Johnson Controls P78ALA-9451 Dual Pressure Control [New]

The Johnson Controls P78ALA-9451 is a PENN P78 Series dual pressure control - one control providing combined high and low pressure protection. Per the manufacturer, "The P77 and P78 Series Pressure Controls are designed primarily for high and low pressure cut-out control, pump-down control, condenser fan cycling, and capacity control on commercial refrigeration and air-conditioning applications. These controls are available in several pressure ranges and are compatible with most common refrigerants." The bulletin adds that "The P78 Series Controls for dual pressure applications are designed primarily for use as combination high and low pressure controls on commercial refrigeration and air-conditioning applications."

A single P78 protects both sides of the system. The control uses a Single-Pole, Double-Throw (SPDT) switch: on the low pressure side A-C opens on a pressure decrease while A-B closes simultaneously, and on the high pressure side A-C opens on a pressure increase while A-D closes simultaneously, so a spare contact can be wired for an alarm or auxiliary circuit. Published features are a splash-proof enclosure, a sight-set calibrated pressure adjustment that displays a visible pressure scale and is fully adjustable through the range without removing the cover, a manual reset lockout option providing trip-free lockout that cannot be overridden or reset until pressure returns to a specified level, and generous wiring space.

* Brand / Manufacturer: Johnson Controls (PENN)
* Model / Part Number: P78ALA-9451
* Series: P78 Series controls for dual pressure applications
* Switch Action: Single-Pole, Double-Throw (SPDT); low side A-C opens on pressure decrease with A-B closing simultaneously, high side A-C opens on pressure increase with A-D closing simultaneously
* Type Code: The Johnson Controls P78 type matrix lists P78LCA (dual pressure, automatic reset) and P78MCA (dual pressure, high-side manual reset). ALA is not among them, so no reset behaviour or range is claimed here
* Low and High Pressure Side Ranges / Differentials: Not published by Johnson Controls for this dash number - the P78 selection chart itemises the -13000C/-15000C codes only. Verify the ranges, differentials and reset behaviour on the control nameplate before ordering
* Electrical Ratings (UL 60730): 120 VAC - primary contact 1 hp, 16 FLA, 96 LRA; secondary contact 0.33 hp, 7.2 FLA, 43.2 LRA. 208 VAC - primary 1 hp, 9.2 FLA, 55.2 LRA; secondary 0.75 hp, 7.6 FLA, 45.6 LRA. 240 VAC - primary 1 hp, 8 FLA, 48 LRA; secondary 1 hp, 8 FLA, 48 LRA
* Resistive / Pilot Duty: 16 resistive A at 24 VAC; 125 VA pilot duty at 24 VAC; 720 VA pilot duty at 120 to 240 VAC
* Pressure Connection: 7/16 in.-20 UNF for 6 mm (1/4 in.) flare nut, or 914 mm (36 in.) capillary with 6 mm (1/4 in.) flare nut
* Ambient Conditions: -40 to 60°C (-40 to 140°F); humidity 0 to 95% RH, non-condensing
* Enclosure: Type 1, cast aluminium
* Dimensions (H x W x D): 122 x 80 x 53 mm (4.80 x 3.15 x 2.09 in.)
* Shipping Weight: 0.7 kg (1.55 lb), individual pack
* Compliance: cULus Listed; UL 60730, File SA516

Typical applications are combination high and low pressure control of commercial refrigeration and air conditioning systems, including high and low pressure cut-out, pump-down control and capacity control. Use this control only as an operating control - where failure or malfunction of the control could lead to personal injury or property damage to the controlled equipment or other property, incorporate and maintain other devices, such as supervisory or alarm systems or safety or limit controls, intended to warn of or protect against failure or malfunction.. Johnson Controls. Johnson Controls. P78ALA-9451.