's man would under no circs design for more than 45 and OAT of -3.0 though he will re-consider the latter at -1.4C now.

 

MCS design process at its finest!

[JamesPa]

Just now, sharpener said:

And he wants to change the cylinder but curiously not any rads (until I queried it). Came as a recommendation from the Vaillant find-an-installer so its a bit of a disservice to them if other things are equal which I think they are, his calcs show 12.5kW which is probably about right and within its capability

Two 'off the wall' installers have now recommended to me a small cylinder (vented or invented) with no internal coil and a PHE.  One suggested putting the small cylinder in the loft, insulated of course, and also predicted that cylinders with coils are history.  I am warming to that conclusion, and of course a UVC in the loft has an easy run for the vent.  There is more than one way to solve the dhw problem, the painting by numbers guys just aren't there yet (and possibly never will be as many of them are dependent on the plumbing simplicity of the ashp system vendors pre-plumbed cylinder).

 

I have challenged MCS on their system sizing methodology in relation to retrofits.  To my surprise I did get a response, and they appear to recognise that there is potentially room for improvement.  Unfortunately they declined my request for permission to publish their response.

 

11 minutes ago, sharpener said:

Has put Mechanical Ventilation = No even though we have MVHR in all bedrooms, has been told not to allow for it but cannot explain why.

The EPC rules do funny things with the various forms of mechanical ventilation, in an attempt to simplify SAP to the point of idiocy.  It may be linked to this.

 

[JamesPa]

34 minutes ago, markocosic said:

When outputs are of the order 10 kW 200W is material but not deal breaking was my point; and with the relative ease with which you can run fridge pipe vs water pipe I'd not give a second thught to spending £0.20 on some longer fridge pipe vs £5k on a hulking great enclosure.

Based on what we both conclude it looks like order 200 watts penalty whether it's water or refrigerant in a 20m run.  As you say something to be avoided, but not at all costs.  Put another way it's about £1-£2 per day when heating, perhaps say £300 per year.  That's 15 years to pay for a 4k enclosure.  Mind you 20m of trench and insulated pipe isn't cheap, so the enclosure begins to look more attractive when you take this into account.

 

The cost of accoustic screens/enclosures for ashps is quite out of proportion, this needs to come down by a factor if 10.  I'm surprised ashp manufacturers haven't done something in this space (I think I read somewhere that Daikin have).

[JohnMo]

21 minutes ago, JamesPa said:

Put another way it's about £1-£2 per day when heating, perhaps say £300 per year. 

200W with a CoP of 3, would cost in electrical terms is 66W, so assuming the 200W loss was 6 months a year 24 hrs a day (which wouldn't be the case); that's closer to £100.  Reality most the time heat loss would be way less than that, as flow temp on a warmer day would have less heat loss and the CoP could 4 or 5.

[DanDee]

On 08/06/2023 at 18:26, DanDee said:

 

We need a split with only the evaporator with the fan outside, the compact compressor+bits inside. Basically a split AC installed vice versa.

@JamesPa so two reasons for a split with the compressor+condenser inside the garage and just the evaporator+fan outside:

Noise reduction and heat loss of the lines.

[JamesPa]

21 minutes ago, JohnMo said:

200W with a CoP of 3, would cost in electrical terms is 66W, so assuming the 200W loss was 6 months a year 24 hrs a day (which wouldn't be the case); that's closer to £100.  Reality most the time heat loss would be way less than that, as flow temp on a warmer day would have less heat loss and the CoP could 4 or 5.

Sorry you are right, I forgot to divide by COP.  Trench and pipe costs are still real, but one off.

 

Of course there is an additional loss due to the increase in refrigerant temp needed (and hence reduction in cop) for a given flow temp to compensate for the temp drop due to the heat loss.  I don't know the speed at which the refrigerant moves through the pipes, so can't work out if that matters.  

[markocosic]

It doesn't matter.

 

Phase change. Phase change. Phase change.

