If I owe back federal taxes and have an installment plan in affect will they take my state refund that I am getting back this year in California?

[DanO]

No, if you have an installment agreement set up, and you don't default on making the monthly payments you will not lose your State refund.  

Any refunds that you might have coming from the IRS going forward, will be used to reduce the tax liability, but it would not reduce the amount of monthly payment.