Hi.

 

If an ASHP has a rated input current of say 10amps (in this question I am ignoring the Maximum input current required presumably for start up) Does that mean that during the active time it always uses 10amps?  By active time I mean when it is trying to produce a temperature change not just when the pumps are just running and the technical stuff is monitoring. 

 

Guidance appreciated 

Edited May 9, 20215 yr by Marvin
change kW for amps

I think the answer is, it depends.

Assuming an inverter type, which is just a confusing word for variable power output, and assuming it has some temperature difference controls, then it may well draw less current.

I suspect the biggest load is the fan as it is trying to move several tonnes of air an hour, and a tonne is a tonne, regardless of what it is made of.

yes, my 9.5kW inverter unit modulates just like a gas boiler and can consume anything from 600W to 3kW. The fan and pump are variable speed as well as the compressor.

Thank you SteamyTea and dpmiller!

On 09/05/2021 at 15:57, SteamyTea said:

I think the answer is, it depends.

Assuming an inverter type, which is just a confusing word for variable power output, and assuming it has some temperature difference controls, then it may well draw less current.

I suspect the biggest load is the fan as it is trying to move several tonnes of air an hour, and a tonne is a tonne, regardless of what it is made of.

 

 

For the benefit of anyone who doesn't know why it's called an inverter controlled ASHP...

 

An inverter takes the AC mains electricity and transforms it to DC (by inverting half the polarised AC electricity to a constant DC).

 

DC motors (i.e. the compressor, fan and pumps) can be controlled variably, which is why they can be scaled to match demand. AC motors can't do that. 

Edited May 17, 20215 yr by George

1 hour ago, George said:

For the benefit of anyone who doesn't know why it's called an inverter controlled ASHP...

 

An inverter takes the AC mains electricity and transforms it to DC (by inverting half the polarised AC electricity to a constant DC).

 

DC motors (i.e. the compressor, fan and pumps) can be controlled variably, which is why they can be scaled to match demand. AC motors can't do that. 

Ummm... the component which turns AC into DC is called a rectifier. The component which turns it back into AC is called an inverter.

The key benefit of this is that it enables you to change fixed-frequency AC (50Hz) into variable frequency AC matched to the running speed you want from your compressor.

On 09/05/2021 at 15:57, SteamyTea said:

inverter

It is a dreadful, and not very descriptive, term.

It will mean different things in different installations i.e PV or HP.

And then there is the common usage meanings.  If I invert my mug of tea, I then need a cloth to clean up.  If I invert my partner, I get told off on here.

 

So, if you invert a DC current, all you are really doing is reversing the electron flow (which isn't a real flow as such, more a jiggling).

But if you invert your HP, you vary the power capability.

 

A stupid term.

1 minute ago, SteamyTea said:

It is a dreadful, and not very descriptive, term.

It will mean different things in different installations i.e PV or HP.

And then there is the common usage meanings.  If I invert my mug of tea, I then need a cloth to clean up.  If I invert my partner, I get told off on here.

 

So, if you invert a DC current, all you are really doing is reversing the electron flow (which isn't a real flow as such, more a jiggling).

But if you invert your HP, you vary the power capability.

 

A stupid term.

No, it has a very specific meaning in electrical engineering - it's a device which converts DC into AC and that's exactly what happens in both PV and heat pump installations. And you don't run your tea or your partner though an inverter.

In the context of motors, I much prefer the term "Variable Speed Drive" or VSD.  It is unambiguous and clearly describes the function, to operate a motor at different speeds.

 

 

11 minutes ago, pdf27 said:

No, it has a very specific meaning in electrical engineering - it's a device which converts DC into AC and that's exactly what happens in both PV and heat pump installations. And you don't run your tea or your partner though an inverter.

Although in Motor Drive applications like ASHPs the Inverter is preceded by a rectifier to create the DC from your mains supply and the pair of these two devices is often referred to as an AC drive, and sometimes - possibly most times, as an inverter, which rather misses the vital role of the rectifier!

56 minutes ago, pdf27 said:

No, it has a very specific meaning in electrical engineering

Yes, but it is still a nonsense term in my opinion.

Why I dislike it.  Engineering needs clarity, just like other industries, with the IT field being the worse, apart from Chemistry that is, they just make up long words to sound impressive (and spray spittle over everyone).

 

Why don't they just call it a converter.

