Tested system not heating well for the office. Found that we had insufficient voltage supplying the air handler which is causing the heat kit to not turn on for secondary stage heating. This is needed to heat properly in these freezing temps. I looked at the panel and found the breaker was missing to the air handler. We Would need to schedule an electrician. We also noticed the system has tons of dust and dirt buildup inside which also can cause restrictions. Owner will not answer the phone.