Heat Pump defrost trigger

[Controlswiz]

Want information as to what makes a Heat Pump Chiller or a Heat Pump Split Unit go to defrost mode?

a) Is it evaporator coil temperature?
b) If so what is the set point for defrost with R134a? What is the defrost cut off point?

[The Viking]

This will vary from manufacturer to manufacturer, sometimes even from model to model...

Optical sensors, flows, pressures and temperatures all have been used to control defrost by one manufacturer or another.

So unless you tell us specifically what kit you are looking at we will not be able to answer your question.


.

[Luke collins]

some schedule on a timer and then cycle the unit back as an AC without the fans running on the condenser to heat the coil quicker to defrost it. Note less defrosts are required when below approx -5 oC then from approx +3/5 external due to the moisture content in the air. I think normally when the ambient is below approx 8 OC they defrost approx once per hour on the Jap machines.