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tradelinkintern
10-11-2011, 04:28 PM
Hello,

I Have a Freezer room at -18 10m long X 8m wide X 4m high, with one door, 2.5m high and 4m wide which is opened about 30 times a day. Outside the door we have 20 plus and the freezer is made from standard polyurethan panels - about 25mms thick.

We have 2 compressors - 7.5HP each, running R404 and the temperature recently has not been keeping at -18. Most of the time it's around -10.

We have had several tecnitians in and each one has given me a different answer. My question is do we have enough power to keep the freezers at -18, or do we need to invest in an extra unit.

Option A that several tecnitians have given me is to to a complete clean up of the units and install a defrosting system that runs on gas, instead of the electrical system that is not working properly at the moment.

Option B is to install another unit.

Obviously big difference in costs and we want to avoid an extra unit if possible.

Many thanks.

nando
10-11-2011, 06:10 PM
Hello,

What are the types of the compressors?
Are the products frozen, so yes what is the temp, when they get inside?
Are you sure that the installation works good? Maybe theres a problem whit a unit, too much ice, not enough gas...

charlie patt
10-11-2011, 07:24 PM
look at the insulation 25 mm thick on a freezer if that is correct forget the fridge kit look at the insulation first

install monkey
10-11-2011, 08:17 PM
beef up the insulation and fit an air curtain

NH3_Sniffer
10-11-2011, 09:34 PM
Hi,

Agree with all of the above, probably best to start with a simple load estimation. This will determine if the kit is upto the job.

As I am not aware of the complete system, it would be unusual to convert an electric D.F to hot gas? usually commercial systems are defrosted by electric heaters within the evaporator coil. If failed they can be replaced individually at relatively low cost. If defrosting is an issue then most probably there will be a build up of ice upon the coil surface and reduce heat transferee. Room temperature will suffer but most importantly liquid refrigerant may return to the compressor and cause ultimate failure.

Make sure coils are completely clear of ice.

compressor.

mikeref
10-11-2011, 11:47 PM
Insulation only 25mm? There is the problem, too much heat infiltration. Coldroom should have 100mm and freezer room, 150mm.

texas64
11-11-2011, 02:04 AM
Here use this calculator to figure up box refrigeration requirements. If the box was keeping -18 degree centigrade before, then the box thickness was ok, unless it has degraded now, possibly showing frost/ice on the outside of the box or the door. Could you give the model numbers for the compressors and of the evaporators? Maybe include some photos please. and draw your layout of the system. I agree with NH3 sniffer. If you are having issues with the defrost, go ahead and repair/replace the necessary parts to ensure proper removal of ice and frost on the evaporators. If your evaporators are accumulating ice and the defrost isn't completely ridding the ice during defrost, you will not reach your desired temperature. You may not even have a defrost problem at all. You should make sure the company that you have hire is sending highly qualified technicians, not people who are learning on your equipment.

texas64
11-11-2011, 02:05 AM
http://www.heatcraftrpd.com/products/PDF%5CMisc%5CCA-QC.pdf

tradelinkintern
11-11-2011, 10:11 AM
Thanks very much for the replies. I hadn't really focused on the insulation, and having read this I went and checked and the door is very leaky - gaps around the edges even when closed. Yes there is huge build up of ice around coils etc which we have been defrosting manually since the system hasn't been able to shake it off.

To start with, I'm going to fix that door, fix the defrosting system and fit air curtains above the door and see how that helps.

Thanks again everyone who helped on this.

taz24
11-11-2011, 11:03 AM
Thanks very much for the replies. I hadn't really focused on the insulation, and having read this I went and checked and the door is very leaky - gaps around the edges even when closed. Yes there is huge build up of ice around coils etc which we have been defrosting manually since the system hasn't been able to shake it off.

To start with, I'm going to fix that door, fix the defrosting system and fit air curtains above the door and see how that helps.

Thanks again everyone who helped on this.

Go back to basics.

How old is it and did it work ok before?

If yes to thoses questions then ask what has changed.

Wall insulation cannot be 25mm that is far too thin!!!!

But the door will cause problems with defrost.

Plus check the timings of the defrost.

Do they defrost together or at differant times?

If they defrost at different times and are not set correctly the one
on defrost just puts all the moisture onto the one still running.

Also has the loading changed? do you stock the same product
now and in the same quantity as you always have.

30 door openings in 24 hours is only just ove one an hour
or is it 30 door opening in 10 hours it makes a big differance.

Do a pump test on both units and make sure they are both still working
correctley.


All the best

taz.