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[Sprocket.]

I've heard more compressors than I could possibly remember. I've also heard my mate's heat pump compressor. It's a scroll compressor and it's almost silent, and certainly quieter than any piston compressor I've ever heard, so regardless of where he works, your neighbour is wrong.

Are heat pumps noisy? - IMS Heat Pumps

How much noise do ground source and air source heat pumps make? This blog post explains the details of expected noise, and what this means.

www.imsheatpumps.co.uk

Most piston compressors operate above the noise level that would require ear protection (85dB>)

Example​	Noise level (decibels)​
Breathing	10
Whispering / rustling leaves	20
Quiet rural area	30
Library / bird calls	40
Heat pump noise limit (MCS)	42
Conversation at home	50
Conversation in an office or restaurant	60
Vacuum cleaner	70
Alarm clock / dishwasher	80

Heat Pump Noise Levels: How Noisy Are They? - Evergreen Energy

There are different types of heat pumps and the volume of noise they make depends on each model. Find out how each heat pump sounds and more.

www.evergreenenergy.co.uk

Thanks for the information and post. I too have heard, installed and maintained many compressors over the last 48 years working as a mechanical maintenance engineer. I know how loud a small garage/workshop compressor can sound at two in the morning, I personally haven’t heard a heat pump so I can’t speak from personal experience.
But I admit my neighbour is prone to slight exaggeration, he wears rigger boots and gloves, goggles and ear defenders when mowing is lawn.
I won’t be installing an heat pump for at least ten years as I have recently retired and only changed my gas fired combi-boiler last August.

 

[what]

If you want to understand how a heat pump works, you can look it up on the internet. The heat is moved from one location to another, not generated by the compressor, as several people people have now pointed out.

Actually its a mixture of both.
Simple explanation here.

Heat Pumps Explained | Worcester Bosch

View Worcester's Greenstar combi and system ground source heats pumps and view how they work

www.worcester-bosch.co.uk

 

[Saul Goodman]

Not correct

Quote the whole post, then explain why it isn't correct.

 

[teuchter]

Quote the whole post, then explain why it isn't correct.

It's pretty straightforward; if the system contains any moving parts like a fan, then a portion of the energy will be converted into mechanical energy rather than heat. Yes you will now try and claim that a "resistive element heating system" contains nothing other than resistive elements, but we all know that's just as true as saying an LED lighting system contains nothing other than LEDs.

 

[Saul Goodman]

It's pretty straightforward; if the system contains any moving parts like a fan, then a portion of the energy will be converted into mechanical energy rather than heat. Yes you will now try and claim that a "resistive element heating system" contains nothing other than resistive elements, but we all know that's just as true as saying an LED lighting system contains nothing other than LEDs.

That falls under distributing the heat, which is why you deliberately omitted that part of the quote.
Nice try but disingenuous at best.

 

[teuchter]

That falls under distributing the heat, which is why you deliberately omitted that part of the quote.
Nice try but disingenuous at best.

Nope, you said

All resistive element heating systems are by definition 100% efficient at converting electricity into heat. They all have a COP of 1.0. So for every watt of electricity you put into the system, you get 1 watt or 3.41 BTU of heat out. The only thing you can effect is how you distribute that heat.

You didn't say that distributing the heat would affect the effficiency, nor did you define whether this distribution occurs within or outside of the system whose efficiency you are describing. And in any case they system could include moving parts that do not affect the distribution of the heat.

An embarrassing blunder, and yet more proof that I am much more expert in engineering matters than you are.

 

[Saul Goodman]

Nope, you said



You didn't say that distributing the heat would affect the effficiency, nor did you define whether this distribution occurs within or outside of the system whose efficiency you are describing. And in any case they system could include moving parts that do not affect the distribution of the heat.

An embarrassing blunder, and yet more proof that I am much more expert in engineering matters than you are.

Nope, all it proves is that you're a dick

 

[Crispy]

It's pretty straightforward; if the system contains any moving parts like a fan, then a portion of the energy will be converted into mechanical energy rather than heat.

Think about what happens to that mechanical energy.

 

[WouldBe]

Quote the whole post, then explain why it isn't correct.

Resistive heating can also produce light which isn't heat.

 

[WouldBe]

Actually its a mixture of both.
Simple explanation here.

Heat Pumps Explained | Worcester Bosch

View Worcester's Greenstar combi and system ground source heats pumps and view how they work

www.worcester-bosch.co.uk

Thats well simplified and doesn't actually explain it. We have already agreed that heat exchangers don't boost the temperature. So if ground temp at an average of around 12C is high enough to evaporate the gas then it would need to be cooled below 12C to convert it back into a liquid. As room temp is around 21C the returning gas will be around the same temp and won't liquify. The only way to liquify it is to compress it which requires energy but you've alread done that to raise the temp to start with so doesn't make sense.

 

[Cloo]

The house insulation is the killer for me. We're a terrace with side return, no cavities to insulate, so to have a heat pump I expect we'd be external insulation layer on 3 walls and triple glazing. 5k doesn't even start to cover it Would love to go for it otherwise.

