ASHP acoustic cover

[Dave Jones]

1 hour ago, PeterW said:

So you can if you wish - bath is 185 litres, tank is 300 litres at 56°C so it will be full in 8 minutes however it won’t run cold until the floor is under approx 30mm of water and the rest is running down the stairs …

 

That 300 litres btw was at a CoP of 3.43 yesterday, and at an overnight run of 10.2p/kWh, so at 13.26kWh of heat that used 3.86kWh of electricity or ~39p

 

Take your favourite combi boiler, at 90% efficiency you would need 14.73kWh of gas at 3.23p, so your combi would cost 47.5p to heat the same volume of water. 
 

So your combi has a lower flow rate (15 litres/min vs 22 litres/min), higher maintenance and service costs, and is over 20% more expensive to run than a heat pump. 
 

Do you have any factual and empirical statements to challenge this ..? Or should we go with hot air and baseless conjecture ..??
 

 

 

 

 

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. 

 

workable for a a couple/single person maybe.

 

not workable in the real world for a family. 

 

Sure could add tanks, and tanks and tanks. or admit defeat and use a combi.

[epsilonGreedy]

1 hour ago, jack said:

There's no way you can pipe into people's homes a scentless explosive gas that leaks better than just about any other gas in existence. 

 

 

I thought natural gas had an extra scent added?

[ProDave]

I spent a week with a relative recently who had a combi boiler for hot water.  Hideous things.  The hot water took ages to warm up for the first time, the temperature delivered to the tap varied with the flow rate. Turn the tap off for a few seconds and turn it back on, then the tap would run cold for a bit as the boiler took time to get going again.

 

The only good point is it will never run out,  but in all other respects I found it a really irritating hot water source.

 

Previous experience with an oil fired combi was better but those work differently maintaining a small internal store (tank) of hot water to give a quick response to demand and even out the peaks and troughs of burner usage so delivered a much better user experience.

[epsilonGreedy]

10 minutes 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. 

 

 

Err. You need to allow for the mixed in cold water to bring the temp down by 25% so probably closer to 6lpm of hot tank water.

 

Also unlike a combi that needs to be kept running for the full shower to avoid cycles of scalding and freezing, a mixer shower can be stopped and restarted.

[jack]

17 minutes ago, epsilonGreedy said:

I thought natural gas had an extra scent added?

 

It does. But if it's only the hydrogen leaking, it won't take the scent (a much bigger molecule) with it.

 

TBF, it may be that any leak sufficient to allow hydrogen out fast enough to cause a dangerous situation will also necessarily allow sufficient odorant out to allow detection. 

[Moonshine]

28 minutes 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. 

 

workable for a a couple/single person maybe.

 

not workable in the real world for a family. 

 

Sure could add tanks, and tanks and tanks. or admit defeat and use a combi.

 

I think that you are missing something quite fundamental, while those people are having showers the ASHP is working to top up the hot water in the cylinder, also the water in the tank is at 55 degrees, showers are at about 40 degrees, so its too simplistic to say it takes the full 100l from the cylinder.

 

I have been asking the same type of questions of the supplier of the ASHP system i am looking to get, based on a 9Kw ASHP and 250l tank, it can heat the water in the tank from cold to 55 degrees in 30-40 minutes (depending on outside temp).

 

However that scenario won't happen as in normal operation the water would not drop down below 20 degrees due to the insulated tank, and it would get up to 55 degrees in 10-15 minutes.

 

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).
3. When the house and tanks are up to temperature, the ASHP only operates to top up the tanks when needed.
4. Demand comes from showers and household activities
   1. Shower 1 - takes 70l of 55 degree hot water from the tank to be mixed with 30l of cold to take your big 100l shower over 10mins.
   2. The ASHP tops up the tank to replenish the heat lost, it may not make up all the heat but there will be some gaps in showers being on
   3. repeat

Edited August 3, 2021 by Moonshine

[IanR]

27 minutes ago, Dave Jones said:

workable for a a couple/single person maybe.

 

not workable in the real world for a family. 

 

I know you don't want to hear it, but an ASHP works perfectly for a family of 5, and as the tank temp seldom drops below 47°C, I'm turning mine down a bit to push the COP up further.

 

 

 

Please offer some data/figures to show how it doesn't work, rather than conjecture.

[Nickfromwales]

36 minutes 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. 

