I have a new Amana PTH15E PTAC. When heat is used, sometimes is quite but sometimes sounds loud (like window AC), why?

Question edited for a lot more clarity.

The new improved energy efficient versions.

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Amana PTAC https://www.amana-ptac.com > products > ptac
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Probably this one. Talk to your installer.

https://www.amana-ptac.com/products/ptac/hec154j

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Question edited for clarity and toss in some CAPS.

You can get wired or wireless.

https://www.amana-ptac.com/products/ptac

Fitting

https://www.google.com/search?q=amana+ptac+connect+to+wall+thermostat

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Maybe something here will help you....

https://ptac4less.com/blog/troubleshoot-reset-amana-ptac/

Hydronic switch open 9 E9 Hydronic switch open (if hydronic configured) - either the aquastat is defective, or the aquastat wiring is cut, or the aquastat is not present at all and the aquastat wires were not permanently connected together as per the set-up instructions.

diagnostic codes for ptac/pthp electronic control

https://www.google.com/search?q=Amana+PTAC+error+code+09

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Sounds like you need a new control board.

on most ptac they have electric heat so there is seperate controls for cooling it is possible a contactoer or compacitor

I don't see this error code in the manual. I do see nP as an error code for Window Switch lockout. I just had this happen to me and they had me reset the control board.

Remove case, flick master switch to OFF for 10 seconds. Press Heat/Cool same time turn switch back on HOLD until off light comes on.

You should be fixed. Just had to do this for my unit. I was playing around with the settings and turned on the window switch option by accident.

Is is the sound of water being thrown around? Some units actually sling the water from the drain pan back onto the coil. This improves efficiency. It's sort of a gurgling sound. Here's more helpful information is you need it:

<a href="http://www.ultimateptac.com/ptac-faqs/">PTAC FAQs</a>

Onl full service comes to mind.