Putting electronic thermostat in GQF 1202 today- any advice?

[msmeower]

My electrician is coming over today to wire a 3255 electronic thermostat into my GQF 1202 cabinet. A local incubator guy told me to leave my back up wafer in line as a back up but the directions that came with the 3255 say not to. Any thoughts? Any other advice about this wiring job?

 

[msmeower]

Update- After the electrician hooked everything up and put the top back on the cabinet, we fired it up and the temp shot up to 115 and we couldn't make it go down! Called GQF and the elecrician talked to the tech and they went over the wiring and it appears the new thermostat was defective. The sensor bulb looked like it had a split wire. Ugh!!!! Meanwhile my eggs are piling up waiting to hatch!!!