Hello All!
At our home, we have a heat pump. When the cooling call ends, the reversing valve is de-energized. When de-energized, the system pressures equalize so quickly that there is a very loud scream which bothers the neighbors (and wakes me up when I'm pretending to be working outside).
The reversing valve is basically a multi-directional solenoid. The coil causes a slide to move inside the unit which directs the flow of refrigerant as needed for heating or cooling, per the room thermostat's call.
My solution is to keep the reversing valve energized for several seconds after the cooling call ends. This lets the system pressures equalize through the expansion valve and there is no scream. Manual testing shows 20 seconds suffices.
To implement, I chose a "Fan Post Flow Delay Timer" which is typically used in furnaces to keep the indoor fan running for a time period after the burners turn off. The reversing valve coil is 24 vac.
The problem is that the reversing valve's solenoid coil draws 5 mA. The timer requires a load of between 40 mA and 1 amp.
I think, possibly incorrectly, that I can install a resistor parallel with the solenoid coil to increase the load on the timer to 45 mA. (A rough sketch is attached.)
My Math = 24 Volts divided by 600 ohms equals 40 mA. Add in the coil & we have a load on the timer of 45 mA.
The conundrum is what wattage does the resistor need to be to prevent it from destroying itself. Is a standard 1/4 watt sufficient?
Is there a better solution to my situation?
Thank You All for your advice & sharing of knowledge. It's much appreciated.
Paul
At our home, we have a heat pump. When the cooling call ends, the reversing valve is de-energized. When de-energized, the system pressures equalize so quickly that there is a very loud scream which bothers the neighbors (and wakes me up when I'm pretending to be working outside).
The reversing valve is basically a multi-directional solenoid. The coil causes a slide to move inside the unit which directs the flow of refrigerant as needed for heating or cooling, per the room thermostat's call.
My solution is to keep the reversing valve energized for several seconds after the cooling call ends. This lets the system pressures equalize through the expansion valve and there is no scream. Manual testing shows 20 seconds suffices.
To implement, I chose a "Fan Post Flow Delay Timer" which is typically used in furnaces to keep the indoor fan running for a time period after the burners turn off. The reversing valve coil is 24 vac.
The problem is that the reversing valve's solenoid coil draws 5 mA. The timer requires a load of between 40 mA and 1 amp.
I think, possibly incorrectly, that I can install a resistor parallel with the solenoid coil to increase the load on the timer to 45 mA. (A rough sketch is attached.)
My Math = 24 Volts divided by 600 ohms equals 40 mA. Add in the coil & we have a load on the timer of 45 mA.
The conundrum is what wattage does the resistor need to be to prevent it from destroying itself. Is a standard 1/4 watt sufficient?
Is there a better solution to my situation?
Thank You All for your advice & sharing of knowledge. It's much appreciated.
Paul
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