Back of the building system servicing the shop and the loft is very low on refrigerant running at 34 PSI suction in emergency override cooling mode and holding 125 psi when turned off System required 66 oz of new r410a to achieve an acceptable running pressure with all four systems and emergency override cooling mode. Current running refrigerant pressures are 130 and 362 Due to the complexity of the system ultraviolet dye is recommended with a recharge to positively identify the location of the refrigerant leak Recommend follow up ultraviolet dye leak search on 4 indoor head units in 2-4 weeks