Split air heat pump - tightness testing and filling

Hello,
a split-type air-to-water heat pump is planned.
The outdoor unit is to be located approximately 10m away from the indoor unit (HAR). Since the base slab has not yet been poured, the question arises whether the connecting lines between the outdoor and indoor units should be laid directly in or under the base slab, or whether the preparations (conduit) should be made there – this would also be the shortest route.
Now my questions:

1.) For charging with refrigerant above a "critical amount," an annual leak test is required. (Currently no information on how much refrigerant we would theoretically need). -> What would this possibly mean for laying the lines in or under the base slab? Alternative: glycol filling?

2.) What would be the requirements for the material of the pipes (plastic, metal)?

3.) What about insulation? On the one hand because of the dew point (condensate formation), on the other hand because of possible transmission heat loss, especially during defrosting or de-icing of the outdoor unit.

4.) How would insulation generally affect the efficiency of the heat pump? (Would laying in or under the base slab be comparable to the brine principle heat pump?)

Thanks for your experiences.

Hi,

I'm not an expert, but I'll share my experience with you:
- Two KG pipes were planned in our case, in which the refrigerant lines were installed.
- The pipes start in the utility room, run under the garage slab, and end behind it.
- Only the refrigerant lines are insulated. Black coated.

Important: In our case, both ends of the KG pipes were open, and as a result, we had a rat in the utility room on Christmas Eve. That was fun! The KG pipe was partially washed out by rain, and that's how the rodent got in.
If you use KG pipes, seal the outside immediately.

Cheers, torsan

, do you have refrigerant on it as something with R1xxx or a glycol mixture? Were there any recommendations from your heating technician or specifications from the manufacturer of the heat pump? Thank you for the tip with the animal opening

I really can't answer that for you. Heating is not "my" topic. I'll check at home to see if I find anything. Yep, the rat thing is a story that could fill an evening! Greetings, torsan