ASHP acoustic cover

[dpmiller]

how can the tank be exhausted if it's being reheated simultaneously?

[PeterW]

3 hours ago, Moonshine said:

This is how i understand it to work, in a morning scenario.

 

1. ASHP switches on to heat the house as a priority.
2. When the house is up to temperature and hot water in the buffer tank, the ASHP heats the main tank (already warm from day before, say 20 degrees).

So with UFH, and the losses that you find in a decent tank, then there is the key option of using E7 and load shifting. For example I programme E7 DHW from 01:30 to 03:00 at 54°C from the ASHP then programme UFH from 03:00 to 07:30 as it is UFH running at 35°C into a 10 tonne concrete slab. That means all core heating is during off peak hours. Floors and towel rails in bathrooms and en-suites then come on at 07:00 to 08:30 which give low level boost heat in those areas. 

 

If required then the tank can be boosted to 70°C by the immersion from 05:30 to 07:00 which adds a fair additional volume of usable water to the tank. 

 

[Moonshine]

28 minutes ago, Tony K said:

 

Thanks.

At the moment I'm looking at a NIBE 2040-12kw air source heat pump. The spec is:

 

  

 

Layout wise, I'm looking at a few options:

 

 

A. In the alcove. Its within 1m of the boundary but would live inside the timber structure that will occupy that inset section, and provide storage for bikes etc. It could therefore be soundproofed. It would require planning permission there of course.

 

B. On the inside facing wall of the bungalow.

 

C. In the garden, somewhere at least 1m from the boundary.

 

D. On the flat roof. Sounds counter-intuitive, but I wonder if in fact noise would be less amplified there. 

 

 

The sound power data here is the most useful information, and is 57 dB(A).

 

How loud it is dependant on the surrounding reflective surfaces.

 

What is the green block in your layout, the extension? 

 

A. i think this is asking for trouble with your neighbours, and getting soundproofing to work with airflow requirements is tricky / expensive so i wouldn't go down this route. You would be looking for something like this https://acousticenclosuresltd.co.uk/air-conditioning-gallery/ and would run to £1k+

 

B. probably the best (or variation).

 

C. I wouldn't have it too far from the house as you would get heat losses in the pipes even with insulated pipework

 

D. Don't put it on the roof, weight / mounting issues and noise source is elevated so can travel further.

 

The noise from the ASHP is all the fan noise and is very directional in the way the fan points.

 

If it was me i would have it against the house to the southern boundary, facing to the east. there would be a fence to the neighbours to the south to attenuate the noise that way.

 

On your site i would put a low wall / fence to the northern side of the ASHP to attenuate noise from it to the north into your garden.

[epsilonGreedy]

55 minutes ago, Dave Jones said:

you lost me at 'immersion heater' im sorry.

 

 

I think what he is saying is that hitting the 60 minute guest mode button will raise the water temperature by 10% or 20% thus expanding the amount of shower temperature water available to the whole household at peak times.

 

Quite a nifty idea and one I will remember as a possible retrofit in case my default setup struggles when we have guests 

[PeterW]

3 hours ago, Dave Jones said:

so you have a 300L tank. For 5 people to have their morning 10min shower with a decent 10lpm shower, person 3 would be freezing as would person 4 and 5. 

Not correct ..

 

300 litres at 56°C gives you around 430 litres at 40°C so you’ve got 43 minutes of flow without any top up. 
 

If you’re in the situation you know you want more then simply you increase the heat capacity. Taking the temperature to 70°C and you have 560 litres at 40°C or 56 minutes of flow at 10lpm…

 

All of this is predicated that you have purely stored water and not decided to recharge it - as soon as you hit the button to reheat then you extend this. 
 

The key fundamental difference is that the UVC can comfortably cover a pair of showers at that flow rate, a combi will

struggle. So you have 5 people sequentially so can’t really have anything more than one concurrent shower whereas the designed solution here can do concurrent showers. 
 

 

[Dave Jones]

4 minutes ago, PeterW said:

Not correct ..

 

300 litres at 56°C gives you around 430 litres at 40°C so you’ve got 43 minutes of flow without any top up. 
 

If you’re in the situation you know you want more then simply you increase the heat capacity. Taking the temperature to 70°C and you have 560 litres at 40°C or 56 minutes of flow at 10lpm…

 

All of this is predicated that you have purely stored water and not decided to recharge it - as soon as you hit the button to reheat then you extend this. 
 

The key fundamental difference is that the UVC can comfortably cover a pair of showers at that flow rate, a combi will

struggle. So you have 5 people sequentially so can’t really have anything more than one concurrent shower whereas the designed solution here can do concurrent showers. 
 

