i bought a house with a sr400na heater that worked great for 2 years.then the igniter went out along with the blower motor and the ignition module. I have replaced all three parts and when i turn on the heater it fires up and heats for about 5 minutes and then something shorts out and trips the 30 amp breaker. so i re-set the breaker and turned on the heater and the blower comes on it call for gas and the gas valve opens and then call for ignitionbut it does not light. so i opened the ignition module and it is fried. so i bought a new ignition module and it ran again for about 5 minutes and tripped the 30 amp breaker and again fried the ignition module. any suggestions. what is causing the short.