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Fridgy Dave
16-06-2011, 01:15 AM
Just wondering what the rule of thumb is with glass door freezer superheat. I have seen cases specified at 5k and flood back badly. I was told 10k but wanted to hear others opinions.
Thanks

S.Palvi (jnr)
16-06-2011, 01:36 AM
Usually 5-7K yes, but if the compressor is situated lower than the blower coil remember a trap higher than the coil to prevent flooding. (asuming the coil is clean and optimal airflow is achieved)

HVACRsaurus
16-06-2011, 06:31 AM
When you say flood back badly, is it just ice on suction of compressor, or is there a measured value of low/no superheat combined with other indicators such as cold discharge temperature and noises from compressor? As suggested in previous post, SH 5 - 7 DegK is normal, but often results in frost at the compressor - sometimes mistaken for floodback. Typical freezer systems normally have suction accumulator to provide some degree of liquid protection.

Fridgy Dave
17-06-2011, 02:11 AM
Not sure whether this rack has an accumulator. Thanks for your input I will try and lower all superheat on all the freezers and see how the system runs.

Magoo
17-06-2011, 04:15 AM
Hi Fridgy Dave.
do a forum search on superheat, there is a lot of discussion on subject to read.
magoo

Fridgy Dave
17-06-2011, 05:43 AM
Thanks magoo I'll check that out

S.Palvi (jnr)
17-06-2011, 08:14 AM
When you say flood back badly, is it just ice on suction of compressor, or is there a measured value of low/no superheat combined with other indicators such as cold discharge temperature and noises from compressor? As suggested in previous post, SH 5 - 7 DegK is normal, but often results in frost at the compressor - sometimes mistaken for floodback. Typical freezer systems normally have suction accumulator to provide some degree of liquid protection.

This is quite true, a colder discharge temp and a cold oil sump usually means liquid. A small SH of below 5 whould be the first indication of liquid overshooting, but also as Gary the VIP mentioned there is alot of factors that needs to be balanced out.