 

 

Peter,  would you share what this system would cost Joe public to install to allow a fair comparison against a tanked system boiler ?

[PeterW]

58 minutes ago, Dave Jones said:

More so in the winter when there is less heat in the air when its needed most.

INCORRECT STATEMENT

 

The “heat energy” in air is registered on the Kelvin scale so runs to absolute zero, not 0°C that you’re using. Energy in the air at 5°C vs -5°C is around 3% difference. Most ASHP are rated at 35/7 which is flow of 35°C and air temperature of 7°C so if the cold is a problem then all the manufacturers would be calling this out. 
 

The limitations run to the liquification point of the refrigerants, and that’s around -35°C which in the U.K. is highly unlikely. 

[IanR]

53 minutes ago, Dave Jones said:

Ian, the 20 minutes was an example of how long it would take to exhaust your tank after which you have zero hot water. 

 

With a 500l tank that would be a flow rate well above mine to deplete all the hot water in 20 mins.

 

However, that's neither here nor there. Leaving the hot tap on full for 20 minutes is not a use case I've ever done, so even though my system could do it, it's not something its designed to do.

 

Needing multiple 15 minute showers at 38°C is a use case used regularly, so the system is designed to cover that. And for times we have guests and there's a higher DHW demand the Hot Water is switched over to "Lux", so the tank is lifted to 55°C.

 

1 hour ago, Dave Jones said:

Heat pumps are a step on the way but they are not the answer.

I'm glad we've moved the needle, even if it is only a little. You were previously stating ASHP are for "niche" builds, and a dead technology.

[PeterW]

2 minutes ago, Dave Jones said:

 

Peter,  would you share what this system would cost Joe public to install to allow a fair comparison against a tanked system boiler ?

300 litre UVC with all fittings £750, install £4/500 depending on location. 9kW ASHP £3k, install equivalent to a gas boiler. 
 

So compared to a standard boiler at £1500 or so, you have an additional cost of around £2750 on a standard build. Over 10 years, that differential is lost in the reduction of any standing charges or servicing for gas, and the guarantee that the price on gas is only going up. 

[joe90]

1 hour ago, Dave Jones said:

Look up this thread in 20 years and I promise i wont say i told you so.

I don’t need to wait that long, mine works very well now as do others here, as you say not the answer for every situation  but that is no reason to say they don’t work. 

[Tony K]

27 minutes ago, Moonshine said:

 

The sound power data here is the most useful information, and is 57 dB(A).

 

How loud it is dependant on the surrounding reflective surfaces.

 

What is the green block in your layout, the extension? 

 

A. i think this is asking for trouble with your neighbours, and getting soundproofing to work with airflow requirements is tricky / expensive so i wouldn't go down this route. You would be looking for something like this https://acousticenclosuresltd.co.uk/air-conditioning-gallery/ and would run to £1k+

 

B. probably the best (or variation).

 

C. I wouldn't have it too far from the house as you would get heat losses in the pipes even with insulated pipework

 

D. Don't put it on the roof, weight / mounting issues and noise source is elevated so can travel further.

 

The noise from the ASHP is all the fan noise and is very directional in the way the fan points.

 

If it was me i would have it against the house to the southern boundary, facing to the east. there would be a fence to the neighbours to the south to attenuate the noise that way.

 

On your site i would put a low wall / fence to the northern side of the ASHP to attenuate noise from it to the north into your garden.

 

Thanks @Moonshine, much appreciated. Ignore the green and grey blocks, it is one L shaped bungalow with a flat roof. 

 

If I opt for position B as you suggest I have a couple of options. The red dot is the obvious place for it, the green is where you suggest:

 

 

The PD regs for ASHPs stipulate that noise levels must stay at or below 42 decibels (dB) from a metre distance away from any habitable room, including (I presume) the host dwelling. 

 

The spec suggests a sound power level of 57db. I am not sure how I can square that spec with the PD regs therefore, unless of course the sound is directed somehow so that despite being near my windows, the actual sound from the ASHP is at or below 42db. Is that how it works in your opinion? Your suggestion of a screening low wall suggests that I can manipulate the direction of sound from the ASHP. Is that so do you think?

 

I am interested in the acoustic enclosures you linked to, thanks. Do you know how they work at all? I wonder if I can make a less industrial looking enclosure to similar effect.

 

I had made these notes some time ago, and would be interested in your views, particularly in whether in fact I would do better to open the doors so the noise can be directed away:

 

 

 

 

 

[PeterW]

Site at green dot and turn at 90 degrees so perpendicular to the building. 

[joe90]

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[Tony K]

6 minutes ago, PeterW said:

Site at green dot and turn at 90 degrees so perpendicular to the building. 

