It is normal. First of all, the electric heating tube is red because there are impurities in the tube wall, so the color with good quality is darker.

Secondly, if the quality is the same and the power is the same, because of the design of the oven, the surface fire always heats up quickly and cools down quickly, so the working time will be more frequent (the continuous power-on time is longer than that of the bottom fire), and the bottom fire is closer to the baking tray, so the heat preservation is better, so the time of standing by is more (heat preservation, electric heating pipe does not heat). When you observe, you will probably only see that the fire is electrified and the fire is insulated.