What about the flexible hose to copper tube connection?
The flexible hose recommended by Dadanco is specially designed for this application. The hose consists of either a stainless steel hose or steel jacketed EPDM type hose with special push on connectors. The connectors contain dual Viton sleeve rings that expand under pressure of the system. In addition the fitting contains a “shark tooth” type of arrangement that grabs the copper tube. The more you try to force the connector off the tube, the more it digs in.
 
What if a pipe leaks?
Leaking pipes or fittings are not an issue. The seamless hard-drawn copper tubing of the secondary water system will have been tested to around 1500kPa as a part of the commissioning. The operating pressure at the coil in the unit is normally around 300 – 400kPa. Ask the question, “How often do sprinkler pipes leak?” It is very rare.
 
Do you need to insulate the return water line in the false ceiling?
This depends on the temperature of the return secondary water. If the flow to the coils was at, say, 13oC, the return could be 15 –16oC. There is no danger of condensation and the pipe would gain heat from the ceiling if it were uninsulated. The ceiling would probably be a return air plenum in current designs, at about 25oC. If the method to calculate heat gain to pipes given in the AIRAH Design Manual DA16 is followed. It will be seen that the gains are very small. The gain helps, in the system heat balance, to cool the return air. Of course, if 3-way valves are used as the automatic control valves, the return line can be at the supply temperature when there is no cooling demand on that unit or zone.
 
This is a practice observed in many older installations. However they invariably insulated the piping in the riser to the plant room as the air was no longer effectively still air and the temperature could be several degrees above the plenum ceiling temperature.

Unless the secondary water is at a lower than dew point temperature, remember the insulation is to reduce thermal gains and not prevent condensation. The costly vapour barrier is not required. It may mean a few more lines in the specification to include a thermal insulation for piping, but the cost saving to the client is worth it.