 

workable for a a couple/single person maybe.

 

not workable in the real world for a family. 

 

Sure could add tanks, and tanks and tanks. or admit defeat and use a combi.

Complete and total nonsense, sorry. 
Please don’t give such non-comprehensive replies as it’s extremely unhelpful.

Allowing for an install with both a high, and a low level cyl stat, the ASHP can be made to kick in during shower number 2. The return water temp would be higher so the HP recovery would be higher / faster. Something to consider. 

 

With PV or an E7/10 boost the tank could be heated to a premium temperature above the normal capacity @55oC. Something else to consider.
 

Direct electric heating via the immersion ‘could’ be strategically directed purely for times where DHW was most needed. It ( the immersion(s) ) can also be used for delivering extra DHW at times of duress, which I call “guest mode” on my installs. Occupants go up to the cylinder and hit a 30 / 60 / 120 min immersion boost switch accordingly. If done an hour before duress the tank temp ( and therefore it’s sustain ) can be elevated significantly thus increasing your lower temp x 300L @ 55oC capacity to a much higher capacity in the same size cylinder. Something else to consider.

 

People do a funny thing after showering, it’s called drying off, squirting on sweet smelling products, etc etc. They also shower typically at 38oC. Therefore that needs to be considered in the calculations for the time needed for the cylinder to recover between showers / bathing. People do a funny thing after getting in the bath too. They get into it. And then they stay there for a while.  

A “couple” could easily manage with a 210L UVC with some  very basic disciplines. 
 

A lot of things can be taken into consideration when sizing a cylinder, and stating all those things makes for a comprehensive reply. 

[Ommm]

Quote

A “couple” could easily manage with a 210L UVC with some  very basic disciplines. 

 

What size cylinder would you recommend for a 3/4 bedroom house (1 bath+shower room, possibility of another shower in the distant future) out of interest?  Bearing in mind sizing for the property rather than the current occupants if you ever plan to sell it, and not assuming those future occupants having any particular usage pattern.

[SteamyTea]

5 hours ago, Dave Jones said:

 

the betamax video player also worked well.

Mine didn't, the sound card kept failing, Sony never got it sorted.

[epsilonGreedy]

1 hour ago, jack said:

 

It does. But if it's only the hydrogen leaking, it won't take the scent (a much bigger molecule) with it.

 

TBF, it may be that any leak sufficient to allow hydrogen out fast enough to cause a dangerous situation will also necessarily allow sufficient odorant out to allow detection. 

 

Little molecules, AH-HA, fair point.

 

I think we will have to adopt hydrogen somewhere because soon there will be ridiculous amounts of surplus wind power overnight and battery technology is not going to give us 1000 GwH of national storage to see us through a winter high pressure. Farming machinery is another niche that could take hydrogen.

[SteamyTea]

There is hydrogen embrittlement as well.  Anything iron based has to be changed.

 

On a more general note, and I keep hearing this 'ASHPs only work in a well insulated, airtight house'.

This is nonsense, fit the wrong size heating system to an house and it will not be optimal.

The cash cost may be an issue, but that is mainly because we are not paying the existential costs combustion technology.

[Tony K]

If I could be a diva and make this all about me for a moment please... ?

 

I started this thread as I was concerned about noise. Replies (for which thanks) have covered :

 

1. Whether an ASHP is right for my SB or not (at least one learned poster has suggested it won't work).

2, Whether they are any good at all.

3. How noisy they are. 

 

1. I think an ASHP will work for me. I have full plans approval which includes a SAP calc based on 90mm PIR insulation between my RC slab and my 65mm UFH/screed, but I can alter that to 100mm insulation and 50mm liquid screed, plus I have ceramic tiles (a very good conductor), I will have significant south facing glazing, allowing heat to soak in the slab and walls in summer and release in winter (overheating to be avoided with a canopy), and I have good overall insulation standards, which matters as much as under floor insulation as far as I can tell. I will place my insulation inside the building, not under the slab. I appreciate the cold bridging effect this can create, but most UFH suppliers advise that my arrangement leads to more efficient performance. 

