Air conditioning question

[pop3]

Is there any retired air conditioning engineers out there or a competent DIY air-con hero ? My question is this , What is the black sticky substance they put on the expansion valve ? Also what is the point of putting that gunge on it and is it really necessary , The reason I ask is I am fitting a replacement unit in my van but it has no black gunge on the expansion valve its just shiny copper.  Thanks for any help you can give.

[Kwasaki]

I'd have to google those questions. ????

[stubuzz]

It stops condensation.

[pop3]

Its not a simple google that's why I'm here, Cant even find a photo of the black gunge over an expansion valve and that's crazy as every unit I have ever seen is sprayed with the bloody stuff  ????

[audaciousnomad]

10 minutes ago, pop3 said:

Its not a simple google that's why I'm here, Cant even find a photo of the black gunge over an expansion valve and that's crazy as every unit I have ever seen is sprayed with the bloody stuff  ????

In refrigeration and air-conditioning applications, insulation needs to be able to protect against condensation. Moisture control is critical to thermal efficiency. If moisture intrudes the insulating material surrounding cold-water piping, thermal efficiency is lost. Foam insulation, unlike fiberglass, is a closed-cell structure that acts as a built-in vapor retarder (jacket) preventing moisture intrusion.

https://www.armacell.us/blog/post/why-its-important-to-check-insulation-on-residential-ac-units-yearly-and-how-to-replace/

Edited August 2, 2021 by audaciousnomad

[pop3]

Right, Thank you that's an informative link , seems like its to stop condensation and insulate the valve, Dont know why they don't just cover it with foam like the rest of the pipework, My guess is it may get very hot,