I belong to a Credit Union and they tell me that the maximum amount I can transfer via ACH is $500. That seems very low to me. Is that normal?
Assuming that the $500 is a monthly limit, yes I would say that is a low number. Even if it were a daily limit, I would still say it is low.
Most financial institutions have a daily and monthly ACH limit to help control fraud and reduce money movement in and out of the institution. Often the limits will be increased after you have been in the financial institution for 6 months to 1 year.
If the credit union is unwilling to grant you a higher limit and this is something you need, I would consider finding another place to bank with. Alliant Credit Union, Ally Bank, and Capital One 360 all have generous ACH transfer limits.