 

2. The ranting video from SkillBuilder actually captures some good points (the 'rant' element is for humorous purposes largely) and is quite clear that whilst ASHP tech isn't always a great fit, it very often is perfectly good in well-insulated new builds with UFH, and especially where the overall system is designed holistically by an engineer. I do not have, nor do I intend to develop, the interest in and knowledge of the subject that some on here clearly have, and so for me the question is who do I engage to produce a holistically designed scheme, and can I implement  bits of it myself to save a few quid. I'd guess the UFH is one, and then ask the installer to give it the once-over. What I've learned from some of the replies on here is that there are a number of small elements that can matter greatly, and which I will pay an installer to do. 

 

3. The only thing I remain concerned about is noise. As some have said, the quietest ones still run at 45-50db, and the fact that the permitted development regs themselves include maximum noise levels speaks volumes. I have gone to new builds to listen to ASHPs and consider the noise noticeable. I will need to better understand this aspect.

 

Does intermittent use vs steady constant use help?

Is it as simple as to say that they are more active (and noisy) in winter when windows are closed, and generally sit silent in the heat of summer when windows are open?

Can I fit any kind of noise-reducing housing around the pump? 

 

 

 

 

[joe90]

3 minutes ago, Tony K said:

I do not have, nor do I intend to develop, the interest in and knowledge of the subject that some on here clearly have, and so for me the question is who do I engage to produce a holistically designed scheme, and can I implement  bits of it myself to save a few quid. I'd guess the UFH is one, and then ask the installer to give it the once-over. What I've learned from some of the replies on here is that there are a number of small elements that can matter greatly, and which I will pay an installer to do. 

I knew nothing about ASHP,s or UFH (despite being very practical and a retired small time builder), through input from forum members I designed and installed my own system. I did not use PHPP but very roughly guessed some info and copied others here (that knew far more than me. ) Jeremy Harris,s blog is an absolute mine of information and definitely a very good read fir self builders, @Nickfromwales also added volumes to my knowledge (and even arranged discount on some parts fir a few of us on the forum). It’s not rocket science but it is different from other heating types . I believe it is well within the practical skills to DIY the installation and many on this forum are very willing to help answer questions. 

[Tony K]

11 minutes ago, joe90 said:

I knew nothing about ASHP,s or UFH (despite being very practical and a retired small time builder), through input from forum members I designed and installed my own system. I did not use PHPP but very roughly guessed some info and copied others here (that knew far more than me. ) Jeremy Harris,s blog is an absolute mine of information and definitely a very good read fir self builders, @Nickfromwales also added volumes to my knowledge (and even arranged discount on some parts fir a few of us on the forum). It’s not rocket science but it is different from other heating types . I believe it is well within the practical skills to DIY the installation and many on this forum are very willing to help answer questions. 

 

I appreciate that @joe90, I really do, but I've not got the time or inclination (and probably not the skill set) to design it myself. I've done a lot of the heavy lifting on this SB, and will be doing plenty more, but getting a system designed is on the 'farm off to others' list and isn't coming off!

 

What I'd really appreciate is any advice from anyone who has tried to contain, reduce, or direct the noise from an ASHP. I'm quite tightly packed in on my site, and the SB itself will be an L shaped one around a courtyard, so my instinct is that the citing of the ASHP is a crucial consideration, as s any noise limiting set up I can arrange. 

[SteamyTea]

28 minutes ago, Tony K said:

I will have significant south facing glazing, allowing heat to soak in the slab and walls in summer and release in winter

You will not get intersessional storage, maybe a few hours at best.  Yo can do the calculations easy enough.

30 minutes ago, Tony K said:

SAP calc based on 90mm PIR insulation between my RC slab and my 65mm UFH/screed, but I can alter that to 100mm insulation and 50mm liquid screed

This makes a difference with UFH, the temperature difference is greater between the floor and the ground, than it is with a radiator based system.  It is why it is called Under Floor Heating, and not Pointy Up Heating.

[Moonshine]

6 minutes ago, Tony K said:

What I'd really appreciate is any advice from anyone who has tried to contain, reduce, or direct the noise from an ASHP

 

i can probably assist ?

 

Do you know the unit you want to use, and have you images of where it is going or plans, also where are you trying to reduce the noise?

[Dave Jones]

2 hours ago, IanR said:

 

I know you don't want to hear it, but an ASHP works perfectly for a family of 5, and as the tank temp seldom drops below 47°C, I'm turning mine down a bit to push the COP up further.

 

 

 

Please offer some data/figures to show how it doesn't work, rather than conjecture.

 

yes i can see a graph showing minimal hot water pull.

