How to Identify and Wire a Heat Cool Unit - 1 Heat 2 Cool Package Unit
Вставка
- Опубліковано 27 жов 2021
- In this video I try to explain how to identify and wire a "heat cool" system but, unlike the last one, this one has a twist. This particular unit is a 80% gas package unit (gas heat with an air conditioner). This type of system should still be fairly easy for any HVAC technician. As with any system you come across, YOU have to be able to identify what unit you are working with in order to know what terminals/circuits are involved. Of course, you then get the proper thermostat and start making things work!
In order to save time, I will try to add to this later by posting a troubleshooting video on the same unit.
Here is how I would put the Sequence of Operation for "Cooling mode "this unit, see the description in the other videos for the fan and heat sequence of operation. It isn't a perfect description but it should help with the thought process!
Cooling Mode
1. Power “ON”
2. Thermostat is in the “COOL” position.
3. Thermostat senses a rise in room temperature above the set point.
4. The thermostat initiates a “Call for cooling” and the switches from “R” to “G” and “R” to “Y” closes. (24 Vac passes across “R” to “G” and energizes the Indoor Fan Relay Coil, 24 Vac passes across “R” to “Y” and energizes the Contactor Coil)
a. The switches on the I.F.R. react and do the opposite of their normal position. (The N.O. switch close, The N.C. switch open). At the same time, the N.O. switch(es) on the contactor close.
5. The high voltage power passes through the N.O. switch(es) that has just closed and powers the Indoor Fan Motor. At the same time, the high voltage power passes through the N.O. switch(es) that has just closed and powers the Compressor and Outdoor Fan Motor.
6. If the motors are good then the motor turns “ON”. The compressor will be in 1st stage cooling and only pumping at partial capacity. Maybe something like 66% capacity.
7. If the thermostat senses an increase in room temperature or is “timing” how long the “Y” circuit is staying energized it will think that the system is not providing enough cooling capacity. At this point, maybe after 5 minutes of running “Y”, it will also energize the Y2 circuit from the thermostat.
8. When Y2 is energized, it will put the compressor into the 2nd stage which will make the compressor pump 100% capacity.
9. Thermostat senses a fall in room temperature in the room.
10. It will de-energize the Y2 circuit and only leave the Y circuit to provide cooling. This will take the system capacity form 100% down to 66% cooling capacity.
11. If the room continues to cool down to the actual setpoint then the thermostat stops “Call for cooling” and the switches from “R” to “G” and “R” to “Y” open. (24 Vac stops passing across “R” to “G” and de-energizes the Indoor Fan Relay Coil, 24 Vac stops passing across “R” to “Y” and de-energizes the Contactor Coil)
12. The switches on the I.F.R. react and go to their normal position. (The N.O. switch(es) open, the N.C. switch(es) close). At the same time, the N.O. switch(es) on the contactor open.
13. The high voltage power stops passing through the N.O. switch(es) that has just opened and stops powering the Indoor Fan Motor. At the same time, the high voltage power stops passing through the N.O. switch(es) that has just opened and stops powering the Compressor and Outdoor Fan Motor.
14. The motors turn “OFF”
Thanks that really help learn how to do field wiring for a new unit and learned something new.
Awesome. Glad it helped a little.
Thanks for checking it out.
Very good information 👌
Use it wisely!
Great vid!
Thanks
Great review, appreciate your videos.
Thanks.
Great video John. Suppose this gas pack unit is not wired to a 2 stage thermostat, can one just put a jumper wire to Y and Y2 on the control board?
I would say yes. I have seen brand new units put in with a jumper like that...I always wondered why they didn't just install a 2 stage thermostat! Its too easy to do it a better way sometimes. Thanks for watching.