 

@PeterW what is achieved through perpendicular positioning please, and are you suggesting the ASHP be located without noise reduction housing?

[epsilonGreedy]

Since we are having a good old ASHP v. Combi mud wresting match I would like to ask what is the medium to long term evidence for relative cost of ownership with respect maintenance?

 

The figures for gas boilers are well known i.e. look at these annual boiler maintenance contracts. My hunch is that ASHPs are going to play up as they are exposed to the weather, however they are not encumberred by the who GasSafe fitter "I won't get out of bed for less than £300" syndrome.

[Dave Jones]

29 minutes ago, PeterW said:

300 litre UVC with all fittings £750, install £4/500 depending on location. 9kW ASHP £3k, install equivalent to a gas boiler. 
 

So compared to a standard boiler at £1500 or so, you have an additional cost of around £2750 on a standard build. Over 10 years, that differential is lost in the reduction of any standing charges or servicing for gas, and the guarantee that the price on gas is only going up. 

 

Peter, that just isn't realistic.  The bargain basement installs are £10k compared to a £2k boiler.

[ProDave]

9 minutes ago, Dave Jones said:

 

Peter, that just isn't realistic.  The bargain basement installs are £10k compared to a £2k boiler.

You have to question WHY they are that expensive.

 

Peter has quoted the material cost as being less than £5K  So why is it you think the bargain basement installed cost is £10K?  That's £5K for install. At say £30 per hour for labour that's 166 hours, or 20 man days labour.

 

Do you really believe it is going to take 20 man days to install an ASHP system?

 

Or could it just be, that introduce a government subsidy under the condition you use an acredited installer, and said installer inflates the price, so the effect of the subsidy is not to save the customer money,but to line the pockets of the installing company?

 

You could of course just buy the kit for £5K and pay an electrician and a plumber to install it which would probably cost about £1000

 

[IanR]

2 hours ago, Tony K said:

At the moment I'm looking at a NIBE 2040-12kw air source heat pump. 

 

That's the unit I have. It's subjective, but It's quiet when running normally, makes a bit more noise when defrosting.

I have mine positioned adjacent to a bedroom wall, close to an opening window. With the window closed I can't hear it. We're very rural, and my light-sleeping wife can hear it at night if we use that bedroom, when there is no other background noise.

Compared to the modern gas combi-boiler I had in my last house the ASHP is significantly quieter within the house. Inside the house I would not know whether or not the ASHP was on.

When outside, during the day and with a little background noise (we have a dual-carriageway around 1km away), you'd need to be within 3m or 4m of it to notice it is on. When it first switches to defrost there is a louder noise that is audible from further away. It defrosts only occasionally in spring, summer or autumn.

Outside of the heating season the ASHP runs two or three times a day for 30min to 60 min.
 

2 hours ago, Tony K said:

A. In the alcove. Its within 1m of the boundary but would live inside the timber structure that will occupy that inset section, and provide storage for bikes etc. It could therefore be soundproofed. It would require planning permission there of course.

 

B. On the inside facing wall of the bungalow.

 

C. In the garden, somewhere at least 1m from the boundary.

 

D. On the flat roof. Sounds counter-intuitive, but I wonder if in fact noise would be less amplified there. 

 

 

A. Not ideal, you can avoid being that close to a neighbour.

B. Yes, positioned as close as possible to the UVC location and at least the Minimum distance from the wall. I think Nibe recommend 150mm, but I went to about 500mm

C. Not ideal, the longer pipe runs will reduce efficiency as you will have to run a higher flow temp to get the same heating and cylinder temp.

D. Not when you have Option B. Risk of vibration noise transfer to inside the house that could be difficult to resolve.

 

Edited to add:
 

I'd not install any noise shielding at the start. Retrofit if you are sensitive to the noise it produces and can't move the run time to a time that doesn't effect you.

Edited August 3, 2021 by IanR

[Tony K]

Thanks @IanR that's very useful. 

 

[PeterW]

58 minutes ago, Dave Jones said:

 

Peter, that just isn't realistic.  The bargain basement installs are £10k compared to a £2k boiler.

Wrong again 

 

A non MCS install is similar to a gas boiler. There is the same amount of water pipes, same connections for a timer, the difference is the electricity vs gas connection. 
 

I can run a 20m 6mm T&E in a single length in less than 2 hours in an open ceiling. Find me a gas fitter who can do the same with a 22mm gas pipe and test it in less than 4…??

 

Any plumber can fit an ASHP. No MCs premium, no GSR… I think on here there are probably a dozen or so self installs vs how many gas boilers that members have installed themselves ..?  None. 
 