[Dave Jones]

2 hours ago, Nickfromwales said:

Complete and total nonsense, sorry. 
Please don’t give such non-comprehensive replies as it’s extremely unhelpful.

Allowing for an install with both a high, and a low level cyl stat, the ASHP can be made to kick in during shower number 2. The return water temp would be higher so the HP recovery would be higher / faster. Something to consider. 

 

With PV or an E7/10 boost the tank could be heated to a premium temperature above the normal capacity @55oC. Something else to consider.
 

Direct electric heating via the immersion ‘could’ be strategically directed purely for times where DHW was most needed. It ( the immersion(s) ) can also be used for delivering extra DHW at times of duress, which I call “guest mode” on my installs. Occupants go up to the cylinder and hit a 30 / 60 / 120 min immersion boost switch accordingly. If done an hour before duress the tank temp ( and therefore it’s sustain ) can be elevated significantly thus increasing your lower temp x 300L @ 55oC capacity to a much higher capacity in the same size cylinder. Something else to consider.

 

People do a funny thing after showering, it’s called drying off, squirting on sweet smelling products, etc etc. They also shower typically at 38oC. Therefore that needs to be considered in the calculations for the time needed for the cylinder to recover between showers / bathing. People do a funny thing after getting in the bath too. They get into it. And then they stay there for a while.  

A “couple” could easily manage with a 210L UVC with some  very basic disciplines. 
 

A lot of things can be taken into consideration when sizing a cylinder, and stating all those things makes for a comprehensive reply. 

 

you lost me at 'immersion heater' im sorry.

[ProDave]

32 minutes ago, Tony K said:

 

I appreciate that @joe90, I really do, but I've not got the time or inclination (and probably not the skill set) to design it myself. I've done a lot of the heavy lifting on this SB, and will be doing plenty more, but getting a system designed is on the 'farm off to others' list and isn't coming off!

 

What I'd really appreciate is any advice from anyone who has tried to contain, reduce, or direct the noise from an ASHP. I'm quite tightly packed in on my site, and the SB itself will be an L shaped one around a courtyard, so my instinct is that the citing of the ASHP is a crucial consideration, as s any noise limiting set up I can arrange. 

Perhaps posting a site layout plan showing the neighbouring houses might give a better answer?

[IanR]

1 minute ago, Dave Jones said:

 

yes i can see a graph showing minimal hot water pull.

 

Really? you'll have to explain how you worked that out.

Your bias is making you jump to incorrect conclusions. What you are seeing is an ASHP reacting to DHW usage.

[Dave Jones]

1 minute ago, IanR said:

 

Really? you'll have to explain how you worked that out.

Your bias is making you jump to incorrect conclusions. What you are seeing is an ASHP reacting to DHW usage.

 

Ian, turn on the hot tap for  20 mins full bore and both you and I know the heat pump will have no chance on keeping up. More so in the winter when there is less heat in the air when its needed most.

 

Now that's not to say at all, that your system as used, could be an acceptable feature for your circumstance.

 

It is however a retrograde step when compared to limitless, paid for on demand proper hot water.

[Tony K]

23 minutes ago, Moonshine said:

 

i can probably assist ?

 

Do you know the unit you want to use, and have you images of where it is going or plans, also where are you trying to reduce the noise?

 

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. 

 

[IanR]

2 minutes ago, Dave Jones said:

 

Ian, turn on the hot tap for  20 mins full bore and both you and I know the heat pump will have no chance on keeping up. More so in the winter when there is less heat in the air when its needed most.

 

Now that's not to say at all, that your system as used, could be an acceptable feature for your circumstance.

 

It is however a retrograde step when compared to limitless, paid for on demand proper hot water.

 

Not sure what "20 mins full bore" would prove or dis-prove. What matters is if the heating and DHW system is designed for the worst case use in the house it's installed in.

 

Unless our winter temps drop to -20°C for long periods, winter has no effect on the ability to produce hot water, just the efficiency it can do it at.

[Dave Jones]

Ian, the 20 minutes was an example of how long it would take to exhaust your tank after which you have zero hot water.  I guess depending on your tank size, pipe diameter and flow this could be quicker or slower. The end result however being them same.

 

I know im a lone voice here on this issue and I accept that. 

 

Heat pumps are a step on the way but they are not the answer. Look up this thread in 20 years and I promise i wont say i told you so.