I think the best exercise to answer your question is first for you to explain what you understand by "sentient".
Trying to define it will get you closer to the answer.
Many of us have certainly gone that path already and know the different steps you will go through that definition-journey so, sooner or later, you will get into the consciousness topic. For this, I advice you to take into account Tononi's Integrated Information Theory.
Tononi proposes with his IIT a way to measure consciousness levels. If you accept his definition of consciousness (fully or partially) I think you have a good approximation to an answer to your question that could be:
"Yes your heatpump is sensient but by a very very low IIT-Phi coefficient."
I personally adhere to IIT. It doesn't explain everything but it is a theory any neuroscientist has to take seriously if he/she wants to keep making progress on explaining our brain.

I recommend you Daniel Dennett's books or if you want to get more technical Stanislas Dehaene.

:up:

Hello Constance @ all,
This is my first post to this forum.
The Self is a topic that interests me a lot this is why I got in here reading your comments.
I see your approach is quite influenced by oriental philosophy that I don't know very well. I'm more a naturalist-cognitivist so my perspective of the Self comes from a different angle what I think could be enriching. Some times different perspectives or beliefs generate frictions or harm other's sensitivity, this is not my intention at all and let me know if you think this post is not convenient for your debate.
I'll post here my manifesto on the Self that I have created that explains my view and I think could be interesting.
Your immediate reaction could be, as mine is some times..."we're talking different" things here! So an interesting debate could be : how would you call then my "Self" or how would I call yours :-).

The ontology of the Self, a manifesto

The self is a phenomena resulting of a cognitive process within the brain that generates the "I", a self-referenced mental-object within brain’s mental "model of the world". The "I" is a representation of the Subject as Being, as owner, creator, agent and receptor of the intentionality of its mental objects. The linguistic representation of the “I” is not needed for a Self to happen.
The mental raise of the self: The mental “model-of-the-world” is a representational mirror of the external reality, a second mental mirror comes from the mental representation of “the others” that makes the self to happen/emerge when the mental process realizes the “invariants” between the other and I (confronting both mirrors). Two confronted mental mirrors that create the self’s singularity.
The Self bio-basis: The self process is confined to synchronous integrated information exchange activity between the cortex pre-frontal ventro-median area and the temporal and parietal (praecuneus) lobes.
Self and experience: The self is not required for experience to happen or to be communicated. A conscious and an unconscious brain can be able to communicate its emotions without being self-conscious, i.e. reflex actions.
Self and time: The Self process "emerges" gradually as our brain matures and as we grow as individuals in a proper stimulating cultural context.
The Self is not something permanent, it dissolves gradually when we address our attention to specific tasks and/or non-referential thoughts. It dissolves and disappear as well when we sleep or die,
The self and evolution: The self makes us more adaptive and effective in our survival and homeostatic goals as a species.
As consciousness, the Self enables even more complex (larger, longer, more realistic and more integrated) models-of-the-world as it enables, i.e., evaluating our judgments against the other’s.
Self and memory: Access to memories is necessary for the self to happen. More accurate and longer memories that contain external descriptions of the world (i.e. science) the more empowered the self is.
Self and society: The main role of the Self is played in society, when interacting with others: it enriches the culture of the societies generating richer cultural models-of-the world. It reinforces the social cohesion via a stronger integration of the individual.
The self enables the feeling of self-confidence that evaluates our judgements, our decisions and actions so that can be self improved or communicated to others seeking improvement.
Self and the existential delusion: The Self is necessary for the emergence of the concepts of "infinite" and "finite" that foster the generation of fear, anxiety and depression as the "model-of-the-world" it generates is much larger than himself. This idea of confinement gets in conflict with its primordial instinct of survival. Systems of believes that sustain a teleological illusion mitigate these negative feelings (religions, intelligent design, spiritualism, mysticism,...).