If the alarm malfunctions, you may be liable for negligence.  Negligence is the failure to exercise due care, that degree of care in this case that a reasonable electrician would have exercised under the same or similar circumstances to prevent foreseeable harm.  If the alarm results in damage to the church or injury to others, you may be liable for negligence.  Your liability would include damage to the church or injury to others which is reasonably foreseeable.  You may be relieved of liability if the damage to the church or injury to others is due to an unforeseeable, intervening act.Depending on your state's laws, there may be penalties for an unlicensed electrician doing the work of an electrician.