I recently bought a house that has a not-terribly-new System 2000. Right at the moment I have hot water but no heat. There is a sticker on the unit that says "Press reset button on relay once." I'm clueless about anything mechanical. Am I supposed to know what and where the relay is? I don't, nor does the manual indicate where it is. In short, can anyone help me find the reset button on my system 2000?

Thanks much,
Gary