Sta-rite SR 330,000 btu heater starts to heat, but shuts off after 1 minute. Digital readout reads EO5

SOURCE: sta rite 400na gives error code 05 after about 30 seconds

I am not sure if you have received an answer to the issue, or not, but just in case! An EO5 error code is an open stack flue sensor, or switch, There are two forms of the stack flue sensor, so you will need to know which one you have on the heater.

What this error code means is that the sensor "read" the flue temp to be over 500 degrees. Usually, it is just gone bad and reading the wrong temp.

SOURCE: Value Stack Flue Sensor

3.5 to 4K If you want to bypass the sensor just jump a 1 dollar resistor in between the two wires. If you want to put another sensor just use a standard gas heater flute sensor(2dollars) and put in line with the resistor

SOURCE: sta rite heater won't start

TURN THE BREAKERS OFF FO R 20 SEC IF PROBLEMS PERSIST SEE CODE A POST

SOURCE: Sta-rite pool heater shuts down as soon as the

Between the two water pipes on the left side of the manifold is a two inch plug. When you take this plug out the thermal regulator assembly will come with it.It consists of "O" rings, a spring and what looks like a thermostat in a car. This is the probal bad part although it could be the spring also. You can get these parts seperatly or in a kit. If this is an older heater the kit is the way to go so you get all the nessary "O" rings and you will be covered on everything you need.

SOURCE: Sta-Rite Max-e-Therm pool heater -- cycling and HLS

make sure that you have adequate water flow going through the heater and that your water chemistry is balanced.