After you have the SunPump model sized properly using a detailed CSA-F280 room-by-room Heat Loss calculation or Mechanical Design plan, the installer can purchase the fully-insulated Line-Set to suit the distance from SunPump to the panels with some extra length.
2017 SP3.1 Line-Set Outside Diameter ACR Line-Set
* from 2017 specifications sheet.
The simple rule is size the OD line set the same as the SunPump Service Valves, there is rarely any reason to change the size. The exception is on l1-way distances greater than 50-75 feet, when you should get advice from the HVAC Mechanic company on long length options.
The correct type is the white coil shown below, not the bare copper tube.
Avoid non-insulated line sets that you add 6-foot insulation onto, because any air gap causes sweating and drips which leads to moisture problems. If you must add insulation, glue the insulation joints with the manufacturer recommended compound, and tape the joints for 100% air-tight seal. It is much better to do it right then have to re-do the insulation. Best practice is to buy full-length insulated line sets, and tape both exposed ends.
SunPump suggests the Installer explicitly quotes on including the manifold and line set as part of his job. Ideally, the Installer would complete the line set connection and pressure test with Nitrogen to ensure there are no leaks before calling the HVAC mechanic to commission the unit. We all want to avoid having a $100 per hour mechanic chasing down leaks or even working on the roof. Best practice is for the installer to braze the tubing and add 150 PSI of Nitrogen from a small tank, leaving the gauge in place as prroof it is complete.
In new construction, it is common to use a pair of 2" diameter tubes as a conduit under the Solar Ready requirements in most building codes. SunPump can use these tubes, a separate one for each of the two line set pipes. If this is the plan, you need to buy individually insulated lines and make a set.
WARNING: Never tape the two bare copper lines together and insulate as one in full copper to copper contact, because the pipes will neutralize the required temperature difference between the liquid and gas. The efficiency of the SunPump will be eliminated by tubes that touch and exchange.
WARNING: Avoid DIY insulation added to bare copper tube. It is possible if you are a perfectionist, otherwise it will sweat and drip.