4 Ton 27 EER GeoCool Geothermal Heat Pump Vertical Package Unit

I am helping a friend install his 4 ton Geocool system. He ordered the standard unit without heat strips. The spec sheet mentions the unit is capable of heating down to 25F input loop antifreeze coolant temp. Is this the standard unit or is something else required to use that low temperature loop fluid? I am asking because when I measure the refrigerant temperatures and pressures it seems to indicate it is low on refrigerant, and I want to be sure there isn't another issue before adding some. Loop coolant temp is about 34F now. Thanks.

Thank you for taking the time to educate and advise. So I have a 1970 sq ft living space upstairs with a walk out basement. So between 3.5 to 4 ton should be sufficient. My question, for max efficiency and longevity is it best to up size to say a 4.5 or 5ton and a 2 stage compressor that works like 67% on the first stage or the 3 to 3.5 ton with a single stage. And thank you again

Can this system be used as a open and or closed loop system? If it can be used either way is the EER different for each type of operation(open vs closed) loop. I have a bored well of 275 ft producing about 20 gpm. Also, I stumbled onto your site when researching geothermal, I've never heard of geocool brand before. Is this your company brand or just a company you have a relationship with?