NetSpa spa heats very slowly or cannot reach the set temperature, especially in cold weather, with no error code.

Safety first: Keep electrical components dry while working around the spa.

• Use the insulated cover: Always keep the NetSpa cover on and properly latched during heating. Replace a waterlogged or damaged cover with a NetSpa-compatible insulated cover.
• Improve insulation: Place an insulating mat under the spa and use windbreaks around it to reduce heat loss.
• Clean filter and check flow: A dirty filter or weak pump reduces heat transfer. Clean or replace the filter cartridge and ensure strong water circulation.
• Allow sufficient time: Portable NetSpa heaters typically raise water temperature by a few degrees per hour. In very cold conditions, preheat over 12–24 hours.

If heating remains abnormally slow despite good insulation and flow, the heater may be partially scaled or underperforming and should be evaluated by a technician.