If the insulation on the thermal bulb line to the suction pipe near the evaporator fails in a room at 85F, what is the likely consequence?

• A. Flood the evaporator
• B. Freeze the evaporator
• C. Increase discharge pressure
• D. Decrease suction pressure

Answer: (A)

The sensing bulb on a thermostatic expansion valve (TXV) is what sets how much refrigerant the valve lets into the evaporator. It responds to the temperature along the suction line near the evaporator. When insulation on that bulb line fails, ambient room heat (85°F) heats the bulb, making the bulb pressure higher. In this TXV design, a higher bulb pressure drives the valve to open more, increasing refrigerant flow into the evaporator.

Too much refrigerant entering the evaporator means not all of it can vaporize, so liquid refrigerant starts to flood the evaporator. That flooding can lead to poor heat absorption, liquid slugging back toward the compressor, and unreliable cooling.

So, the most likely consequence is flooding of the evaporator due to misregulated flow from the overheated sensing bulb. The other options would be more about different fault cascades and aren’t the immediate outcome of the bulb sensing line being heated by the room.