Hello, The pressure switch is the only reset switch on this unit. You will need to shut the power off and remove the back panel and it is located on the liquid line (small copper line) down at the bottom. It has a red push rubber switch that you push in.
Take a look at page 3. http://www.acfurnaceparts.com/Service%20Manuals/XC15.pdf
I hope this information was helpful.
I was able to locate the swithch. Thanks! But it doesn't seem to have solved the problem. The LSOM has a yellow alert flashing 6 times, which would seem to indicate a bigger problem.