However, there are instances where the reversing valve is off when running cool mode. But when calling for normal heat, it goes into the cooling cycle. It will operate and blow heat like I've died and gone to hell, but it won't go the other direction and cool. It works fine in cooling. (Tapping on the valve, making sure there was power to the valve, made sure that I was using the B terminal instead of the O terminal, etc.) not all reversing valves energize in heating most do not. For example, solenoid coil energized for cooling (Figure 1); solenoid coil failure mode to heat cycle. Shown here, the heat pump cooling works like any cooling system when it is in cooling mode. Heat pumps and heat/cool units: many original equipment manufacturers connect the system tubing to the Ranco reversing valve based on which mode (heat or cool) the system will operate, should the solenoid coil fail. This valve is specialized for heat pumps, and when issues arise with the reversing valve in your heat pump, there will be operational issues. In a heat pump, a reversing valve controls the direction of the flow of refrigerant. B on the stat is reversing valve energized in heating mode. When the reversing valve is called upon to shift from the "down" position, the pilot solenoid valve is energized, closing its compressor discharge pressure port and connecting the chamber on top of the piston to the compressor suction line. If it was -20 outside, and your reversing valve failed, you will still have heat, you can survive (don't tell that to my customers) without a/c but you will die without heat in reality. This determines whether you are going to heat or going to cool. The main difference is that a heat pump can both heat and cool a home, whereas an air conditioner just cools a home. With the reversing valve de-energized the flow reverses. The determination for mode of operation is the presence or absence of an “O” signal from the stat. On my newer CrapAir unit, it appears the reversing valve is stuck. Therefore, it is important the check the manufacturer's specifications of the heat pump system that you are using before you can do a proper connection to the thermostat. The selenoid energized.The other unit wired the same way working fine. A refrigerant reversing valve with an electromechanical solenoid coil is used to reverse refrigerant flow during unit operation (see Figure 10-14). I tried everything. Your stat has no common. This is a job for your local Carrier expert. It is generally soldered to the pipes or copper tubing, which are typically going in and out the device towards the other parts of the heat pump. 0 = cooling reversing valve, energized in cooling mode. Video of a confirmed diagnosis of a 3-way reversing valve not cooling but heating ok. A heat pump has a few extra parts that allow it to reverse the direction of heat exchange. Please check your heating and cooling system manual or consult a professional HVAC technician if you do not know which option to select. Cool Low Pressure Gas. If I cut breaker of to unit you can hear valve coil click as it is de-energizing, or if you put unit in heating cycle you can hear valve click as it is de-energizing. In Figures 2 and 3, the pilot valve has been configured so that when the pilot valve is de-energized, the system is in the heating mode, and energizing the pilot valve the system is in cooling mode. In a heat pump system when the reversing valve is energized (cool mode), the unit will run in cool mode and the refrigerant will follow the path indicated on the bottom. Condensing unit runs, but just won't push the gas back the other way. lennox energize in cooling for instance. Coils: The condenser and evaporating coil heat or cool the air depending on the directional flow of refrigerant. A reversing valve is usually found close to the compressor or condenser of the heat pump. If the Reversing Valve is energized on a call for heating, what Terminal on the Sub-Base must be used? If the valve breaks, the heat pump will be trapped in one mode or the other. Wire it in and set the reversing valve to stay on cool cycle and never reverse to heat and viola. Some units use energized reversing valve during cool and some de-energized. In most cases, the reversing valve is energized when running cool mode. If the reversing valve is energized during this test, ... the suction gases can absorb heat from the wayward hot gas bleeding across the valve diminishing the amount of sensible heat rise across the valve. HEAT PUMP SYSTEM: Configure the reversing valve for O (energized in cool) or B (energized in heat) and enable/ disable Emergency Heat and/or Auxiliary Heat. Reversing valves can easily be configured for opposite operation. Basically before heat pumps refrigerant flowed one direction. Start studying Reversing Valve 4 Way- Valve Heat Pumps. I have found that the reversing valve is energized on the cooling cycle, but also even if thermostat is set to off position valve is still energized. This reversing valve solenoid, partially controlled by the HP thermostat, is generally energized in the cooling mode (except as noted above). So you should be able to check the wiring at the air handler. The solenoid does not actually shift the main valve, it only shifts a much smaller pilot valve that then uses system pressure to shift the valve. There should be no voltage at the O/B terminal with No Call for heat or cool. A broken reversing valve will mean a heat pump that is trapped in one mode or the other. Welcome to the forums. 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