Air Conditioning - Humidistat Question

I had a dehumidification humidistat installed. The installation manual states that I must have a coil with an expansion valve and a freeze-stat to prevent coil freeze-up. The HVAC tech tried to explain what component was susceptible to freezing up and I thought he mentioned something about the refrigerant and that my cooling would not be affected. However, I was unable to follow his explanation.

Can you help explain how this expansion valve and freeze-stat works and what component (or liquid) of the system is being protected from freezing up?

Thanks,
Jerry

When your unit is dehumidifying it will slow the fan speed down. This helps the coil get colder to remove more humidity. The freeze stat will measure the temperature to keep it from freezing the coil.

When your unit is dehumidifying it will slow the fan speed down. This helps the coil get colder to remove more humidity. The freeze stat will measure the temperature to keep it from freezing the coil.

Thanks for the return. So, is it correct to say that the surrounding air and moisture is what can collect on the coil and freeze? And second, if the freeze stat does activate, will my air conditioner shut down?

What is the purpose of the expansion valve?

Jerry

Freeze stat will shut down the compressor when freeze temp on the coil is reached. Expansion valve controls the refrigerant flow thru the Evaporator coil it automatically adjusts refrigerant flow by sensing the refrigerant temps as it leaves the Evaporator coil. There are a bunch of different types but they all are used to control the refrigerant flow based upon system loading. When your humidistat slows the fan speed the expansion valve compensates (reduces flow) up to its limit however the coil can still freeze as a typical expansion valve can only adjust a certain amount so the freeze stat should cut off the compressor at that point. A engineered and matched system is important to prevent problems. If some clown head wants to field engineer your system he is simply rolling the dice with your dollars LOL might work OK might not. What type of system are we modifying here and are we using factory recommended parts??

Freeze stat will shut down the compressor when freeze temp on the coil is reached. Expansion valve controls the refrigerant flow thru the Evaporator coil it automatically adjusts refrigerant flow by sensing the refrigerant temps as it leaves the Evaporator coil. There are a bunch of different types but they all are used to control the refrigerant flow based upon system loading. When your humidistat slows the fan speed the expansion valve compensates (reduces flow) up to its limit however the coil can still freeze as a typical expansion valve can only adjust a certain amount so the freeze stat should cut off the compressor at that point. A engineered and matched system is important to prevent problems. If some clown head wants to field engineer your system he is simply rolling the dice with your dollars LOL might work OK might not. What type of system are we modifying here and are we using factory recommended parts??

Thanks so much for your explanation. For some reason, I did not realize refrigerant could freeze. Perhaps you can answer my next questions.

When my dehumidification humidistat was installed, the HVAC tech told me to set it at 50%

1. Does that seem reasonable?

As I understand it, when the humidity reaches 50% the airflow is reduced 15%. During early winter when I use heat, my house hygrometer can read 55% or higher.

2. So, at 55%, will my airflow for heat also be reduced 15%?

Jerry