Edited May 17, 20215 yr by SteamyTea

2 hours ago, SteamyTea said:

Yes, but it is still a nonsense term in my opinion.

Why I dislike it.  Engineering needs clarity, just like other industries

 

It isn't a nonsense term, its meaning is perfectly clear and precise to people working within the industry. There's more to something being nonsense or unclear than you not being familiar with it.

 

2 hours ago, SteamyTea said:

Why don't they just call it a converter.

Because the word converter is already in use within the same field. An inverter is one type of power converter.

1 hour ago, pdf27 said:

Ummm... the component which turns AC into DC is called a rectifier. The component which turns it back into AC is called an inverter.

The key benefit of this is that it enables you to change fixed-frequency AC (50Hz) into variable frequency AC matched to the running speed you want from your compressor.

 

I stand corrected.

 

I'm the wrong type of engineer and clearly I missed the first step when I looked into why my ASHP was 'inverter driven'.

 

 

So is it AC(50Hz) -> rectifier -> DC -> inverter -> AC(variable) inside the ASHP?

 

 

^precisely.

5 hours ago, ProDave said:

In the context of motors, I much prefer the term "Variable Speed Drive" or VSD.  It is unambiguous and clearly describes the function, to operate a motor at different speeds.

For a lot of industrial applications they do. I'm somewhat at a loss as to why they prefer to use "inverter drive" as a marketing term for heat pumps, but it seems to work.

 

4 hours ago, SteamyTea said:

Yes, but it is still a nonsense term in my opinion.

Why I dislike it.  Engineering needs clarity, just like other industries, with the IT field being the worse, apart from Chemistry that is, they just make up long words to sound impressive (and spray spittle over everyone).

 

Why don't they just call it a converter.

What the engineers call it is kind of irrelevant here - for instance the marketing blurb doesn't mention a rectifier, but that's kind of a critical component. The term "inverter" has precisely one meaning in electrical engineering, as does "converter". An inverter is a particular type of converter, and in turn there are a large number of possible types of inverter.

 

3 hours ago, George said:

So is it AC(50Hz) -> rectifier -> DC -> inverter -> AC(variable) inside the ASHP?

Precisely. There are some subtleties but that's fundamentally what is going on.

Good old Wikipedia explains why they are called what they are.

My Father was an electrical engineer, a dreadful commutator.

 

 

The origins of electromechanical inverters explain the source of the term inverter. Early AC-to-DC converters used an induction or synchronous AC motor direct-connected to a generator (dynamo) so that the generator's commutator reversed its connections at exactly the right moments to produce DC. A later development is the synchronous converter, in which the motor and generator windings are combined into one armature, with slip rings at one end and a commutator at the other and only one field frame. The result with either is AC-in, DC-out. With an M-G set, the DC can be considered to be separately generated from the AC; with a synchronous converter, in a certain sense it can be considered to be "mechanically rectified AC". Given the right auxiliary and control equipment, an M-G set or rotary converter can be "run backwards", converting DC to AC. Hence an inverter is an inverted converter

4 minutes ago, SteamyTea said:

Good old Wikipedia explains why they are called what they are.

My Father was an electrical engineer, a dreadful commutator.

 

 

The origins of electromechanical inverters explain the source of the term inverter. Early AC-to-DC converters used an induction or synchronous AC motor direct-connected to a generator (dynamo) so that the generator's commutator reversed its connections at exactly the right moments to produce DC. A later development is the synchronous converter, in which the motor and generator windings are combined into one armature, with slip rings at one end and a commutator at the other and only one field frame. The result with either is AC-in, DC-out. With an M-G set, the DC can be considered to be separately generated from the AC; with a synchronous converter, in a certain sense it can be considered to be "mechanically rectified AC". Given the right auxiliary and control equipment, an M-G set or rotary converter can be "run backwards", converting DC to AC. Hence an inverter is an inverted converter

So

 

Can you ...

 

Invert your partner ?

Convert your partner?

Rectify your partner ?

 

Possibly all at once ? 

So thank you everybody for that thrilling journey of thought.

 

I guess the answer is no, the energy used varies with demand.

 

1 minute ago, Marvin said:

So thank you everybody for that thrilling journey of thought.

Sometimes you wish you never posted the question . I feel like that very often 

1 hour ago, pocster said:

Sometimes you wish you never posted the question . I feel like that very often 

Every day is a school day ?

11 minutes ago, joe90 said:

Every day is a school day ?

Yep . I learned nothing there aswell