 

The refrigerant evaporates at whatever temperature the expansion valve tells it to.

 

Heating run hours are not 8760, deltaT won't be as high for much of the year, and pipes not exposed to wind lose less heat, loss won't be 200W, and COP won't be 3. (Try 100W and COP 4) The losses are not ideal but not deal-breakers.

 

Yes it would be nice to have all the important gubbins inside. Keeps refrigerant warm too and avoids crackcase heating etc.

 

They put the compressor outside, on rubber feet, in an outdoor unit, on the top of a frame, set in the ground, for noise reasons I understand. Keeps it quieter indoors.

 

Do the lines even need to be buried?

[markocosic]

2 hours ago, JamesPa said:

 

I have challenged MCS on their system sizing methodology in relation to retrofits.  To my surprise I did get a response, and they appear to recognise that there is potentially room for improvement.  Unfortunately they declined my request for permission to publish their response.

 

Are you subject to a non disclosure agreement/gagging order?

 

That would be both unusual and out of order.

 

Unless expressly prohibited from publishing you're not prohibited from publishing even if they decline to formally sanction it.

[JamesPa]

10 hours ago, markocosic said:

 

Are you subject to a non disclosure agreement/gagging order?

 

That would be both unusual and out of order.

 

Unless expressly prohibited from publishing you're not prohibited from publishing even if they decline to formally sanction it.

No I'm not.  But I want them to answer the next question I'm going to put to them!

[DanDee]

12 hours ago, DanDee said:

@JamesPa so two reasons for a split with the compressor+condenser inside the garage and just the evaporator+fan outside:

Noise reduction and heat loss of the lines.

haha this^^^

 

 

[JamesPa]

On 07/06/2023 at 22:56, Jonshine said:

Hi,

 

In the simplest possible form, which will give the most energy-efficient (and lowest-running-cost) outcome for a split ASHP system, and will the difference in efficiency be large or small:

 

Option One: Eight metres of external refrigerant piping plus an enclosure (specified to back static air pressure of no greater than 20 Pascals) around the ASHP (like this one Heat Pump Enclosure - there is a similar grating on the other side, and an 'S' bend between them, with the unit in the middle of the 'S', with the top of the 'S' being the exhaust and the bottom of the 'S' being the intake.)

 

Option Two: Sixteen metres of external refrigerant piping without an enclosure, in a position surrounded by two outbuildings, a fence, and a hedge, with a couple of metres space in front of the fans and on one side, and a few tens of centimetres clearance on the other (meeting and slightly exceeding the manufacturers recommended distances.

 

Thanks!

 

Yours,

 

Jon

I think my 2year journey into the world of heat pumps has now reduced to a remarkably similar question.  My house has a measured demand of 7.5kW, a calculated demand of 10.5kW using MCS assumptions, and requires 16kW according to two MCS full 3hour surveys who ignored fabric upgrades that they couldn't see.

 

The perfect location technically is on top of my flat garage roof directly above the boiler.  I can just squeak in within the PD noise rules with a 60dB unit, which several 10-12kW (single fan - which is a requirement in this location) units are, or I could choose the Vaillant 7kW R290 mono unit at 54dB (claimed) which is good for 7.5-8kW, looks very nice indeed, and will end up a few dB below the PD limit but still 5dB above what my LPA will agree to under express consent. 

 

To install the Vaillant I either need an MCS installer who will believe my measured losses and ignore the conventional fabric calculations, or go non-MCS requiring express consent, which means additional attenuation.  Even if I choose the former I could still be subject to a noise complaint and, since the environmental health officer has declared his position (namely that he does not accept the PD rules), I fear it might be upheld or at best it will cause grief.

 

Alternatively I can stick more or less any unit I choose (split or mono) some 15m down the garden, avoiding any issues with noise but requiring a 15m-20m trench and removal and replacement of about 10 linear m of block paving.