 

[what]

Ok this is standard vapour compression cycle of refrigeration machines. A heat pump is a refrigeration machine used in reverse if being used to heat a space. Link below gives it in more detail

The Vapour Compression Cycle - Heat Pump Association

www.heatpumps.org.uk

 

[Saul Goodman]

Thats well simplified and doesn't actually explain it. We have already agreed that heat exchangers don't boost the temperature. So if ground temp at an average of around 12C is high enough to evaporate the gas then it would need to be cooled below 12C to convert it back into a liquid. As room temp is around 21C the returning gas will be around the same temp and won't liquify. The only way to liquify it is to compress it which requires energy but you've alread done that to raise the temp to start with so doesn't make sense.

Try to think of it as trying to freeze the ground.

 

[Crispy]

Resistive heating can also produce light which isn't heat.

It becomes heat as soon as it hits something.

 

[what]

Thats well simplified and doesn't actually explain it. We have already agreed that heat exchangers don't boost the temperature. So if ground temp at an average of around 12C is high enough to evaporate the gas then it would need to be cooled below 12C to convert it back into a liquid. As room temp is around 21C the returning gas will be around the same temp and won't liquify. The only way to liquify it is to compress it which requires energy but you've alread done that to raise the temp to start with so doesn't make sense.

Forgot to hit reply. See reply a few above.

 

[teuchter]

Think about what happens to that mechanical energy.

It will move some dust particles from the floor onto a shelf, thus being converted into potential energy rather than heat.

 

[WouldBe]

It becomes heat as soon as it hits something.

IR would but visible light is less likely to.

 

[WouldBe]

Try to think of it as trying to freeze the ground.

I understand that but the raise in temperature is due to compressing the refrigerant which is done electrically and I'm not sure the temp of the air or ground is actually relevant.

 

[Crispy]

It will move some dust particles from the floor onto a shelf, thus being converted into potential energy rather than heat.

Everyone be sure to brush any shelf dust onto the floor to recover the stored energy during cold weather.

 

[teuchter]

I understand that but the raise in temperature is due to compressing the refrigerant which is done electrically and I'm not sure the temp of the air or ground is actually relevant.

This is going to be the next "plane and conveyor belt", isn't it.

 

[MrCurry]

For anyone interested in how these things actually work, this is what the ground source heat pump which heats my house has been doing today. The first graph shows the “supply line” (heating water which runs thru the radiator system to heat the house) and tap water tank temps.

The heating is done in pulses rather than continuously. More efficient that way apparently. Around midday the tap water temp was boosted up because it got too low. The supply line temps go up as outdoor temps drop and vice versa.

The second graph is the refrigerant circuit with ”brine in” being the temp of the fluid coming into the heat pump from the borehole and “brine out“ being the temp of the fluid the heat pump is sending back out to be recirculated through the hole to collect more heat. When the supply line is being boosted up, the brine out is running just 2-3C lower than the incoming brine temps, which are 8-10C mostly, except when a big amount of heat was being taken for the tapwater cycle when it drops further.

Obviously for an air source heat pump you don‘t have a brine circuit, but the principle is the same, a small temp drop from a large volume of air gets you enough heat to provide a large temp increase in a much smaller volume of heating water.

 

[Leafster]

For anyone interested in how these things actually work, this is what the ground source heat pump which heats my house has been doing today. The first graph shows the “supply line” (heating water which runs thru the radiator system to heat the house) and tap water tank temps.

The heating is done in pulses rather than continuously. More efficient that way apparently. Around midday the tap water temp was boosted up because it got too low. The supply line temps go up as outdoor temps drop and vice versa.

The second graph is the refrigerant circuit with ”brine in” being the temp of the fluid coming into the heat pump from the borehole and “brine out“ being the temp of the fluid the heat pump is sending back out to be recirculated through the hole to collect more heat. When the supply line is being boosted up, the brine out is running just 2-3C lower than the incoming brine temps, which are 8-10C mostly, except when a big amount of heat was being taken for the tapwater cycle when it drops further.

Obviously for an air source heat pump you don‘t have a brine circuit, but the principle is the same, a small temp drop from a large volume of air gets you enough heat to provide a large temp increase in a much smaller volume of heating water.

View attachment 293568
View attachment 293569

So, if I've understood the graphs correctly, your heating appears to be on all the time but the temperature of the water to the radiators is lower than we might have with a gas boiler?

The fact that it's on for longer allows it to maintain a stable comfortable room temperature even though the radiators don't ever get as hot as with a gas boiler?

 

[MrCurry]

So, if I've understood the graphs correctly, your heating appears to be on all the time but the temperature of the water to the radiators is lower than we might have with a gas boiler?

The fact that it's on for longer allows it to maintain a stable comfortable room temperature even though the radiators don't ever get as hot as with a gas boiler?

I didn’t want to make that post any more complicated, but the heating supply runs fairly low as I have underfloor heating. It’s all configurable in any case and can be set to higher temps to suit radiator systems.

