York YPAL 051 User Manual

JOHNSON CONTROLS

FORM 100.50-NOM6 (1207)

The first 12 alarms involve controls intended to 
protect the compressors.  Each compressor system is 
equipped with external circuitry monitoring hardware 
intended to protect the compressor in case the operating 
characteristics of the refrigerant system fall outside the 
safe operating envelope for the compressor.  The type of 
protection varies depending on the type of compressor 
used.  

YPAL 050 Compressors 1A, 1B, 2A, and 2B
YPAL 051 Compressors 1A, 1B, 2A, and 2B
YPAL 060 Compressors 1A and 2A
YPAL 061 Compressor 1A

The Compressor Safety Circuit consists of a high-
pressure cutout switch.  Each of the compressors is also 
protected by internal line break switch imbedded in the 
windings of the compressor that protects the compressor 
from excessive current or temperatures.  The Unit 
Controller will not be able to identify the internal line 
break switch is open and no fault will be generated or 
reported by the Unit Controller.

If the internal line break is open it will appear as 
a compressor failure.  To trouble shoot verify the 
compressor contactor for the compressor that is not 
running, is closed and line voltage is present on the 
load and line side of all three legs.  If so remove power 
from the unit and remove the cover from the compressor 
control box.  Check for an open winding.  If all three 
winding are open carefully check the compressor shell.  
If the shell is hot no determination can be made until the 
shell has cooled.  If the shell is cool and a winding is 
open the compressor is defective.  If the windings close 
as the compressor cools the internal line break switch 
was open.  Some possible causes for an open switch are, 
high discharge super heat (low charge), start of a bearing 
failure (partial locked rotor), or high voltage.

The above units also have a low- pressure cutout that 
will be discussed later.

Since tandem compressors are used there is a single high 
pressure switch for system 1 and one for system 2.  If 
the high pressure switch opens both of the compressors 
for that system will be turned off.  If the high pressure 
switch for system 1, (compressors 1A, 1B), opens it will 
generate both a 01 and 02 alarm code.  Likewise if the 
high pressure switch opens for system 2, (compressors 
2A, 2B), opens it will generate both a 03 and 04 alarm 
code.  

The high pressure switch opens at 625 PSIG and closes 
at 500 PSIG.  In order to generate a high pressure 
lockout the high pressure switch must open three times 
within a 2 hour window.

24 VAC power is supplied to the system 1 high pressure 
switch circuit from wire 399 at terminal HPS1 of the P15 
connector.  The binary input back to the Unit Controller 
from the high pressure switch is wire 400 at terminal 
HPS1 of the P15 connector.  The above input is then 
jumpered to terminal HSP2 of the P15 connector.

24 VAC power is supplied to the system 2 high pressure 
switch circuit from wire 431 at terminal HPS3 of the P16 
connector.  The binary input back to the Unit Controller 
from the high pressure switch is wire 432 at terminal 
HPS3 of the P16 connector.  The above input is then 
jumpered to terminal HPS4 of the P16 connector.

Because there is no external compressor protection 
module on these models jumpers are placed between 
terminals C10 and C10 of the P12 connector for 
compressor 1A, C20 and C20 of the P12 connector for 
compressor 1B, C30 and C30 of the P12 connector for 
compressor 2A, and C40 and C40 of the P12 connector 
for compressor 2B.

YPAL 060 Compressors 1B and 2B
YPAL 061 Compressors 1B, 2A and 2B

The high pressure switches are connected as described 
above; however, the compressors identified above 
employ a compressor protection module.  24 VAC 
power is supplied to the compressor protection module 
for compressor 1B from wire 441 at terminal C20 of 
the P12 connector.  The binary input back to the Unit 
Controller from the compressor protection module is 
wire 440 at terminal C20 of the P12 connector.