There are several variations of these controls. They can be purchased designed for low-pressure, high-pressure, or fan cycling control. The low-pressure and fan cycling controls are generally automatic reset types, while the high-pressure control can be ordered as either an automatic or manual reset type.  

The controls can be used to directly control a load or used as a pilot control device. Always verify that the ampacity of the control can handle the amperage draw of its load, otherwise, the control could fail prematurely. If the pressure control cannot handle the load directly, an isolation relay can be used to allow it to control a load at a lower amperage draw.  

There are two basic methods of connecting these switches to a system. A popular style incorporates a ¼-inch SAE female flare fitting with an integral Schrader valve depressor, so they can be replaced without recovering or isolating the refrigerant charge. This can be a major advantage when compared to the older style pressure controls. They are also available with a ¼-inch copper stub, so they can be brazed/soldered into a system. When replacing or adding an encapsulated pressure control with a ¼-inch SAE female flare fitting and integral Schrader valve depressor, it is a good practice to mark the system. That’s so the next technician on the job knows that the control has a Schrader valve and that the control can easily be removed from the system without recovering or isolating the refrigerant charge. 

It is best to position these controls on the top side of the refrigerant lines. This reduces the possibility of sediment accumulating in the control. When installing these valves on the high side of a system with a reciprocating compressor, it is best to position them away from the compressor discharge to minimize the effects of pressure pulsation. Always double wrench when tightening, and do not overtighten the flare nuts on these controls, as this may damage the threads on the flare nuts or flare connectors, resulting in a refrigerant leak.  

A failing pressure control may prevent its contacts from fully closing, leading to a voltage drop at the load, such as a contactor, which will then cause it to chatter and fail to close completely. This might not happen all the time, which can be quite frustrating as technicians attempt to troubleshoot a system problem. These pressure controls tend to be less reliable when compared to older-style controls, so the tradeoff for cost and ease of replacement can be reliability.