Winter Operation

Many spas are designed to operate outdoors.  An easy way to deternmine if it will operate efficiently during our Canadian winters is to assess the insulation.  The higher the density (cell size) of the insulation the higher the R factor.  In most cases, full foam insulation will gain the most efficient operation.  In many cases where there is not full foam, insulation can be added, but should only be done under the supervision of a spa technician because the pumps & control system must have sufficient air circulation for proper operation.

Winter Breakdown

The best insurance is knowing what to do.  Do not let your spa freeze.
If your spa has shut down in the winter here is what to do:

Do not drain the spa - if you want to drain the spa, it can only be done immediately after it has stopped running & must be properly winterized by sucking out the lines & equipment (pumps & control pack), blowing out the lines & equipment, then adding antifreeze to the lines & equipment, including down the skimmer.
Winterizing a spa is best done by a professional if the spa has more than a few jets.

Assess the situation:
As long as the pumps are still circulating and moving water there is little concern of a freeze up.

Do not attempt to restart a frozen spa.

If your GFCI or high limit has tripped very recently, then try turning the heat down as far as possible or off.  Attempt to diagnose what caused the spa to fail/shutdown before restarting.

Reset the GFI or high limit to see if it will allow the pump to circulate, with confirmed water movement, without tripping again.  If the pump is on but there is no water movement, then turn the spa off (read on).

Do not attempt to restart a frozen spa.

If you cannot reset the GFCI or if your pump has stopped working, then you must put a space heater into the area of exposed plumbing & equipment (pump & control pack) to keep it from freezing.  As long as the spa is insulated and you leave the water in the spa & the cover on, then the rest of the plumbing will not freeze for days or weeks, depending on how well insulated the spa is.
Be cautious when placing the space heater, not too close to plumbing etc.  If the heater has multiple settings, use the lowest heat output setting.
If you are unable to close the access door with the heater inside it will be necessary to place blankets, towels or tarps over the open spaces.
Check the area often to assure it is staying warm but not damaging the equipment.
If the spa is already frozen, be cautious with a space heater because the plumbing may have already burst & can leak water on to the heater & equipment (pumps & control pack) as it thaws.  If the spa is already frozen you are best to call a professional.