Quote Originally Posted by pilko View Post
@ mad fridgie,
Just took a look into my heat pump, It does have an accumulator. Is it OK to go ahead and run defrost with indoor fan stoopped? If yes:-

1 What precautions should I take?

2 What if anything can I monitor to reduce risk of damage?

regards

pilko
OK, firstly lets look at control, and also taking note of the "Pros" concerns. (remember I do NOT know your particular equipment)
Because of how you measuring ice, you could but a defrost fail safe in (If after "x" mins the coil is not defrost slowing bring fan on. (you will still have a cold draft when the fan is on, but is a "just in case")
That covers all issues about the ability to defrost.

As far as protection, firstly look at the size of your accumulator (volume), is the volume greater than the total volume of liquid refrigerant in your system. ( again not quite a true fact but thing of the volume of refrigerant as water "2kg of refrigerant = 2 litres") The weight of refrigerant should be indicated on the outside unit. If the accumulator volume is over or close to the refrigerant volume, then no worries.
If it is greatly smaller, then install a larger one.
We could look at electrical protection, but would be expensive and very complicated software.
pressure transducers, temp sensors, comp current sensor, with pressure/temp comparability.