I limit my HRV from running more than about 1 minute every fourty minutes during cold temperatures. I compare the dewpoints between inside and outside, and if not advantageous to the humidity in the home, keep it very short (1 minute).
I have found that despite multiple humidifiers I cannot keep the humidity levels higher than about 26% if I run the HRV too long under cold weather. It dries the house right out and colds, nose bleeds, and dry throats become frequent.
Note: I found using relative humidity levels useless. You can have high Rh outside, bring it into the home, and still drop the RH% in the house, when it warms up. Dewpoint indicates the absolute humidity in the air, no matter what the temperature.