Why it is not allowed to use the pvc type material to be used as the chilled water pipe marker or duct markers in indoor application?

Cannot withstand thermal expansion and contraction due to small break point in the curve of stress and strain diagram.

Personal Experience that I  faced with PVC material while Installing a 2 inch dia pipe for a AHU in Pharmaceutical firm, Within 3 months of working period I came across maintenance issues like Leakages in  joints, Reduced Flow Rate while scale formation and Condensation issues.

I Strongly suggest to go for Black Steel Sc 40 Pipes.

In Chilled Water System , the rate of flow  is very high as such the pressure can not be handled by PVC Pipe . Also the temperature will be Of Range 6 C. in General Balck steel Pipes are recommended for Chilled Water System

if you check HVAC Systems & Equipment [2008] S45 SI Table 5 page 45.6

you can find that PVC, CPVC, PB, steel, copper pipes are allowed to use for 50 mm and smaller 

PLASTIC PIPING

Nonmetallic pipe is widely used in HVAC and plumbing. Plastic is light, generally inexpensive, and corrosion-resistant. Plastic also has a low “C” factor (i.e., its surface is very smooth), which .

Plastic piping materials fall into two main categories: thermoplastic and thermosetting. Thermoplastics melt and are formed by extruding or molding. They are usually used without reinforcing filaments.

Thermosets are cured and cannot be reformed. They are normally used with glass fiber reinforcing filaments.

Return water temperatures and excursions thereof are also a concern.  PVC is limited to 60 C maximum service temperature, and PVC to about 80 C (some push it a bit farther than that, but it's noticeably softened already at 80 C).  We've made that mistake before, and had some saggy, nasty-looking return water piping.  Never lost containment, but needed a lot of support to avoid looking like spaghetti...

PVC type material dont have the longivity like the other GI metal pipe or other metals do. PVC material will soon have wear and tear due to the chillness In water. Rate of flow of water will be very high and PVC material cannot handle that much high flow rate as compare to the GI pipes