Ditto what Deanna Leigh said.
I think for your son, it's just the normal developmental sort of "fears." And, you recently moved. This can jar their usual selves.
For me, my daughter, ever since she was a baby, she was always "noise" sensitive/sensory sensitive. Not in a "problem" sort of way where we had to get clinical help...but just as Parents, we learned that about her.
She is now 6 years old, and it has gradually lessened. BUT, since she was a baby, and yes, a toddler, and yes even now....she simply cannot tolerate "loud" noises.
As a Toddler, we once took her to a Sesame Street show... and she told us it was TOO loud and we had to leave. We suspected that that would happen, and well we were right.
To this day, my girl does not even like going to the movie theater because it is too "loud" and she does not like it.
For her, loud noises just gets her really agitated and irritated & upset to varying degrees.
As a baby & toddler, yes, loud things scared her hysterically.
In Kindergarten, my girl had a hard time with her PE Teacher, because he had a VERY loud voice...and it really would upset her and give her anxiety. With that situation, she spent time with a school counselor. And, then she was fine.
But also, as Deanna Leigh said, at the age your son is, they DO develop "fears." It is purely developmental based. Your son is not the only one. It is normal and common. So, it is probably a "phase" and will pass. But for each child, the length of the "phase" varies. It may take him time to outgrow it. Deanna Leigh gave great suggestions as how you could help your son with the heating noises. I would try it.
At various ages, they develop different "fears." But it's all normal and common. Fears of the dark, or noises, or shadows in the night, of their imagination, etc. And yes, you just moved into another home... he is probably having to adjust and having a transition change... give him time... lots of time. No pressure, no scolding, just hopefully something will help allay his fears.
I don't have a solution for you per say, but how about a space heater? Maybe that would help. Maybe those are "quieter"? Sears or Costco may have those.
All the best,
Susan