In Fig. 15-13 a typical, simplified, thermostatic expansion valve is shown. In the type of equipment being serviced, this type of metering device is most effective. By using a device such as this in a piece of equipment, the cost is elevated. The use of this valve requires a receiver to be used also. If it cost more to manufacture a unit such as this, why not use a different metering device? The advantage of this type of metering device is its ability to respond to variable load factors. Look at the diagram in Fig. 15-13 again. The sensing bulb is mounted to the suction line at the outlet of the evaporator coil. If the temperature is too high, the valve will open to allow more refrigerant to enter the coil. If the temperature being sensed should become low, the valve will throttle down the amount of refrigerant flowing into the coil. That is the greatest advantage to this type of metering device, it senses gain in heat load and can compensate for it. For example, at a wedding when people are sitting inactively, the heat buildup will be low. If the reception were in the same room, and people started dancing, the heat load would increase. The device used in a commercial type of refrigeration system where people are constantly opening and closing the appliance works very well keeping up with the demand.