both lines in same insualtion

[r.bartlett]

Sorry; but what part of Hot travels to cold, do you not understand? Also; it's just as likely that both pipes ARE touching!

This is the basics, that most engineers should know. Furthermore, we as professionals in our industry are entrusted to do a good and proper job, so that the system runs as efficiently as possible. Insulating both lines individually is paramount to achieving this.

Of course, you can just throw a system in and just be happy that it works; forget insulating the lines properly, getting the charge right or leak testing the system. Hell, just purge the system, why should we bother vacuuming; I mean it seems to work...

Why not answer the questions which would actually help your 'big effect' contention.

what temperature in this example do you think
a)the suction pipe is
b ) what temperature the phase change pipe is
c)which of these two is the 'hot' one in your opinion

what is the actual contact area between two touching (or not) round 8m pipes lose in a piece of lagging in sq milimetres

then calculate how much heat transfer is happening in this real life example . Please confirm if you are working on the two pipes touching 100%,75% 50% etc of the 8m as 1/2" and especially 1/4" are very difficult to get to lie straight.

Once you come back with an answer based on an actual calculation rather than a shooting from the hip 'big affect' we can confirm if it does or does not have any real effect on efficiency.

I await your 'professional engineer' response.