In the context of swapping a gas boiler for a heat pump system you‘d need to set it up to feed the house heating the same or very similar temps otherwise your room temps would surely vary, unless the thermostats can even things out.

 

[WouldBe]

For anyone interested in how these things actually work, this is what the ground source heat pump which heats my house has been doing today. The first graph shows the “supply line” (heating water which runs thru the radiator system to heat the house) and tap water tank temps.

The heating is done in pulses rather than continuously. More efficient that way apparently. Around midday the tap water temp was boosted up because it got too low. The supply line temps go up as outdoor temps drop and vice versa.

The second graph is the refrigerant circuit with ”brine in” being the temp of the fluid coming into the heat pump from the borehole and “brine out“ being the temp of the fluid the heat pump is sending back out to be recirculated through the hole to collect more heat. When the supply line is being boosted up, the brine out is running just 2-3C lower than the incoming brine temps, which are 8-10C mostly, except when a big amount of heat was being taken for the tapwater cycle when it drops further.

Obviously for an air source heat pump you don‘t have a brine circuit, but the principle is the same, a small temp drop from a large volume of air gets you enough heat to provide a large temp increase in a much smaller volume of heating water.

View attachment 293568
View attachment 293569

And there are times there where you are pumping warmer brine back into the ground than your getting back out.

 

[WouldBe]

This is going to be the next "plane and conveyor belt", isn't it.

No it's not at least not for me. Gases including refrigerants follow Boyles? law. Where Pressure = Temp / Volume.

I don't see any Delta (i.e. change in temp) infront of the T component so starting temp would appear to be irrelevant.

 

[Leafster]

I didn’t want to make that post any more complicated, but the heating supply runs fairly low as I have underfloor heating. It’s all configurable in any case and can be set to higher temps to suit radiator systems.

In the context of swapping a gas boiler for a heat pump system you‘d need to set it up to feed the house heating the same or very similar temps otherwise your room temps would surely vary, unless the thermostats can even things out.

I wondered whether you might have underfloor heating (because of the lower supply line temperature and being on for longer)

 

[MrCurry]

And there are times there where you are pumping warmer brine back into the ground that your getting back out.

That’s because of the on/off heating cycle and the fact the heatpump is indoors.

When the heatpump is on it‘s drawing heat from the brine and the brine output temp is lower. When the heatpump isn‘t heating the water, the flow of brine slows then stops and the output brine is briefly warmer because it’s just passed thru a warm indoors environment (where the heat pump is) compared with the brine which is coming in from outside.

As soon as the brine flow starts up the outgoing temps will be below the incoming.

 

[WouldBe]

That’s because of the on/off heating cycle and the fact the heatpump is indoors.

When the heatpump is on it‘s drawing heat from the brine and the brine output temp is lower. When the heatpump isn‘t heating the water, the flow of brine slows then stops and the output brine is briefly warmer because it’s just passed thru a warm indoors environment (where the heat pump is) compared with the brine which is coming in from outside.

As soon as the brine flow starts up the outgoing temps will be below the incoming.

The last 2 peaks seem to correspond to when the pump is running.

 

[MrCurry]

The last 2 peaks seem to correspond to when the pump is running.

You can’t see when the heatpump is running from what I posted before. i think you’re inferring it (wrongly) from the supply line temp, when you see it rising.

I’ve put all the traces on one graph, and added the “discharge pipe” temps, which is the internal intermediate step between the compressor output heat exchanger and the heating and hot water supplies. The discharge pipe output is mixed into the supply line and tapwater feeds with variable position valves, which is why the supply line is much lower, because the hotter “discharge pipe” water is being mixed in to raise the supply line. This discharge pipe temp is where you see when the compressor runs, as soon as the discharge pipe temps start climbing the compressor just kicked in.

The vertical scale gets compressed due to the range of temperatures, but you can still see the peaks in the brine temp and each time the brine output temp rises to a peak it’s when the compressor has been off a while. As soon as the discharge pipe temps start to climb, the “brine out” temps drop, because that’s where the heat is coming from.

 

[WouldBe]

You can’t see when the heatpump is running from what I posted before. i think you’re inferring it (wrongly) from the supply line temp, when you see it rising.

I’ve put all the traces on one graph, and added the “discharge pipe” temps, which is the internal intermediate step between the compressor output heat exchanger and the heating and hot water supplies. The discharge pipe output is mixed into the supply line and tapwater feeds with variable position valves, which is why the supply line is much lower, because the hotter “discharge pipe” water is being mixed in to raise the supply line. This discharge pipe temp is where you see when the compressor runs, as soon as the discharge pipe temps start climbing the compressor just kicked in.

The vertical scale gets compressed due to the range of temperatures, but you can still see the peaks in the brine temp and each time the brine output temp rises to a peak it’s when the compressor has been off a while. As soon as the discharge pipe temps start to climb, the “brine out” temps drop, because that’s where the heat is coming from.

View attachment 293586

And yet the supply line and discharge line follow each other almost perfectly. So my previous statement still stands.