 

In practice therefore it boils down to Vaillant plus some enclosure/screening on my garage roof, or more or less anything 15m down the garden.  If I could create a screen for say £1K which looked sensible on the flat roof and worked structurally, that would probably be my preference, albeit at a risk that the unit would be audible inside my own house, fortunately at a non sensitive location.

 

Perhaps illogically I'm a bit nervous about splits, they seem much less commonly available than monoblocs and often a generation behind, but the thought of running a 15m-20m buried water line doesn't appeal, whereas a refrigerant line is definitely easier (I might even, if I run refrigerant, be able to circumvent digging up the block paving as there is an old drain pipe under the path in question that possibly could be repurposed). 

 

Alternatively I could just do nothing and wait until my gas boiler, now about 15 years old, packs up and hope that ASHP technology has advanced enough by then that its all a lot easier.  But then it would likely be a distress purchase which is never a great idea.

 

I think most sane souls would have given up by now, but im not a quitter.  If I knew there were some technology genuinely around the corner which would help I would wait.  Sadly I probably wont be able to get to the installer show in Birmingham later this month to find out!

[sharpener]

3 hours ago, JamesPa said:

Sadly I probably wont be able to get to the installer show in Birmingham later this month to find out!

 

I am hoping to get to this, fortunately my travel plans that week mean I can come via the NEC at neglible increase in mileage. Am hoping to glean some info about what may be upcoming in the R290 space and maybe find out what RED are up to (but I see their rather cryptic web page features a combined manifold and LLH which does not strike me as the best of ideas).

 

PS while posting, has anyone got a link to the pipe flow calc thing that was here, it had drop-downs for common UK Cu/poly pipe sizes and would calc flow rate, volume and pressure drop for a given length with an animation, I remember it and can visualise it but d***ed if I can find the bookmark!

 

Edited June 12, 2023 by sharpener

[TonyT]

I would dig the 15m and have peace of mind and have the unit further from the house 

[DanDee]

22 minutes ago, sharpener said:

PS while posting, has anyone got a link to the pipe flow calc thing that was here, it had drop-downs for common UK Cu/poly pipe sizes and would calc flow rate, volume and pressure drop for a given length with an animation, I remember it and can visualise it but d***ed if I can find the bookmark!

 

https://heatpumps.co.uk/technical/flow-rate-and-pressure-drop-simulator/

[sharpener]

That's the one, thanks @DanDee, also lots of other good stuff I didn't know was there.

 

[DanDee]

On 08/06/2023 at 23:54, sharpener said:

 

Can you provide a link to the specific enclosure you have in mind? Do they warrant its performance with your particular HP and what dB reduction do they state it will achieve? Also how does it vary across the spectrum?

@sharpener @JamesPa @Jonshine a lucky random find

 

https://images.richmond.gov.uk/iam/IAMCache/3333292/3333292.pdf from page 15

 

and more

https://docs.planning.org.uk/20210615/78/QUP0YSJIGLP00/0mgh2zt2xdeiy9p3.pdf

https://docs.planning.org.uk/20210310/115/QPNDF6RPKT500/tcjj94yevv879ot1.pdf

http://planning.southkesteven.gov.uk/SKDC/S15-1537/1297830.pdf

http://planning.southkesteven.gov.uk/SKDC/S15-1537/1297829.pdf

3333292.pdf

Edited June 12, 2023 by DanDee

[DanDee]

33 minutes ago, DanDee said:

@sharpener @JamesPa @Jonshine a lucky random find

 

https://images.richmond.gov.uk/iam/IAMCache/3333292/3333292.pdf from page 15

 

and more

https://docs.planning.org.uk/20210615/78/QUP0YSJIGLP00/0mgh2zt2xdeiy9p3.pdf

https://docs.planning.org.uk/20210310/115/QPNDF6RPKT500/tcjj94yevv879ot1.pdf

http://planning.southkesteven.gov.uk/SKDC/S15-1537/1297830.pdf

http://planning.southkesteven.gov.uk/SKDC/S15-1537/1297829.pdf

3333292.pdf 4.07 MB · 0 downloads

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