mysterylectricity
Electrical
- May 16, 2005
- 7
Hi,
As a rule of thumb, what are maximum case temperatures of small compressors? Stat cooled in particular. Is it worthwhile to make a distinction between the "average" temperature of the housing and the peak temperatures of the housing immediately adjacent to the HP line?
My reasons for asking are two fold.
I have a single stage freeze drier whose performance seemed to drop a few notches suddenly about a year ago, and has remained the same (ie: hasn't gotten worse) since.
I'm suspecting crud in the capillary. The compressor seems to be running pretty dang hot, but I think in these types of applications they run hot anyway.
Which brings me to the more important reason for asking. I'll be designing similar systems and need to be able to know when too hot is too hot. These systems usually operate at points outside of factory specifications for evaporator temperatures (-60 to -80 C from ambient 32C ambient, single stage) and therefore outside the normal ranage of flow through the compressor. If there's any truth to the claim that media flow through the compressor helps to cool it (it's hard for me to reconcile this with the fact that the overall load under these condtions is very low), I might be in trouble. Nevertheless preliminary indications suggest that standard HBP compressors are used unmodified.
I seemd to have temporarily misplaced my non-contact thermometer but it seems like after running this unit flat out for a few hours (SOP), I can hold my finger on it very lightly for a few seconds: if I apply any pressure it's painfull immediately. I'd guesstimate ~160-180F, and fairly consistent over the entire case and even the discharge port. It's a Danfoss FR7.5B, porbably running R-12, rated about 400-500W thermal lift. Is that a normal operating temp?
-Jeff
As a rule of thumb, what are maximum case temperatures of small compressors? Stat cooled in particular. Is it worthwhile to make a distinction between the "average" temperature of the housing and the peak temperatures of the housing immediately adjacent to the HP line?
My reasons for asking are two fold.
I have a single stage freeze drier whose performance seemed to drop a few notches suddenly about a year ago, and has remained the same (ie: hasn't gotten worse) since.
I'm suspecting crud in the capillary. The compressor seems to be running pretty dang hot, but I think in these types of applications they run hot anyway.
Which brings me to the more important reason for asking. I'll be designing similar systems and need to be able to know when too hot is too hot. These systems usually operate at points outside of factory specifications for evaporator temperatures (-60 to -80 C from ambient 32C ambient, single stage) and therefore outside the normal ranage of flow through the compressor. If there's any truth to the claim that media flow through the compressor helps to cool it (it's hard for me to reconcile this with the fact that the overall load under these condtions is very low), I might be in trouble. Nevertheless preliminary indications suggest that standard HBP compressors are used unmodified.
I seemd to have temporarily misplaced my non-contact thermometer but it seems like after running this unit flat out for a few hours (SOP), I can hold my finger on it very lightly for a few seconds: if I apply any pressure it's painfull immediately. I'd guesstimate ~160-180F, and fairly consistent over the entire case and even the discharge port. It's a Danfoss FR7.5B, porbably running R-12, rated about 400-500W thermal lift. Is that a normal operating temp?
-Jeff
