My Kenwood oven has two "thermostats" on the main frame, not the standard temperature controlling ones, but apparently for overtemperature protection.
I think I would have *expected* them to be closed circuit, and to open on overtemperature (like the safety protection on tumble dryer heaters) but does anyone know for sure? I'll go and test them anyway.
I have it sussed, the open circuit one closes when it is warmed, the closed circuit one opens. The first one must turn on the fan, the second one is the "fire" protection. I think I will wire a neon to the second to see if that is why I am having problems. I wonder if I have an insulation problem and that this trip is getting too hot, too soon.
Cabinet overheat stats often get too sensitive when the connectors on them start self-heating due to increasing connector resistance - they usually carry the full element current. This might be obvious if the wire insulation near the connector has deteriorated. Sliding the connector off and back on can help. If the connector pulls off easily, closing it slightly with pliers to make it a more firm connection can help.
The other way they can fail is that the crimp connection between the connector and the wire starts going high resistance. Seen this on many Smeg ovens across the whole wiring loom.
The stat can also self-heat internally if the stat switch contact starts increasing resistance. That needs a new stat.
Thanks, excellent point. One of the connectors insulating sleeves has gone slightly dark and brittle, I will measure the internal resistance more carefully tomorrow. Waiting for eSpares to deliver a new element tomorrow, if the stat looks toasted I might short it out temporarily. Fortunately it is readily accessible with only the back panel to come off. Unlike the bottom element which was quite a pig.
According to the links you posted the operating temperatures are 160 or
175C. That is too low for an oven unless both switch something on when the operating temperature is reached.I would have expected an over temperature protection cut-out to be >250C, or >500C for self cleaning ovens.
This is outside the oven insulation, on the back plate at about the level of the gas pipes
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