The Importance of Maintaining Vacuum Pumps With Oil Changes
Maintaining vacuum pump oil and changing it regularly is very important—especially in HVAC work. Here’s why it matters and what
Model numbers that this document pertains to: 38AUQ/40RUQ, 50FCQ, 50GCQ, 50HCQ, 50KCQ, 50TCQ
No matter how long you have been in the business, when you come across your first Carrier lite commercial heat pump system it is going to throw your thought process for a loop! You will notice that the unit is a heat pump but there is no reversing valve wire on any of the wire terminals. In fact, there isn’t an “O” terminal at all.
When you are installing a thermostat on MOST residential and commercial heat pumps, typically the orange wire goes to the reversing valve. However, when you are installing a lite commercial Carrier system there is no need to consider the reversing valve. So, what are we supposed to do with the orange (reversing valve) wire? You will not use it because the system controls the reversing valve on its own.
The defrost control board that Carrier utilizes on their lite commercial products has logic built into the board to take care of the reversing valve(s), you simply tell the unit if there is a need for heat or a need for cool. When these systems receive a call for Y1 or Y1 & Y2 then the defrost board will energize the revering valve(s) as needed. When the systems are given a W1 call for Heat then the unit will crank up in high stage. The unit only has one refrigeration heating stage even if it is a “2 stage” unit. The “W2” terminals on split units are actually not inputs but rather outputs to engage the electric heat strips when the system goes into defrost; on the package units the “W2” is an input and it engages the electric strip heat if equipped.
When it comes time to program the thermostat it should be programed as conventional NOT as a heat pump. If the system has two compressors or a single compressor that does staging, the unit is 2 stage cooling BUT only one stage heating. The unit will respond with high stage heating when W1 has 24vac. Use the chart bellow to help decide the specifications needed for a thermostat to operate your unit:
Conventional Thermostat | With electric heat | Without electric heat |
One Stage cooling | 2Heat 1Cool | 1Heat 1Cool |
Two Stage cooling | 2Heat 2Cool | 1Heat 2cool |
Maintaining vacuum pump oil and changing it regularly is very important—especially in HVAC work. Here’s why it matters and what
It is very important this time of year for spring maintenance for the air conditioning system.Proper annual maintenance will help
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