And your £2k boiler ..??! That includes all gas pipework and commissioning and something that can do 18 litres / min ..? That didn’t fall off the cheap shelf in B&Q..?? Any main brand is £12-1400 now plus the half as much again on install for a replacement, probably £1k or more for a new build where they are pulling the gas in. 
 

 

[Nickfromwales]

3 hours ago, Dave Jones said:

 

you lost me at 'immersion heater' im sorry.

I think you lost me at "Complete......" tbh

[PeterW]

2 hours ago, epsilonGreedy said:

My hunch is that ASHPs are going to play up as they are exposed to the weather, however they are not encumberred by the who GasSafe fitter "I won't get out of bed for less than £300" syndrome.

we have a pair of Fujitsu A2A and a Sanyo CO2 12kW A2W heat pump on maintenance contract for a local place and it’s £275 per service and they are done twice a year. The main service cost is the fan coil units on the A2A as they are stripped every 6 months to have filters and coils cleaned and check the drains etc. The Sanyo has had its cover off once, and that was to check the insulation where a mouse had been chewing it !

[puntloos]

8 hours ago, IanR said:

C. Not ideal, the longer pipe runs will reduce efficiency as you will have to run a higher flow temp to get the same heating and cylinder temp.

 

@Moonshine and @IanR - can you explain why this is a big problem?

 

Clearly, having a warmish water flow in a pipe that needs to cross 10m of garden in the middle of winter is less ideal than something stapled to your heat envelope. But insulation is surprisingly good, and wrapping say 10m outside pipe in say 200mm worth of insulation.. surely that would only drop temp "a bit"?

 

Can someone perhaps compare the 2 situations Tony listed, e.g ,simplifying for calculation purposes, and assuming the ASHP runs for an hour in both cases

 

B/ ASHP is stapled to the wall, so let's assume "0m" of piping, hot water entering house is 35C

C/ ASHP center garden, needs 10m external piping buried 500 mil deep, with say 200mm insulation

 

-> the question is - how warm will the water in C be for various cases, (-10? 0? +10)

 

 

 

Edited August 4, 2021 by puntloos

[Moonshine]

3 hours ago, puntloos said:

@Moonshine and @IanR - can you explain why this is a big problem?

 

It seems unwarranted in this case and adds to the cost, I don't know the sums for the heat looses and it would be good.if someone can do it.

To me the best part is no part at all.

[Moonshine]

12 hours ago, Tony K said:

 

Thanks @Moonshine, much appreciated. Ignore the green and grey blocks, it is one L shaped bungalow with a flat roof. 

 

If I opt for position B as you suggest I have a couple of options. The red dot is the obvious place for it, the green is where you suggest:

 

 

The PD regs for ASHPs stipulate that noise levels must stay at or below 42 decibels (dB) from a metre distance away from any habitable room, including (I presume) the host dwelling. 

 

The spec suggests a sound power level of 57db. I am not sure how I can square that spec with the PD regs therefore, unless of course the sound is directed somehow so that despite being near my windows, the actual sound from the ASHP is at or below 42db. Is that how it works in your opinion? Your suggestion of a screening low wall suggests that I can manipulate the direction of sound from the ASHP. Is that so do you think?

 

I am interested in the acoustic enclosures you linked to, thanks. Do you know how they work at all? I wonder if I can make a less industrial looking enclosure to similar effect.

 

I had made these notes some time ago, and would be interested in your views, particularly in whether in fact I would do better to open the doors so the noise can be directed away:

 

 

 

 

 

 

You are incorrect in the 42 dB applying to the host dwelling and this is actually applied at the nearest house, so in effect you don't need to worry about the noise level at your house if you don't need to.

 

Is the ASHP going in as PD or under your planning application? if under your planning application then you won't need a MCS020 certified installation which will save you money. 

 

Your local authority may ask for a noise assessment to be done for planning, but this is easy and when i did mine just followed the methodology set out in MCS020, and submitted that (there is a MCS020 noise tab in the following spreadsheet)

 

https://mcscertified.com/wp-content/uploads/2019/09/MCS-Heat-Pump-Calculator.xlsm

 

For option B or the variant of it, it seems that the neighboring properties are over 20m away with a fence acting as a barrier, so a unit with a sound power of 57 dBA will be fine for planning.

 

The issue of noise is really reducing the impact on your own home and garden and isn't a concern for the planners. 

 

your red dot does seem the most logical place to put the unit on the facade, but will have more of an impact on the garden than the location of the green dot, though the green dot is just outside the main bedroom. is the build masonry or timber frame?

 

The acoustic enclosures do work to a degree, but i have not found one that reduces the noise by a level as claimed, and i haven't found one that looks 'nice'. 

Edited August 4, 2021 by Moonshine