HRV in the summer?

[wingedfish]

Generally no. Warm air holds more moisture than cool air ( do not confuse this with humidity) so bringing in outside air will add moisture to the house in summer, which will be in direct combat with the AC.

But just for the benefit of ventilation, some leave it on low all year. This will equate to some associated electrical costs and a/c inefficiencies but outweighed by the benefits.