If an owner wants to be refunded a credit card payment to pay by ACH would the HOA also be refunded the credit card processing fees? Is there any additional cost to refund a payment?

If the HOA is intentionally passing the credit card fees onto the owner(an option in the payment processing settings) the owner will be refunded the entire amount of the payment(minus the fees the owner paid to process the transansaction). The HOA will not receive a refund on fees because the owner paid them. 

If the HOA is absorbing the payment processing fees and the owner is requesting a refund so he can pay by ACH, the HOA then has the option to add a one time fee to the owner's unit account to recover the processing fee.